[PATCH v10 bpf-next 0/9] Add skb + xdp dynptrs

[PATCH v10 bpf-next 0/9] Add skb + xdp dynptrs

[Joanne Koong]

This patchset is the 2nd in the dynptr series. The 1st can be found here [0].

This patchset adds skb and xdp type dynptrs, which have two main benefits for
packet parsing:
    * allowing operations on sizes that are not statically known at
      compile-time (eg variable-sized accesses).
    * more ergonomic and less brittle iteration through data (eg does not need
      manual if checking for being within bounds of data_end)

When comparing the differences in runtime for packet parsing without dynptrs
vs. with dynptrs, there is no noticeable difference. Patch 9 contains more
details as well as examples of how to use skb and xdp dynptrs.

[0]
https://lore.kernel.org/bpf/20220523210712.3641569-1-joannelkoong@gmail.com/

--
Changelog:

v9 = https://lore.kernel.org/bpf/20230127191703.3864860-1-joannelkoong@gmail.com/
v9 -> v10:
    * Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr interface
    * Add some more tests
    * Split up patchset into more parts to make it easier to review

v8 = https://lore.kernel.org/bpf/20230126233439.3739120-1-joannelkoong@gmail.com/
v8 -> v9:
    * Fix dynptr_get_type() to check non-stack dynptrs 

v7 = https://lore.kernel.org/bpf/20221021011510.1890852-1-joannelkoong@gmail.com/
v7 -> v8:
    * Change helpers to kfuncs
    * Add 2 new patches (1/5 and 2/5)

v6 = https://lore.kernel.org/bpf/20220907183129.745846-1-joannelkoong@gmail.com/
v6 -> v7
    * Change bpf_dynptr_data() to return read-only data slices if the skb prog
      is read-only (Martin)
    * Add test "skb_invalid_write" to test that writes to rd-only data slices
      are rejected

v5 = https://lore.kernel.org/bpf/20220831183224.3754305-1-joannelkoong@gmail.com/
v5 -> v6
    * Address kernel test robot errors by static inlining

v4 = https://lore.kernel.org/bpf/20220822235649.2218031-1-joannelkoong@gmail.com/
v4 -> v5
    * Address kernel test robot errors for configs w/out CONFIG_NET set
    * For data slices, return PTR_TO_MEM instead of PTR_TO_PACKET (Kumar)
    * Split selftests into subtests (Andrii)
    * Remove insn patching. Use rdonly and rdwr protos for dynptr skb
      construction (Andrii)
    * bpf_dynptr_data() returns NULL for rd-only dynptrs. There will be a
      separate bpf_dynptr_data_rdonly() added later (Andrii and Kumar)

v3 = https://lore.kernel.org/bpf/20220822193442.657638-1-joannelkoong@gmail.com/
v3 -> v4
    * Forgot to commit --amend the kernel test robot error fixups

v2 = https://lore.kernel.org/bpf/20220811230501.2632393-1-joannelkoong@gmail.com/
v2 -> v3
    * Fix kernel test robot build test errors

v1 = https://lore.kernel.org/bpf/20220726184706.954822-1-joannelkoong@gmail.com/
v1 -> v2
  * Return data slices to rd-only skb dynptrs (Martin)
  * bpf_dynptr_write allows writes to frags for skb dynptrs, but always
    invalidates associated data slices (Martin)
  * Use switch casing instead of ifs (Andrii)
  * Use 0xFD for experimental kind number in the selftest (Zvi)
  * Put selftest conversions w/ dynptrs into new files (Alexei)
  * Add new selftest "test_cls_redirect_dynptr.c" 

Joanne Koong (9):
  bpf: Support "sk_buff" and "xdp_buff" as valid kfunc arg types
  bpf: Refactor process_dynptr_func
  bpf: Allow initializing dynptrs in kfuncs
  bpf: Define no-ops for externally called bpf dynptr functions
  bpf: Refactor verifier dynptr into get_dynptr_arg_reg
  bpf: Add skb dynptrs
  bpf: Add xdp dynptrs
  bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr
  selftests/bpf: tests for using dynptrs to parse skb and xdp buffers

 include/linux/bpf.h                           |  95 +-
 include/linux/bpf_verifier.h                  |   3 -
 include/linux/filter.h                        |  46 +
 include/uapi/linux/bpf.h                      |  18 +-
 kernel/bpf/btf.c                              |  22 +
 kernel/bpf/helpers.c                          | 174 +++-
 kernel/bpf/verifier.c                         | 365 +++++--
 net/core/filter.c                             | 108 +-
 tools/include/uapi/linux/bpf.h                |  18 +-
 .../selftests/bpf/prog_tests/cls_redirect.c   |  25 +
 .../testing/selftests/bpf/prog_tests/dynptr.c |  69 +-
 .../selftests/bpf/prog_tests/l4lb_all.c       |   2 +
 .../bpf/prog_tests/parse_tcp_hdr_opt.c        |  93 ++
 .../selftests/bpf/prog_tests/xdp_attach.c     |  11 +-
 .../testing/selftests/bpf/progs/dynptr_fail.c | 274 ++++-
 .../selftests/bpf/progs/dynptr_success.c      |  51 +-
 .../bpf/progs/test_cls_redirect_dynptr.c      | 975 ++++++++++++++++++
 .../bpf/progs/test_l4lb_noinline_dynptr.c     | 486 +++++++++
 .../bpf/progs/test_parse_tcp_hdr_opt.c        | 119 +++
 .../bpf/progs/test_parse_tcp_hdr_opt_dynptr.c | 118 +++
 .../selftests/bpf/progs/test_xdp_dynptr.c     | 257 +++++
 .../selftests/bpf/test_tcp_hdr_options.h      |   1 +
 22 files changed, 3151 insertions(+), 179 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_dynptr.c

-- 
2.30.2

[PATCH v10 bpf-next 1/9] bpf: Support "sk_buff" and "xdp_buff" as valid kfunc arg types

[Joanne Koong]

The bpf mirror of the in-kernel sk_buff and xdp_buff data structures are
__sk_buff and xdp_md. Currently, when we pass in the program ctx to a
kfunc where the program ctx is a skb or xdp buffer, we reject the
program if the in-kernel definition is sk_buff/xdp_buff instead of
__sk_buff/xdp_md.

This change allows "sk_buff <--> __sk_buff" and "xdp_buff <--> xdp_md"
to be recognized as valid matches. The user program may pass in their
program ctx as a __sk_buff or xdp_md, and the in-kernel definition
of the kfunc may define this arg as a sk_buff or xdp_buff.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 kernel/bpf/btf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6582735ef1fc..ae321c358699 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5675,6 +5675,10 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
 		bpf_log(log, "Please fix kernel include/linux/bpf_types.h\n");
 		return NULL;
 	}
+	if (strcmp(ctx_tname, "__sk_buff") == 0 && strcmp(tname, "sk_buff") == 0)
+		return ctx_type;
+	if (strcmp(ctx_tname, "xdp_md") == 0 && strcmp(tname, "xdp_buff") == 0)
+		return ctx_type;
 	/* only compare that prog's ctx type name is the same as
 	 * kernel expects. No need to compare field by field.
 	 * It's ok for bpf prog to do:
-- 
2.30.2

[PATCH v10 bpf-next 2/9] bpf: Refactor process_dynptr_func

[Joanne Koong]

This change cleans up process_dynptr_func's flow to be more intuitive
and updates some comments with more context.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/bpf_verifier.h |  3 --
 kernel/bpf/verifier.c        | 58 ++++++++++++++++++------------------
 2 files changed, 29 insertions(+), 32 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index cf1bb1cf4a7b..b26ff2a8f63b 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -616,9 +616,6 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
 			   enum bpf_arg_type arg_type);
 int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 		   u32 regno, u32 mem_size);
-struct bpf_call_arg_meta;
-int process_dynptr_func(struct bpf_verifier_env *env, int regno,
-			enum bpf_arg_type arg_type, struct bpf_call_arg_meta *meta);
 
 /* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
 static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 272563a0b770..23a7749e8463 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -955,39 +955,49 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env *env,
 	return 0;
 }
 
-static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-				       int spi)
+static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
 {
+	int spi;
+
 	if (reg->type == CONST_PTR_TO_DYNPTR)
 		return false;
 
-	/* For -ERANGE (i.e. spi not falling into allocated stack slots), we
-	 * will do check_mem_access to check and update stack bounds later, so
-	 * return true for that case.
+	spi = dynptr_get_spi(env, reg);
+
+	/* -ERANGE (i.e. spi not falling into allocated stack slots) isn't an
+	 * error because this just means the stack state hasn't been updated yet.
+	 * We will do check_mem_access to check and update stack bounds later.
 	 */
-	if (spi < 0)
-		return spi == -ERANGE;
-	/* We allow overwriting existing unreferenced STACK_DYNPTR slots, see
-	 * mark_stack_slots_dynptr which calls destroy_if_dynptr_stack_slot to
-	 * ensure dynptr objects at the slots we are touching are completely
-	 * destructed before we reinitialize them for a new one. For referenced
-	 * ones, destroy_if_dynptr_stack_slot returns an error early instead of
-	 * delaying it until the end where the user will get "Unreleased
+	if (spi < 0 && spi != -ERANGE)
+		return false;
+
+	/* We don't need to check if the stack slots are marked by previous
+	 * dynptr initializations because we allow overwriting existing unreferenced
+	 * STACK_DYNPTR slots, see mark_stack_slots_dynptr which calls
+	 * destroy_if_dynptr_stack_slot to ensure dynptr objects at the slots we are
+	 * touching are completely destructed before we reinitialize them for a new
+	 * one. For referenced ones, destroy_if_dynptr_stack_slot returns an error early
+	 * instead of delaying it until the end where the user will get "Unreleased
 	 * reference" error.
 	 */
 	return true;
 }
 
-static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-				     int spi)
+static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
 {
 	struct bpf_func_state *state = func(env, reg);
-	int i;
+	int i, spi;
 
-	/* This already represents first slot of initialized bpf_dynptr */
+	/* This already represents first slot of initialized bpf_dynptr.
+	 *
+	 * CONST_PTR_TO_DYNPTR already has fixed and var_off as 0 due to
+	 * check_func_arg_reg_off's logic, so we don't need to check its
+	 * offset and alignment.
+	 */
 	if (reg->type == CONST_PTR_TO_DYNPTR)
 		return true;
 
+	spi = dynptr_get_spi(env, reg);
 	if (spi < 0)
 		return false;
 	if (!state->stack[spi].spilled_ptr.dynptr.first_slot)
@@ -6210,7 +6220,6 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
 			enum bpf_arg_type arg_type, struct bpf_call_arg_meta *meta)
 {
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
-	int spi = 0;
 
 	/* MEM_UNINIT and MEM_RDONLY are exclusive, when applied to an
 	 * ARG_PTR_TO_DYNPTR (or ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_*):
@@ -6219,15 +6228,6 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
 		verbose(env, "verifier internal error: misconfigured dynptr helper type flags\n");
 		return -EFAULT;
 	}
-	/* CONST_PTR_TO_DYNPTR already has fixed and var_off as 0 due to
-	 * check_func_arg_reg_off's logic. We only need to check offset
-	 * and its alignment for PTR_TO_STACK.
-	 */
-	if (reg->type == PTR_TO_STACK) {
-		spi = dynptr_get_spi(env, reg);
-		if (spi < 0 && spi != -ERANGE)
-			return spi;
-	}
 
 	/*  MEM_UNINIT - Points to memory that is an appropriate candidate for
 	 *		 constructing a mutable bpf_dynptr object.
@@ -6245,7 +6245,7 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
 	 *		 to.
 	 */
 	if (arg_type & MEM_UNINIT) {
-		if (!is_dynptr_reg_valid_uninit(env, reg, spi)) {
+		if (!is_dynptr_reg_valid_uninit(env, reg)) {
 			verbose(env, "Dynptr has to be an uninitialized dynptr\n");
 			return -EINVAL;
 		}
@@ -6268,7 +6268,7 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
 			return -EINVAL;
 		}
 
-		if (!is_dynptr_reg_valid_init(env, reg, spi)) {
+		if (!is_dynptr_reg_valid_init(env, reg)) {
 			verbose(env,
 				"Expected an initialized dynptr as arg #%d\n",
 				regno);
-- 
2.30.2

[PATCH v10 bpf-next 3/9] bpf: Allow initializing dynptrs in kfuncs

[Joanne Koong]

This change allows kfuncs to take in an uninitialized dynptr as a
parameter. Before this change, only helper functions could successfully
use uninitialized dynptrs. This change moves the memory access check
(including stack state growing and slot marking) into
process_dynptr_func(), which both helpers and kfuncs call into.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 kernel/bpf/verifier.c | 67 ++++++++++++++-----------------------------
 1 file changed, 22 insertions(+), 45 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 23a7749e8463..de99fa02b8d8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -268,7 +268,6 @@ struct bpf_call_arg_meta {
 	u32 ret_btf_id;
 	u32 subprogno;
 	struct btf_field *kptr_field;
-	u8 uninit_dynptr_regno;
 };
 
 struct btf *btf_vmlinux;
@@ -6216,10 +6215,11 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
  * Helpers which do not mutate the bpf_dynptr set MEM_RDONLY in their argument
  * type, and declare it as 'const struct bpf_dynptr *' in their prototype.
  */
-int process_dynptr_func(struct bpf_verifier_env *env, int regno,
-			enum bpf_arg_type arg_type, struct bpf_call_arg_meta *meta)
+int process_dynptr_func(struct bpf_verifier_env *env, int regno, int insn_idx,
+			enum bpf_arg_type arg_type)
 {
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
+	int err;
 
 	/* MEM_UNINIT and MEM_RDONLY are exclusive, when applied to an
 	 * ARG_PTR_TO_DYNPTR (or ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_*):
@@ -6245,23 +6245,23 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
 	 *		 to.
 	 */
 	if (arg_type & MEM_UNINIT) {
+		int i;
+
 		if (!is_dynptr_reg_valid_uninit(env, reg)) {
 			verbose(env, "Dynptr has to be an uninitialized dynptr\n");
 			return -EINVAL;
 		}
 
-		/* We only support one dynptr being uninitialized at the moment,
-		 * which is sufficient for the helper functions we have right now.
-		 */
-		if (meta->uninit_dynptr_regno) {
-			verbose(env, "verifier internal error: multiple uninitialized dynptr args\n");
-			return -EFAULT;
+		/* we write BPF_DW bits (8 bytes) at a time */
+		for (i = 0; i < BPF_DYNPTR_SIZE; i += 8) {
+			err = check_mem_access(env, insn_idx, regno,
+					       i, BPF_DW, BPF_WRITE, -1, false);
+			if (err)
+				return err;
 		}
 
-		meta->uninit_dynptr_regno = regno;
+		err = mark_stack_slots_dynptr(env, reg, arg_type, insn_idx);
 	} else /* MEM_RDONLY and None case from above */ {
-		int err;
-
 		/* For the reg->type == PTR_TO_STACK case, bpf_dynptr is never const */
 		if (reg->type == CONST_PTR_TO_DYNPTR && !(arg_type & MEM_RDONLY)) {
 			verbose(env, "cannot pass pointer to const bpf_dynptr, the helper mutates it\n");
@@ -6297,10 +6297,8 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
 		}
 
 		err = mark_dynptr_read(env, reg);
-		if (err)
-			return err;
 	}
-	return 0;
+	return err;
 }
 
 static bool arg_type_is_mem_size(enum bpf_arg_type type)
@@ -6694,7 +6692,8 @@ static int dynptr_ref_obj_id(struct bpf_verifier_env *env, struct bpf_reg_state
 
 static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			  struct bpf_call_arg_meta *meta,
-			  const struct bpf_func_proto *fn)
+			  const struct bpf_func_proto *fn,
+			  int insn_idx)
 {
 	u32 regno = BPF_REG_1 + arg;
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
@@ -6907,7 +6906,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_mem_size_reg(env, reg, regno, true, meta);
 		break;
 	case ARG_PTR_TO_DYNPTR:
-		err = process_dynptr_func(env, regno, arg_type, meta);
+		err = process_dynptr_func(env, regno, insn_idx, arg_type);
 		if (err)
 			return err;
 		break;
@@ -8197,7 +8196,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	meta.func_id = func_id;
 	/* check args */
 	for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
-		err = check_func_arg(env, i, &meta, fn);
+		err = check_func_arg(env, i, &meta, fn, insn_idx);
 		if (err)
 			return err;
 	}
@@ -8222,30 +8221,6 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 
 	regs = cur_regs(env);
 
-	/* This can only be set for PTR_TO_STACK, as CONST_PTR_TO_DYNPTR cannot
-	 * be reinitialized by any dynptr helper. Hence, mark_stack_slots_dynptr
-	 * is safe to do directly.
-	 */
-	if (meta.uninit_dynptr_regno) {
-		if (regs[meta.uninit_dynptr_regno].type == CONST_PTR_TO_DYNPTR) {
-			verbose(env, "verifier internal error: CONST_PTR_TO_DYNPTR cannot be initialized\n");
-			return -EFAULT;
-		}
-		/* we write BPF_DW bits (8 bytes) at a time */
-		for (i = 0; i < BPF_DYNPTR_SIZE; i += 8) {
-			err = check_mem_access(env, insn_idx, meta.uninit_dynptr_regno,
-					       i, BPF_DW, BPF_WRITE, -1, false);
-			if (err)
-				return err;
-		}
-
-		err = mark_stack_slots_dynptr(env, &regs[meta.uninit_dynptr_regno],
-					      fn->arg_type[meta.uninit_dynptr_regno - BPF_REG_1],
-					      insn_idx);
-		if (err)
-			return err;
-	}
-
 	if (meta.release_regno) {
 		err = -EINVAL;
 		/* This can only be set for PTR_TO_STACK, as CONST_PTR_TO_DYNPTR cannot
@@ -9455,7 +9430,8 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env,
 						  &meta->arg_rbtree_root.field);
 }
 
-static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
+static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
+			    int insn_idx)
 {
 	const char *func_name = meta->func_name, *ref_tname;
 	const struct btf *btf = meta->btf;
@@ -9652,7 +9628,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				return -EINVAL;
 			}
 
-			ret = process_dynptr_func(env, regno, ARG_PTR_TO_DYNPTR | MEM_RDONLY, NULL);
+			ret = process_dynptr_func(env, regno, insn_idx,
+						  ARG_PTR_TO_DYNPTR | MEM_RDONLY);
 			if (ret < 0)
 				return ret;
 			break;
@@ -9860,7 +9837,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	}
 
 	/* Check the arguments */
-	err = check_kfunc_args(env, &meta);
+	err = check_kfunc_args(env, &meta, insn_idx);
 	if (err < 0)
 		return err;
 	/* In case of release function, we get register number of refcounted
-- 
2.30.2

[PATCH v10 bpf-next 4/9] bpf: Define no-ops for externally called bpf dynptr functions

[Joanne Koong]

Some bpf dynptr functions will be called from places where
if CONFIG_BPF_SYSCALL is not set, then the dynptr function is
undefined. For example, when skb type dynptrs are added in the
next commit, dynptr functions are called from net/core/filter.c

This patch defines no-op implementations of these dynptr functions
so that they do not break compilation by being an undefined reference.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/bpf.h | 75 +++++++++++++++++++++++++++------------------
 1 file changed, 45 insertions(+), 30 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 520b238abd5a..296841a31749 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1124,6 +1124,33 @@ static __always_inline __nocfi unsigned int bpf_dispatcher_nop_func(
 	return bpf_func(ctx, insnsi);
 }
 
+/* the implementation of the opaque uapi struct bpf_dynptr */
+struct bpf_dynptr_kern {
+	void *data;
+	/* Size represents the number of usable bytes of dynptr data.
+	 * If for example the offset is at 4 for a local dynptr whose data is
+	 * of type u64, the number of usable bytes is 4.
+	 *
+	 * The upper 8 bits are reserved. It is as follows:
+	 * Bits 0 - 23 = size
+	 * Bits 24 - 30 = dynptr type
+	 * Bit 31 = whether dynptr is read-only
+	 */
+	u32 size;
+	u32 offset;
+} __aligned(8);
+
+enum bpf_dynptr_type {
+	BPF_DYNPTR_TYPE_INVALID,
+	/* Points to memory that is local to the bpf program */
+	BPF_DYNPTR_TYPE_LOCAL,
+	/* Underlying data is a ringbuf record */
+	BPF_DYNPTR_TYPE_RINGBUF,
+};
+
+int bpf_dynptr_check_size(u32 size);
+u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr);
+
 #ifdef CONFIG_BPF_JIT
 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
 int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
@@ -2266,6 +2293,11 @@ static inline bool has_current_bpf_ctx(void)
 }
 
 void notrace bpf_prog_inc_misses_counter(struct bpf_prog *prog);
+
+void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,
+		     enum bpf_dynptr_type type, u32 offset, u32 size);
+void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr);
+void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr);
 #else /* !CONFIG_BPF_SYSCALL */
 static inline struct bpf_prog *bpf_prog_get(u32 ufd)
 {
@@ -2495,6 +2527,19 @@ static inline void bpf_prog_inc_misses_counter(struct bpf_prog *prog)
 static inline void bpf_cgrp_storage_free(struct cgroup *cgroup)
 {
 }
+
+static inline void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,
+				   enum bpf_dynptr_type type, u32 offset, u32 size)
+{
+}
+
+static inline void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr)
+{
+}
+
+static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
+{
+}
 #endif /* CONFIG_BPF_SYSCALL */
 
 void __bpf_free_used_btfs(struct bpf_prog_aux *aux,
@@ -2913,36 +2958,6 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
 			u32 num_args, struct bpf_bprintf_data *data);
 void bpf_bprintf_cleanup(struct bpf_bprintf_data *data);
 
-/* the implementation of the opaque uapi struct bpf_dynptr */
-struct bpf_dynptr_kern {
-	void *data;
-	/* Size represents the number of usable bytes of dynptr data.
-	 * If for example the offset is at 4 for a local dynptr whose data is
-	 * of type u64, the number of usable bytes is 4.
-	 *
-	 * The upper 8 bits are reserved. It is as follows:
-	 * Bits 0 - 23 = size
-	 * Bits 24 - 30 = dynptr type
-	 * Bit 31 = whether dynptr is read-only
-	 */
-	u32 size;
-	u32 offset;
-} __aligned(8);
-
-enum bpf_dynptr_type {
-	BPF_DYNPTR_TYPE_INVALID,
-	/* Points to memory that is local to the bpf program */
-	BPF_DYNPTR_TYPE_LOCAL,
-	/* Underlying data is a kernel-produced ringbuf record */
-	BPF_DYNPTR_TYPE_RINGBUF,
-};
-
-void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,
-		     enum bpf_dynptr_type type, u32 offset, u32 size);
-void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr);
-int bpf_dynptr_check_size(u32 size);
-u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr);
-
 #ifdef CONFIG_BPF_LSM
 void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype);
 void bpf_cgroup_atype_put(int cgroup_atype);
-- 
2.30.2

[PATCH v10 bpf-next 5/9] bpf: Refactor verifier dynptr into get_dynptr_arg_reg

[Joanne Koong]

This commit refactors the logic for determining which register in a
function is the dynptr into "get_dynptr_arg_reg". This will be used
in the future when the dynptr reg for BPF_FUNC_dynptr_write will need
to be obtained in order to support writes for skb dynptrs.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 kernel/bpf/verifier.c | 80 +++++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 30 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index de99fa02b8d8..babc82e93ae6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6664,6 +6664,28 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
 	}
 }
 
+static struct bpf_reg_state *get_dynptr_arg_reg(struct bpf_verifier_env *env,
+						const struct bpf_func_proto *fn,
+						struct bpf_reg_state *regs)
+{
+	struct bpf_reg_state *state = NULL;
+	int i;
+
+	for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++)
+		if (arg_type_is_dynptr(fn->arg_type[i])) {
+			if (state) {
+				verbose(env, "verifier internal error: multiple dynptr args\n");
+				return NULL;
+			}
+			state = &regs[BPF_REG_1 + i];
+		}
+
+	if (!state)
+		verbose(env, "verifier internal error: no dynptr arg found\n");
+
+	return state;
+}
+
 static int dynptr_id(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
 {
 	struct bpf_func_state *state = func(env, reg);
@@ -8305,43 +8327,41 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		}
 		break;
 	case BPF_FUNC_dynptr_data:
-		for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
-			if (arg_type_is_dynptr(fn->arg_type[i])) {
-				struct bpf_reg_state *reg = &regs[BPF_REG_1 + i];
-				int id, ref_obj_id;
-
-				if (meta.dynptr_id) {
-					verbose(env, "verifier internal error: meta.dynptr_id already set\n");
-					return -EFAULT;
-				}
-
-				if (meta.ref_obj_id) {
-					verbose(env, "verifier internal error: meta.ref_obj_id already set\n");
-					return -EFAULT;
-				}
+	{
+		struct bpf_reg_state *reg;
+		int id, ref_obj_id;
 
-				id = dynptr_id(env, reg);
-				if (id < 0) {
-					verbose(env, "verifier internal error: failed to obtain dynptr id\n");
-					return id;
-				}
+		reg = get_dynptr_arg_reg(env, fn, regs);
+		if (!reg)
+			return -EFAULT;
 
-				ref_obj_id = dynptr_ref_obj_id(env, reg);
-				if (ref_obj_id < 0) {
-					verbose(env, "verifier internal error: failed to obtain dynptr ref_obj_id\n");
-					return ref_obj_id;
-				}
 
-				meta.dynptr_id = id;
-				meta.ref_obj_id = ref_obj_id;
-				break;
-			}
+		if (meta.dynptr_id) {
+			verbose(env, "verifier internal error: meta.dynptr_id already set\n");
+			return -EFAULT;
 		}
-		if (i == MAX_BPF_FUNC_REG_ARGS) {
-			verbose(env, "verifier internal error: no dynptr in bpf_dynptr_data()\n");
+		if (meta.ref_obj_id) {
+			verbose(env, "verifier internal error: meta.ref_obj_id already set\n");
 			return -EFAULT;
 		}
+
+		id = dynptr_id(env, reg);
+		if (id < 0) {
+			verbose(env, "verifier internal error: failed to obtain dynptr id\n");
+			return id;
+		}
+
+		ref_obj_id = dynptr_ref_obj_id(env, reg);
+		if (ref_obj_id < 0) {
+			verbose(env, "verifier internal error: failed to obtain dynptr ref_obj_id\n");
+			return ref_obj_id;
+		}
+
+		meta.dynptr_id = id;
+		meta.ref_obj_id = ref_obj_id;
+
 		break;
+	}
 	case BPF_FUNC_user_ringbuf_drain:
 		err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
 					set_user_ringbuf_callback_state);
-- 
2.30.2

[PATCH v10 bpf-next 6/9] bpf: Add skb dynptrs

[Joanne Koong]

Add skb dynptrs, which are dynptrs whose underlying pointer points
to a skb. The dynptr acts on skb data. skb dynptrs have two main
benefits. One is that they allow operations on sizes that are not
statically known at compile-time (eg variable-sized accesses).
Another is that parsing the packet data through dynptrs (instead of
through direct access of skb->data and skb->data_end) can be more
ergonomic and less brittle (eg does not need manual if checking for
being within bounds of data_end).

For bpf prog types that don't support writes on skb data, the dynptr is
read-only (bpf_dynptr_write() will return an error)

For reads and writes through the bpf_dynptr_read() and bpf_dynptr_write()
interfaces, reading and writing from/to data in the head as well as from/to
non-linear paged buffers is supported. Data slices through the
bpf_dynptr_data API are not supported; instead bpf_dynptr_slice() and
bpf_dynptr_slice_rdwr() (added in subsequent commit) should be used.

For examples of how skb dynptrs can be used, please see the attached
selftests.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/bpf.h            | 14 ++++++-
 include/linux/filter.h         | 18 ++++++++
 include/uapi/linux/bpf.h       | 14 ++++++-
 kernel/bpf/btf.c               | 18 ++++++++
 kernel/bpf/helpers.c           | 76 +++++++++++++++++++++++++++-------
 kernel/bpf/verifier.c          | 70 ++++++++++++++++++++++++++++++-
 net/core/filter.c              | 67 ++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h | 14 ++++++-
 8 files changed, 270 insertions(+), 21 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 296841a31749..3d18be35a5e6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -607,11 +607,14 @@ enum bpf_type_flag {
 	 */
 	NON_OWN_REF		= BIT(14 + BPF_BASE_TYPE_BITS),
 
+	/* DYNPTR points to sk_buff */
+	DYNPTR_TYPE_SKB		= BIT(15 + BPF_BASE_TYPE_BITS),
+
 	__BPF_TYPE_FLAG_MAX,
 	__BPF_TYPE_LAST_FLAG	= __BPF_TYPE_FLAG_MAX - 1,
 };
 
-#define DYNPTR_TYPE_FLAG_MASK	(DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF)
+#define DYNPTR_TYPE_FLAG_MASK	(DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB)
 
 /* Max number of base types. */
 #define BPF_BASE_TYPE_LIMIT	(1UL << BPF_BASE_TYPE_BITS)
@@ -1146,6 +1149,8 @@ enum bpf_dynptr_type {
 	BPF_DYNPTR_TYPE_LOCAL,
 	/* Underlying data is a ringbuf record */
 	BPF_DYNPTR_TYPE_RINGBUF,
+	/* Underlying data is a sk_buff */
+	BPF_DYNPTR_TYPE_SKB,
 };
 
 int bpf_dynptr_check_size(u32 size);
@@ -2846,6 +2851,8 @@ u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
 				struct bpf_insn *insn_buf,
 				struct bpf_prog *prog,
 				u32 *target_size);
+int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
+			       struct bpf_dynptr_kern *ptr);
 #else
 static inline bool bpf_sock_common_is_valid_access(int off, int size,
 						   enum bpf_access_type type,
@@ -2867,6 +2874,11 @@ static inline u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
 {
 	return 0;
 }
+static inline int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
+					     struct bpf_dynptr_kern *ptr)
+{
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_INET
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 1727898f1641..de18e844d15e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1542,4 +1542,22 @@ static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u64 index
 	return XDP_REDIRECT;
 }
 
+#ifdef CONFIG_NET
+int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len);
+int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from,
+			  u32 len, u64 flags);
+#else /* CONFIG_NET */
+static inline int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset,
+				       void *to, u32 len)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset,
+					const void *from, u32 len, u64 flags)
+{
+	return -EOPNOTSUPP;
+}
+#endif /* CONFIG_NET */
+
 #endif /* __LINUX_FILTER_H__ */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1503f61336b6..4c229e0866db 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5320,11 +5320,17 @@ union bpf_attr {
  *	Description
  *		Write *len* bytes from *src* into *dst*, starting from *offset*
  *		into *dst*.
- *		*flags* is currently unused.
+ *
+ *		*flags* must be 0 except for skb-type dynptrs.
+ *
+ *		For skb-type dynptrs:
+ *		    *  For *flags*, please see the flags accepted by
+ *		       **bpf_skb_store_bytes**\ ().
  *	Return
  *		0 on success, -E2BIG if *offset* + *len* exceeds the length
  *		of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*
- *		is a read-only dynptr or if *flags* is not 0.
+ *		is a read-only dynptr or if *flags* is not correct. For skb-type dynptrs,
+ *		other errors correspond to errors returned by **bpf_skb_store_bytes**\ ().
  *
  * void *bpf_dynptr_data(const struct bpf_dynptr *ptr, u32 offset, u32 len)
  *	Description
@@ -5332,6 +5338,10 @@ union bpf_attr {
  *
  *		*len* must be a statically known value. The returned data slice
  *		is invalidated whenever the dynptr is invalidated.
+ *
+ *		skb type dynptrs may not use bpf_dynptr_data. They should
+ *		instead use bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
+ *
  *	Return
  *		Pointer to the underlying dynptr data, NULL if the dynptr is
  *		read-only, if the dynptr is invalid, or if the offset and length
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ae321c358699..ea2ab8cc3710 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -207,6 +207,11 @@ enum btf_kfunc_hook {
 	BTF_KFUNC_HOOK_TRACING,
 	BTF_KFUNC_HOOK_SYSCALL,
 	BTF_KFUNC_HOOK_FMODRET,
+	BTF_KFUNC_HOOK_CGROUP_SKB,
+	BTF_KFUNC_HOOK_SCHED_ACT,
+	BTF_KFUNC_HOOK_SK_SKB,
+	BTF_KFUNC_HOOK_SOCKET_FILTER,
+	BTF_KFUNC_HOOK_LWT,
 	BTF_KFUNC_HOOK_MAX,
 };
 
@@ -7699,6 +7704,19 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
 		return BTF_KFUNC_HOOK_TRACING;
 	case BPF_PROG_TYPE_SYSCALL:
 		return BTF_KFUNC_HOOK_SYSCALL;
+	case BPF_PROG_TYPE_CGROUP_SKB:
+		return BTF_KFUNC_HOOK_CGROUP_SKB;
+	case BPF_PROG_TYPE_SCHED_ACT:
+		return BTF_KFUNC_HOOK_SCHED_ACT;
+	case BPF_PROG_TYPE_SK_SKB:
+		return BTF_KFUNC_HOOK_SK_SKB;
+	case BPF_PROG_TYPE_SOCKET_FILTER:
+		return BTF_KFUNC_HOOK_SOCKET_FILTER;
+	case BPF_PROG_TYPE_LWT_OUT:
+	case BPF_PROG_TYPE_LWT_IN:
+	case BPF_PROG_TYPE_LWT_XMIT:
+	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
+		return BTF_KFUNC_HOOK_LWT;
 	default:
 		return BTF_KFUNC_HOOK_MAX;
 	}
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 5b278a38ae58..b9d357bdbd1d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1420,11 +1420,21 @@ static bool bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern *ptr)
 	return ptr->size & DYNPTR_RDONLY_BIT;
 }
 
+void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
+{
+	ptr->size |= DYNPTR_RDONLY_BIT;
+}
+
 static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_type type)
 {
 	ptr->size |= type << DYNPTR_TYPE_SHIFT;
 }
 
+static enum bpf_dynptr_type bpf_dynptr_get_type(const struct bpf_dynptr_kern *ptr)
+{
+	return (ptr->size & ~(DYNPTR_RDONLY_BIT)) >> DYNPTR_TYPE_SHIFT;
+}
+
 u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr)
 {
 	return ptr->size & DYNPTR_SIZE_MASK;
@@ -1497,6 +1507,7 @@ static const struct bpf_func_proto bpf_dynptr_from_mem_proto = {
 BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, const struct bpf_dynptr_kern *, src,
 	   u32, offset, u64, flags)
 {
+	enum bpf_dynptr_type type;
 	int err;
 
 	if (!src->data || flags)
@@ -1506,13 +1517,23 @@ BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, const struct bpf_dynptr_kern
 	if (err)
 		return err;
 
-	/* Source and destination may possibly overlap, hence use memmove to
-	 * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr
-	 * pointing to overlapping PTR_TO_MAP_VALUE regions.
-	 */
-	memmove(dst, src->data + src->offset + offset, len);
+	type = bpf_dynptr_get_type(src);
 
-	return 0;
+	switch (type) {
+	case BPF_DYNPTR_TYPE_LOCAL:
+	case BPF_DYNPTR_TYPE_RINGBUF:
+		/* Source and destination may possibly overlap, hence use memmove to
+		 * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr
+		 * pointing to overlapping PTR_TO_MAP_VALUE regions.
+		 */
+		memmove(dst, src->data + src->offset + offset, len);
+		return 0;
+	case BPF_DYNPTR_TYPE_SKB:
+		return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len);
+	default:
+		WARN_ONCE(true, "bpf_dynptr_read: unknown dynptr type %d\n", type);
+		return -EFAULT;
+	}
 }
 
 static const struct bpf_func_proto bpf_dynptr_read_proto = {
@@ -1529,22 +1550,36 @@ static const struct bpf_func_proto bpf_dynptr_read_proto = {
 BPF_CALL_5(bpf_dynptr_write, const struct bpf_dynptr_kern *, dst, u32, offset, void *, src,
 	   u32, len, u64, flags)
 {
+	enum bpf_dynptr_type type;
 	int err;
 
-	if (!dst->data || flags || bpf_dynptr_is_rdonly(dst))
+	if (!dst->data || bpf_dynptr_is_rdonly(dst))
 		return -EINVAL;
 
 	err = bpf_dynptr_check_off_len(dst, offset, len);
 	if (err)
 		return err;
 
-	/* Source and destination may possibly overlap, hence use memmove to
-	 * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr
-	 * pointing to overlapping PTR_TO_MAP_VALUE regions.
-	 */
-	memmove(dst->data + dst->offset + offset, src, len);
+	type = bpf_dynptr_get_type(dst);
 
-	return 0;
+	switch (type) {
+	case BPF_DYNPTR_TYPE_LOCAL:
+	case BPF_DYNPTR_TYPE_RINGBUF:
+		if (flags)
+			return -EINVAL;
+		/* Source and destination may possibly overlap, hence use memmove to
+		 * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr
+		 * pointing to overlapping PTR_TO_MAP_VALUE regions.
+		 */
+		memmove(dst->data + dst->offset + offset, src, len);
+		return 0;
+	case BPF_DYNPTR_TYPE_SKB:
+		return __bpf_skb_store_bytes(dst->data, dst->offset + offset, src, len,
+					     flags);
+	default:
+		WARN_ONCE(true, "bpf_dynptr_write: unknown dynptr type %d\n", type);
+		return -EFAULT;
+	}
 }
 
 static const struct bpf_func_proto bpf_dynptr_write_proto = {
@@ -1560,6 +1595,7 @@ static const struct bpf_func_proto bpf_dynptr_write_proto = {
 
 BPF_CALL_3(bpf_dynptr_data, const struct bpf_dynptr_kern *, ptr, u32, offset, u32, len)
 {
+	enum bpf_dynptr_type type;
 	int err;
 
 	if (!ptr->data)
@@ -1572,7 +1608,19 @@ BPF_CALL_3(bpf_dynptr_data, const struct bpf_dynptr_kern *, ptr, u32, offset, u3
 	if (bpf_dynptr_is_rdonly(ptr))
 		return 0;
 
-	return (unsigned long)(ptr->data + ptr->offset + offset);
+	type = bpf_dynptr_get_type(ptr);
+
+	switch (type) {
+	case BPF_DYNPTR_TYPE_LOCAL:
+	case BPF_DYNPTR_TYPE_RINGBUF:
+		return (unsigned long)(ptr->data + ptr->offset + offset);
+	case BPF_DYNPTR_TYPE_SKB:
+		/* skb dynptrs should use bpf_dynptr_slice / bpf_dynptr_slice_rdwr */
+		return 0;
+	default:
+		WARN_ONCE(true, "bpf_dynptr_data: unknown dynptr type %d\n", type);
+		return 0;
+	}
 }
 
 static const struct bpf_func_proto bpf_dynptr_data_proto = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index babc82e93ae6..7297f0d83792 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -750,6 +750,8 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum bpf_arg_type arg_type)
 		return BPF_DYNPTR_TYPE_LOCAL;
 	case DYNPTR_TYPE_RINGBUF:
 		return BPF_DYNPTR_TYPE_RINGBUF;
+	case DYNPTR_TYPE_SKB:
+		return BPF_DYNPTR_TYPE_SKB;
 	default:
 		return BPF_DYNPTR_TYPE_INVALID;
 	}
@@ -6286,6 +6288,9 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno, int insn_idx,
 			case DYNPTR_TYPE_RINGBUF:
 				err_extra = "ringbuf";
 				break;
+			case DYNPTR_TYPE_SKB:
+				err_extra = "skb ";
+				break;
 			default:
 				err_extra = "<unknown>";
 				break;
@@ -6712,6 +6717,24 @@ static int dynptr_ref_obj_id(struct bpf_verifier_env *env, struct bpf_reg_state
 	return state->stack[spi].spilled_ptr.ref_obj_id;
 }
 
+static enum bpf_dynptr_type dynptr_get_type(struct bpf_verifier_env *env,
+					    struct bpf_reg_state *reg)
+{
+	struct bpf_func_state *state = func(env, reg);
+	int spi;
+
+	if (reg->type == CONST_PTR_TO_DYNPTR)
+		return reg->dynptr.type;
+
+	spi = __get_spi(reg->off);
+	if (spi < 0) {
+		verbose(env, "verifier internal error: invalid spi when querying dynptr type\n");
+		return BPF_DYNPTR_TYPE_INVALID;
+	}
+
+	return state->stack[spi].spilled_ptr.dynptr.type;
+}
+
 static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			  struct bpf_call_arg_meta *meta,
 			  const struct bpf_func_proto *fn,
@@ -8362,6 +8385,27 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 
 		break;
 	}
+	case BPF_FUNC_dynptr_write:
+	{
+		enum bpf_dynptr_type dynptr_type;
+		struct bpf_reg_state *reg;
+
+		reg = get_dynptr_arg_reg(env, fn, regs);
+		if (!reg)
+			return -EFAULT;
+
+		dynptr_type = dynptr_get_type(env, reg);
+		if (dynptr_type == BPF_DYNPTR_TYPE_INVALID)
+			return -EFAULT;
+
+		if (dynptr_type == BPF_DYNPTR_TYPE_SKB)
+			/* this will trigger clear_all_pkt_pointers(), which will
+			 * invalidate all dynptr slices associated with the skb
+			 */
+			changes_data = true;
+
+		break;
+	}
 	case BPF_FUNC_user_ringbuf_drain:
 		err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
 					set_user_ringbuf_callback_state);
@@ -8872,6 +8916,7 @@ enum special_kfunc_type {
 	KF_bpf_rbtree_remove,
 	KF_bpf_rbtree_add,
 	KF_bpf_rbtree_first,
+	KF_bpf_dynptr_from_skb,
 };
 
 BTF_SET_START(special_kfunc_set)
@@ -8886,6 +8931,7 @@ BTF_ID(func, bpf_rdonly_cast)
 BTF_ID(func, bpf_rbtree_remove)
 BTF_ID(func, bpf_rbtree_add)
 BTF_ID(func, bpf_rbtree_first)
+BTF_ID(func, bpf_dynptr_from_skb)
 BTF_SET_END(special_kfunc_set)
 
 BTF_ID_LIST(special_kfunc_list)
@@ -8902,6 +8948,7 @@ BTF_ID(func, bpf_rcu_read_unlock)
 BTF_ID(func, bpf_rbtree_remove)
 BTF_ID(func, bpf_rbtree_add)
 BTF_ID(func, bpf_rbtree_first)
+BTF_ID(func, bpf_dynptr_from_skb)
 
 static bool is_kfunc_bpf_rcu_read_lock(struct bpf_kfunc_call_arg_meta *meta)
 {
@@ -9642,17 +9689,25 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				return ret;
 			break;
 		case KF_ARG_PTR_TO_DYNPTR:
+		{
+			enum bpf_arg_type dynptr_arg_type = ARG_PTR_TO_DYNPTR;
+
 			if (reg->type != PTR_TO_STACK &&
 			    reg->type != CONST_PTR_TO_DYNPTR) {
 				verbose(env, "arg#%d expected pointer to stack or dynptr_ptr\n", i);
 				return -EINVAL;
 			}
 
-			ret = process_dynptr_func(env, regno, insn_idx,
-						  ARG_PTR_TO_DYNPTR | MEM_RDONLY);
+			if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb])
+				dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_SKB;
+			else
+				dynptr_arg_type |= MEM_RDONLY;
+
+			ret = process_dynptr_func(env, regno, insn_idx, dynptr_arg_type);
 			if (ret < 0)
 				return ret;
 			break;
+		}
 		case KF_ARG_PTR_TO_LIST_HEAD:
 			if (reg->type != PTR_TO_MAP_VALUE &&
 			    reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
@@ -16318,6 +16373,17 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		   desc->func_id == special_kfunc_list[KF_bpf_rdonly_cast]) {
 		insn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);
 		*cnt = 1;
+	} else if (desc->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb]) {
+		bool seen_direct_write = env->seen_direct_write;
+		bool is_rdonly = !may_access_direct_pkt_data(env, NULL, BPF_WRITE);
+
+		if (is_rdonly)
+			insn->imm = BPF_CALL_IMM(bpf_dynptr_from_skb_rdonly);
+
+		/* restore env->seen_direct_write to its original value, since
+		 * may_access_direct_pkt_data mutates it
+		 */
+		env->seen_direct_write = seen_direct_write;
 	}
 	return 0;
 }
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ce06a72a5ba..34250a4d3b7a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1721,6 +1721,12 @@ static const struct bpf_func_proto bpf_skb_store_bytes_proto = {
 	.arg5_type	= ARG_ANYTHING,
 };
 
+int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from,
+			  u32 len, u64 flags)
+{
+	return ____bpf_skb_store_bytes(skb, offset, from, len, flags);
+}
+
 BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
 	   void *, to, u32, len)
 {
@@ -1751,6 +1757,11 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
 	.arg4_type	= ARG_CONST_SIZE,
 };
 
+int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len)
+{
+	return ____bpf_skb_load_bytes(skb, offset, to, len);
+}
+
 BPF_CALL_4(bpf_flow_dissector_load_bytes,
 	   const struct bpf_flow_dissector *, ctx, u32, offset,
 	   void *, to, u32, len)
@@ -11608,3 +11619,59 @@ bpf_sk_base_func_proto(enum bpf_func_id func_id)
 
 	return func;
 }
+
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "Global functions as their definitions will be in vmlinux BTF");
+__bpf_kfunc int bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags,
+				    struct bpf_dynptr_kern *ptr)
+{
+	if (flags) {
+		bpf_dynptr_set_null(ptr);
+		return -EINVAL;
+	}
+
+	bpf_dynptr_init(ptr, skb, BPF_DYNPTR_TYPE_SKB, 0, skb->len);
+
+	return 0;
+}
+__diag_pop();
+
+int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
+			       struct bpf_dynptr_kern *ptr)
+{
+	int err;
+
+	err = bpf_dynptr_from_skb(skb, flags, ptr);
+	if (err)
+		return err;
+
+	bpf_dynptr_set_rdonly(ptr);
+
+	return 0;
+}
+
+BTF_SET8_START(bpf_kfunc_check_set_skb)
+BTF_ID_FLAGS(func, bpf_dynptr_from_skb)
+BTF_SET8_END(bpf_kfunc_check_set_skb)
+
+static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
+	.owner = THIS_MODULE,
+	.set = &bpf_kfunc_check_set_skb,
+};
+
+static int __init bpf_kfunc_init(void)
+{
+	int ret;
+
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_ACT, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SK_SKB, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SOCKET_FILTER, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SKB, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_OUT, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_IN, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_XMIT, &bpf_kfunc_set_skb);
+	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_SEG6LOCAL, &bpf_kfunc_set_skb);
+}
+late_initcall(bpf_kfunc_init);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 1503f61336b6..4c229e0866db 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5320,11 +5320,17 @@ union bpf_attr {
  *	Description
  *		Write *len* bytes from *src* into *dst*, starting from *offset*
  *		into *dst*.
- *		*flags* is currently unused.
+ *
+ *		*flags* must be 0 except for skb-type dynptrs.
+ *
+ *		For skb-type dynptrs:
+ *		    *  For *flags*, please see the flags accepted by
+ *		       **bpf_skb_store_bytes**\ ().
  *	Return
  *		0 on success, -E2BIG if *offset* + *len* exceeds the length
  *		of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*
- *		is a read-only dynptr or if *flags* is not 0.
+ *		is a read-only dynptr or if *flags* is not correct. For skb-type dynptrs,
+ *		other errors correspond to errors returned by **bpf_skb_store_bytes**\ ().
  *
  * void *bpf_dynptr_data(const struct bpf_dynptr *ptr, u32 offset, u32 len)
  *	Description
@@ -5332,6 +5338,10 @@ union bpf_attr {
  *
  *		*len* must be a statically known value. The returned data slice
  *		is invalidated whenever the dynptr is invalidated.
+ *
+ *		skb type dynptrs may not use bpf_dynptr_data. They should
+ *		instead use bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
+ *
  *	Return
  *		Pointer to the underlying dynptr data, NULL if the dynptr is
  *		read-only, if the dynptr is invalid, or if the offset and length
-- 
2.30.2

[PATCH v10 bpf-next 7/9] bpf: Add xdp dynptrs

[Joanne Koong]

Add xdp dynptrs, which are dynptrs whose underlying pointer points
to a xdp_buff. The dynptr acts on xdp data. xdp dynptrs have two main
benefits. One is that they allow operations on sizes that are not
statically known at compile-time (eg variable-sized accesses).
Another is that parsing the packet data through dynptrs (instead of
through direct access of xdp->data and xdp->data_end) can be more
ergonomic and less brittle (eg does not need manual if checking for
being within bounds of data_end).

For reads and writes on the dynptr, this includes reading/writing
from/to and across fragments. Data slices through the bpf_dynptr_data
API are not supported; instead bpf_dynptr_slice() and
bpf_dynptr_slice_rdwr() should be used.

For examples of how xdp dynptrs can be used, please see the attached
selftests.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/bpf.h            |  8 +++++++-
 include/linux/filter.h         | 14 +++++++++++++
 include/uapi/linux/bpf.h       |  3 +--
 kernel/bpf/helpers.c           |  9 ++++++++-
 kernel/bpf/verifier.c          | 10 +++++++++
 net/core/filter.c              | 37 ++++++++++++++++++++++++++++++++--
 tools/include/uapi/linux/bpf.h |  3 +--
 7 files changed, 76 insertions(+), 8 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3d18be35a5e6..92e4636f13fa 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -610,11 +610,15 @@ enum bpf_type_flag {
 	/* DYNPTR points to sk_buff */
 	DYNPTR_TYPE_SKB		= BIT(15 + BPF_BASE_TYPE_BITS),
 
+	/* DYNPTR points to xdp_buff */
+	DYNPTR_TYPE_XDP		= BIT(16 + BPF_BASE_TYPE_BITS),
+
 	__BPF_TYPE_FLAG_MAX,
 	__BPF_TYPE_LAST_FLAG	= __BPF_TYPE_FLAG_MAX - 1,
 };
 
-#define DYNPTR_TYPE_FLAG_MASK	(DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB)
+#define DYNPTR_TYPE_FLAG_MASK	(DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB \
+				 | DYNPTR_TYPE_XDP)
 
 /* Max number of base types. */
 #define BPF_BASE_TYPE_LIMIT	(1UL << BPF_BASE_TYPE_BITS)
@@ -1151,6 +1155,8 @@ enum bpf_dynptr_type {
 	BPF_DYNPTR_TYPE_RINGBUF,
 	/* Underlying data is a sk_buff */
 	BPF_DYNPTR_TYPE_SKB,
+	/* Underlying data is a xdp_buff */
+	BPF_DYNPTR_TYPE_XDP,
 };
 
 int bpf_dynptr_check_size(u32 size);
diff --git a/include/linux/filter.h b/include/linux/filter.h
index de18e844d15e..3f6992261ec5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1546,6 +1546,8 @@ static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u64 index
 int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len);
 int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from,
 			  u32 len, u64 flags);
+int __bpf_xdp_load_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len);
+int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len);
 #else /* CONFIG_NET */
 static inline int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset,
 				       void *to, u32 len)
@@ -1558,6 +1560,18 @@ static inline int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset,
 {
 	return -EOPNOTSUPP;
 }
+
+static inline int __bpf_xdp_load_bytes(struct xdp_buff *xdp, u32 offset,
+				       void *buf, u32 len)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset,
+					void *buf, u32 len)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_NET */
 
 #endif /* __LINUX_FILTER_H__ */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4c229e0866db..e7435acbdd30 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5339,9 +5339,8 @@ union bpf_attr {
  *		*len* must be a statically known value. The returned data slice
  *		is invalidated whenever the dynptr is invalidated.
  *
- *		skb type dynptrs may not use bpf_dynptr_data. They should
+ *		skb and xdp type dynptrs may not use bpf_dynptr_data. They should
  *		instead use bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
- *
  *	Return
  *		Pointer to the underlying dynptr data, NULL if the dynptr is
  *		read-only, if the dynptr is invalid, or if the offset and length
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index b9d357bdbd1d..989be97b0f81 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1530,6 +1530,8 @@ BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, const struct bpf_dynptr_kern
 		return 0;
 	case BPF_DYNPTR_TYPE_SKB:
 		return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len);
+	case BPF_DYNPTR_TYPE_XDP:
+		return __bpf_xdp_load_bytes(src->data, src->offset + offset, dst, len);
 	default:
 		WARN_ONCE(true, "bpf_dynptr_read: unknown dynptr type %d\n", type);
 		return -EFAULT;
@@ -1576,6 +1578,10 @@ BPF_CALL_5(bpf_dynptr_write, const struct bpf_dynptr_kern *, dst, u32, offset, v
 	case BPF_DYNPTR_TYPE_SKB:
 		return __bpf_skb_store_bytes(dst->data, dst->offset + offset, src, len,
 					     flags);
+	case BPF_DYNPTR_TYPE_XDP:
+		if (flags)
+			return -EINVAL;
+		return __bpf_xdp_store_bytes(dst->data, dst->offset + offset, src, len);
 	default:
 		WARN_ONCE(true, "bpf_dynptr_write: unknown dynptr type %d\n", type);
 		return -EFAULT;
@@ -1615,7 +1621,8 @@ BPF_CALL_3(bpf_dynptr_data, const struct bpf_dynptr_kern *, ptr, u32, offset, u3
 	case BPF_DYNPTR_TYPE_RINGBUF:
 		return (unsigned long)(ptr->data + ptr->offset + offset);
 	case BPF_DYNPTR_TYPE_SKB:
-		/* skb dynptrs should use bpf_dynptr_slice / bpf_dynptr_slice_rdwr */
+	case BPF_DYNPTR_TYPE_XDP:
+		/* skb and xdp dynptrs should use bpf_dynptr_slice / bpf_dynptr_slice_rdwr */
 		return 0;
 	default:
 		WARN_ONCE(true, "bpf_dynptr_data: unknown dynptr type %d\n", type);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7297f0d83792..0b767134ecaa 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -752,6 +752,8 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum bpf_arg_type arg_type)
 		return BPF_DYNPTR_TYPE_RINGBUF;
 	case DYNPTR_TYPE_SKB:
 		return BPF_DYNPTR_TYPE_SKB;
+	case DYNPTR_TYPE_XDP:
+		return BPF_DYNPTR_TYPE_XDP;
 	default:
 		return BPF_DYNPTR_TYPE_INVALID;
 	}
@@ -6291,6 +6293,9 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno, int insn_idx,
 			case DYNPTR_TYPE_SKB:
 				err_extra = "skb ";
 				break;
+			case DYNPTR_TYPE_XDP:
+				err_extra = "xdp ";
+				break;
 			default:
 				err_extra = "<unknown>";
 				break;
@@ -8917,6 +8922,7 @@ enum special_kfunc_type {
 	KF_bpf_rbtree_add,
 	KF_bpf_rbtree_first,
 	KF_bpf_dynptr_from_skb,
+	KF_bpf_dynptr_from_xdp,
 };
 
 BTF_SET_START(special_kfunc_set)
@@ -8932,6 +8938,7 @@ BTF_ID(func, bpf_rbtree_remove)
 BTF_ID(func, bpf_rbtree_add)
 BTF_ID(func, bpf_rbtree_first)
 BTF_ID(func, bpf_dynptr_from_skb)
+BTF_ID(func, bpf_dynptr_from_xdp)
 BTF_SET_END(special_kfunc_set)
 
 BTF_ID_LIST(special_kfunc_list)
@@ -8949,6 +8956,7 @@ BTF_ID(func, bpf_rbtree_remove)
 BTF_ID(func, bpf_rbtree_add)
 BTF_ID(func, bpf_rbtree_first)
 BTF_ID(func, bpf_dynptr_from_skb)
+BTF_ID(func, bpf_dynptr_from_xdp)
 
 static bool is_kfunc_bpf_rcu_read_lock(struct bpf_kfunc_call_arg_meta *meta)
 {
@@ -9700,6 +9708,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 
 			if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb])
 				dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_SKB;
+			else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_xdp])
+				dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_XDP;
 			else
 				dynptr_arg_type |= MEM_RDONLY;
 
diff --git a/net/core/filter.c b/net/core/filter.c
index 34250a4d3b7a..dcf1e6d2582d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3839,7 +3839,7 @@ static const struct bpf_func_proto sk_skb_change_head_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
-BPF_CALL_1(bpf_xdp_get_buff_len, struct  xdp_buff*, xdp)
+BPF_CALL_1(bpf_xdp_get_buff_len, struct xdp_buff*, xdp)
 {
 	return xdp_get_buff_len(xdp);
 }
@@ -3999,6 +3999,11 @@ static const struct bpf_func_proto bpf_xdp_load_bytes_proto = {
 	.arg4_type	= ARG_CONST_SIZE,
 };
 
+int __bpf_xdp_load_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len)
+{
+	return ____bpf_xdp_load_bytes(xdp, offset, buf, len);
+}
+
 BPF_CALL_4(bpf_xdp_store_bytes, struct xdp_buff *, xdp, u32, offset,
 	   void *, buf, u32, len)
 {
@@ -4026,6 +4031,11 @@ static const struct bpf_func_proto bpf_xdp_store_bytes_proto = {
 	.arg4_type	= ARG_CONST_SIZE,
 };
 
+int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len)
+{
+	return ____bpf_xdp_store_bytes(xdp, offset, buf, len);
+}
+
 static int bpf_xdp_frags_increase_tail(struct xdp_buff *xdp, int offset)
 {
 	struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
@@ -11635,6 +11645,19 @@ __bpf_kfunc int bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags,
 
 	return 0;
 }
+
+__bpf_kfunc int bpf_dynptr_from_xdp(struct xdp_buff *xdp, u64 flags,
+				    struct bpf_dynptr_kern *ptr)
+{
+	if (flags) {
+		bpf_dynptr_set_null(ptr);
+		return -EINVAL;
+	}
+
+	bpf_dynptr_init(ptr, xdp, BPF_DYNPTR_TYPE_XDP, 0, xdp_get_buff_len(xdp));
+
+	return 0;
+}
 __diag_pop();
 
 int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
@@ -11655,11 +11678,20 @@ BTF_SET8_START(bpf_kfunc_check_set_skb)
 BTF_ID_FLAGS(func, bpf_dynptr_from_skb)
 BTF_SET8_END(bpf_kfunc_check_set_skb)
 
+BTF_SET8_START(bpf_kfunc_check_set_xdp)
+BTF_ID_FLAGS(func, bpf_dynptr_from_xdp)
+BTF_SET8_END(bpf_kfunc_check_set_xdp)
+
 static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
 	.owner = THIS_MODULE,
 	.set = &bpf_kfunc_check_set_skb,
 };
 
+static const struct btf_kfunc_id_set bpf_kfunc_set_xdp = {
+	.owner = THIS_MODULE,
+	.set = &bpf_kfunc_check_set_xdp,
+};
+
 static int __init bpf_kfunc_init(void)
 {
 	int ret;
@@ -11672,6 +11704,7 @@ static int __init bpf_kfunc_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_OUT, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_IN, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_XMIT, &bpf_kfunc_set_skb);
-	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_SEG6LOCAL, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_SEG6LOCAL, &bpf_kfunc_set_skb);
+	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);
 }
 late_initcall(bpf_kfunc_init);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4c229e0866db..e7435acbdd30 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5339,9 +5339,8 @@ union bpf_attr {
  *		*len* must be a statically known value. The returned data slice
  *		is invalidated whenever the dynptr is invalidated.
  *
- *		skb type dynptrs may not use bpf_dynptr_data. They should
+ *		skb and xdp type dynptrs may not use bpf_dynptr_data. They should
  *		instead use bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
- *
  *	Return
  *		Pointer to the underlying dynptr data, NULL if the dynptr is
  *		read-only, if the dynptr is invalid, or if the offset and length
-- 
2.30.2

[PATCH v10 bpf-next 8/9] bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr

[Joanne Koong]

Two new kfuncs are added, bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
The user must pass in a buffer to store the contents of the data slice
if a direct pointer to the data cannot be obtained.

For skb and xdp type dynptrs, these two APIs are the only way to obtain
a data slice. However, for other types of dynptrs, there is no
difference between bpf_dynptr_slice(_rdwr) and bpf_dynptr_data.

For skb type dynptrs, the data is copied into the user provided buffer
if any of the data is not in the linear portion of the skb. For xdp type
dynptrs, the data is copied into the user provided buffer if the data is
between xdp frags.

If the skb is cloned and a call to bpf_dynptr_data_rdwr is made, then
the skb will be uncloned (see bpf_unclone_prologue()).

Please note that any bpf_dynptr_write() automatically invalidates any prior
data slices of the skb dynptr. This is because the skb may be cloned or
may need to pull its paged buffer into the head. As such, any
bpf_dynptr_write() will automatically have its prior data slices
invalidated, even if the write is to data in the skb head of an uncloned
skb. Please note as well that any other helper calls that change the
underlying packet buffer (eg bpf_skb_pull_data()) invalidates any data
slices of the skb dynptr as well, for the same reasons.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/filter.h         | 14 ++++++
 include/uapi/linux/bpf.h       |  5 ++
 kernel/bpf/helpers.c           | 91 ++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c          | 88 ++++++++++++++++++++++++++++++--
 net/core/filter.c              |  6 +--
 tools/include/uapi/linux/bpf.h |  5 ++
 6 files changed, 202 insertions(+), 7 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 3f6992261ec5..efa5d4a1677e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1548,6 +1548,9 @@ int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from,
 			  u32 len, u64 flags);
 int __bpf_xdp_load_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len);
 int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len);
+void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len);
+void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
+		      void *buf, unsigned long len, bool flush);
 #else /* CONFIG_NET */
 static inline int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset,
 				       void *to, u32 len)
@@ -1572,6 +1575,17 @@ static inline int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset,
 {
 	return -EOPNOTSUPP;
 }
+
+static inline void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len)
+{
+	return NULL;
+}
+
+static inline void *bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off, void *buf,
+				     unsigned long len, bool flush)
+{
+	return NULL;
+}
 #endif /* CONFIG_NET */
 
 #endif /* __LINUX_FILTER_H__ */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e7435acbdd30..ac406af207c3 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5324,6 +5324,11 @@ union bpf_attr {
  *		*flags* must be 0 except for skb-type dynptrs.
  *
  *		For skb-type dynptrs:
+ *		    *  All data slices of the dynptr are automatically
+ *		       invalidated after **bpf_dynptr_write**\ (). This is
+ *		       because writing may pull the skb and change the
+ *		       underlying packet buffer.
+ *
  *		    *  For *flags*, please see the flags accepted by
  *		       **bpf_skb_store_bytes**\ ().
  *	Return
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 989be97b0f81..0586f54e4f9e 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2177,6 +2177,94 @@ __bpf_kfunc struct task_struct *bpf_task_from_pid(s32 pid)
 	return p;
 }
 
+/**
+ * bpf_dynptr_slice - Obtain a read-only pointer to the dynptr data.
+ *
+ * For non-skb and non-xdp type dynptrs, there is no difference between
+ * bpf_dynptr_slice and bpf_dynptr_data.
+ *
+ * If the intention is to write to the data slice, please use
+ * bpf_dynptr_slice_rdwr.
+ *
+ * @ptr: The dynptr whose data slice to retrieve
+ * @offset: Offset into the dynptr
+ * @buffer: User-provided buffer to copy contents into
+ * @buffer__sz: Size (in bytes) of the buffer. This is the length of the
+ * requested slice
+ *
+ * @returns: NULL if the call failed (eg invalid dynptr), pointer to a read-only
+ * data slice (can be either direct pointer to the data or a pointer to the user
+ * provided buffer, with its contents containing the data, if unable to obtain
+ * direct pointer)
+ */
+__bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset,
+				   void *buffer, u32 buffer__sz)
+{
+	enum bpf_dynptr_type type;
+	u32 len = buffer__sz;
+	int err;
+
+	if (!ptr->data)
+		return 0;
+
+	err = bpf_dynptr_check_off_len(ptr, offset, len);
+	if (err)
+		return 0;
+
+	type = bpf_dynptr_get_type(ptr);
+
+	switch (type) {
+	case BPF_DYNPTR_TYPE_LOCAL:
+	case BPF_DYNPTR_TYPE_RINGBUF:
+		return ptr->data + ptr->offset + offset;
+	case BPF_DYNPTR_TYPE_SKB:
+		return skb_header_pointer(ptr->data, ptr->offset + offset, len, buffer);
+	case BPF_DYNPTR_TYPE_XDP:
+	{
+		void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len);
+		if (xdp_ptr)
+			return xdp_ptr;
+
+		bpf_xdp_copy_buf(ptr->data, ptr->offset + offset, buffer, len, false);
+		return buffer;
+	}
+	default:
+		WARN_ONCE(true, "unknown dynptr type %d\n", type);
+		return 0;
+	}
+}
+
+/**
+ * bpf_dynptr_slice_rdwr - Obtain a pointer to the dynptr data.
+ *
+ * For non-skb and non-xdp type dynptrs, there is no difference between
+ * bpf_dynptr_slice and bpf_dynptr_data.
+ *
+ * @ptr: The dynptr whose data slice to retrieve
+ * @offset: Offset into the dynptr
+ * @buffer: User-provided buffer to copy contents into
+ * @buffer__sz: Size (in bytes) of the buffer. This is the length of the
+ * requested slice
+ *
+ * @returns: NULL if the call failed (eg invalid dynptr), pointer to a
+ * data slice (can be either direct pointer to the data or a pointer to the user
+ * provided buffer, with its contents containing the data, if unable to obtain
+ * direct pointer)
+ */
+__bpf_kfunc void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr_kern *ptr, u32 offset,
+					void *buffer, u32 buffer__sz)
+{
+	if (!ptr->data || bpf_dynptr_is_rdonly(ptr))
+		return 0;
+
+	/* bpf_dynptr_slice_rdwr is the same logic as bpf_dynptr_slice.
+	 *
+	 * For skb-type dynptrs, the verifier has already ensured that the skb
+	 * head is writable (see bpf_unclone_prologue()).
+	 */
+	return bpf_dynptr_slice(ptr, offset, buffer, buffer__sz);
+}
+
 __bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj)
 {
 	return obj;
@@ -2224,6 +2312,8 @@ BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL)
 BTF_SET8_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
@@ -2271,6 +2361,7 @@ static int __init kfunc_init(void)
 	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &generic_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &generic_kfunc_set);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &generic_kfunc_set);
 	ret = ret ?: register_btf_id_dtor_kfuncs(generic_dtors,
 						  ARRAY_SIZE(generic_dtors),
 						  THIS_MODULE);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0b767134ecaa..aa8d48b00cc2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -759,6 +759,22 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum bpf_arg_type arg_type)
 	}
 }
 
+static enum bpf_type_flag get_dynptr_type_flag(enum bpf_dynptr_type type)
+{
+	switch (type) {
+	case BPF_DYNPTR_TYPE_LOCAL:
+		return DYNPTR_TYPE_LOCAL;
+	case BPF_DYNPTR_TYPE_RINGBUF:
+		return DYNPTR_TYPE_RINGBUF;
+	case BPF_DYNPTR_TYPE_SKB:
+		return DYNPTR_TYPE_SKB;
+	case BPF_DYNPTR_TYPE_XDP:
+		return DYNPTR_TYPE_XDP;
+	default:
+		return 0;
+	}
+}
+
 static bool dynptr_type_refcounted(enum bpf_dynptr_type type)
 {
 	return type == BPF_DYNPTR_TYPE_RINGBUF;
@@ -1677,6 +1693,12 @@ static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg)
 	       reg->type == PTR_TO_PACKET_END;
 }
 
+static bool reg_is_dynptr_slice_pkt(const struct bpf_reg_state *reg)
+{
+	return base_type(reg->type) == PTR_TO_MEM &&
+		(reg->type & DYNPTR_TYPE_SKB || reg->type & DYNPTR_TYPE_XDP);
+}
+
 /* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
 static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg,
 				    enum bpf_reg_type which)
@@ -7404,6 +7426,9 @@ static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
 
 /* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
  * are now invalid, so turn them into unknown SCALAR_VALUE.
+ *
+ * This also applies to dynptr slices belonging to skb and xdp dynptrs,
+ * since these slices point to packet data.
  */
 static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
 {
@@ -7411,7 +7436,7 @@ static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
 	struct bpf_reg_state *reg;
 
 	bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
-		if (reg_is_pkt_pointer_any(reg))
+		if (reg_is_pkt_pointer_any(reg) || reg_is_dynptr_slice_pkt(reg))
 			__mark_reg_unknown(env, reg);
 	}));
 }
@@ -8667,6 +8692,11 @@ struct bpf_kfunc_call_arg_meta {
 	struct {
 		struct btf_field *field;
 	} arg_rbtree_root;
+	struct {
+		enum bpf_dynptr_type type;
+		u32 id;
+	} initialized_dynptr;
+	u64 mem_size;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -8923,6 +8953,8 @@ enum special_kfunc_type {
 	KF_bpf_rbtree_first,
 	KF_bpf_dynptr_from_skb,
 	KF_bpf_dynptr_from_xdp,
+	KF_bpf_dynptr_slice,
+	KF_bpf_dynptr_slice_rdwr,
 };
 
 BTF_SET_START(special_kfunc_set)
@@ -8939,6 +8971,8 @@ BTF_ID(func, bpf_rbtree_add)
 BTF_ID(func, bpf_rbtree_first)
 BTF_ID(func, bpf_dynptr_from_skb)
 BTF_ID(func, bpf_dynptr_from_xdp)
+BTF_ID(func, bpf_dynptr_slice)
+BTF_ID(func, bpf_dynptr_slice_rdwr)
 BTF_SET_END(special_kfunc_set)
 
 BTF_ID_LIST(special_kfunc_list)
@@ -8957,6 +8991,8 @@ BTF_ID(func, bpf_rbtree_add)
 BTF_ID(func, bpf_rbtree_first)
 BTF_ID(func, bpf_dynptr_from_skb)
 BTF_ID(func, bpf_dynptr_from_xdp)
+BTF_ID(func, bpf_dynptr_slice)
+BTF_ID(func, bpf_dynptr_slice_rdwr)
 
 static bool is_kfunc_bpf_rcu_read_lock(struct bpf_kfunc_call_arg_meta *meta)
 {
@@ -9710,12 +9746,24 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_SKB;
 			else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_xdp])
 				dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_XDP;
-			else
+			else if (reg->type == CONST_PTR_TO_DYNPTR)
 				dynptr_arg_type |= MEM_RDONLY;
 
 			ret = process_dynptr_func(env, regno, insn_idx, dynptr_arg_type);
 			if (ret < 0)
 				return ret;
+
+			if (!(dynptr_arg_type & MEM_UNINIT)) {
+				int id = dynptr_id(env, reg);
+
+				if (id < 0) {
+					verbose(env, "verifier internal error: failed to obtain dynptr id\n");
+					return id;
+				}
+				meta->initialized_dynptr.id = id;
+				meta->initialized_dynptr.type = dynptr_get_type(env, reg);
+			}
+
 			break;
 		}
 		case KF_ARG_PTR_TO_LIST_HEAD:
@@ -9966,8 +10014,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		}
 	}
 
-	for (i = 0; i < CALLER_SAVED_REGS; i++)
-		mark_reg_not_init(env, regs, caller_saved[i]);
+	mark_reg_not_init(env, regs, caller_saved[BPF_REG_0]);
 
 	/* Check return type */
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
@@ -10053,6 +10100,36 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 				regs[BPF_REG_0].type = PTR_TO_BTF_ID | PTR_UNTRUSTED;
 				regs[BPF_REG_0].btf = desc_btf;
 				regs[BPF_REG_0].btf_id = meta.arg_constant.value;
+			} else if (meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice] ||
+				   meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {
+				enum bpf_type_flag type_flag = get_dynptr_type_flag(meta.initialized_dynptr.type);
+
+				mark_reg_known_zero(env, regs, BPF_REG_0);
+
+				if (!tnum_is_const(regs[BPF_REG_4].var_off)) {
+					verbose(env, "mem_size must be a constant\n");
+					return -EINVAL;
+				}
+				regs[BPF_REG_0].mem_size = regs[BPF_REG_4].var_off.value;
+
+				/* PTR_MAYBE_NULL will be added when is_kfunc_ret_null is checked */
+				regs[BPF_REG_0].type = PTR_TO_MEM | type_flag;
+
+				if (meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice])
+					regs[BPF_REG_0].type |= MEM_RDONLY;
+				else
+					env->seen_direct_write = true;
+
+				if (!meta.initialized_dynptr.id) {
+					verbose(env, "verifier internal error: no dynptr id\n");
+					return -EFAULT;
+				}
+				regs[BPF_REG_0].dynptr_id = meta.initialized_dynptr.id;
+
+				/* we don't need to set BPF_REG_0's ref obj id
+				 * because packet slices are not refcounted (see
+				 * dynptr_type_refcounted)
+				 */
 			} else {
 				verbose(env, "kernel function %s unhandled dynamic return type\n",
 					meta.func_name);
@@ -10112,6 +10189,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			regs[BPF_REG_0].id = ++env->id_gen;
 	} /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */
 
+	for (i = BPF_REG_1; i < CALLER_SAVED_REGS; i++)
+		mark_reg_not_init(env, regs, caller_saved[i]);
+
 	nargs = btf_type_vlen(func_proto);
 	args = (const struct btf_param *)(func_proto + 1);
 	for (i = 0; i < nargs; i++) {
diff --git a/net/core/filter.c b/net/core/filter.c
index dcf1e6d2582d..0bd62b2b25e1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3894,8 +3894,8 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
-static void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
-			     void *buf, unsigned long len, bool flush)
+void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
+		      void *buf, unsigned long len, bool flush)
 {
 	unsigned long ptr_len, ptr_off = 0;
 	skb_frag_t *next_frag, *end_frag;
@@ -3941,7 +3941,7 @@ static void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
 	}
 }
 
-static void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len)
+void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len)
 {
 	struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
 	u32 size = xdp->data_end - xdp->data;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index e7435acbdd30..ac406af207c3 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5324,6 +5324,11 @@ union bpf_attr {
  *		*flags* must be 0 except for skb-type dynptrs.
  *
  *		For skb-type dynptrs:
+ *		    *  All data slices of the dynptr are automatically
+ *		       invalidated after **bpf_dynptr_write**\ (). This is
+ *		       because writing may pull the skb and change the
+ *		       underlying packet buffer.
+ *
  *		    *  For *flags*, please see the flags accepted by
  *		       **bpf_skb_store_bytes**\ ().
  *	Return
-- 
2.30.2

[PATCH v10 bpf-next 9/9] selftests/bpf: tests for using dynptrs to parse skb and xdp buffers

[Joanne Koong]

Test skb and xdp dynptr functionality in the following ways:

1) progs/test_cls_redirect_dynptr.c
   * Rewrite "progs/test_cls_redirect.c" test to use dynptrs to parse
     skb data

   * This is a great example of how dynptrs can be used to simplify a
     lot of the parsing logic for non-statically known values.

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t cls_redirect"):
         original version: 0.092 sec
         with dynptrs: 0.078 sec

2) progs/test_xdp_dynptr.c
   * Rewrite "progs/test_xdp.c" test to use dynptrs to parse xdp data

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t xdp_attach"):
         original version: 0.118 sec
         with dynptrs: 0.094 sec

3) progs/test_l4lb_noinline_dynptr.c
   * Rewrite "progs/test_l4lb_noinline.c" test to use dynptrs to parse
     skb data

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t l4lb_all"):
         original version: 0.062 sec
         with dynptrs: 0.081 sec

     For number of processed verifier instructions:
         original version: 6268 insns
         with dynptrs: 2588 insns

4) progs/test_parse_tcp_hdr_opt_dynptr.c
   * Add sample code for parsing tcp hdr opt lookup using dynptrs.
     This logic is lifted from a real-world use case of packet parsing
     in katran [0], a layer 4 load balancer. The original version
     "progs/test_parse_tcp_hdr_opt.c" (not using dynptrs) is included
     here as well, for comparison.

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t parse_tcp_hdr_opt"):
         original version: 0.031 sec
         with dynptrs: 0.045 sec

5) progs/dynptr_success.c
   * Add test case "test_skb_readonly" for testing attempts at writes
     on a prog type with read-only skb ctx.
   * Add "test_dynptr_skb_data" for testing that bpf_dynptr_data isn't
     supported for skb progs.

6) progs/dynptr_fail.c
   * Add test cases "skb_invalid_data_slice{1,2,3,4}" and
     "xdp_invalid_data_slice{1,2}" for testing that helpers that modify the
     underlying packet buffer automatically invalidate the associated
     data slice.
   * Add test cases "skb_invalid_ctx" and "xdp_invalid_ctx" for testing
     that prog types that do not support bpf_dynptr_from_skb/xdp don't
     have access to the API.
   * Add test case "dynptr_slice_var_len{1,2}" for testing that
     variable-sized len can't be passed in to bpf_dynptr_slice
   * Add test case "skb_invalid_slice_write" for testing that writes to a
     read-only data slice are rejected by the verifier.
   * Add test case " data_slice_out_of_bounds_skb for testing that
     writes to an area outside the slice are rejected.

[0]
https://github.com/facebookincubator/katran/blob/main/katran/lib/bpf/pckt_parsing.h

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 .../selftests/bpf/prog_tests/cls_redirect.c   |  25 +
 .../testing/selftests/bpf/prog_tests/dynptr.c |  69 +-
 .../selftests/bpf/prog_tests/l4lb_all.c       |   2 +
 .../bpf/prog_tests/parse_tcp_hdr_opt.c        |  93 ++
 .../selftests/bpf/prog_tests/xdp_attach.c     |  11 +-
 .../testing/selftests/bpf/progs/dynptr_fail.c | 274 ++++-
 .../selftests/bpf/progs/dynptr_success.c      |  51 +-
 .../bpf/progs/test_cls_redirect_dynptr.c      | 975 ++++++++++++++++++
 .../bpf/progs/test_l4lb_noinline_dynptr.c     | 486 +++++++++
 .../bpf/progs/test_parse_tcp_hdr_opt.c        | 119 +++
 .../bpf/progs/test_parse_tcp_hdr_opt_dynptr.c | 118 +++
 .../selftests/bpf/progs/test_xdp_dynptr.c     | 257 +++++
 .../selftests/bpf/test_tcp_hdr_options.h      |   1 +
 13 files changed, 2464 insertions(+), 17 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_dynptr.c

diff --git a/tools/testing/selftests/bpf/prog_tests/cls_redirect.c b/tools/testing/selftests/bpf/prog_tests/cls_redirect.c
index 224f016b0a53..2a55f717fc07 100644
--- a/tools/testing/selftests/bpf/prog_tests/cls_redirect.c
+++ b/tools/testing/selftests/bpf/prog_tests/cls_redirect.c
@@ -13,6 +13,7 @@
 
 #include "progs/test_cls_redirect.h"
 #include "test_cls_redirect.skel.h"
+#include "test_cls_redirect_dynptr.skel.h"
 #include "test_cls_redirect_subprogs.skel.h"
 
 #define ENCAP_IP INADDR_LOOPBACK
@@ -446,6 +447,28 @@ static void test_cls_redirect_common(struct bpf_program *prog)
 	close_fds((int *)conns, sizeof(conns) / sizeof(conns[0][0]));
 }
 
+static void test_cls_redirect_dynptr(void)
+{
+	struct test_cls_redirect_dynptr *skel;
+	int err;
+
+	skel = test_cls_redirect_dynptr__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	skel->rodata->ENCAPSULATION_IP = htonl(ENCAP_IP);
+	skel->rodata->ENCAPSULATION_PORT = htons(ENCAP_PORT);
+
+	err = test_cls_redirect_dynptr__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	test_cls_redirect_common(skel->progs.cls_redirect);
+
+cleanup:
+	test_cls_redirect_dynptr__destroy(skel);
+}
+
 static void test_cls_redirect_inlined(void)
 {
 	struct test_cls_redirect *skel;
@@ -496,4 +519,6 @@ void test_cls_redirect(void)
 		test_cls_redirect_inlined();
 	if (test__start_subtest("cls_redirect_subprogs"))
 		test_cls_redirect_subprogs();
+	if (test__start_subtest("cls_redirect_dynptr"))
+		test_cls_redirect_dynptr();
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index b99264ec0d9c..3bb9fabccd9f 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -2,16 +2,29 @@
 /* Copyright (c) 2022 Facebook */
 
 #include <test_progs.h>
+#include <network_helpers.h>
 #include "dynptr_fail.skel.h"
 #include "dynptr_success.skel.h"
 
-static const char * const success_tests[] = {
-	"test_read_write",
-	"test_data_slice",
-	"test_ringbuf",
+enum test_setup_type {
+	/* no set up is required. the prog will just be loaded */
+	SETUP_NONE,
+	SETUP_SYSCALL_SLEEP,
+	SETUP_SKB_PROG,
 };
 
-static void verify_success(const char *prog_name)
+static struct {
+	const char *prog_name;
+	enum test_setup_type type;
+} success_tests[] = {
+	{"test_read_write", SETUP_SYSCALL_SLEEP},
+	{"test_dynptr_data", SETUP_SYSCALL_SLEEP},
+	{"test_ringbuf", SETUP_SYSCALL_SLEEP},
+	{"test_skb_readonly", SETUP_SKB_PROG},
+	{"test_dynptr_skb_data", SETUP_SKB_PROG},
+};
+
+static void verify_success(const char *prog_name, enum test_setup_type setup_type)
 {
 	struct dynptr_success *skel;
 	struct bpf_program *prog;
@@ -31,15 +44,45 @@ static void verify_success(const char *prog_name)
 	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
 		goto cleanup;
 
-	link = bpf_program__attach(prog);
-	if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
-		goto cleanup;
+	switch (setup_type) {
+	case SETUP_SYSCALL_SLEEP:
+		link = bpf_program__attach(prog);
+		if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
+			goto cleanup;
 
-	usleep(1);
+		usleep(1);
 
-	ASSERT_EQ(skel->bss->err, 0, "err");
+		bpf_link__destroy(link);
+		break;
+	case SETUP_SKB_PROG:
+	{
+		int prog_fd, err;
+		char buf[64];
+
+		LIBBPF_OPTS(bpf_test_run_opts, topts,
+			    .data_in = &pkt_v4,
+			    .data_size_in = sizeof(pkt_v4),
+			    .data_out = buf,
+			    .data_size_out = sizeof(buf),
+			    .repeat = 1,
+		);
+
+		prog_fd = bpf_program__fd(prog);
+		if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
+			goto cleanup;
 
-	bpf_link__destroy(link);
+		err = bpf_prog_test_run_opts(prog_fd, &topts);
+
+		if (!ASSERT_OK(err, "test_run"))
+			goto cleanup;
+
+		break;
+	}
+	case SETUP_NONE:
+		ASSERT_EQ(0, 1, "internal error: SETUP_NONE unimplemented");
+	}
+
+	ASSERT_EQ(skel->bss->err, 0, "err");
 
 cleanup:
 	dynptr_success__destroy(skel);
@@ -50,10 +93,10 @@ void test_dynptr(void)
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(success_tests); i++) {
-		if (!test__start_subtest(success_tests[i]))
+		if (!test__start_subtest(success_tests[i].prog_name))
 			continue;
 
-		verify_success(success_tests[i]);
+		verify_success(success_tests[i].prog_name, success_tests[i].type);
 	}
 
 	RUN_TESTS(dynptr_fail);
diff --git a/tools/testing/selftests/bpf/prog_tests/l4lb_all.c b/tools/testing/selftests/bpf/prog_tests/l4lb_all.c
index 9c1a18573ffd..1eab286b14fe 100644
--- a/tools/testing/selftests/bpf/prog_tests/l4lb_all.c
+++ b/tools/testing/selftests/bpf/prog_tests/l4lb_all.c
@@ -93,4 +93,6 @@ void test_l4lb_all(void)
 		test_l4lb("test_l4lb.bpf.o");
 	if (test__start_subtest("l4lb_noinline"))
 		test_l4lb("test_l4lb_noinline.bpf.o");
+	if (test__start_subtest("l4lb_noinline_dynptr"))
+		test_l4lb("test_l4lb_noinline_dynptr.bpf.o");
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c b/tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c
new file mode 100644
index 000000000000..ab042fdcfe55
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "test_parse_tcp_hdr_opt.skel.h"
+#include "test_parse_tcp_hdr_opt_dynptr.skel.h"
+#include "test_tcp_hdr_options.h"
+
+struct test_pkt {
+	struct ipv6_packet pk6_v6;
+	u8 options[16];
+} __packed;
+
+struct test_pkt pkt = {
+	.pk6_v6.eth.h_proto = __bpf_constant_htons(ETH_P_IPV6),
+	.pk6_v6.iph.nexthdr = IPPROTO_TCP,
+	.pk6_v6.iph.payload_len = __bpf_constant_htons(MAGIC_BYTES),
+	.pk6_v6.tcp.urg_ptr = 123,
+	.pk6_v6.tcp.doff = 9, /* 16 bytes of options */
+
+	.options = {
+		TCPOPT_MSS, 4, 0x05, 0xB4, TCPOPT_NOP, TCPOPT_NOP,
+		0, 6, 0, 0, 0, 9, TCPOPT_EOL
+	},
+};
+
+static void test_parse_opt(void)
+{
+	struct test_parse_tcp_hdr_opt *skel;
+	struct bpf_program *prog;
+	char buf[128];
+	int err;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = &pkt,
+		    .data_size_in = sizeof(pkt),
+		    .data_out = buf,
+		    .data_size_out = sizeof(buf),
+		    .repeat = 3,
+	);
+
+	skel = test_parse_tcp_hdr_opt__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	pkt.options[6] = skel->rodata->tcp_hdr_opt_kind_tpr;
+	prog = skel->progs.xdp_ingress_v6;
+
+	err = bpf_prog_test_run_opts(bpf_program__fd(prog), &topts);
+	ASSERT_OK(err, "ipv6 test_run");
+	ASSERT_EQ(topts.retval, XDP_PASS, "ipv6 test_run retval");
+	ASSERT_EQ(skel->bss->server_id, 0x9000000, "server id");
+
+	test_parse_tcp_hdr_opt__destroy(skel);
+}
+
+static void test_parse_opt_dynptr(void)
+{
+	struct test_parse_tcp_hdr_opt_dynptr *skel;
+	struct bpf_program *prog;
+	char buf[128];
+	int err;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = &pkt,
+		    .data_size_in = sizeof(pkt),
+		    .data_out = buf,
+		    .data_size_out = sizeof(buf),
+		    .repeat = 3,
+	);
+
+	skel = test_parse_tcp_hdr_opt_dynptr__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	pkt.options[6] = skel->rodata->tcp_hdr_opt_kind_tpr;
+	prog = skel->progs.xdp_ingress_v6;
+
+	err = bpf_prog_test_run_opts(bpf_program__fd(prog), &topts);
+	ASSERT_OK(err, "ipv6 test_run");
+	ASSERT_EQ(topts.retval, XDP_PASS, "ipv6 test_run retval");
+	ASSERT_EQ(skel->bss->server_id, 0x9000000, "server id");
+
+	test_parse_tcp_hdr_opt_dynptr__destroy(skel);
+}
+
+void test_parse_tcp_hdr_opt(void)
+{
+	if (test__start_subtest("parse_tcp_hdr_opt"))
+		test_parse_opt();
+	if (test__start_subtest("parse_tcp_hdr_opt_dynptr"))
+		test_parse_opt_dynptr();
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
index 062fbc8c8e5e..cefbe8b45447 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
@@ -4,11 +4,10 @@
 #define IFINDEX_LO 1
 #define XDP_FLAGS_REPLACE		(1U << 4)
 
-void serial_test_xdp_attach(void)
+static void test_xdp_attach(const char *file)
 {
 	__u32 duration = 0, id1, id2, id0 = 0, len;
 	struct bpf_object *obj1, *obj2, *obj3;
-	const char *file = "./test_xdp.bpf.o";
 	struct bpf_prog_info info = {};
 	int err, fd1, fd2, fd3;
 	LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
@@ -85,3 +84,11 @@ void serial_test_xdp_attach(void)
 out_1:
 	bpf_object__close(obj1);
 }
+
+void serial_test_xdp_attach(void)
+{
+	if (test__start_subtest("xdp_attach"))
+		test_xdp_attach("./test_xdp.bpf.o");
+	if (test__start_subtest("xdp_attach_dynptr"))
+		test_xdp_attach("./test_xdp_dynptr.bpf.o");
+}
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 5950ad6ec2e6..20d5798853e4 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -5,10 +5,20 @@
 #include <string.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include <linux/if_ether.h>
 #include "bpf_misc.h"
 
 char _license[] SEC("license") = "GPL";
 
+extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+
 struct test_info {
 	int x;
 	struct bpf_dynptr ptr;
@@ -244,6 +254,27 @@ int data_slice_out_of_bounds_ringbuf(void *ctx)
 	return 0;
 }
 
+/* A data slice can't be accessed out of bounds */
+SEC("?tc")
+__failure __msg("value is outside of the allowed memory range")
+int data_slice_out_of_bounds_skb(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	/* this should fail */
+	*(__u8*)(hdr + 1) = 1;
+
+	return SK_PASS;
+}
+
 SEC("?raw_tp")
 __failure __msg("value is outside of the allowed memory range")
 int data_slice_out_of_bounds_map_value(void *ctx)
@@ -399,7 +430,6 @@ int invalid_helper2(void *ctx)
 
 	/* this should fail */
 	bpf_dynptr_read(read_data, sizeof(read_data), (void *)&ptr + 8, 0, 0);
-
 	return 0;
 }
 
@@ -1044,6 +1074,193 @@ int dynptr_read_into_slot(void *ctx)
 	return 0;
 }
 
+/* bpf_dynptr_slice()s are read-only and cannot be written to */
+SEC("?tc")
+__failure __msg("R0 cannot write into rdonly_mem")
+int skb_invalid_slice_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	/* this should fail */
+	hdr->h_proto = 1;
+
+	return SK_PASS;
+}
+
+/* The read-only data slice is invalidated whenever a helper changes packet data */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int skb_invalid_data_slice1(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	val = hdr->h_proto;
+
+	if (bpf_skb_pull_data(skb, skb->len))
+		return SK_DROP;
+
+	/* this should fail */
+	val = hdr->h_proto;
+
+	return SK_PASS;
+}
+
+/* The read-write data slice is invalidated whenever a helper changes packet data */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int skb_invalid_data_slice2(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	hdr->h_proto = 123;
+
+	if (bpf_skb_pull_data(skb, skb->len))
+		return SK_DROP;
+
+	/* this should fail */
+	hdr->h_proto = 1;
+
+	return SK_PASS;
+}
+
+/* The read-only data slice is invalidated whenever bpf_dynptr_write() is called */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int skb_invalid_data_slice3(struct __sk_buff *skb)
+{
+	char write_data[64] = "hello there, world!!";
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	val = hdr->h_proto;
+
+	bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0);
+
+	/* this should fail */
+	val = hdr->h_proto;
+
+	return SK_PASS;
+}
+
+/* The read-write data slice is invalidated whenever bpf_dynptr_write() is called */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int skb_invalid_data_slice4(struct __sk_buff *skb)
+{
+	char write_data[64] = "hello there, world!!";
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+	hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	hdr->h_proto = 123;
+
+	bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0);
+
+	/* this should fail */
+	hdr->h_proto = 1;
+
+	return SK_PASS;
+}
+
+/* The read-only data slice is invalidated whenever a helper changes packet data */
+SEC("?xdp")
+__failure __msg("invalid mem access 'scalar'")
+int xdp_invalid_data_slice1(struct xdp_md *xdp)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr);
+	hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	val = hdr->h_proto;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(*hdr)))
+		return XDP_DROP;
+
+	/* this should fail */
+	val = hdr->h_proto;
+
+	return XDP_PASS;
+}
+
+/* The read-write data slice is invalidated whenever a helper changes packet data */
+SEC("?xdp")
+__failure __msg("invalid mem access 'scalar'")
+int xdp_invalid_data_slice2(struct xdp_md *xdp)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr);
+	hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
+	if (!hdr)
+		return SK_DROP;
+
+	hdr->h_proto = 9;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(*hdr)))
+		return XDP_DROP;
+
+	/* this should fail */
+	hdr->h_proto = 1;
+
+	return XDP_PASS;
+}
+
+/* Only supported prog type can create skb-type dynptrs */
+SEC("?raw_tp")
+__failure __msg("calling kernel function bpf_dynptr_from_skb is not allowed")
+int skb_invalid_ctx(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_from_skb(ctx, 0, &ptr);
+
+	return 0;
+}
+
 /* Reject writes to dynptr slot for uninit arg */
 SEC("?raw_tp")
 __failure __msg("potential write to dynptr at off=-16")
@@ -1061,6 +1278,61 @@ int uninit_write_into_slot(void *ctx)
 	return 0;
 }
 
+/* Only supported prog type can create xdp-type dynptrs */
+SEC("?raw_tp")
+__failure __msg("calling kernel function bpf_dynptr_from_xdp is not allowed")
+int xdp_invalid_ctx(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_from_xdp(ctx, 0, &ptr);
+
+	return 0;
+}
+
+__u32 hdr_size = sizeof(struct ethhdr);
+/* Can't pass in variable-sized len to bpf_dynptr_slice */
+SEC("?tc")
+__failure __msg("unbounded memory access")
+int dynptr_slice_var_len1(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	/* this should fail */
+	hdr = bpf_dynptr_slice(&ptr, 0, buffer, hdr_size);
+	if (!hdr)
+		return SK_DROP;
+
+	return SK_PASS;
+}
+
+/* Can't pass in variable-sized len to bpf_dynptr_slice */
+SEC("?tc")
+__failure __msg("mem_size must be a constant")
+int dynptr_slice_var_len2(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	char buffer[sizeof(*hdr)] = {};
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	if (hdr_size <= sizeof(buffer)) {
+		/* this should fail */
+		hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, hdr_size);
+		if (!hdr)
+			return SK_DROP;
+		hdr->h_proto = 12;
+	}
+
+	return SK_PASS;
+}
+
 static int callback(__u32 index, void *data)
 {
         *(__u32 *)data = 123;
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index 35db7c6c1fc7..e7b93ab1ec83 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -9,6 +9,9 @@
 
 char _license[] SEC("license") = "GPL";
 
+extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+
 int pid, err, val;
 
 struct sample {
@@ -62,7 +65,7 @@ int test_read_write(void *ctx)
 }
 
 SEC("tp/syscalls/sys_enter_nanosleep")
-int test_data_slice(void *ctx)
+int test_dynptr_data(void *ctx)
 {
 	__u32 key = 0, val = 235, *map_val;
 	struct bpf_dynptr ptr;
@@ -163,3 +166,49 @@ int test_ringbuf(void *ctx)
 	bpf_ringbuf_discard_dynptr(&ptr, 0);
 	return 0;
 }
+
+SEC("cgroup_skb/egress")
+int test_skb_readonly(struct __sk_buff *skb)
+{
+	__u8 write_data[2] = {1, 2};
+	struct bpf_dynptr ptr;
+	__u64 *data;
+	int ret;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 0;
+	}
+
+	/* since cgroup skbs are read only, writes should fail */
+	ret = bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0);
+	if (ret != -EINVAL) {
+		err = 2;
+		return 0;
+	}
+
+	return 0;
+}
+
+SEC("cgroup_skb/egress")
+int test_dynptr_skb_data(struct __sk_buff *skb)
+{
+	__u8 write_data[2] = {1, 2};
+	struct bpf_dynptr ptr;
+	__u64 *data;
+	int ret;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 0;
+	}
+
+	/* This should return NULL. Must use bpf_dynptr_slice API */
+	data = bpf_dynptr_data(&ptr, 0, 1);
+	if (data) {
+		err = 2;
+		return 0;
+	}
+
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c b/tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c
new file mode 100644
index 000000000000..ca4c00d8c20e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c
@@ -0,0 +1,975 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+// Copyright (c) 2019, 2020 Cloudflare
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <linux/bpf.h>
+#include <linux/icmp.h>
+#include <linux/icmpv6.h>
+#include <linux/if_ether.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/pkt_cls.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+#include "test_cls_redirect.h"
+
+#define offsetofend(TYPE, MEMBER) \
+	(offsetof(TYPE, MEMBER) + sizeof((((TYPE *)0)->MEMBER)))
+
+#define IP_OFFSET_MASK (0x1FFF)
+#define IP_MF (0x2000)
+
+char _license[] SEC("license") = "Dual BSD/GPL";
+
+extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+
+/**
+ * Destination port and IP used for UDP encapsulation.
+ */
+volatile const __be16 ENCAPSULATION_PORT;
+volatile const __be32 ENCAPSULATION_IP;
+
+typedef struct {
+	uint64_t processed_packets_total;
+	uint64_t l3_protocol_packets_total_ipv4;
+	uint64_t l3_protocol_packets_total_ipv6;
+	uint64_t l4_protocol_packets_total_tcp;
+	uint64_t l4_protocol_packets_total_udp;
+	uint64_t accepted_packets_total_syn;
+	uint64_t accepted_packets_total_syn_cookies;
+	uint64_t accepted_packets_total_last_hop;
+	uint64_t accepted_packets_total_icmp_echo_request;
+	uint64_t accepted_packets_total_established;
+	uint64_t forwarded_packets_total_gue;
+	uint64_t forwarded_packets_total_gre;
+
+	uint64_t errors_total_unknown_l3_proto;
+	uint64_t errors_total_unknown_l4_proto;
+	uint64_t errors_total_malformed_ip;
+	uint64_t errors_total_fragmented_ip;
+	uint64_t errors_total_malformed_icmp;
+	uint64_t errors_total_unwanted_icmp;
+	uint64_t errors_total_malformed_icmp_pkt_too_big;
+	uint64_t errors_total_malformed_tcp;
+	uint64_t errors_total_malformed_udp;
+	uint64_t errors_total_icmp_echo_replies;
+	uint64_t errors_total_malformed_encapsulation;
+	uint64_t errors_total_encap_adjust_failed;
+	uint64_t errors_total_encap_buffer_too_small;
+	uint64_t errors_total_redirect_loop;
+	uint64_t errors_total_encap_mtu_violate;
+} metrics_t;
+
+typedef enum {
+	INVALID = 0,
+	UNKNOWN,
+	ECHO_REQUEST,
+	SYN,
+	SYN_COOKIE,
+	ESTABLISHED,
+} verdict_t;
+
+typedef struct {
+	uint16_t src, dst;
+} flow_ports_t;
+
+_Static_assert(
+	sizeof(flow_ports_t) !=
+		offsetofend(struct bpf_sock_tuple, ipv4.dport) -
+			offsetof(struct bpf_sock_tuple, ipv4.sport) - 1,
+	"flow_ports_t must match sport and dport in struct bpf_sock_tuple");
+_Static_assert(
+	sizeof(flow_ports_t) !=
+		offsetofend(struct bpf_sock_tuple, ipv6.dport) -
+			offsetof(struct bpf_sock_tuple, ipv6.sport) - 1,
+	"flow_ports_t must match sport and dport in struct bpf_sock_tuple");
+
+struct iphdr_info {
+	void *hdr;
+	__u64 len;
+};
+
+typedef int ret_t;
+
+/* This is a bit of a hack. We need a return value which allows us to
+ * indicate that the regular flow of the program should continue,
+ * while allowing functions to use XDP_PASS and XDP_DROP, etc.
+ */
+static const ret_t CONTINUE_PROCESSING = -1;
+
+/* Convenience macro to call functions which return ret_t.
+ */
+#define MAYBE_RETURN(x)                           \
+	do {                                      \
+		ret_t __ret = x;                  \
+		if (__ret != CONTINUE_PROCESSING) \
+			return __ret;             \
+	} while (0)
+
+static bool ipv4_is_fragment(const struct iphdr *ip)
+{
+	uint16_t frag_off = ip->frag_off & bpf_htons(IP_OFFSET_MASK);
+	return (ip->frag_off & bpf_htons(IP_MF)) != 0 || frag_off > 0;
+}
+
+static int pkt_parse_ipv4(struct bpf_dynptr *dynptr, __u64 *offset, struct iphdr *iphdr)
+{
+	if (bpf_dynptr_read(iphdr, sizeof(*iphdr), dynptr, *offset, 0))
+		return -1;
+
+	*offset += sizeof(*iphdr);
+
+	if (iphdr->ihl < 5)
+		return -1;
+
+	/* skip ipv4 options */
+	*offset += (iphdr->ihl - 5) * 4;
+
+	return 0;
+}
+
+/* Parse the L4 ports from a packet, assuming a layout like TCP or UDP. */
+static bool pkt_parse_icmp_l4_ports(struct bpf_dynptr *dynptr, __u64 *offset, flow_ports_t *ports)
+{
+	if (bpf_dynptr_read(ports, sizeof(*ports), dynptr, *offset, 0))
+		return false;
+
+	*offset += sizeof(*ports);
+
+	/* Ports in the L4 headers are reversed, since we are parsing an ICMP
+	 * payload which is going towards the eyeball.
+	 */
+	uint16_t dst = ports->src;
+	ports->src = ports->dst;
+	ports->dst = dst;
+	return true;
+}
+
+static uint16_t pkt_checksum_fold(uint32_t csum)
+{
+	/* The highest reasonable value for an IPv4 header
+	 * checksum requires two folds, so we just do that always.
+	 */
+	csum = (csum & 0xffff) + (csum >> 16);
+	csum = (csum & 0xffff) + (csum >> 16);
+	return (uint16_t)~csum;
+}
+
+static void pkt_ipv4_checksum(struct iphdr *iph)
+{
+	iph->check = 0;
+
+	/* An IP header without options is 20 bytes. Two of those
+	 * are the checksum, which we always set to zero. Hence,
+	 * the maximum accumulated value is 18 / 2 * 0xffff = 0x8fff7,
+	 * which fits in 32 bit.
+	 */
+	_Static_assert(sizeof(struct iphdr) == 20, "iphdr must be 20 bytes");
+	uint32_t acc = 0;
+	uint16_t *ipw = (uint16_t *)iph;
+
+	for (size_t i = 0; i < sizeof(struct iphdr) / 2; i++)
+		acc += ipw[i];
+
+	iph->check = pkt_checksum_fold(acc);
+}
+
+static bool pkt_skip_ipv6_extension_headers(struct bpf_dynptr *dynptr, __u64 *offset,
+					    const struct ipv6hdr *ipv6, uint8_t *upper_proto,
+					    bool *is_fragment)
+{
+	/* We understand five extension headers.
+	 * https://tools.ietf.org/html/rfc8200#section-4.1 states that all
+	 * headers should occur once, except Destination Options, which may
+	 * occur twice. Hence we give up after 6 headers.
+	 */
+	struct {
+		uint8_t next;
+		uint8_t len;
+	} exthdr = {
+		.next = ipv6->nexthdr,
+	};
+	*is_fragment = false;
+
+	for (int i = 0; i < 6; i++) {
+		switch (exthdr.next) {
+		case IPPROTO_FRAGMENT:
+			*is_fragment = true;
+			/* NB: We don't check that hdrlen == 0 as per spec. */
+			/* fallthrough; */
+
+		case IPPROTO_HOPOPTS:
+		case IPPROTO_ROUTING:
+		case IPPROTO_DSTOPTS:
+		case IPPROTO_MH:
+			if (bpf_dynptr_read(&exthdr, sizeof(exthdr), dynptr, *offset, 0))
+				return false;
+
+			/* hdrlen is in 8-octet units, and excludes the first 8 octets. */
+			*offset += (exthdr.len + 1) * 8;
+
+			/* Decode next header */
+			break;
+
+		default:
+			/* The next header is not one of the known extension
+			 * headers, treat it as the upper layer header.
+			 *
+			 * This handles IPPROTO_NONE.
+			 *
+			 * Encapsulating Security Payload (50) and Authentication
+			 * Header (51) also end up here (and will trigger an
+			 * unknown proto error later). They have a custom header
+			 * format and seem too esoteric to care about.
+			 */
+			*upper_proto = exthdr.next;
+			return true;
+		}
+	}
+
+	/* We never found an upper layer header. */
+	return false;
+}
+
+static int pkt_parse_ipv6(struct bpf_dynptr *dynptr, __u64 *offset, struct ipv6hdr *ipv6,
+			  uint8_t *proto, bool *is_fragment)
+{
+	if (bpf_dynptr_read(ipv6, sizeof(*ipv6), dynptr, *offset, 0))
+		return -1;
+
+	*offset += sizeof(*ipv6);
+
+	if (!pkt_skip_ipv6_extension_headers(dynptr, offset, ipv6, proto, is_fragment))
+		return -1;
+
+	return 0;
+}
+
+/* Global metrics, per CPU
+ */
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, unsigned int);
+	__type(value, metrics_t);
+} metrics_map SEC(".maps");
+
+static metrics_t *get_global_metrics(void)
+{
+	uint64_t key = 0;
+	return bpf_map_lookup_elem(&metrics_map, &key);
+}
+
+static ret_t accept_locally(struct __sk_buff *skb, encap_headers_t *encap)
+{
+	const int payload_off =
+		sizeof(*encap) +
+		sizeof(struct in_addr) * encap->unigue.hop_count;
+	int32_t encap_overhead = payload_off - sizeof(struct ethhdr);
+
+	/* Changing the ethertype if the encapsulated packet is ipv6 */
+	if (encap->gue.proto_ctype == IPPROTO_IPV6)
+		encap->eth.h_proto = bpf_htons(ETH_P_IPV6);
+
+	if (bpf_skb_adjust_room(skb, -encap_overhead, BPF_ADJ_ROOM_MAC,
+				BPF_F_ADJ_ROOM_FIXED_GSO |
+				BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||
+	    bpf_csum_level(skb, BPF_CSUM_LEVEL_DEC))
+		return TC_ACT_SHOT;
+
+	return bpf_redirect(skb->ifindex, BPF_F_INGRESS);
+}
+
+static ret_t forward_with_gre(struct __sk_buff *skb, struct bpf_dynptr *dynptr,
+			      encap_headers_t *encap, struct in_addr *next_hop,
+			      metrics_t *metrics)
+{
+	const int payload_off =
+		sizeof(*encap) +
+		sizeof(struct in_addr) * encap->unigue.hop_count;
+	int32_t encap_overhead =
+		payload_off - sizeof(struct ethhdr) - sizeof(struct iphdr);
+	int32_t delta = sizeof(struct gre_base_hdr) - encap_overhead;
+	__u8 encap_buffer[sizeof(encap_gre_t)] = {};
+	uint16_t proto = ETH_P_IP;
+	uint32_t mtu_len = 0;
+	encap_gre_t *encap_gre;
+
+	metrics->forwarded_packets_total_gre++;
+
+	/* Loop protection: the inner packet's TTL is decremented as a safeguard
+	 * against any forwarding loop. As the only interesting field is the TTL
+	 * hop limit for IPv6, it is easier to use bpf_skb_load_bytes/bpf_skb_store_bytes
+	 * as they handle the split packets if needed (no need for the data to be
+	 * in the linear section).
+	 */
+	if (encap->gue.proto_ctype == IPPROTO_IPV6) {
+		proto = ETH_P_IPV6;
+		uint8_t ttl;
+		int rc;
+
+		rc = bpf_skb_load_bytes(
+			skb, payload_off + offsetof(struct ipv6hdr, hop_limit),
+			&ttl, 1);
+		if (rc != 0) {
+			metrics->errors_total_malformed_encapsulation++;
+			return TC_ACT_SHOT;
+		}
+
+		if (ttl == 0) {
+			metrics->errors_total_redirect_loop++;
+			return TC_ACT_SHOT;
+		}
+
+		ttl--;
+		rc = bpf_skb_store_bytes(
+			skb, payload_off + offsetof(struct ipv6hdr, hop_limit),
+			&ttl, 1, 0);
+		if (rc != 0) {
+			metrics->errors_total_malformed_encapsulation++;
+			return TC_ACT_SHOT;
+		}
+	} else {
+		uint8_t ttl;
+		int rc;
+
+		rc = bpf_skb_load_bytes(
+			skb, payload_off + offsetof(struct iphdr, ttl), &ttl,
+			1);
+		if (rc != 0) {
+			metrics->errors_total_malformed_encapsulation++;
+			return TC_ACT_SHOT;
+		}
+
+		if (ttl == 0) {
+			metrics->errors_total_redirect_loop++;
+			return TC_ACT_SHOT;
+		}
+
+		/* IPv4 also has a checksum to patch. While the TTL is only one byte,
+		 * this function only works for 2 and 4 bytes arguments (the result is
+		 * the same).
+		 */
+		rc = bpf_l3_csum_replace(
+			skb, payload_off + offsetof(struct iphdr, check), ttl,
+			ttl - 1, 2);
+		if (rc != 0) {
+			metrics->errors_total_malformed_encapsulation++;
+			return TC_ACT_SHOT;
+		}
+
+		ttl--;
+		rc = bpf_skb_store_bytes(
+			skb, payload_off + offsetof(struct iphdr, ttl), &ttl, 1,
+			0);
+		if (rc != 0) {
+			metrics->errors_total_malformed_encapsulation++;
+			return TC_ACT_SHOT;
+		}
+	}
+
+	if (bpf_check_mtu(skb, skb->ifindex, &mtu_len, delta, 0)) {
+		metrics->errors_total_encap_mtu_violate++;
+		return TC_ACT_SHOT;
+	}
+
+	if (bpf_skb_adjust_room(skb, delta, BPF_ADJ_ROOM_NET,
+				BPF_F_ADJ_ROOM_FIXED_GSO |
+				BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||
+	    bpf_csum_level(skb, BPF_CSUM_LEVEL_INC)) {
+		metrics->errors_total_encap_adjust_failed++;
+		return TC_ACT_SHOT;
+	}
+
+	if (bpf_skb_pull_data(skb, sizeof(encap_gre_t))) {
+		metrics->errors_total_encap_buffer_too_small++;
+		return TC_ACT_SHOT;
+	}
+
+	encap_gre = bpf_dynptr_slice_rdwr(dynptr, 0, encap_buffer, sizeof(encap_buffer));
+	if (!encap_gre) {
+		metrics->errors_total_encap_buffer_too_small++;
+		return TC_ACT_SHOT;
+	}
+
+	encap_gre->ip.protocol = IPPROTO_GRE;
+	encap_gre->ip.daddr = next_hop->s_addr;
+	encap_gre->ip.saddr = ENCAPSULATION_IP;
+	encap_gre->ip.tot_len =
+		bpf_htons(bpf_ntohs(encap_gre->ip.tot_len) + delta);
+	encap_gre->gre.flags = 0;
+	encap_gre->gre.protocol = bpf_htons(proto);
+	pkt_ipv4_checksum((void *)&encap_gre->ip);
+
+	return bpf_redirect(skb->ifindex, 0);
+}
+
+static ret_t forward_to_next_hop(struct __sk_buff *skb, struct bpf_dynptr *dynptr,
+				 encap_headers_t *encap, struct in_addr *next_hop,
+				 metrics_t *metrics)
+{
+	/* swap L2 addresses */
+	/* This assumes that packets are received from a router.
+	 * So just swapping the MAC addresses here will make the packet go back to
+	 * the router, which will send it to the appropriate machine.
+	 */
+	unsigned char temp[ETH_ALEN];
+	memcpy(temp, encap->eth.h_dest, sizeof(temp));
+	memcpy(encap->eth.h_dest, encap->eth.h_source,
+	       sizeof(encap->eth.h_dest));
+	memcpy(encap->eth.h_source, temp, sizeof(encap->eth.h_source));
+
+	if (encap->unigue.next_hop == encap->unigue.hop_count - 1 &&
+	    encap->unigue.last_hop_gre) {
+		return forward_with_gre(skb, dynptr, encap, next_hop, metrics);
+	}
+
+	metrics->forwarded_packets_total_gue++;
+	uint32_t old_saddr = encap->ip.saddr;
+	encap->ip.saddr = encap->ip.daddr;
+	encap->ip.daddr = next_hop->s_addr;
+	if (encap->unigue.next_hop < encap->unigue.hop_count) {
+		encap->unigue.next_hop++;
+	}
+
+	/* Remove ip->saddr, add next_hop->s_addr */
+	const uint64_t off = offsetof(typeof(*encap), ip.check);
+	int ret = bpf_l3_csum_replace(skb, off, old_saddr, next_hop->s_addr, 4);
+	if (ret < 0) {
+		return TC_ACT_SHOT;
+	}
+
+	return bpf_redirect(skb->ifindex, 0);
+}
+
+static ret_t skip_next_hops(__u64 *offset, int n)
+{
+	__u32 res;
+	switch (n) {
+	case 1:
+		*offset += sizeof(struct in_addr);
+	case 0:
+		return CONTINUE_PROCESSING;
+
+	default:
+		return TC_ACT_SHOT;
+	}
+}
+
+/* Get the next hop from the GLB header.
+ *
+ * Sets next_hop->s_addr to 0 if there are no more hops left.
+ * pkt is positioned just after the variable length GLB header
+ * iff the call is successful.
+ */
+static ret_t get_next_hop(struct bpf_dynptr *dynptr, __u64 *offset, encap_headers_t *encap,
+			  struct in_addr *next_hop)
+{
+	if (encap->unigue.next_hop > encap->unigue.hop_count)
+		return TC_ACT_SHOT;
+
+	/* Skip "used" next hops. */
+	MAYBE_RETURN(skip_next_hops(offset, encap->unigue.next_hop));
+
+	if (encap->unigue.next_hop == encap->unigue.hop_count) {
+		/* No more next hops, we are at the end of the GLB header. */
+		next_hop->s_addr = 0;
+		return CONTINUE_PROCESSING;
+	}
+
+	if (bpf_dynptr_read(next_hop, sizeof(*next_hop), dynptr, *offset, 0))
+		return TC_ACT_SHOT;
+
+	*offset += sizeof(*next_hop);
+
+	/* Skip the remainig next hops (may be zero). */
+	return skip_next_hops(offset, encap->unigue.hop_count - encap->unigue.next_hop - 1);
+}
+
+/* Fill a bpf_sock_tuple to be used with the socket lookup functions.
+ * This is a kludge that let's us work around verifier limitations:
+ *
+ *    fill_tuple(&t, foo, sizeof(struct iphdr), 123, 321)
+ *
+ * clang will substitue a costant for sizeof, which allows the verifier
+ * to track it's value. Based on this, it can figure out the constant
+ * return value, and calling code works while still being "generic" to
+ * IPv4 and IPv6.
+ */
+static uint64_t fill_tuple(struct bpf_sock_tuple *tuple, void *iph,
+				    uint64_t iphlen, uint16_t sport, uint16_t dport)
+{
+	switch (iphlen) {
+	case sizeof(struct iphdr): {
+		struct iphdr *ipv4 = (struct iphdr *)iph;
+		tuple->ipv4.daddr = ipv4->daddr;
+		tuple->ipv4.saddr = ipv4->saddr;
+		tuple->ipv4.sport = sport;
+		tuple->ipv4.dport = dport;
+		return sizeof(tuple->ipv4);
+	}
+
+	case sizeof(struct ipv6hdr): {
+		struct ipv6hdr *ipv6 = (struct ipv6hdr *)iph;
+		memcpy(&tuple->ipv6.daddr, &ipv6->daddr,
+		       sizeof(tuple->ipv6.daddr));
+		memcpy(&tuple->ipv6.saddr, &ipv6->saddr,
+		       sizeof(tuple->ipv6.saddr));
+		tuple->ipv6.sport = sport;
+		tuple->ipv6.dport = dport;
+		return sizeof(tuple->ipv6);
+	}
+
+	default:
+		return 0;
+	}
+}
+
+static verdict_t classify_tcp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple,
+			      uint64_t tuplen, void *iph, struct tcphdr *tcp)
+{
+	struct bpf_sock *sk =
+		bpf_skc_lookup_tcp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0);
+
+	if (sk == NULL)
+		return UNKNOWN;
+
+	if (sk->state != BPF_TCP_LISTEN) {
+		bpf_sk_release(sk);
+		return ESTABLISHED;
+	}
+
+	if (iph != NULL && tcp != NULL) {
+		/* Kludge: we've run out of arguments, but need the length of the ip header. */
+		uint64_t iphlen = sizeof(struct iphdr);
+
+		if (tuplen == sizeof(tuple->ipv6))
+			iphlen = sizeof(struct ipv6hdr);
+
+		if (bpf_tcp_check_syncookie(sk, iph, iphlen, tcp,
+					    sizeof(*tcp)) == 0) {
+			bpf_sk_release(sk);
+			return SYN_COOKIE;
+		}
+	}
+
+	bpf_sk_release(sk);
+	return UNKNOWN;
+}
+
+static verdict_t classify_udp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, uint64_t tuplen)
+{
+	struct bpf_sock *sk =
+		bpf_sk_lookup_udp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0);
+
+	if (sk == NULL)
+		return UNKNOWN;
+
+	if (sk->state == BPF_TCP_ESTABLISHED) {
+		bpf_sk_release(sk);
+		return ESTABLISHED;
+	}
+
+	bpf_sk_release(sk);
+	return UNKNOWN;
+}
+
+static verdict_t classify_icmp(struct __sk_buff *skb, uint8_t proto, struct bpf_sock_tuple *tuple,
+			       uint64_t tuplen, metrics_t *metrics)
+{
+	switch (proto) {
+	case IPPROTO_TCP:
+		return classify_tcp(skb, tuple, tuplen, NULL, NULL);
+
+	case IPPROTO_UDP:
+		return classify_udp(skb, tuple, tuplen);
+
+	default:
+		metrics->errors_total_malformed_icmp++;
+		return INVALID;
+	}
+}
+
+static verdict_t process_icmpv4(struct __sk_buff *skb, struct bpf_dynptr *dynptr, __u64 *offset,
+				metrics_t *metrics)
+{
+	struct icmphdr icmp;
+	struct iphdr ipv4;
+
+	if (bpf_dynptr_read(&icmp, sizeof(icmp), dynptr, *offset, 0)) {
+		metrics->errors_total_malformed_icmp++;
+		return INVALID;
+	}
+
+	*offset += sizeof(icmp);
+
+	/* We should never receive encapsulated echo replies. */
+	if (icmp.type == ICMP_ECHOREPLY) {
+		metrics->errors_total_icmp_echo_replies++;
+		return INVALID;
+	}
+
+	if (icmp.type == ICMP_ECHO)
+		return ECHO_REQUEST;
+
+	if (icmp.type != ICMP_DEST_UNREACH || icmp.code != ICMP_FRAG_NEEDED) {
+		metrics->errors_total_unwanted_icmp++;
+		return INVALID;
+	}
+
+	if (pkt_parse_ipv4(dynptr, offset, &ipv4)) {
+		metrics->errors_total_malformed_icmp_pkt_too_big++;
+		return INVALID;
+	}
+
+	/* The source address in the outer IP header is from the entity that
+	 * originated the ICMP message. Use the original IP header to restore
+	 * the correct flow tuple.
+	 */
+	struct bpf_sock_tuple tuple;
+	tuple.ipv4.saddr = ipv4.daddr;
+	tuple.ipv4.daddr = ipv4.saddr;
+
+	if (!pkt_parse_icmp_l4_ports(dynptr, offset, (flow_ports_t *)&tuple.ipv4.sport)) {
+		metrics->errors_total_malformed_icmp_pkt_too_big++;
+		return INVALID;
+	}
+
+	return classify_icmp(skb, ipv4.protocol, &tuple,
+			     sizeof(tuple.ipv4), metrics);
+}
+
+static verdict_t process_icmpv6(struct bpf_dynptr *dynptr, __u64 *offset, struct __sk_buff *skb,
+				metrics_t *metrics)
+{
+	struct bpf_sock_tuple tuple;
+	struct ipv6hdr ipv6;
+	struct icmp6hdr icmp6;
+	bool is_fragment;
+	uint8_t l4_proto;
+
+	if (bpf_dynptr_read(&icmp6, sizeof(icmp6), dynptr, *offset, 0)) {
+		metrics->errors_total_malformed_icmp++;
+		return INVALID;
+	}
+
+	/* We should never receive encapsulated echo replies. */
+	if (icmp6.icmp6_type == ICMPV6_ECHO_REPLY) {
+		metrics->errors_total_icmp_echo_replies++;
+		return INVALID;
+	}
+
+	if (icmp6.icmp6_type == ICMPV6_ECHO_REQUEST) {
+		return ECHO_REQUEST;
+	}
+
+	if (icmp6.icmp6_type != ICMPV6_PKT_TOOBIG) {
+		metrics->errors_total_unwanted_icmp++;
+		return INVALID;
+	}
+
+	if (pkt_parse_ipv6(dynptr, offset, &ipv6, &l4_proto, &is_fragment)) {
+		metrics->errors_total_malformed_icmp_pkt_too_big++;
+		return INVALID;
+	}
+
+	if (is_fragment) {
+		metrics->errors_total_fragmented_ip++;
+		return INVALID;
+	}
+
+	/* Swap source and dest addresses. */
+	memcpy(&tuple.ipv6.saddr, &ipv6.daddr, sizeof(tuple.ipv6.saddr));
+	memcpy(&tuple.ipv6.daddr, &ipv6.saddr, sizeof(tuple.ipv6.daddr));
+
+	if (!pkt_parse_icmp_l4_ports(dynptr, offset, (flow_ports_t *)&tuple.ipv6.sport)) {
+		metrics->errors_total_malformed_icmp_pkt_too_big++;
+		return INVALID;
+	}
+
+	return classify_icmp(skb, l4_proto, &tuple, sizeof(tuple.ipv6),
+			     metrics);
+}
+
+static verdict_t process_tcp(struct bpf_dynptr *dynptr, __u64 *offset, struct __sk_buff *skb,
+			     struct iphdr_info *info, metrics_t *metrics)
+{
+	struct bpf_sock_tuple tuple;
+	struct tcphdr tcp;
+	uint64_t tuplen;
+
+	metrics->l4_protocol_packets_total_tcp++;
+
+	if (bpf_dynptr_read(&tcp, sizeof(tcp), dynptr, *offset, 0)) {
+		metrics->errors_total_malformed_tcp++;
+		return INVALID;
+	}
+
+	*offset += sizeof(tcp);
+
+	if (tcp.syn)
+		return SYN;
+
+	tuplen = fill_tuple(&tuple, info->hdr, info->len, tcp.source, tcp.dest);
+	return classify_tcp(skb, &tuple, tuplen, info->hdr, &tcp);
+}
+
+static verdict_t process_udp(struct bpf_dynptr *dynptr, __u64 *offset, struct __sk_buff *skb,
+			     struct iphdr_info *info, metrics_t *metrics)
+{
+	struct bpf_sock_tuple tuple;
+	struct udphdr udph;
+	uint64_t tuplen;
+
+	metrics->l4_protocol_packets_total_udp++;
+
+	if (bpf_dynptr_read(&udph, sizeof(udph), dynptr, *offset, 0)) {
+		metrics->errors_total_malformed_udp++;
+		return INVALID;
+	}
+	*offset += sizeof(udph);
+
+	tuplen = fill_tuple(&tuple, info->hdr, info->len, udph.source, udph.dest);
+	return classify_udp(skb, &tuple, tuplen);
+}
+
+static verdict_t process_ipv4(struct __sk_buff *skb, struct bpf_dynptr *dynptr,
+			      __u64 *offset, metrics_t *metrics)
+{
+	struct iphdr ipv4;
+	struct iphdr_info info = {
+		.hdr = &ipv4,
+		.len = sizeof(ipv4),
+	};
+
+	metrics->l3_protocol_packets_total_ipv4++;
+
+	if (pkt_parse_ipv4(dynptr, offset, &ipv4)) {
+		metrics->errors_total_malformed_ip++;
+		return INVALID;
+	}
+
+	if (ipv4.version != 4) {
+		metrics->errors_total_malformed_ip++;
+		return INVALID;
+	}
+
+	if (ipv4_is_fragment(&ipv4)) {
+		metrics->errors_total_fragmented_ip++;
+		return INVALID;
+	}
+
+	switch (ipv4.protocol) {
+	case IPPROTO_ICMP:
+		return process_icmpv4(skb, dynptr, offset, metrics);
+
+	case IPPROTO_TCP:
+		return process_tcp(dynptr, offset, skb, &info, metrics);
+
+	case IPPROTO_UDP:
+		return process_udp(dynptr, offset, skb, &info, metrics);
+
+	default:
+		metrics->errors_total_unknown_l4_proto++;
+		return INVALID;
+	}
+}
+
+static verdict_t process_ipv6(struct __sk_buff *skb, struct bpf_dynptr *dynptr,
+			      __u64 *offset, metrics_t *metrics)
+{
+	struct ipv6hdr ipv6;
+	struct iphdr_info info = {
+		.hdr = &ipv6,
+		.len = sizeof(ipv6),
+	};
+	uint8_t l4_proto;
+	bool is_fragment;
+
+	metrics->l3_protocol_packets_total_ipv6++;
+
+	if (pkt_parse_ipv6(dynptr, offset, &ipv6, &l4_proto, &is_fragment)) {
+		metrics->errors_total_malformed_ip++;
+		return INVALID;
+	}
+
+	if (ipv6.version != 6) {
+		metrics->errors_total_malformed_ip++;
+		return INVALID;
+	}
+
+	if (is_fragment) {
+		metrics->errors_total_fragmented_ip++;
+		return INVALID;
+	}
+
+	switch (l4_proto) {
+	case IPPROTO_ICMPV6:
+		return process_icmpv6(dynptr, offset, skb, metrics);
+
+	case IPPROTO_TCP:
+		return process_tcp(dynptr, offset, skb, &info, metrics);
+
+	case IPPROTO_UDP:
+		return process_udp(dynptr, offset, skb, &info, metrics);
+
+	default:
+		metrics->errors_total_unknown_l4_proto++;
+		return INVALID;
+	}
+}
+
+SEC("tc")
+int cls_redirect(struct __sk_buff *skb)
+{
+	__u8 encap_buffer[sizeof(encap_headers_t)] = {};
+	struct bpf_dynptr dynptr;
+	struct in_addr next_hop;
+	/* Tracks offset of the dynptr. This will be unnecessary once
+	 * bpf_dynptr_advance() is available.
+	 */
+	__u64 off = 0;
+
+	bpf_dynptr_from_skb(skb, 0, &dynptr);
+
+	metrics_t *metrics = get_global_metrics();
+	if (metrics == NULL)
+		return TC_ACT_SHOT;
+
+	metrics->processed_packets_total++;
+
+	/* Pass bogus packets as long as we're not sure they're
+	 * destined for us.
+	 */
+	if (skb->protocol != bpf_htons(ETH_P_IP))
+		return TC_ACT_OK;
+
+	encap_headers_t *encap;
+
+	/* Make sure that all encapsulation headers are available in
+	 * the linear portion of the skb. This makes it easy to manipulate them.
+	 */
+	if (bpf_skb_pull_data(skb, sizeof(*encap)))
+		return TC_ACT_OK;
+
+	encap = bpf_dynptr_slice_rdwr(&dynptr, 0, encap_buffer, sizeof(encap_buffer));
+	if (!encap)
+		return TC_ACT_OK;
+
+	off += sizeof(*encap);
+
+	if (encap->ip.ihl != 5)
+		/* We never have any options. */
+		return TC_ACT_OK;
+
+	if (encap->ip.daddr != ENCAPSULATION_IP ||
+	    encap->ip.protocol != IPPROTO_UDP)
+		return TC_ACT_OK;
+
+	/* TODO Check UDP length? */
+	if (encap->udp.dest != ENCAPSULATION_PORT)
+		return TC_ACT_OK;
+
+	/* We now know that the packet is destined to us, we can
+	 * drop bogus ones.
+	 */
+	if (ipv4_is_fragment((void *)&encap->ip)) {
+		metrics->errors_total_fragmented_ip++;
+		return TC_ACT_SHOT;
+	}
+
+	if (encap->gue.variant != 0) {
+		metrics->errors_total_malformed_encapsulation++;
+		return TC_ACT_SHOT;
+	}
+
+	if (encap->gue.control != 0) {
+		metrics->errors_total_malformed_encapsulation++;
+		return TC_ACT_SHOT;
+	}
+
+	if (encap->gue.flags != 0) {
+		metrics->errors_total_malformed_encapsulation++;
+		return TC_ACT_SHOT;
+	}
+
+	if (encap->gue.hlen !=
+	    sizeof(encap->unigue) / 4 + encap->unigue.hop_count) {
+		metrics->errors_total_malformed_encapsulation++;
+		return TC_ACT_SHOT;
+	}
+
+	if (encap->unigue.version != 0) {
+		metrics->errors_total_malformed_encapsulation++;
+		return TC_ACT_SHOT;
+	}
+
+	if (encap->unigue.reserved != 0)
+		return TC_ACT_SHOT;
+
+	MAYBE_RETURN(get_next_hop(&dynptr, &off, encap, &next_hop));
+
+	if (next_hop.s_addr == 0) {
+		metrics->accepted_packets_total_last_hop++;
+		return accept_locally(skb, encap);
+	}
+
+	verdict_t verdict;
+	switch (encap->gue.proto_ctype) {
+	case IPPROTO_IPIP:
+		verdict = process_ipv4(skb, &dynptr, &off, metrics);
+		break;
+
+	case IPPROTO_IPV6:
+		verdict = process_ipv6(skb, &dynptr, &off, metrics);
+		break;
+
+	default:
+		metrics->errors_total_unknown_l3_proto++;
+		return TC_ACT_SHOT;
+	}
+
+	switch (verdict) {
+	case INVALID:
+		/* metrics have already been bumped */
+		return TC_ACT_SHOT;
+
+	case UNKNOWN:
+		return forward_to_next_hop(skb, &dynptr, encap, &next_hop, metrics);
+
+	case ECHO_REQUEST:
+		metrics->accepted_packets_total_icmp_echo_request++;
+		break;
+
+	case SYN:
+		if (encap->unigue.forward_syn) {
+			return forward_to_next_hop(skb, &dynptr, encap, &next_hop,
+						   metrics);
+		}
+
+		metrics->accepted_packets_total_syn++;
+		break;
+
+	case SYN_COOKIE:
+		metrics->accepted_packets_total_syn_cookies++;
+		break;
+
+	case ESTABLISHED:
+		metrics->accepted_packets_total_established++;
+		break;
+	}
+
+	return accept_locally(skb, encap);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c b/tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c
new file mode 100644
index 000000000000..d01ecc8b7716
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c
@@ -0,0 +1,486 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+#include <stddef.h>
+#include <stdbool.h>
+#include <string.h>
+#include <linux/pkt_cls.h>
+#include <linux/bpf.h>
+#include <linux/in.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/icmp.h>
+#include <linux/icmpv6.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <bpf/bpf_helpers.h>
+#include "test_iptunnel_common.h"
+#include <bpf/bpf_endian.h>
+
+extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+
+static __always_inline __u32 rol32(__u32 word, unsigned int shift)
+{
+	return (word << shift) | (word >> ((-shift) & 31));
+}
+
+/* copy paste of jhash from kernel sources to make sure llvm
+ * can compile it into valid sequence of bpf instructions
+ */
+#define __jhash_mix(a, b, c)			\
+{						\
+	a -= c;  a ^= rol32(c, 4);  c += b;	\
+	b -= a;  b ^= rol32(a, 6);  a += c;	\
+	c -= b;  c ^= rol32(b, 8);  b += a;	\
+	a -= c;  a ^= rol32(c, 16); c += b;	\
+	b -= a;  b ^= rol32(a, 19); a += c;	\
+	c -= b;  c ^= rol32(b, 4);  b += a;	\
+}
+
+#define __jhash_final(a, b, c)			\
+{						\
+	c ^= b; c -= rol32(b, 14);		\
+	a ^= c; a -= rol32(c, 11);		\
+	b ^= a; b -= rol32(a, 25);		\
+	c ^= b; c -= rol32(b, 16);		\
+	a ^= c; a -= rol32(c, 4);		\
+	b ^= a; b -= rol32(a, 14);		\
+	c ^= b; c -= rol32(b, 24);		\
+}
+
+#define JHASH_INITVAL		0xdeadbeef
+
+typedef unsigned int u32;
+
+static __noinline u32 jhash(const void *key, u32 length, u32 initval)
+{
+	u32 a, b, c;
+	const unsigned char *k = key;
+
+	a = b = c = JHASH_INITVAL + length + initval;
+
+	while (length > 12) {
+		a += *(u32 *)(k);
+		b += *(u32 *)(k + 4);
+		c += *(u32 *)(k + 8);
+		__jhash_mix(a, b, c);
+		length -= 12;
+		k += 12;
+	}
+	switch (length) {
+	case 12: c += (u32)k[11]<<24;
+	case 11: c += (u32)k[10]<<16;
+	case 10: c += (u32)k[9]<<8;
+	case 9:  c += k[8];
+	case 8:  b += (u32)k[7]<<24;
+	case 7:  b += (u32)k[6]<<16;
+	case 6:  b += (u32)k[5]<<8;
+	case 5:  b += k[4];
+	case 4:  a += (u32)k[3]<<24;
+	case 3:  a += (u32)k[2]<<16;
+	case 2:  a += (u32)k[1]<<8;
+	case 1:  a += k[0];
+		 __jhash_final(a, b, c);
+	case 0: /* Nothing left to add */
+		break;
+	}
+
+	return c;
+}
+
+static __noinline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)
+{
+	a += initval;
+	b += initval;
+	c += initval;
+	__jhash_final(a, b, c);
+	return c;
+}
+
+static __noinline u32 jhash_2words(u32 a, u32 b, u32 initval)
+{
+	return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
+}
+
+#define PCKT_FRAGMENTED 65343
+#define IPV4_HDR_LEN_NO_OPT 20
+#define IPV4_PLUS_ICMP_HDR 28
+#define IPV6_PLUS_ICMP_HDR 48
+#define RING_SIZE 2
+#define MAX_VIPS 12
+#define MAX_REALS 5
+#define CTL_MAP_SIZE 16
+#define CH_RINGS_SIZE (MAX_VIPS * RING_SIZE)
+#define F_IPV6 (1 << 0)
+#define F_HASH_NO_SRC_PORT (1 << 0)
+#define F_ICMP (1 << 0)
+#define F_SYN_SET (1 << 1)
+
+struct packet_description {
+	union {
+		__be32 src;
+		__be32 srcv6[4];
+	};
+	union {
+		__be32 dst;
+		__be32 dstv6[4];
+	};
+	union {
+		__u32 ports;
+		__u16 port16[2];
+	};
+	__u8 proto;
+	__u8 flags;
+};
+
+struct ctl_value {
+	union {
+		__u64 value;
+		__u32 ifindex;
+		__u8 mac[6];
+	};
+};
+
+struct vip_meta {
+	__u32 flags;
+	__u32 vip_num;
+};
+
+struct real_definition {
+	union {
+		__be32 dst;
+		__be32 dstv6[4];
+	};
+	__u8 flags;
+};
+
+struct vip_stats {
+	__u64 bytes;
+	__u64 pkts;
+};
+
+struct eth_hdr {
+	unsigned char eth_dest[ETH_ALEN];
+	unsigned char eth_source[ETH_ALEN];
+	unsigned short eth_proto;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, MAX_VIPS);
+	__type(key, struct vip);
+	__type(value, struct vip_meta);
+} vip_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, CH_RINGS_SIZE);
+	__type(key, __u32);
+	__type(value, __u32);
+} ch_rings SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, MAX_REALS);
+	__type(key, __u32);
+	__type(value, struct real_definition);
+} reals SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(max_entries, MAX_VIPS);
+	__type(key, __u32);
+	__type(value, struct vip_stats);
+} stats SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, CTL_MAP_SIZE);
+	__type(key, __u32);
+	__type(value, struct ctl_value);
+} ctl_array SEC(".maps");
+
+static __noinline __u32 get_packet_hash(struct packet_description *pckt, bool ipv6)
+{
+	if (ipv6)
+		return jhash_2words(jhash(pckt->srcv6, 16, MAX_VIPS),
+				    pckt->ports, CH_RINGS_SIZE);
+	else
+		return jhash_2words(pckt->src, pckt->ports, CH_RINGS_SIZE);
+}
+
+static __noinline bool get_packet_dst(struct real_definition **real,
+				      struct packet_description *pckt,
+				      struct vip_meta *vip_info,
+				      bool is_ipv6)
+{
+	__u32 hash = get_packet_hash(pckt, is_ipv6);
+	__u32 key = RING_SIZE * vip_info->vip_num + hash % RING_SIZE;
+	__u32 *real_pos;
+
+	if (hash != 0x358459b7 /* jhash of ipv4 packet */  &&
+	    hash != 0x2f4bc6bb /* jhash of ipv6 packet */)
+		return false;
+
+	real_pos = bpf_map_lookup_elem(&ch_rings, &key);
+	if (!real_pos)
+		return false;
+	key = *real_pos;
+	*real = bpf_map_lookup_elem(&reals, &key);
+	if (!(*real))
+		return false;
+	return true;
+}
+
+static __noinline int parse_icmpv6(struct bpf_dynptr *skb_ptr, __u64 off,
+				   struct packet_description *pckt)
+{
+	__u8 buffer[sizeof(struct ipv6hdr)] = {};
+	struct icmp6hdr *icmp_hdr;
+	struct ipv6hdr *ip6h;
+
+	icmp_hdr = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
+	if (!icmp_hdr)
+		return TC_ACT_SHOT;
+
+	if (icmp_hdr->icmp6_type != ICMPV6_PKT_TOOBIG)
+		return TC_ACT_OK;
+	off += sizeof(struct icmp6hdr);
+	ip6h = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
+	if (!ip6h)
+		return TC_ACT_SHOT;
+	pckt->proto = ip6h->nexthdr;
+	pckt->flags |= F_ICMP;
+	memcpy(pckt->srcv6, ip6h->daddr.s6_addr32, 16);
+	memcpy(pckt->dstv6, ip6h->saddr.s6_addr32, 16);
+	return TC_ACT_UNSPEC;
+}
+
+static __noinline int parse_icmp(struct bpf_dynptr *skb_ptr, __u64 off,
+				 struct packet_description *pckt)
+{
+	__u8 buffer_icmp[sizeof(struct iphdr)] = {};
+	__u8 buffer_ip[sizeof(struct iphdr)] = {};
+	struct icmphdr *icmp_hdr;
+	struct iphdr *iph;
+
+	icmp_hdr = bpf_dynptr_slice(skb_ptr, off, buffer_icmp, sizeof(buffer_icmp));
+	if (!icmp_hdr)
+		return TC_ACT_SHOT;
+	if (icmp_hdr->type != ICMP_DEST_UNREACH ||
+	    icmp_hdr->code != ICMP_FRAG_NEEDED)
+		return TC_ACT_OK;
+	off += sizeof(struct icmphdr);
+	iph = bpf_dynptr_slice(skb_ptr, off, buffer_ip, sizeof(buffer_ip));
+	if (!iph || iph->ihl != 5)
+		return TC_ACT_SHOT;
+	pckt->proto = iph->protocol;
+	pckt->flags |= F_ICMP;
+	pckt->src = iph->daddr;
+	pckt->dst = iph->saddr;
+	return TC_ACT_UNSPEC;
+}
+
+static __noinline bool parse_udp(struct bpf_dynptr *skb_ptr, __u64 off,
+				 struct packet_description *pckt)
+{
+	__u8 buffer[sizeof(struct udphdr)] = {};
+	struct udphdr *udp;
+
+	udp = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
+	if (!udp)
+		return false;
+
+	if (!(pckt->flags & F_ICMP)) {
+		pckt->port16[0] = udp->source;
+		pckt->port16[1] = udp->dest;
+	} else {
+		pckt->port16[0] = udp->dest;
+		pckt->port16[1] = udp->source;
+	}
+	return true;
+}
+
+static __noinline bool parse_tcp(struct bpf_dynptr *skb_ptr, __u64 off,
+				 struct packet_description *pckt)
+{
+	__u8 buffer[sizeof(struct tcphdr)] = {};
+	struct tcphdr *tcp;
+
+	tcp = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
+	if (!tcp)
+		return false;
+
+	if (tcp->syn)
+		pckt->flags |= F_SYN_SET;
+
+	if (!(pckt->flags & F_ICMP)) {
+		pckt->port16[0] = tcp->source;
+		pckt->port16[1] = tcp->dest;
+	} else {
+		pckt->port16[0] = tcp->dest;
+		pckt->port16[1] = tcp->source;
+	}
+	return true;
+}
+
+static __noinline int process_packet(struct bpf_dynptr *skb_ptr,
+				     struct eth_hdr *eth, __u64 off,
+				     bool is_ipv6, struct __sk_buff *skb)
+{
+	struct packet_description pckt = {};
+	struct bpf_tunnel_key tkey = {};
+	struct vip_stats *data_stats;
+	struct real_definition *dst;
+	struct vip_meta *vip_info;
+	struct ctl_value *cval;
+	__u32 v4_intf_pos = 1;
+	__u32 v6_intf_pos = 2;
+	struct ipv6hdr *ip6h;
+	struct vip vip = {};
+	struct iphdr *iph;
+	int tun_flag = 0;
+	__u16 pkt_bytes;
+	__u64 iph_len;
+	__u32 ifindex;
+	__u8 protocol;
+	__u32 vip_num;
+	int action;
+
+	tkey.tunnel_ttl = 64;
+	if (is_ipv6) {
+		__u8 buffer[sizeof(struct ipv6hdr)] = {};
+
+		ip6h = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
+		if (!ip6h)
+			return TC_ACT_SHOT;
+
+		iph_len = sizeof(struct ipv6hdr);
+		protocol = ip6h->nexthdr;
+		pckt.proto = protocol;
+		pkt_bytes = bpf_ntohs(ip6h->payload_len);
+		off += iph_len;
+		if (protocol == IPPROTO_FRAGMENT) {
+			return TC_ACT_SHOT;
+		} else if (protocol == IPPROTO_ICMPV6) {
+			action = parse_icmpv6(skb_ptr, off, &pckt);
+			if (action >= 0)
+				return action;
+			off += IPV6_PLUS_ICMP_HDR;
+		} else {
+			memcpy(pckt.srcv6, ip6h->saddr.s6_addr32, 16);
+			memcpy(pckt.dstv6, ip6h->daddr.s6_addr32, 16);
+		}
+	} else {
+		__u8 buffer[sizeof(struct iphdr)] = {};
+
+		iph = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
+		if (!iph || iph->ihl != 5)
+			return TC_ACT_SHOT;
+
+		protocol = iph->protocol;
+		pckt.proto = protocol;
+		pkt_bytes = bpf_ntohs(iph->tot_len);
+		off += IPV4_HDR_LEN_NO_OPT;
+
+		if (iph->frag_off & PCKT_FRAGMENTED)
+			return TC_ACT_SHOT;
+		if (protocol == IPPROTO_ICMP) {
+			action = parse_icmp(skb_ptr, off, &pckt);
+			if (action >= 0)
+				return action;
+			off += IPV4_PLUS_ICMP_HDR;
+		} else {
+			pckt.src = iph->saddr;
+			pckt.dst = iph->daddr;
+		}
+	}
+	protocol = pckt.proto;
+
+	if (protocol == IPPROTO_TCP) {
+		if (!parse_tcp(skb_ptr, off, &pckt))
+			return TC_ACT_SHOT;
+	} else if (protocol == IPPROTO_UDP) {
+		if (!parse_udp(skb_ptr, off, &pckt))
+			return TC_ACT_SHOT;
+	} else {
+		return TC_ACT_SHOT;
+	}
+
+	if (is_ipv6)
+		memcpy(vip.daddr.v6, pckt.dstv6, 16);
+	else
+		vip.daddr.v4 = pckt.dst;
+
+	vip.dport = pckt.port16[1];
+	vip.protocol = pckt.proto;
+	vip_info = bpf_map_lookup_elem(&vip_map, &vip);
+	if (!vip_info) {
+		vip.dport = 0;
+		vip_info = bpf_map_lookup_elem(&vip_map, &vip);
+		if (!vip_info)
+			return TC_ACT_SHOT;
+		pckt.port16[1] = 0;
+	}
+
+	if (vip_info->flags & F_HASH_NO_SRC_PORT)
+		pckt.port16[0] = 0;
+
+	if (!get_packet_dst(&dst, &pckt, vip_info, is_ipv6))
+		return TC_ACT_SHOT;
+
+	if (dst->flags & F_IPV6) {
+		cval = bpf_map_lookup_elem(&ctl_array, &v6_intf_pos);
+		if (!cval)
+			return TC_ACT_SHOT;
+		ifindex = cval->ifindex;
+		memcpy(tkey.remote_ipv6, dst->dstv6, 16);
+		tun_flag = BPF_F_TUNINFO_IPV6;
+	} else {
+		cval = bpf_map_lookup_elem(&ctl_array, &v4_intf_pos);
+		if (!cval)
+			return TC_ACT_SHOT;
+		ifindex = cval->ifindex;
+		tkey.remote_ipv4 = dst->dst;
+	}
+	vip_num = vip_info->vip_num;
+	data_stats = bpf_map_lookup_elem(&stats, &vip_num);
+	if (!data_stats)
+		return TC_ACT_SHOT;
+	data_stats->pkts++;
+	data_stats->bytes += pkt_bytes;
+	bpf_skb_set_tunnel_key(skb, &tkey, sizeof(tkey), tun_flag);
+	*(u32 *)eth->eth_dest = tkey.remote_ipv4;
+	return bpf_redirect(ifindex, 0);
+}
+
+SEC("tc")
+int balancer_ingress(struct __sk_buff *ctx)
+{
+	__u8 buffer[sizeof(struct eth_hdr)] = {};
+	struct bpf_dynptr ptr;
+	struct eth_hdr *eth;
+	__u32 eth_proto;
+	__u32 nh_off;
+
+	nh_off = sizeof(struct eth_hdr);
+
+	bpf_dynptr_from_skb(ctx, 0, &ptr);
+	eth = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
+	if (!eth)
+		return TC_ACT_SHOT;
+	eth_proto = eth->eth_proto;
+	if (eth_proto == bpf_htons(ETH_P_IP))
+		return process_packet(&ptr, eth, nh_off, false, ctx);
+	else if (eth_proto == bpf_htons(ETH_P_IPV6))
+		return process_packet(&ptr, eth, nh_off, true, ctx);
+	else
+		return TC_ACT_SHOT;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c
new file mode 100644
index 000000000000..79bab9b50e9e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* This parsing logic is taken from the open source library katran, a layer 4
+ * load balancer.
+ *
+ * This code logic using dynptrs can be found in test_parse_tcp_hdr_opt_dynptr.c
+ *
+ * https://github.com/facebookincubator/katran/blob/main/katran/lib/bpf/pckt_parsing.h
+ */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/tcp.h>
+#include <stdbool.h>
+#include <linux/ipv6.h>
+#include <linux/if_ether.h>
+#include "test_tcp_hdr_options.h"
+
+char _license[] SEC("license") = "GPL";
+
+/* Kind number used for experiments */
+const __u32 tcp_hdr_opt_kind_tpr = 0xFD;
+/* Length of the tcp header option */
+const __u32 tcp_hdr_opt_len_tpr = 6;
+/* maximum number of header options to check to lookup server_id */
+const __u32 tcp_hdr_opt_max_opt_checks = 15;
+
+__u32 server_id;
+
+struct hdr_opt_state {
+	__u32 server_id;
+	__u8 byte_offset;
+	__u8 hdr_bytes_remaining;
+};
+
+static int parse_hdr_opt(const struct xdp_md *xdp, struct hdr_opt_state *state)
+{
+	const void *data = (void *)(long)xdp->data;
+	const void *data_end = (void *)(long)xdp->data_end;
+	__u8 *tcp_opt, kind, hdr_len;
+
+	tcp_opt = (__u8 *)(data + state->byte_offset);
+	if (tcp_opt + 1 > data_end)
+		return -1;
+
+	kind = tcp_opt[0];
+
+	if (kind == TCPOPT_EOL)
+		return -1;
+
+	if (kind == TCPOPT_NOP) {
+		state->hdr_bytes_remaining--;
+		state->byte_offset++;
+		return 0;
+	}
+
+	if (state->hdr_bytes_remaining < 2 ||
+	    tcp_opt + sizeof(__u8) + sizeof(__u8) > data_end)
+		return -1;
+
+	hdr_len = tcp_opt[1];
+	if (hdr_len > state->hdr_bytes_remaining)
+		return -1;
+
+	if (kind == tcp_hdr_opt_kind_tpr) {
+		if (hdr_len != tcp_hdr_opt_len_tpr)
+			return -1;
+
+		if (tcp_opt + tcp_hdr_opt_len_tpr > data_end)
+			return -1;
+
+		state->server_id = *(__u32 *)&tcp_opt[2];
+		return 1;
+	}
+
+	state->hdr_bytes_remaining -= hdr_len;
+	state->byte_offset += hdr_len;
+	return 0;
+}
+
+SEC("xdp")
+int xdp_ingress_v6(struct xdp_md *xdp)
+{
+	const void *data = (void *)(long)xdp->data;
+	const void *data_end = (void *)(long)xdp->data_end;
+	struct hdr_opt_state opt_state = {};
+	__u8 tcp_hdr_opt_len = 0;
+	struct tcphdr *tcp_hdr;
+	__u64 tcp_offset = 0;
+	__u32 off;
+	int err;
+
+	tcp_offset = sizeof(struct ethhdr) + sizeof(struct ipv6hdr);
+	tcp_hdr = (struct tcphdr *)(data + tcp_offset);
+	if (tcp_hdr + 1 > data_end)
+		return XDP_DROP;
+
+	tcp_hdr_opt_len = (tcp_hdr->doff * 4) - sizeof(struct tcphdr);
+	if (tcp_hdr_opt_len < tcp_hdr_opt_len_tpr)
+		return XDP_DROP;
+
+	opt_state.hdr_bytes_remaining = tcp_hdr_opt_len;
+	opt_state.byte_offset = sizeof(struct tcphdr) + tcp_offset;
+
+	/* max number of bytes of options in tcp header is 40 bytes */
+	for (int i = 0; i < tcp_hdr_opt_max_opt_checks; i++) {
+		err = parse_hdr_opt(xdp, &opt_state);
+
+		if (err || !opt_state.hdr_bytes_remaining)
+			break;
+	}
+
+	if (!opt_state.server_id)
+		return XDP_DROP;
+
+	server_id = opt_state.server_id;
+
+	return XDP_PASS;
+}
diff --git a/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
new file mode 100644
index 000000000000..2d35bce186a3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* This logic is lifted from a real-world use case of packet parsing, used in
+ * the open source library katran, a layer 4 load balancer.
+ *
+ * This test demonstrates how to parse packet contents using dynptrs. The
+ * original code (parsing without dynptrs) can be found in test_parse_tcp_hdr_opt.c
+ */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/tcp.h>
+#include <stdbool.h>
+#include <linux/ipv6.h>
+#include <linux/if_ether.h>
+#include "test_tcp_hdr_options.h"
+
+char _license[] SEC("license") = "GPL";
+
+extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+
+/* Kind number used for experiments */
+const __u32 tcp_hdr_opt_kind_tpr = 0xFD;
+/* Length of the tcp header option */
+const __u32 tcp_hdr_opt_len_tpr = 6;
+/* maximum number of header options to check to lookup server_id */
+const __u32 tcp_hdr_opt_max_opt_checks = 15;
+
+__u32 server_id;
+
+static int parse_hdr_opt(struct bpf_dynptr *ptr, __u32 *off, __u8 *hdr_bytes_remaining,
+			 __u32 *server_id)
+{
+	__u8 *tcp_opt, kind, hdr_len;
+	__u8 buffer[sizeof(kind) + sizeof(hdr_len) + sizeof(*server_id)];
+	__u8 *data;
+
+	__builtin_memset(buffer, 0, sizeof(buffer));
+
+	data = bpf_dynptr_slice(ptr, *off, buffer, sizeof(buffer));
+	if (!data)
+		return -1;
+
+	kind = data[0];
+
+	if (kind == TCPOPT_EOL)
+		return -1;
+
+	if (kind == TCPOPT_NOP) {
+		*off += 1;
+		*hdr_bytes_remaining -= 1;
+		return 0;
+	}
+
+	if (*hdr_bytes_remaining < 2)
+		return -1;
+
+	hdr_len = data[1];
+	if (hdr_len > *hdr_bytes_remaining)
+		return -1;
+
+	if (kind == tcp_hdr_opt_kind_tpr) {
+		if (hdr_len != tcp_hdr_opt_len_tpr)
+			return -1;
+
+		__builtin_memcpy(server_id, (__u32 *)(data + 2), sizeof(*server_id));
+		return 1;
+	}
+
+	*off += hdr_len;
+	*hdr_bytes_remaining -= hdr_len;
+	return 0;
+}
+
+SEC("xdp")
+int xdp_ingress_v6(struct xdp_md *xdp)
+{
+	__u8 buffer[sizeof(struct tcphdr)] = {};
+	__u8 hdr_bytes_remaining;
+	struct tcphdr *tcp_hdr;
+	__u8 tcp_hdr_opt_len;
+	int err = 0;
+	__u32 off;
+
+	struct bpf_dynptr ptr;
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr);
+
+	off = sizeof(struct ethhdr) + sizeof(struct ipv6hdr);
+
+	tcp_hdr = bpf_dynptr_slice(&ptr, off, buffer, sizeof(buffer));
+	if (!tcp_hdr)
+		return XDP_DROP;
+
+	tcp_hdr_opt_len = (tcp_hdr->doff * 4) - sizeof(struct tcphdr);
+	if (tcp_hdr_opt_len < tcp_hdr_opt_len_tpr)
+		return XDP_DROP;
+
+	hdr_bytes_remaining = tcp_hdr_opt_len;
+
+	off += sizeof(struct tcphdr);
+
+	/* max number of bytes of options in tcp header is 40 bytes */
+	for (int i = 0; i < tcp_hdr_opt_max_opt_checks; i++) {
+		err = parse_hdr_opt(&ptr, &off, &hdr_bytes_remaining, &server_id);
+
+		if (err || !hdr_bytes_remaining)
+			break;
+	}
+
+	if (!server_id)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c b/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
new file mode 100644
index 000000000000..4c49fd42da6f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta */
+#include <stddef.h>
+#include <string.h>
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/in.h>
+#include <linux/udp.h>
+#include <linux/tcp.h>
+#include <linux/pkt_cls.h>
+#include <sys/socket.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+#include "test_iptunnel_common.h"
+
+extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags,
+			       struct bpf_dynptr *ptr) __ksym;
+extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
+			      void *buffer, __u32 buffer__sz) __ksym;
+
+const size_t tcphdr_sz = sizeof(struct tcphdr);
+const size_t udphdr_sz = sizeof(struct udphdr);
+const size_t ethhdr_sz = sizeof(struct ethhdr);
+const size_t iphdr_sz = sizeof(struct iphdr);
+const size_t ipv6hdr_sz = sizeof(struct ipv6hdr);
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(max_entries, 256);
+	__type(key, __u32);
+	__type(value, __u64);
+} rxcnt SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, MAX_IPTNL_ENTRIES);
+	__type(key, struct vip);
+	__type(value, struct iptnl_info);
+} vip2tnl SEC(".maps");
+
+static __always_inline void count_tx(__u32 protocol)
+{
+	__u64 *rxcnt_count;
+
+	rxcnt_count = bpf_map_lookup_elem(&rxcnt, &protocol);
+	if (rxcnt_count)
+		*rxcnt_count += 1;
+}
+
+static __always_inline int get_dport(void *trans_data, __u8 protocol)
+{
+	struct tcphdr *th;
+	struct udphdr *uh;
+
+	switch (protocol) {
+	case IPPROTO_TCP:
+		th = (struct tcphdr *)trans_data;
+		return th->dest;
+	case IPPROTO_UDP:
+		uh = (struct udphdr *)trans_data;
+		return uh->dest;
+	default:
+		return 0;
+	}
+}
+
+static __always_inline void set_ethhdr(struct ethhdr *new_eth,
+				       const struct ethhdr *old_eth,
+				       const struct iptnl_info *tnl,
+				       __be16 h_proto)
+{
+	memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
+	memcpy(new_eth->h_dest, tnl->dmac, sizeof(new_eth->h_dest));
+	new_eth->h_proto = h_proto;
+}
+
+static __always_inline int handle_ipv4(struct xdp_md *xdp, struct bpf_dynptr *xdp_ptr)
+{
+	__u8 eth_buffer[ethhdr_sz + iphdr_sz + ethhdr_sz];
+	__u8 iph_buffer_tcp[iphdr_sz + tcphdr_sz];
+	__u8 iph_buffer_udp[iphdr_sz + udphdr_sz];
+	struct bpf_dynptr new_xdp_ptr;
+	struct iptnl_info *tnl;
+	struct ethhdr *new_eth;
+	struct ethhdr *old_eth;
+	__u32 transport_hdr_sz;
+	struct iphdr *iph;
+	__u16 *next_iph;
+	__u16 payload_len;
+	struct vip vip = {};
+	int dport;
+	__u32 csum = 0;
+	int i;
+
+	__builtin_memset(eth_buffer, 0, sizeof(eth_buffer));
+	__builtin_memset(iph_buffer_tcp, 0, sizeof(iph_buffer_tcp));
+	__builtin_memset(iph_buffer_udp, 0, sizeof(iph_buffer_udp));
+
+	if (ethhdr_sz + iphdr_sz + tcphdr_sz > xdp->data_end - xdp->data)
+		iph = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, iph_buffer_udp, sizeof(iph_buffer_udp));
+	else
+		iph = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, iph_buffer_tcp, sizeof(iph_buffer_tcp));
+
+	if (!iph)
+		return XDP_DROP;
+
+	dport = get_dport(iph + 1, iph->protocol);
+	if (dport == -1)
+		return XDP_DROP;
+
+	vip.protocol = iph->protocol;
+	vip.family = AF_INET;
+	vip.daddr.v4 = iph->daddr;
+	vip.dport = dport;
+	payload_len = bpf_ntohs(iph->tot_len);
+
+	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
+	/* It only does v4-in-v4 */
+	if (!tnl || tnl->family != AF_INET)
+		return XDP_PASS;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)iphdr_sz))
+		return XDP_DROP;
+
+	bpf_dynptr_from_xdp(xdp, 0, &new_xdp_ptr);
+	new_eth = bpf_dynptr_slice_rdwr(&new_xdp_ptr, 0, eth_buffer, sizeof(eth_buffer));
+	if (!new_eth)
+		return XDP_DROP;
+
+	iph = (struct iphdr *)(new_eth + 1);
+	old_eth = (struct ethhdr *)(iph + 1);
+
+	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IP));
+
+	iph->version = 4;
+	iph->ihl = iphdr_sz >> 2;
+	iph->frag_off =	0;
+	iph->protocol = IPPROTO_IPIP;
+	iph->check = 0;
+	iph->tos = 0;
+	iph->tot_len = bpf_htons(payload_len + iphdr_sz);
+	iph->daddr = tnl->daddr.v4;
+	iph->saddr = tnl->saddr.v4;
+	iph->ttl = 8;
+
+	next_iph = (__u16 *)iph;
+	for (i = 0; i < iphdr_sz >> 1; i++)
+		csum += *next_iph++;
+
+	iph->check = ~((csum & 0xffff) + (csum >> 16));
+
+	count_tx(vip.protocol);
+
+	return XDP_TX;
+}
+
+static __always_inline int handle_ipv6(struct xdp_md *xdp, struct bpf_dynptr *xdp_ptr)
+{
+	__u8 eth_buffer[ethhdr_sz + ipv6hdr_sz + ethhdr_sz];
+	__u8 ip6h_buffer_tcp[ipv6hdr_sz + tcphdr_sz];
+	__u8 ip6h_buffer_udp[ipv6hdr_sz + udphdr_sz];
+	struct bpf_dynptr new_xdp_ptr;
+	struct iptnl_info *tnl;
+	struct ethhdr *new_eth;
+	struct ethhdr *old_eth;
+	__u32 transport_hdr_sz;
+	struct ipv6hdr *ip6h;
+	__u16 payload_len;
+	struct vip vip = {};
+	int dport;
+
+	__builtin_memset(eth_buffer, 0, sizeof(eth_buffer));
+	__builtin_memset(ip6h_buffer_tcp, 0, sizeof(ip6h_buffer_tcp));
+	__builtin_memset(ip6h_buffer_udp, 0, sizeof(ip6h_buffer_udp));
+
+	if (ethhdr_sz + iphdr_sz + tcphdr_sz > xdp->data_end - xdp->data)
+		ip6h = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, ip6h_buffer_udp, sizeof(ip6h_buffer_udp));
+	else
+		ip6h = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, ip6h_buffer_tcp, sizeof(ip6h_buffer_tcp));
+
+	if (!ip6h)
+		return XDP_DROP;
+
+	dport = get_dport(ip6h + 1, ip6h->nexthdr);
+	if (dport == -1)
+		return XDP_DROP;
+
+	vip.protocol = ip6h->nexthdr;
+	vip.family = AF_INET6;
+	memcpy(vip.daddr.v6, ip6h->daddr.s6_addr32, sizeof(vip.daddr));
+	vip.dport = dport;
+	payload_len = ip6h->payload_len;
+
+	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
+	/* It only does v6-in-v6 */
+	if (!tnl || tnl->family != AF_INET6)
+		return XDP_PASS;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)ipv6hdr_sz))
+		return XDP_DROP;
+
+	bpf_dynptr_from_xdp(xdp, 0, &new_xdp_ptr);
+	new_eth = bpf_dynptr_slice_rdwr(&new_xdp_ptr, 0, eth_buffer, sizeof(eth_buffer));
+	if (!new_eth)
+		return XDP_DROP;
+
+	ip6h = (struct ipv6hdr *)(new_eth + 1);
+	old_eth = (struct ethhdr *)(ip6h + 1);
+
+	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IPV6));
+
+	ip6h->version = 6;
+	ip6h->priority = 0;
+	memset(ip6h->flow_lbl, 0, sizeof(ip6h->flow_lbl));
+	ip6h->payload_len = bpf_htons(bpf_ntohs(payload_len) + ipv6hdr_sz);
+	ip6h->nexthdr = IPPROTO_IPV6;
+	ip6h->hop_limit = 8;
+	memcpy(ip6h->saddr.s6_addr32, tnl->saddr.v6, sizeof(tnl->saddr.v6));
+	memcpy(ip6h->daddr.s6_addr32, tnl->daddr.v6, sizeof(tnl->daddr.v6));
+
+	count_tx(vip.protocol);
+
+	return XDP_TX;
+}
+
+SEC("xdp")
+int _xdp_tx_iptunnel(struct xdp_md *xdp)
+{
+	__u8 buffer[ethhdr_sz];
+	struct bpf_dynptr ptr;
+	struct ethhdr *eth;
+	__u16 h_proto;
+
+	__builtin_memset(buffer, 0, sizeof(buffer));
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr);
+	eth = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer));
+	if (!eth)
+		return XDP_DROP;
+
+	h_proto = eth->h_proto;
+
+	if (h_proto == bpf_htons(ETH_P_IP))
+		return handle_ipv4(xdp, &ptr);
+	else if (h_proto == bpf_htons(ETH_P_IPV6))
+
+		return handle_ipv6(xdp, &ptr);
+	else
+		return XDP_DROP;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/test_tcp_hdr_options.h b/tools/testing/selftests/bpf/test_tcp_hdr_options.h
index 6118e3ab61fc..56c9f8a3ad3d 100644
--- a/tools/testing/selftests/bpf/test_tcp_hdr_options.h
+++ b/tools/testing/selftests/bpf/test_tcp_hdr_options.h
@@ -50,6 +50,7 @@ struct linum_err {
 
 #define TCPOPT_EOL		0
 #define TCPOPT_NOP		1
+#define TCPOPT_MSS		2
 #define TCPOPT_WINDOW		3
 #define TCPOPT_EXP		254
 
-- 
2.30.2

Re: [PATCH v10 bpf-next 9/9] selftests/bpf: tests for using dynptrs to parse skb and xdp buffers

[Toke Høiland-Jørgensen]

Joanne Koong <joannelkoong@gmail.com> writes:

> Test skb and xdp dynptr functionality in the following ways:

One question on one of the usage examples:

[...]

> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c b/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
> new file mode 100644
> index 000000000000..4c49fd42da6f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
> @@ -0,0 +1,257 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Meta */
> +#include <stddef.h>
> +#include <string.h>
> +#include <linux/bpf.h>
> +#include <linux/if_ether.h>
> +#include <linux/if_packet.h>
> +#include <linux/ip.h>
> +#include <linux/ipv6.h>
> +#include <linux/in.h>
> +#include <linux/udp.h>
> +#include <linux/tcp.h>
> +#include <linux/pkt_cls.h>
> +#include <sys/socket.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_endian.h>
> +#include "test_iptunnel_common.h"
> +
> +extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags,
> +			       struct bpf_dynptr *ptr) __ksym;
> +extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
> +			      void *buffer, __u32 buffer__sz) __ksym;
> +extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
> +			      void *buffer, __u32 buffer__sz) __ksym;
> +
> +const size_t tcphdr_sz = sizeof(struct tcphdr);
> +const size_t udphdr_sz = sizeof(struct udphdr);
> +const size_t ethhdr_sz = sizeof(struct ethhdr);
> +const size_t iphdr_sz = sizeof(struct iphdr);
> +const size_t ipv6hdr_sz = sizeof(struct ipv6hdr);
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
> +	__uint(max_entries, 256);
> +	__type(key, __u32);
> +	__type(value, __u64);
> +} rxcnt SEC(".maps");
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_HASH);
> +	__uint(max_entries, MAX_IPTNL_ENTRIES);
> +	__type(key, struct vip);
> +	__type(value, struct iptnl_info);
> +} vip2tnl SEC(".maps");
> +
> +static __always_inline void count_tx(__u32 protocol)
> +{
> +	__u64 *rxcnt_count;
> +
> +	rxcnt_count = bpf_map_lookup_elem(&rxcnt, &protocol);
> +	if (rxcnt_count)
> +		*rxcnt_count += 1;
> +}
> +
> +static __always_inline int get_dport(void *trans_data, __u8 protocol)
> +{
> +	struct tcphdr *th;
> +	struct udphdr *uh;
> +
> +	switch (protocol) {
> +	case IPPROTO_TCP:
> +		th = (struct tcphdr *)trans_data;
> +		return th->dest;
> +	case IPPROTO_UDP:
> +		uh = (struct udphdr *)trans_data;
> +		return uh->dest;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static __always_inline void set_ethhdr(struct ethhdr *new_eth,
> +				       const struct ethhdr *old_eth,
> +				       const struct iptnl_info *tnl,
> +				       __be16 h_proto)
> +{
> +	memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
> +	memcpy(new_eth->h_dest, tnl->dmac, sizeof(new_eth->h_dest));
> +	new_eth->h_proto = h_proto;
> +}
> +
> +static __always_inline int handle_ipv4(struct xdp_md *xdp, struct bpf_dynptr *xdp_ptr)
> +{
> +	__u8 eth_buffer[ethhdr_sz + iphdr_sz + ethhdr_sz];
> +	__u8 iph_buffer_tcp[iphdr_sz + tcphdr_sz];
> +	__u8 iph_buffer_udp[iphdr_sz + udphdr_sz];
> +	struct bpf_dynptr new_xdp_ptr;
> +	struct iptnl_info *tnl;
> +	struct ethhdr *new_eth;
> +	struct ethhdr *old_eth;
> +	__u32 transport_hdr_sz;
> +	struct iphdr *iph;
> +	__u16 *next_iph;
> +	__u16 payload_len;
> +	struct vip vip = {};
> +	int dport;
> +	__u32 csum = 0;
> +	int i;
> +
> +	__builtin_memset(eth_buffer, 0, sizeof(eth_buffer));
> +	__builtin_memset(iph_buffer_tcp, 0, sizeof(iph_buffer_tcp));
> +	__builtin_memset(iph_buffer_udp, 0, sizeof(iph_buffer_udp));
> +
> +	if (ethhdr_sz + iphdr_sz + tcphdr_sz > xdp->data_end - xdp->data)
> +		iph = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, iph_buffer_udp, sizeof(iph_buffer_udp));
> +	else
> +		iph = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, iph_buffer_tcp, sizeof(iph_buffer_tcp));
> +
> +	if (!iph)
> +		return XDP_DROP;
> +
> +	dport = get_dport(iph + 1, iph->protocol);
> +	if (dport == -1)
> +		return XDP_DROP;
> +
> +	vip.protocol = iph->protocol;
> +	vip.family = AF_INET;
> +	vip.daddr.v4 = iph->daddr;
> +	vip.dport = dport;
> +	payload_len = bpf_ntohs(iph->tot_len);
> +
> +	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
> +	/* It only does v4-in-v4 */
> +	if (!tnl || tnl->family != AF_INET)
> +		return XDP_PASS;
> +
> +	if (bpf_xdp_adjust_head(xdp, 0 - (int)iphdr_sz))
> +		return XDP_DROP;
> +
> +	bpf_dynptr_from_xdp(xdp, 0, &new_xdp_ptr);
> +	new_eth = bpf_dynptr_slice_rdwr(&new_xdp_ptr, 0, eth_buffer, sizeof(eth_buffer));
> +	if (!new_eth)
> +		return XDP_DROP;

Here the program just gets a new pointer using bpf_dynptr_slice_rdwr()
and proceeds to write to it directly without any further checks. But
what happens if the pointer points to the eth_buffer? Presumably the
program would need to check this and do a bpf_dynptr_write() at the end
in this case? Would be good to have this in the example, as this is
basically the only documentation that exists, and people are probably
going to copy-paste code from here :)

-Toke



> +	iph = (struct iphdr *)(new_eth + 1);
> +	old_eth = (struct ethhdr *)(iph + 1);
> +
> +	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IP));
> +
> +	iph->version = 4;
> +	iph->ihl = iphdr_sz >> 2;
> +	iph->frag_off =	0;
> +	iph->protocol = IPPROTO_IPIP;
> +	iph->check = 0;
> +	iph->tos = 0;
> +	iph->tot_len = bpf_htons(payload_len + iphdr_sz);
> +	iph->daddr = tnl->daddr.v4;
> +	iph->saddr = tnl->saddr.v4;
> +	iph->ttl = 8;
> +
> +	next_iph = (__u16 *)iph;
> +	for (i = 0; i < iphdr_sz >> 1; i++)
> +		csum += *next_iph++;
> +
> +	iph->check = ~((csum & 0xffff) + (csum >> 16));
> +
> +	count_tx(vip.protocol);
> +
> +	return XDP_TX;
> +}
> +
> +static __always_inline int handle_ipv6(struct xdp_md *xdp, struct bpf_dynptr *xdp_ptr)
> +{
> +	__u8 eth_buffer[ethhdr_sz + ipv6hdr_sz + ethhdr_sz];
> +	__u8 ip6h_buffer_tcp[ipv6hdr_sz + tcphdr_sz];
> +	__u8 ip6h_buffer_udp[ipv6hdr_sz + udphdr_sz];
> +	struct bpf_dynptr new_xdp_ptr;
> +	struct iptnl_info *tnl;
> +	struct ethhdr *new_eth;
> +	struct ethhdr *old_eth;
> +	__u32 transport_hdr_sz;
> +	struct ipv6hdr *ip6h;
> +	__u16 payload_len;
> +	struct vip vip = {};
> +	int dport;
> +
> +	__builtin_memset(eth_buffer, 0, sizeof(eth_buffer));
> +	__builtin_memset(ip6h_buffer_tcp, 0, sizeof(ip6h_buffer_tcp));
> +	__builtin_memset(ip6h_buffer_udp, 0, sizeof(ip6h_buffer_udp));
> +
> +	if (ethhdr_sz + iphdr_sz + tcphdr_sz > xdp->data_end - xdp->data)
> +		ip6h = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, ip6h_buffer_udp, sizeof(ip6h_buffer_udp));
> +	else
> +		ip6h = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, ip6h_buffer_tcp, sizeof(ip6h_buffer_tcp));
> +
> +	if (!ip6h)
> +		return XDP_DROP;
> +
> +	dport = get_dport(ip6h + 1, ip6h->nexthdr);
> +	if (dport == -1)
> +		return XDP_DROP;
> +
> +	vip.protocol = ip6h->nexthdr;
> +	vip.family = AF_INET6;
> +	memcpy(vip.daddr.v6, ip6h->daddr.s6_addr32, sizeof(vip.daddr));
> +	vip.dport = dport;
> +	payload_len = ip6h->payload_len;
> +
> +	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
> +	/* It only does v6-in-v6 */
> +	if (!tnl || tnl->family != AF_INET6)
> +		return XDP_PASS;
> +
> +	if (bpf_xdp_adjust_head(xdp, 0 - (int)ipv6hdr_sz))
> +		return XDP_DROP;
> +
> +	bpf_dynptr_from_xdp(xdp, 0, &new_xdp_ptr);
> +	new_eth = bpf_dynptr_slice_rdwr(&new_xdp_ptr, 0, eth_buffer, sizeof(eth_buffer));
> +	if (!new_eth)
> +		return XDP_DROP;
> +
> +	ip6h = (struct ipv6hdr *)(new_eth + 1);
> +	old_eth = (struct ethhdr *)(ip6h + 1);
> +
> +	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IPV6));
> +
> +	ip6h->version = 6;
> +	ip6h->priority = 0;
> +	memset(ip6h->flow_lbl, 0, sizeof(ip6h->flow_lbl));
> +	ip6h->payload_len = bpf_htons(bpf_ntohs(payload_len) + ipv6hdr_sz);
> +	ip6h->nexthdr = IPPROTO_IPV6;
> +	ip6h->hop_limit = 8;
> +	memcpy(ip6h->saddr.s6_addr32, tnl->saddr.v6, sizeof(tnl->saddr.v6));
> +	memcpy(ip6h->daddr.s6_addr32, tnl->daddr.v6, sizeof(tnl->daddr.v6));
> +
> +	count_tx(vip.protocol);
> +
> +	return XDP_TX;
> +}
> +
> +SEC("xdp")
> +int _xdp_tx_iptunnel(struct xdp_md *xdp)
> +{
> +	__u8 buffer[ethhdr_sz];
> +	struct bpf_dynptr ptr;
> +	struct ethhdr *eth;
> +	__u16 h_proto;
> +
> +	__builtin_memset(buffer, 0, sizeof(buffer));
> +
> +	bpf_dynptr_from_xdp(xdp, 0, &ptr);
> +	eth = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer));
> +	if (!eth)
> +		return XDP_DROP;
> +
> +	h_proto = eth->h_proto;
> +
> +	if (h_proto == bpf_htons(ETH_P_IP))
> +		return handle_ipv4(xdp, &ptr);
> +	else if (h_proto == bpf_htons(ETH_P_IPV6))
> +
> +		return handle_ipv6(xdp, &ptr);
> +	else
> +		return XDP_DROP;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/test_tcp_hdr_options.h b/tools/testing/selftests/bpf/test_tcp_hdr_options.h
> index 6118e3ab61fc..56c9f8a3ad3d 100644
> --- a/tools/testing/selftests/bpf/test_tcp_hdr_options.h
> +++ b/tools/testing/selftests/bpf/test_tcp_hdr_options.h
> @@ -50,6 +50,7 @@ struct linum_err {
>  
>  #define TCPOPT_EOL		0
>  #define TCPOPT_NOP		1
> +#define TCPOPT_MSS		2
>  #define TCPOPT_WINDOW		3
>  #define TCPOPT_EXP		254
>  
> -- 
> 2.30.2

Re: [PATCH v10 bpf-next 9/9] selftests/bpf: tests for using dynptrs to parse skb and xdp buffers

[Joanne Koong]

On Fri, Feb 17, 2023 at 5:05 AM Toke Høiland-Jørgensen <toke@kernel.org> wrote:
>
> Joanne Koong <joannelkoong@gmail.com> writes:
>
> > Test skb and xdp dynptr functionality in the following ways:
>
> One question on one of the usage examples:
>
> [...]
>
> > diff --git a/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c b/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
> > new file mode 100644
> > index 000000000000..4c49fd42da6f
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
> > @@ -0,0 +1,257 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2022 Meta */
> > +#include <stddef.h>
> > +#include <string.h>
> > +#include <linux/bpf.h>
> > +#include <linux/if_ether.h>
> > +#include <linux/if_packet.h>
> > +#include <linux/ip.h>
> > +#include <linux/ipv6.h>
> > +#include <linux/in.h>
> > +#include <linux/udp.h>
> > +#include <linux/tcp.h>
> > +#include <linux/pkt_cls.h>
> > +#include <sys/socket.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_endian.h>
> > +#include "test_iptunnel_common.h"
> > +
> > +extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags,
> > +                            struct bpf_dynptr *ptr) __ksym;
> > +extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
> > +                           void *buffer, __u32 buffer__sz) __ksym;
> > +extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
> > +                           void *buffer, __u32 buffer__sz) __ksym;
> > +
> > +const size_t tcphdr_sz = sizeof(struct tcphdr);
> > +const size_t udphdr_sz = sizeof(struct udphdr);
> > +const size_t ethhdr_sz = sizeof(struct ethhdr);
> > +const size_t iphdr_sz = sizeof(struct iphdr);
> > +const size_t ipv6hdr_sz = sizeof(struct ipv6hdr);
> > +
> > +struct {
> > +     __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
> > +     __uint(max_entries, 256);
> > +     __type(key, __u32);
> > +     __type(value, __u64);
> > +} rxcnt SEC(".maps");
> > +
> > +struct {
> > +     __uint(type, BPF_MAP_TYPE_HASH);
> > +     __uint(max_entries, MAX_IPTNL_ENTRIES);
> > +     __type(key, struct vip);
> > +     __type(value, struct iptnl_info);
> > +} vip2tnl SEC(".maps");
> > +
> > +static __always_inline void count_tx(__u32 protocol)
> > +{
> > +     __u64 *rxcnt_count;
> > +
> > +     rxcnt_count = bpf_map_lookup_elem(&rxcnt, &protocol);
> > +     if (rxcnt_count)
> > +             *rxcnt_count += 1;
> > +}
> > +
> > +static __always_inline int get_dport(void *trans_data, __u8 protocol)
> > +{
> > +     struct tcphdr *th;
> > +     struct udphdr *uh;
> > +
> > +     switch (protocol) {
> > +     case IPPROTO_TCP:
> > +             th = (struct tcphdr *)trans_data;
> > +             return th->dest;
> > +     case IPPROTO_UDP:
> > +             uh = (struct udphdr *)trans_data;
> > +             return uh->dest;
> > +     default:
> > +             return 0;
> > +     }
> > +}
> > +
> > +static __always_inline void set_ethhdr(struct ethhdr *new_eth,
> > +                                    const struct ethhdr *old_eth,
> > +                                    const struct iptnl_info *tnl,
> > +                                    __be16 h_proto)
> > +{
> > +     memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
> > +     memcpy(new_eth->h_dest, tnl->dmac, sizeof(new_eth->h_dest));
> > +     new_eth->h_proto = h_proto;
> > +}
> > +
> > +static __always_inline int handle_ipv4(struct xdp_md *xdp, struct bpf_dynptr *xdp_ptr)
> > +{
> > +     __u8 eth_buffer[ethhdr_sz + iphdr_sz + ethhdr_sz];
> > +     __u8 iph_buffer_tcp[iphdr_sz + tcphdr_sz];
> > +     __u8 iph_buffer_udp[iphdr_sz + udphdr_sz];
> > +     struct bpf_dynptr new_xdp_ptr;
> > +     struct iptnl_info *tnl;
> > +     struct ethhdr *new_eth;
> > +     struct ethhdr *old_eth;
> > +     __u32 transport_hdr_sz;
> > +     struct iphdr *iph;
> > +     __u16 *next_iph;
> > +     __u16 payload_len;
> > +     struct vip vip = {};
> > +     int dport;
> > +     __u32 csum = 0;
> > +     int i;
> > +
> > +     __builtin_memset(eth_buffer, 0, sizeof(eth_buffer));
> > +     __builtin_memset(iph_buffer_tcp, 0, sizeof(iph_buffer_tcp));
> > +     __builtin_memset(iph_buffer_udp, 0, sizeof(iph_buffer_udp));
> > +
> > +     if (ethhdr_sz + iphdr_sz + tcphdr_sz > xdp->data_end - xdp->data)
> > +             iph = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, iph_buffer_udp, sizeof(iph_buffer_udp));
> > +     else
> > +             iph = bpf_dynptr_slice(xdp_ptr, ethhdr_sz, iph_buffer_tcp, sizeof(iph_buffer_tcp));
> > +
> > +     if (!iph)
> > +             return XDP_DROP;
> > +
> > +     dport = get_dport(iph + 1, iph->protocol);
> > +     if (dport == -1)
> > +             return XDP_DROP;
> > +
> > +     vip.protocol = iph->protocol;
> > +     vip.family = AF_INET;
> > +     vip.daddr.v4 = iph->daddr;
> > +     vip.dport = dport;
> > +     payload_len = bpf_ntohs(iph->tot_len);
> > +
> > +     tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
> > +     /* It only does v4-in-v4 */
> > +     if (!tnl || tnl->family != AF_INET)
> > +             return XDP_PASS;
> > +
> > +     if (bpf_xdp_adjust_head(xdp, 0 - (int)iphdr_sz))
> > +             return XDP_DROP;
> > +
> > +     bpf_dynptr_from_xdp(xdp, 0, &new_xdp_ptr);
> > +     new_eth = bpf_dynptr_slice_rdwr(&new_xdp_ptr, 0, eth_buffer, sizeof(eth_buffer));
> > +     if (!new_eth)
> > +             return XDP_DROP;
>
> Here the program just gets a new pointer using bpf_dynptr_slice_rdwr()
> and proceeds to write to it directly without any further checks. But
> what happens if the pointer points to the eth_buffer? Presumably the
> program would need to check this and do a bpf_dynptr_write() at the end
> in this case? Would be good to have this in the example, as this is
> basically the only documentation that exists, and people are probably
> going to copy-paste code from here :)
>
> -Toke
>

Ooh good catch, thanks! i forgot to change this for the other examples
as well; I will update this :)

>
>
> > +     iph = (struct iphdr *)(new_eth + 1);
> > +     old_eth = (struct ethhdr *)(iph + 1);
[...]

Re: [PATCH v10 bpf-next 8/9] bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr

[Joanne Koong]

On Thu, Feb 16, 2023 at 3:00 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Two new kfuncs are added, bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
> The user must pass in a buffer to store the contents of the data slice
> if a direct pointer to the data cannot be obtained.
>
> For skb and xdp type dynptrs, these two APIs are the only way to obtain
> a data slice. However, for other types of dynptrs, there is no
> difference between bpf_dynptr_slice(_rdwr) and bpf_dynptr_data.
>
> For skb type dynptrs, the data is copied into the user provided buffer
> if any of the data is not in the linear portion of the skb. For xdp type
> dynptrs, the data is copied into the user provided buffer if the data is
> between xdp frags.
>
> If the skb is cloned and a call to bpf_dynptr_data_rdwr is made, then
> the skb will be uncloned (see bpf_unclone_prologue()).
>
> Please note that any bpf_dynptr_write() automatically invalidates any prior
> data slices of the skb dynptr. This is because the skb may be cloned or
> may need to pull its paged buffer into the head. As such, any
> bpf_dynptr_write() will automatically have its prior data slices
> invalidated, even if the write is to data in the skb head of an uncloned
> skb. Please note as well that any other helper calls that change the
> underlying packet buffer (eg bpf_skb_pull_data()) invalidates any data
> slices of the skb dynptr as well, for the same reasons.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  include/linux/filter.h         | 14 ++++++
>  include/uapi/linux/bpf.h       |  5 ++
>  kernel/bpf/helpers.c           | 91 ++++++++++++++++++++++++++++++++++
>  kernel/bpf/verifier.c          | 88 ++++++++++++++++++++++++++++++--
>  net/core/filter.c              |  6 +--
>  tools/include/uapi/linux/bpf.h |  5 ++
>  6 files changed, 202 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 3f6992261ec5..efa5d4a1677e 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -1548,6 +1548,9 @@ int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from,
>                           u32 len, u64 flags);
>  int __bpf_xdp_load_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len);
>  int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset, void *buf, u32 len);
> +void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len);
> +void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
> +                     void *buf, unsigned long len, bool flush);
>  #else /* CONFIG_NET */
>  static inline int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset,
>                                        void *to, u32 len)
> @@ -1572,6 +1575,17 @@ static inline int __bpf_xdp_store_bytes(struct xdp_buff *xdp, u32 offset,
>  {
>         return -EOPNOTSUPP;
>  }
> +
> +static inline void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len)
> +{
> +       return NULL;
> +}
> +
> +static inline void *bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off, void *buf,
> +                                    unsigned long len, bool flush)
> +{
> +       return NULL;
> +}
>  #endif /* CONFIG_NET */
>
>  #endif /* __LINUX_FILTER_H__ */
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index e7435acbdd30..ac406af207c3 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5324,6 +5324,11 @@ union bpf_attr {
>   *             *flags* must be 0 except for skb-type dynptrs.
>   *
>   *             For skb-type dynptrs:
> + *                 *  All data slices of the dynptr are automatically
> + *                    invalidated after **bpf_dynptr_write**\ (). This is
> + *                    because writing may pull the skb and change the
> + *                    underlying packet buffer.
> + *
>   *                 *  For *flags*, please see the flags accepted by
>   *                    **bpf_skb_store_bytes**\ ().
>   *     Return
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 989be97b0f81..0586f54e4f9e 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -2177,6 +2177,94 @@ __bpf_kfunc struct task_struct *bpf_task_from_pid(s32 pid)
>         return p;
>  }
>
> +/**
> + * bpf_dynptr_slice - Obtain a read-only pointer to the dynptr data.
> + *
> + * For non-skb and non-xdp type dynptrs, there is no difference between
> + * bpf_dynptr_slice and bpf_dynptr_data.
> + *
> + * If the intention is to write to the data slice, please use
> + * bpf_dynptr_slice_rdwr.
> + *
> + * @ptr: The dynptr whose data slice to retrieve
> + * @offset: Offset into the dynptr
> + * @buffer: User-provided buffer to copy contents into
> + * @buffer__sz: Size (in bytes) of the buffer. This is the length of the
> + * requested slice
> + *
> + * @returns: NULL if the call failed (eg invalid dynptr), pointer to a read-only
> + * data slice (can be either direct pointer to the data or a pointer to the user
> + * provided buffer, with its contents containing the data, if unable to obtain
> + * direct pointer)
> + */
> +__bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset,
> +                                  void *buffer, u32 buffer__sz)
> +{
> +       enum bpf_dynptr_type type;
> +       u32 len = buffer__sz;
> +       int err;
> +
> +       if (!ptr->data)
> +               return 0;
> +
> +       err = bpf_dynptr_check_off_len(ptr, offset, len);
> +       if (err)
> +               return 0;
> +
> +       type = bpf_dynptr_get_type(ptr);
> +
> +       switch (type) {
> +       case BPF_DYNPTR_TYPE_LOCAL:
> +       case BPF_DYNPTR_TYPE_RINGBUF:
> +               return ptr->data + ptr->offset + offset;
> +       case BPF_DYNPTR_TYPE_SKB:
> +               return skb_header_pointer(ptr->data, ptr->offset + offset, len, buffer);
> +       case BPF_DYNPTR_TYPE_XDP:
> +       {
> +               void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len);
> +               if (xdp_ptr)
> +                       return xdp_ptr;
> +
> +               bpf_xdp_copy_buf(ptr->data, ptr->offset + offset, buffer, len, false);
> +               return buffer;
> +       }
> +       default:
> +               WARN_ONCE(true, "unknown dynptr type %d\n", type);
> +               return 0;
> +       }
> +}
> +
> +/**
> + * bpf_dynptr_slice_rdwr - Obtain a pointer to the dynptr data.
> + *
> + * For non-skb and non-xdp type dynptrs, there is no difference between
> + * bpf_dynptr_slice and bpf_dynptr_data.
> + *
> + * @ptr: The dynptr whose data slice to retrieve
> + * @offset: Offset into the dynptr
> + * @buffer: User-provided buffer to copy contents into
> + * @buffer__sz: Size (in bytes) of the buffer. This is the length of the
> + * requested slice
> + *
> + * @returns: NULL if the call failed (eg invalid dynptr), pointer to a
> + * data slice (can be either direct pointer to the data or a pointer to the user
> + * provided buffer, with its contents containing the data, if unable to obtain
> + * direct pointer)
> + */
> +__bpf_kfunc void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr_kern *ptr, u32 offset,
> +                                       void *buffer, u32 buffer__sz)
> +{
> +       if (!ptr->data || bpf_dynptr_is_rdonly(ptr))
> +               return 0;
> +
> +       /* bpf_dynptr_slice_rdwr is the same logic as bpf_dynptr_slice.
> +        *
> +        * For skb-type dynptrs, the verifier has already ensured that the skb
> +        * head is writable (see bpf_unclone_prologue()).
> +        */
> +       return bpf_dynptr_slice(ptr, offset, buffer, buffer__sz);
> +}
> +
>  __bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj)
>  {
>         return obj;
> @@ -2224,6 +2312,8 @@ BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE)
>  BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
>  #endif
>  BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
> +BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)
> +BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL)

upon further thought, I think these two should be listed in the
"common_btf_ids" BTF set, not "generic_btf_ids", since common_btf_ids
is registered for BPF_PROG_TYPE_UNSPEC prog types

>  BTF_SET8_END(generic_btf_ids)
>
>  static const struct btf_kfunc_id_set generic_kfunc_set = {
> @@ -2271,6 +2361,7 @@ static int __init kfunc_init(void)
>         ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
>         ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &generic_kfunc_set);
>         ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &generic_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &generic_kfunc_set);
>         ret = ret ?: register_btf_id_dtor_kfuncs(generic_dtors,
>                                                   ARRAY_SIZE(generic_dtors),
>                                                   THIS_MODULE);
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 0b767134ecaa..aa8d48b00cc2 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -759,6 +759,22 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum bpf_arg_type arg_type)
>         }
>  }
>
> +static enum bpf_type_flag get_dynptr_type_flag(enum bpf_dynptr_type type)
> +{
> +       switch (type) {
> +       case BPF_DYNPTR_TYPE_LOCAL:
> +               return DYNPTR_TYPE_LOCAL;
> +       case BPF_DYNPTR_TYPE_RINGBUF:
> +               return DYNPTR_TYPE_RINGBUF;
> +       case BPF_DYNPTR_TYPE_SKB:
> +               return DYNPTR_TYPE_SKB;
> +       case BPF_DYNPTR_TYPE_XDP:
> +               return DYNPTR_TYPE_XDP;
> +       default:
> +               return 0;
> +       }
> +}
> +
>  static bool dynptr_type_refcounted(enum bpf_dynptr_type type)
>  {
>         return type == BPF_DYNPTR_TYPE_RINGBUF;
> @@ -1677,6 +1693,12 @@ static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg)
>                reg->type == PTR_TO_PACKET_END;
>  }
>
> +static bool reg_is_dynptr_slice_pkt(const struct bpf_reg_state *reg)
> +{
> +       return base_type(reg->type) == PTR_TO_MEM &&
> +               (reg->type & DYNPTR_TYPE_SKB || reg->type & DYNPTR_TYPE_XDP);
> +}
> +
>  /* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
>  static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg,
>                                     enum bpf_reg_type which)
> @@ -7404,6 +7426,9 @@ static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
>
>  /* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
>   * are now invalid, so turn them into unknown SCALAR_VALUE.
> + *
> + * This also applies to dynptr slices belonging to skb and xdp dynptrs,
> + * since these slices point to packet data.
>   */
>  static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
>  {
> @@ -7411,7 +7436,7 @@ static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
>         struct bpf_reg_state *reg;
>
>         bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
> -               if (reg_is_pkt_pointer_any(reg))
> +               if (reg_is_pkt_pointer_any(reg) || reg_is_dynptr_slice_pkt(reg))
>                         __mark_reg_unknown(env, reg);
>         }));
>  }
> @@ -8667,6 +8692,11 @@ struct bpf_kfunc_call_arg_meta {
>         struct {
>                 struct btf_field *field;
>         } arg_rbtree_root;
> +       struct {
> +               enum bpf_dynptr_type type;
> +               u32 id;
> +       } initialized_dynptr;
> +       u64 mem_size;
>  };
>
>  static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
> @@ -8923,6 +8953,8 @@ enum special_kfunc_type {
>         KF_bpf_rbtree_first,
>         KF_bpf_dynptr_from_skb,
>         KF_bpf_dynptr_from_xdp,
> +       KF_bpf_dynptr_slice,
> +       KF_bpf_dynptr_slice_rdwr,
>  };
>
>  BTF_SET_START(special_kfunc_set)
> @@ -8939,6 +8971,8 @@ BTF_ID(func, bpf_rbtree_add)
>  BTF_ID(func, bpf_rbtree_first)
>  BTF_ID(func, bpf_dynptr_from_skb)
>  BTF_ID(func, bpf_dynptr_from_xdp)
> +BTF_ID(func, bpf_dynptr_slice)
> +BTF_ID(func, bpf_dynptr_slice_rdwr)
>  BTF_SET_END(special_kfunc_set)
>
>  BTF_ID_LIST(special_kfunc_list)
> @@ -8957,6 +8991,8 @@ BTF_ID(func, bpf_rbtree_add)
>  BTF_ID(func, bpf_rbtree_first)
>  BTF_ID(func, bpf_dynptr_from_skb)
>  BTF_ID(func, bpf_dynptr_from_xdp)
> +BTF_ID(func, bpf_dynptr_slice)
> +BTF_ID(func, bpf_dynptr_slice_rdwr)
>
>  static bool is_kfunc_bpf_rcu_read_lock(struct bpf_kfunc_call_arg_meta *meta)
>  {
> @@ -9710,12 +9746,24 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
>                                 dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_SKB;
>                         else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_xdp])
>                                 dynptr_arg_type |= MEM_UNINIT | DYNPTR_TYPE_XDP;
> -                       else
> +                       else if (reg->type == CONST_PTR_TO_DYNPTR)
>                                 dynptr_arg_type |= MEM_RDONLY;
>
>                         ret = process_dynptr_func(env, regno, insn_idx, dynptr_arg_type);
>                         if (ret < 0)
>                                 return ret;
> +
> +                       if (!(dynptr_arg_type & MEM_UNINIT)) {
> +                               int id = dynptr_id(env, reg);
> +
> +                               if (id < 0) {
> +                                       verbose(env, "verifier internal error: failed to obtain dynptr id\n");
> +                                       return id;
> +                               }
> +                               meta->initialized_dynptr.id = id;
> +                               meta->initialized_dynptr.type = dynptr_get_type(env, reg);
> +                       }
> +
>                         break;
>                 }
>                 case KF_ARG_PTR_TO_LIST_HEAD:
> @@ -9966,8 +10014,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
>                 }
>         }
>
> -       for (i = 0; i < CALLER_SAVED_REGS; i++)
> -               mark_reg_not_init(env, regs, caller_saved[i]);
> +       mark_reg_not_init(env, regs, caller_saved[BPF_REG_0]);
>
>         /* Check return type */
>         t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
> @@ -10053,6 +10100,36 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
>                                 regs[BPF_REG_0].type = PTR_TO_BTF_ID | PTR_UNTRUSTED;
>                                 regs[BPF_REG_0].btf = desc_btf;
>                                 regs[BPF_REG_0].btf_id = meta.arg_constant.value;
> +                       } else if (meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice] ||
> +                                  meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {
> +                               enum bpf_type_flag type_flag = get_dynptr_type_flag(meta.initialized_dynptr.type);
> +
> +                               mark_reg_known_zero(env, regs, BPF_REG_0);
> +
> +                               if (!tnum_is_const(regs[BPF_REG_4].var_off)) {
> +                                       verbose(env, "mem_size must be a constant\n");
> +                                       return -EINVAL;
> +                               }
> +                               regs[BPF_REG_0].mem_size = regs[BPF_REG_4].var_off.value;
> +
> +                               /* PTR_MAYBE_NULL will be added when is_kfunc_ret_null is checked */
> +                               regs[BPF_REG_0].type = PTR_TO_MEM | type_flag;
> +
> +                               if (meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice])
> +                                       regs[BPF_REG_0].type |= MEM_RDONLY;
> +                               else
> +                                       env->seen_direct_write = true;
> +
> +                               if (!meta.initialized_dynptr.id) {
> +                                       verbose(env, "verifier internal error: no dynptr id\n");
> +                                       return -EFAULT;
> +                               }
> +                               regs[BPF_REG_0].dynptr_id = meta.initialized_dynptr.id;
> +
> +                               /* we don't need to set BPF_REG_0's ref obj id
> +                                * because packet slices are not refcounted (see
> +                                * dynptr_type_refcounted)
> +                                */
>                         } else {
>                                 verbose(env, "kernel function %s unhandled dynamic return type\n",
>                                         meta.func_name);
> @@ -10112,6 +10189,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
>                         regs[BPF_REG_0].id = ++env->id_gen;
>         } /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */
>
> +       for (i = BPF_REG_1; i < CALLER_SAVED_REGS; i++)
> +               mark_reg_not_init(env, regs, caller_saved[i]);
> +
>         nargs = btf_type_vlen(func_proto);
>         args = (const struct btf_param *)(func_proto + 1);
>         for (i = 0; i < nargs; i++) {
> diff --git a/net/core/filter.c b/net/core/filter.c
> index dcf1e6d2582d..0bd62b2b25e1 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3894,8 +3894,8 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = {
>         .arg2_type      = ARG_ANYTHING,
>  };
>
> -static void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
> -                            void *buf, unsigned long len, bool flush)
> +void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
> +                     void *buf, unsigned long len, bool flush)
>  {
>         unsigned long ptr_len, ptr_off = 0;
>         skb_frag_t *next_frag, *end_frag;
> @@ -3941,7 +3941,7 @@ static void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
>         }
>  }
>
> -static void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len)
> +void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len)
>  {
>         struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
>         u32 size = xdp->data_end - xdp->data;
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index e7435acbdd30..ac406af207c3 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -5324,6 +5324,11 @@ union bpf_attr {
>   *             *flags* must be 0 except for skb-type dynptrs.
>   *
>   *             For skb-type dynptrs:
> + *                 *  All data slices of the dynptr are automatically
> + *                    invalidated after **bpf_dynptr_write**\ (). This is
> + *                    because writing may pull the skb and change the
> + *                    underlying packet buffer.
> + *
>   *                 *  For *flags*, please see the flags accepted by
>   *                    **bpf_skb_store_bytes**\ ().
>   *     Return
> --
> 2.30.2
>

Re: [PATCH v10 bpf-next 6/9] bpf: Add skb dynptrs

[Andrii Nakryiko]

On Thu, Feb 16, 2023 at 2:56 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Add skb dynptrs, which are dynptrs whose underlying pointer points
> to a skb. The dynptr acts on skb data. skb dynptrs have two main
> benefits. One is that they allow operations on sizes that are not
> statically known at compile-time (eg variable-sized accesses).
> Another is that parsing the packet data through dynptrs (instead of
> through direct access of skb->data and skb->data_end) can be more
> ergonomic and less brittle (eg does not need manual if checking for
> being within bounds of data_end).
>
> For bpf prog types that don't support writes on skb data, the dynptr is
> read-only (bpf_dynptr_write() will return an error)
>
> For reads and writes through the bpf_dynptr_read() and bpf_dynptr_write()
> interfaces, reading and writing from/to data in the head as well as from/to
> non-linear paged buffers is supported. Data slices through the
> bpf_dynptr_data API are not supported; instead bpf_dynptr_slice() and
> bpf_dynptr_slice_rdwr() (added in subsequent commit) should be used.
>
> For examples of how skb dynptrs can be used, please see the attached
> selftests.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  include/linux/bpf.h            | 14 ++++++-
>  include/linux/filter.h         | 18 ++++++++
>  include/uapi/linux/bpf.h       | 14 ++++++-
>  kernel/bpf/btf.c               | 18 ++++++++
>  kernel/bpf/helpers.c           | 76 +++++++++++++++++++++++++++-------
>  kernel/bpf/verifier.c          | 70 ++++++++++++++++++++++++++++++-
>  net/core/filter.c              | 67 ++++++++++++++++++++++++++++++
>  tools/include/uapi/linux/bpf.h | 14 ++++++-
>  8 files changed, 270 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 296841a31749..3d18be35a5e6 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -607,11 +607,14 @@ enum bpf_type_flag {
>          */
>         NON_OWN_REF             = BIT(14 + BPF_BASE_TYPE_BITS),
>
> +       /* DYNPTR points to sk_buff */
> +       DYNPTR_TYPE_SKB         = BIT(15 + BPF_BASE_TYPE_BITS),
> +
>         __BPF_TYPE_FLAG_MAX,
>         __BPF_TYPE_LAST_FLAG    = __BPF_TYPE_FLAG_MAX - 1,
>  };
>
> -#define DYNPTR_TYPE_FLAG_MASK  (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF)
> +#define DYNPTR_TYPE_FLAG_MASK  (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB)
>
>  /* Max number of base types. */
>  #define BPF_BASE_TYPE_LIMIT    (1UL << BPF_BASE_TYPE_BITS)
> @@ -1146,6 +1149,8 @@ enum bpf_dynptr_type {
>         BPF_DYNPTR_TYPE_LOCAL,
>         /* Underlying data is a ringbuf record */
>         BPF_DYNPTR_TYPE_RINGBUF,
> +       /* Underlying data is a sk_buff */
> +       BPF_DYNPTR_TYPE_SKB,
>  };
>
>  int bpf_dynptr_check_size(u32 size);
> @@ -2846,6 +2851,8 @@ u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
>                                 struct bpf_insn *insn_buf,
>                                 struct bpf_prog *prog,
>                                 u32 *target_size);
> +int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
> +                              struct bpf_dynptr_kern *ptr);
>  #else
>  static inline bool bpf_sock_common_is_valid_access(int off, int size,
>                                                    enum bpf_access_type type,
> @@ -2867,6 +2874,11 @@ static inline u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
>  {
>         return 0;
>  }
> +static inline int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
> +                                            struct bpf_dynptr_kern *ptr)
> +{
> +       return 0;


should this return -EOPNOTSUPP instead?

> +}
>  #endif
>
>  #ifdef CONFIG_INET

[...]

Re: [PATCH v10 bpf-next 0/9] Add skb + xdp dynptrs

[Andrii Nakryiko]

On Thu, Feb 16, 2023 at 2:56 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> This patchset is the 2nd in the dynptr series. The 1st can be found here [0].
>
> This patchset adds skb and xdp type dynptrs, which have two main benefits for
> packet parsing:
>     * allowing operations on sizes that are not statically known at
>       compile-time (eg variable-sized accesses).
>     * more ergonomic and less brittle iteration through data (eg does not need
>       manual if checking for being within bounds of data_end)
>
> When comparing the differences in runtime for packet parsing without dynptrs
> vs. with dynptrs, there is no noticeable difference. Patch 9 contains more
> details as well as examples of how to use skb and xdp dynptrs.
>
> [0]
> https://lore.kernel.org/bpf/20220523210712.3641569-1-joannelkoong@gmail.com/
>
> --

Looks good to me overall, but s390x CI fails, please take a look at [0]

  [0] https://github.com/kernel-patches/bpf/actions/runs/4207628899/jobs/7303067297

> Changelog:
>
> v9 = https://lore.kernel.org/bpf/20230127191703.3864860-1-joannelkoong@gmail.com/
> v9 -> v10:
>     * Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr interface
>     * Add some more tests
>     * Split up patchset into more parts to make it easier to review
>
> v8 = https://lore.kernel.org/bpf/20230126233439.3739120-1-joannelkoong@gmail.com/
> v8 -> v9:
>     * Fix dynptr_get_type() to check non-stack dynptrs
>
> v7 = https://lore.kernel.org/bpf/20221021011510.1890852-1-joannelkoong@gmail.com/
> v7 -> v8:
>     * Change helpers to kfuncs
>     * Add 2 new patches (1/5 and 2/5)
>
> v6 = https://lore.kernel.org/bpf/20220907183129.745846-1-joannelkoong@gmail.com/
> v6 -> v7
>     * Change bpf_dynptr_data() to return read-only data slices if the skb prog
>       is read-only (Martin)
>     * Add test "skb_invalid_write" to test that writes to rd-only data slices
>       are rejected
>
> v5 = https://lore.kernel.org/bpf/20220831183224.3754305-1-joannelkoong@gmail.com/
> v5 -> v6
>     * Address kernel test robot errors by static inlining
>
> v4 = https://lore.kernel.org/bpf/20220822235649.2218031-1-joannelkoong@gmail.com/
> v4 -> v5
>     * Address kernel test robot errors for configs w/out CONFIG_NET set
>     * For data slices, return PTR_TO_MEM instead of PTR_TO_PACKET (Kumar)
>     * Split selftests into subtests (Andrii)
>     * Remove insn patching. Use rdonly and rdwr protos for dynptr skb
>       construction (Andrii)
>     * bpf_dynptr_data() returns NULL for rd-only dynptrs. There will be a
>       separate bpf_dynptr_data_rdonly() added later (Andrii and Kumar)
>
> v3 = https://lore.kernel.org/bpf/20220822193442.657638-1-joannelkoong@gmail.com/
> v3 -> v4
>     * Forgot to commit --amend the kernel test robot error fixups
>
> v2 = https://lore.kernel.org/bpf/20220811230501.2632393-1-joannelkoong@gmail.com/
> v2 -> v3
>     * Fix kernel test robot build test errors
>
> v1 = https://lore.kernel.org/bpf/20220726184706.954822-1-joannelkoong@gmail.com/
> v1 -> v2
>   * Return data slices to rd-only skb dynptrs (Martin)
>   * bpf_dynptr_write allows writes to frags for skb dynptrs, but always
>     invalidates associated data slices (Martin)
>   * Use switch casing instead of ifs (Andrii)
>   * Use 0xFD for experimental kind number in the selftest (Zvi)
>   * Put selftest conversions w/ dynptrs into new files (Alexei)
>   * Add new selftest "test_cls_redirect_dynptr.c"
>
> Joanne Koong (9):
>   bpf: Support "sk_buff" and "xdp_buff" as valid kfunc arg types
>   bpf: Refactor process_dynptr_func
>   bpf: Allow initializing dynptrs in kfuncs
>   bpf: Define no-ops for externally called bpf dynptr functions
>   bpf: Refactor verifier dynptr into get_dynptr_arg_reg
>   bpf: Add skb dynptrs
>   bpf: Add xdp dynptrs
>   bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr
>   selftests/bpf: tests for using dynptrs to parse skb and xdp buffers
>
>  include/linux/bpf.h                           |  95 +-
>  include/linux/bpf_verifier.h                  |   3 -
>  include/linux/filter.h                        |  46 +
>  include/uapi/linux/bpf.h                      |  18 +-
>  kernel/bpf/btf.c                              |  22 +
>  kernel/bpf/helpers.c                          | 174 +++-
>  kernel/bpf/verifier.c                         | 365 +++++--
>  net/core/filter.c                             | 108 +-
>  tools/include/uapi/linux/bpf.h                |  18 +-
>  .../selftests/bpf/prog_tests/cls_redirect.c   |  25 +
>  .../testing/selftests/bpf/prog_tests/dynptr.c |  69 +-
>  .../selftests/bpf/prog_tests/l4lb_all.c       |   2 +
>  .../bpf/prog_tests/parse_tcp_hdr_opt.c        |  93 ++
>  .../selftests/bpf/prog_tests/xdp_attach.c     |  11 +-
>  .../testing/selftests/bpf/progs/dynptr_fail.c | 274 ++++-
>  .../selftests/bpf/progs/dynptr_success.c      |  51 +-
>  .../bpf/progs/test_cls_redirect_dynptr.c      | 975 ++++++++++++++++++
>  .../bpf/progs/test_l4lb_noinline_dynptr.c     | 486 +++++++++
>  .../bpf/progs/test_parse_tcp_hdr_opt.c        | 119 +++
>  .../bpf/progs/test_parse_tcp_hdr_opt_dynptr.c | 118 +++
>  .../selftests/bpf/progs/test_xdp_dynptr.c     | 257 +++++
>  .../selftests/bpf/test_tcp_hdr_options.h      |   1 +
>  22 files changed, 3151 insertions(+), 179 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_dynptr.c
>
> --
> 2.30.2
>

Re: [PATCH v10 bpf-next 8/9] bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr

[Alexei Starovoitov]

On Thu, Feb 16, 2023 at 02:55:23PM -0800, Joanne Koong wrote:
> +
> +/**
> + * bpf_dynptr_slice_rdwr - Obtain a pointer to the dynptr data.
> + *
> + * For non-skb and non-xdp type dynptrs, there is no difference between
> + * bpf_dynptr_slice and bpf_dynptr_data.
> + *
> + * @ptr: The dynptr whose data slice to retrieve
> + * @offset: Offset into the dynptr
> + * @buffer: User-provided buffer to copy contents into
> + * @buffer__sz: Size (in bytes) of the buffer. This is the length of the
> + * requested slice
> + *
> + * @returns: NULL if the call failed (eg invalid dynptr), pointer to a
> + * data slice (can be either direct pointer to the data or a pointer to the user
> + * provided buffer, with its contents containing the data, if unable to obtain
> + * direct pointer)

The doc probably should say that the returned pointer is writeable and
the user must do if (ptr != buffer) bpf_dynptr_write() to reflect the changes.

Maybe document all kfuncs similar to Documentation/bpf/cpumasks.rst ?

Should we also document that bpf_dynptr_slice[_rdwr] do not change skb
configuration and because of that the ctx->data/data_end pointers are not invalidated
by either skb_header_pointer or bpf_xdp_pointer ?

> + */
> +__bpf_kfunc void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr_kern *ptr, u32 offset,
> +					void *buffer, u32 buffer__sz)
> +{
> +	if (!ptr->data || bpf_dynptr_is_rdonly(ptr))
> +		return 0;
> +
> +	/* bpf_dynptr_slice_rdwr is the same logic as bpf_dynptr_slice.
> +	 *
> +	 * For skb-type dynptrs, the verifier has already ensured that the skb
> +	 * head is writable (see bpf_unclone_prologue()).
> +	 */

This is way too terse. It needs much more detailed comment explaining why it's safe
to write into the returned pointer.
For example it's far from obvious that bpf_dynptr_slice()->skb_header_pointer()
returns a pointer to a head or copies into a buffer. _only_. and no other logic.
Without looking into implementation details one could come up with skb_header_pointer()
behavior that returns a pointer to a middle part of a frag if {offset, len} combination allows.
And in such case it will not be safe to write into such pointer.
Because bpf_unclone_prologue() only makes sure that the head is writeable.
One can look at bpf_unclone_prologue() and see that it's doing bpf_skb_pull_data(skb, 0);
But without looking further it's also not at all obvious that arg2 == 0 means
'make head writeable'.

Also 'For skb-type dynptrs, the verifier has already ensured that the skb head is writable'
is partially true.
skb-type dynptrs are available to cgroup-scoped skb hooks and there bpf_dynptr_slice_rdwr()
will always be failing, since bpf_dynptr_is_rdonly() will be true.
It probably will be better user experience if the verifier rejects
bpf_dynptr_slice_rdwr() in hooks where may_access_direct_pkt_data() returns false.

> +	return bpf_dynptr_slice(ptr, offset, buffer, buffer__sz);
> +}
> +
...
> +			} else if (meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice] ||
> +				   meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {
> +				enum bpf_type_flag type_flag = get_dynptr_type_flag(meta.initialized_dynptr.type);
> +
> +				mark_reg_known_zero(env, regs, BPF_REG_0);
> +
> +				if (!tnum_is_const(regs[BPF_REG_4].var_off)) {
> +					verbose(env, "mem_size must be a constant\n");
> +					return -EINVAL;
> +				}
> +				regs[BPF_REG_0].mem_size = regs[BPF_REG_4].var_off.value;
> +
> +				/* PTR_MAYBE_NULL will be added when is_kfunc_ret_null is checked */
> +				regs[BPF_REG_0].type = PTR_TO_MEM | type_flag;
> +
> +				if (meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice])
> +					regs[BPF_REG_0].type |= MEM_RDONLY;
> +				else
> +					env->seen_direct_write = true;

This bit kinda makes it that bpf_dynptr_slice_rdwr() will "fail" in cg-skb hook,
but it will do so with:
        if (ops->gen_prologue || env->seen_direct_write) {
                if (!ops->gen_prologue) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                }

which will confuse users.