[PATCH bpf-next v4 0/5] New BPF helpers to accelerate synproxy

[PATCH bpf-next v4 0/5] New BPF helpers to accelerate synproxy

[Maxim Mikityanskiy]

The first patch of this series is an improvement to the existing
syncookie BPF helper. The second patch is a documentation fix.

The third patch allows BPF helpers to accept memory regions of fixed
size without doing runtime size checks.

The two last patches add new functionality that allows XDP to
accelerate iptables synproxy.

v1 of this series [1] used to include a patch that exposed conntrack
lookup to BPF using stable helpers. It was superseded by series [2] by
Kumar Kartikeya Dwivedi, which implements this functionality using
unstable helpers.

The fourth patch adds new helpers to issue and check SYN cookies without
binding to a socket, which is useful in the synproxy scenario.

The fifth patch adds a selftest, which consists of a script, an XDP
program and a userspace control application. The XDP program uses
socketless SYN cookie helpers and queries conntrack status instead of
socket status. The userspace control application allows to tune
parameters of the XDP program. This program also serves as a minimal
example of usage of the new functionality.

The draft of the new functionality was presented on Netdev 0x15 [3].

v2 changes:

Split into two series, submitted bugfixes to bpf, dropped the conntrack
patches, implemented the timestamp cookie in BPF using bpf_loop, dropped
the timestamp cookie patch.

v3 changes:

Moved some patches from bpf to bpf-next, dropped the patch that changed
error codes, split the new helpers into IPv4/IPv6, added verifier
functionality to accept memory regions of fixed size.

v4 changes:

Converted the selftest to the test_progs runner. Replaced some
deprecated functions in xdp_synproxy userspace helper.

[1]: https://lore.kernel.org/bpf/20211020095815.GJ28644@breakpoint.cc/t/
[2]: https://lore.kernel.org/bpf/20220114163953.1455836-1-memxor@gmail.com/
[3]: https://netdevconf.info/0x15/session.html?Accelerating-synproxy-with-XDP

Maxim Mikityanskiy (5):
  bpf: Use ipv6_only_sock in bpf_tcp_gen_syncookie
  bpf: Fix documentation of th_len in bpf_tcp_{gen,check}_syncookie
  bpf: Allow helpers to accept pointers with a fixed size
  bpf: Add helpers to issue and check SYN cookies in XDP
  bpf: Add selftests for raw syncookie helpers

 include/linux/bpf.h                           |  10 +
 include/net/tcp.h                             |   1 +
 include/uapi/linux/bpf.h                      | 100 ++-
 kernel/bpf/verifier.c                         |  26 +-
 net/core/filter.c                             | 128 ++-
 net/ipv4/tcp_input.c                          |   3 +-
 scripts/bpf_doc.py                            |   4 +
 tools/include/uapi/linux/bpf.h                | 100 ++-
 tools/testing/selftests/bpf/.gitignore        |   1 +
 tools/testing/selftests/bpf/Makefile          |   2 +-
 .../selftests/bpf/prog_tests/xdp_synproxy.c   | 101 +++
 .../selftests/bpf/progs/xdp_synproxy_kern.c   | 750 ++++++++++++++++++
 tools/testing/selftests/bpf/xdp_synproxy.c    | 418 ++++++++++
 13 files changed, 1622 insertions(+), 22 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_synproxy.c
 create mode 100644 tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
 create mode 100644 tools/testing/selftests/bpf/xdp_synproxy.c

-- 
2.30.2

[PATCH bpf-next v4 1/5] bpf: Use ipv6_only_sock in bpf_tcp_gen_syncookie

[Maxim Mikityanskiy]

Instead of querying the sk_ipv6only field directly, use the dedicated
ipv6_only_sock helper.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Lorenz Bauer <lmb@cloudflare.com>
Acked-by: Petar Penkov <ppenkov@google.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 03655f2074ae..7d896c14e20f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7090,7 +7090,7 @@ BPF_CALL_5(bpf_tcp_gen_syncookie, struct sock *, sk, void *, iph, u32, iph_len,
 	 */
 	switch (((struct iphdr *)iph)->version) {
 	case 4:
-		if (sk->sk_family == AF_INET6 && sk->sk_ipv6only)
+		if (sk->sk_family == AF_INET6 && ipv6_only_sock(sk))
 			return -EINVAL;
 
 		mss = tcp_v4_get_syncookie(sk, iph, th, &cookie);
-- 
2.30.2

[PATCH bpf-next v4 2/5] bpf: Fix documentation of th_len in bpf_tcp_{gen,check}_syncookie

[Maxim Mikityanskiy]

bpf_tcp_gen_syncookie expects the full length of the TCP header (with
all options), and bpf_tcp_check_syncookie accepts lengths bigger than
sizeof(struct tcphdr). Fix the documentation that says these lengths
should be exactly sizeof(struct tcphdr).

While at it, fix a typo in the name of struct ipv6hdr.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
---
 include/uapi/linux/bpf.h       | 10 ++++++----
 tools/include/uapi/linux/bpf.h | 10 ++++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 99fab54ae9c0..34afdd27d0bf 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3573,10 +3573,11 @@ union bpf_attr {
  *
  * 		*iph* points to the start of the IPv4 or IPv6 header, while
  * 		*iph_len* contains **sizeof**\ (**struct iphdr**) or
- * 		**sizeof**\ (**struct ip6hdr**).
+ * 		**sizeof**\ (**struct ipv6hdr**).
  *
  * 		*th* points to the start of the TCP header, while *th_len*
- * 		contains **sizeof**\ (**struct tcphdr**).
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  * 	Return
  * 		0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
  * 		error otherwise.
@@ -3759,10 +3760,11 @@ union bpf_attr {
  *
  *		*iph* points to the start of the IPv4 or IPv6 header, while
  *		*iph_len* contains **sizeof**\ (**struct iphdr**) or
- *		**sizeof**\ (**struct ip6hdr**).
+ *		**sizeof**\ (**struct ipv6hdr**).
  *
  *		*th* points to the start of the TCP header, while *th_len*
- *		contains the length of the TCP header.
+ *		contains the length of the TCP header with options (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  *	Return
  *		On success, lower 32 bits hold the generated SYN cookie in
  *		followed by 16 bits which hold the MSS value for that cookie,
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 99fab54ae9c0..34afdd27d0bf 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3573,10 +3573,11 @@ union bpf_attr {
  *
  * 		*iph* points to the start of the IPv4 or IPv6 header, while
  * 		*iph_len* contains **sizeof**\ (**struct iphdr**) or
- * 		**sizeof**\ (**struct ip6hdr**).
+ * 		**sizeof**\ (**struct ipv6hdr**).
  *
  * 		*th* points to the start of the TCP header, while *th_len*
- * 		contains **sizeof**\ (**struct tcphdr**).
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  * 	Return
  * 		0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
  * 		error otherwise.
@@ -3759,10 +3760,11 @@ union bpf_attr {
  *
  *		*iph* points to the start of the IPv4 or IPv6 header, while
  *		*iph_len* contains **sizeof**\ (**struct iphdr**) or
- *		**sizeof**\ (**struct ip6hdr**).
+ *		**sizeof**\ (**struct ipv6hdr**).
  *
  *		*th* points to the start of the TCP header, while *th_len*
- *		contains the length of the TCP header.
+ *		contains the length of the TCP header with options (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  *	Return
  *		On success, lower 32 bits hold the generated SYN cookie in
  *		followed by 16 bits which hold the MSS value for that cookie,
-- 
2.30.2

[PATCH bpf-next v4 3/5] bpf: Allow helpers to accept pointers with a fixed size

[Maxim Mikityanskiy]

Before this commit, the BPF verifier required ARG_PTR_TO_MEM arguments
to be followed by ARG_CONST_SIZE holding the size of the memory region.
The helpers had to check that size in runtime.

There are cases where the size expected by a helper is a compile-time
constant. Checking it in runtime is an unnecessary overhead and waste of
BPF registers.

This commit allows helpers to accept ARG_PTR_TO_MEM arguments without
the corresponding ARG_CONST_SIZE, given that they define the memory
region size in struct bpf_func_proto.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
---
 include/linux/bpf.h   | 10 ++++++++++
 kernel/bpf/verifier.c | 26 +++++++++++++++-----------
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 88449fbbe063..988749057610 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -465,6 +465,16 @@ struct bpf_func_proto {
 		};
 		u32 *arg_btf_id[5];
 	};
+	union {
+		struct {
+			size_t arg1_size;
+			size_t arg2_size;
+			size_t arg3_size;
+			size_t arg4_size;
+			size_t arg5_size;
+		};
+		size_t arg_size[5];
+	};
 	int *ret_btf_id; /* return value btf_id */
 	bool (*allowed)(const struct bpf_prog *prog);
 };
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0db6cd8dcb35..73b90427aba7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5573,6 +5573,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		 * next is_mem_size argument below.
 		 */
 		meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MEM);
+		if (fn->arg_size[arg]) {
+			err = check_helper_mem_access(env, regno,
+						      fn->arg_size[arg], false,
+						      meta);
+		}
 	} else if (arg_type_is_mem_size(arg_type)) {
 		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
 
@@ -5912,13 +5917,12 @@ static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
 	return count <= 1;
 }
 
-static bool check_args_pair_invalid(enum bpf_arg_type arg_curr,
-				    enum bpf_arg_type arg_next)
+static bool check_args_pair_invalid(const struct bpf_func_proto *fn, int arg)
 {
-	return (arg_type_is_mem_ptr(arg_curr) &&
-	        !arg_type_is_mem_size(arg_next)) ||
-	       (!arg_type_is_mem_ptr(arg_curr) &&
-		arg_type_is_mem_size(arg_next));
+	if (arg_type_is_mem_ptr(fn->arg_type[arg]))
+		return arg_type_is_mem_size(fn->arg_type[arg + 1]) ==
+			!!fn->arg_size[arg];
+	return arg_type_is_mem_size(fn->arg_type[arg + 1]) || fn->arg_size[arg];
 }
 
 static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
@@ -5929,11 +5933,11 @@ static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
 	 * helper function specification.
 	 */
 	if (arg_type_is_mem_size(fn->arg1_type) ||
-	    arg_type_is_mem_ptr(fn->arg5_type)  ||
-	    check_args_pair_invalid(fn->arg1_type, fn->arg2_type) ||
-	    check_args_pair_invalid(fn->arg2_type, fn->arg3_type) ||
-	    check_args_pair_invalid(fn->arg3_type, fn->arg4_type) ||
-	    check_args_pair_invalid(fn->arg4_type, fn->arg5_type))
+	    (arg_type_is_mem_ptr(fn->arg5_type) && !fn->arg5_size) ||
+	    check_args_pair_invalid(fn, 1) ||
+	    check_args_pair_invalid(fn, 2) ||
+	    check_args_pair_invalid(fn, 3) ||
+	    check_args_pair_invalid(fn, 4))
 		return false;
 
 	return true;
-- 
2.30.2

[PATCH bpf-next v4 4/5] bpf: Add helpers to issue and check SYN cookies in XDP

[Maxim Mikityanskiy]

The new helpers bpf_tcp_raw_{gen,check}_syncookie_ipv{4,6} allow an XDP
program to generate SYN cookies in response to TCP SYN packets and to
check those cookies upon receiving the first ACK packet (the final
packet of the TCP handshake).

Unlike bpf_tcp_{gen,check}_syncookie these new helpers don't need a
listening socket on the local machine, which allows to use them together
with synproxy to accelerate SYN cookie generation.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
---
 include/net/tcp.h              |   1 +
 include/uapi/linux/bpf.h       |  90 +++++++++++++++++++++++
 net/core/filter.c              | 126 +++++++++++++++++++++++++++++++++
 net/ipv4/tcp_input.c           |   3 +-
 scripts/bpf_doc.py             |   4 ++
 tools/include/uapi/linux/bpf.h |  90 +++++++++++++++++++++++
 6 files changed, 313 insertions(+), 1 deletion(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index d486d7b6112d..1e34eb776888 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -432,6 +432,7 @@ u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
 			 struct tcphdr *th, u32 *cookie);
 u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
 			 struct tcphdr *th, u32 *cookie);
+u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss);
 u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
 			  const struct tcp_request_sock_ops *af_ops,
 			  struct sock *sk, struct tcphdr *th);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 34afdd27d0bf..f2f7c8c7058d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5131,6 +5131,92 @@ union bpf_attr {
  *		The **hash_algo** is returned on success,
  *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *		invalid arguments are passed.
+ *
+ * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th, u32 th_len)
+ *	Description
+ *		Try to issue a SYN cookie for the packet with corresponding
+ *		IPv4/TCP headers, *iph* and *th*, without depending on a
+ *		listening socket.
+ *
+ *		*iph* points to the IPv4 header.
+ *
+ *		*th* points to the start of the TCP header, while *th_len*
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
+ *	Return
+ *		On success, lower 32 bits hold the generated SYN cookie in
+ *		followed by 16 bits which hold the MSS value for that cookie,
+ *		and the top 16 bits are unused.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EINVAL** if *th_len* is invalid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ * s64 bpf_tcp_raw_gen_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th, u32 th_len)
+ *	Description
+ *		Try to issue a SYN cookie for the packet with corresponding
+ *		IPv6/TCP headers, *iph* and *th*, without depending on a
+ *		listening socket.
+ *
+ *		*iph* points to the IPv6 header.
+ *
+ *		*th* points to the start of the TCP header, while *th_len*
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
+ *	Return
+ *		On success, lower 32 bits hold the generated SYN cookie in
+ *		followed by 16 bits which hold the MSS value for that cookie,
+ *		and the top 16 bits are unused.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EINVAL** if *th_len* is invalid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ *		**-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
+ *
+ * int bpf_tcp_raw_check_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th)
+ *	Description
+ *		Check whether *iph* and *th* contain a valid SYN cookie ACK
+ *		without depending on a listening socket.
+ *
+ *		*iph* points to the IPv4 header.
+ *
+ *		*th* points to the TCP header.
+ *	Return
+ *		0 if *iph* and *th* are a valid SYN cookie ACK.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EACCES** if the SYN cookie is not valid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ * int bpf_tcp_raw_check_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th)
+ *	Description
+ *		Check whether *iph* and *th* contain a valid SYN cookie ACK
+ *		without depending on a listening socket.
+ *
+ *		*iph* points to the IPv6 header.
+ *
+ *		*th* points to the TCP header.
+ *	Return
+ *		0 if *iph* and *th* are a valid SYN cookie ACK.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EACCES** if the SYN cookie is not valid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ *		**-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5327,6 +5413,10 @@ union bpf_attr {
 	FN(copy_from_user_task),	\
 	FN(skb_set_tstamp),		\
 	FN(ima_file_hash),		\
+	FN(tcp_raw_gen_syncookie_ipv4),	\
+	FN(tcp_raw_gen_syncookie_ipv6),	\
+	FN(tcp_raw_check_syncookie_ipv4),	\
+	FN(tcp_raw_check_syncookie_ipv6),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/net/core/filter.c b/net/core/filter.c
index 7d896c14e20f..ffbef1ae8aee 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7425,6 +7425,124 @@ static const struct bpf_func_proto bpf_skb_set_tstamp_proto = {
 	.arg3_type      = ARG_ANYTHING,
 };
 
+BPF_CALL_3(bpf_tcp_raw_gen_syncookie_ipv4, struct iphdr *, iph,
+	   struct tcphdr *, th, u32, th_len)
+{
+#ifdef CONFIG_SYN_COOKIES
+	u32 cookie;
+	u16 mss;
+
+	if (unlikely(th_len < sizeof(*th) || th_len != th->doff * 4))
+		return -EINVAL;
+
+	mss = tcp_parse_mss_option(th, 0) ?: TCP_MSS_DEFAULT;
+	cookie = __cookie_v4_init_sequence(iph, th, &mss);
+
+	return cookie | ((u64)mss << 32);
+#else
+	return -EOPNOTSUPP;
+#endif /* CONFIG_SYN_COOKIES */
+}
+
+static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv4_proto = {
+	.func		= bpf_tcp_raw_gen_syncookie_ipv4,
+	.gpl_only	= true, /* __cookie_v4_init_sequence() is GPL */
+	.pkt_access	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_MEM,
+	.arg1_size	= sizeof(struct iphdr),
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+};
+
+BPF_CALL_3(bpf_tcp_raw_gen_syncookie_ipv6, struct ipv6hdr *, iph,
+	   struct tcphdr *, th, u32, th_len)
+{
+#ifndef CONFIG_SYN_COOKIES
+	return -EOPNOTSUPP;
+#elif !IS_BUILTIN(CONFIG_IPV6)
+	return -EPROTONOSUPPORT;
+#else
+	const u16 mss_clamp = IPV6_MIN_MTU - sizeof(struct tcphdr) -
+		sizeof(struct ipv6hdr);
+	u32 cookie;
+	u16 mss;
+
+	if (unlikely(th_len < sizeof(*th) || th_len != th->doff * 4))
+		return -EINVAL;
+
+	mss = tcp_parse_mss_option(th, 0) ?: mss_clamp;
+	cookie = __cookie_v6_init_sequence(iph, th, &mss);
+
+	return cookie | ((u64)mss << 32);
+#endif
+}
+
+static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv6_proto = {
+	.func		= bpf_tcp_raw_gen_syncookie_ipv6,
+	.gpl_only	= true, /* __cookie_v6_init_sequence() is GPL */
+	.pkt_access	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_MEM,
+	.arg1_size	= sizeof(struct ipv6hdr),
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+};
+
+BPF_CALL_2(bpf_tcp_raw_check_syncookie_ipv4, struct iphdr *, iph,
+	   struct tcphdr *, th)
+{
+#ifdef CONFIG_SYN_COOKIES
+	u32 cookie = ntohl(th->ack_seq) - 1;
+
+	if (__cookie_v4_check(iph, th, cookie) > 0)
+		return 0;
+
+	return -EACCES;
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
+static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_ipv4_proto = {
+	.func		= bpf_tcp_raw_check_syncookie_ipv4,
+	.gpl_only	= true, /* __cookie_v4_check is GPL */
+	.pkt_access	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_MEM,
+	.arg1_size	= sizeof(struct iphdr),
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg2_size	= sizeof(struct tcphdr),
+};
+
+BPF_CALL_2(bpf_tcp_raw_check_syncookie_ipv6, struct ipv6hdr *, iph,
+	   struct tcphdr *, th)
+{
+#ifndef CONFIG_SYN_COOKIES
+	return -EOPNOTSUPP;
+#elif !IS_BUILTIN(CONFIG_IPV6)
+	return -EPROTONOSUPPORT;
+#else
+	u32 cookie = ntohl(th->ack_seq) - 1;
+
+	if (__cookie_v6_check(iph, th, cookie) > 0)
+		return 0;
+
+	return -EACCES;
+#endif
+}
+
+static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_ipv6_proto = {
+	.func		= bpf_tcp_raw_check_syncookie_ipv6,
+	.gpl_only	= true, /* __cookie_v6_check is GPL */
+	.pkt_access	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_MEM,
+	.arg1_size	= sizeof(struct ipv6hdr),
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg2_size	= sizeof(struct tcphdr),
+};
+
 #endif /* CONFIG_INET */
 
 bool bpf_helper_changes_pkt_data(void *func)
@@ -7837,6 +7955,14 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_tcp_check_syncookie_proto;
 	case BPF_FUNC_tcp_gen_syncookie:
 		return &bpf_tcp_gen_syncookie_proto;
+	case BPF_FUNC_tcp_raw_gen_syncookie_ipv4:
+		return &bpf_tcp_raw_gen_syncookie_ipv4_proto;
+	case BPF_FUNC_tcp_raw_gen_syncookie_ipv6:
+		return &bpf_tcp_raw_gen_syncookie_ipv6_proto;
+	case BPF_FUNC_tcp_raw_check_syncookie_ipv4:
+		return &bpf_tcp_raw_check_syncookie_ipv4_proto;
+	case BPF_FUNC_tcp_raw_check_syncookie_ipv6:
+		return &bpf_tcp_raw_check_syncookie_ipv6_proto;
 #endif
 	default:
 		return bpf_sk_base_func_proto(func_id);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2088f93fa37b..3682ee405eb7 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3963,7 +3963,7 @@ static bool smc_parse_options(const struct tcphdr *th,
 /* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
  * value on success.
  */
-static u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss)
+u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss)
 {
 	const unsigned char *ptr = (const unsigned char *)(th + 1);
 	int length = (th->doff * 4) - sizeof(struct tcphdr);
@@ -4002,6 +4002,7 @@ static u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss)
 	}
 	return mss;
 }
+EXPORT_SYMBOL_GPL(tcp_parse_mss_option);
 
 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
  * But, this can also be called on packets in the established flow when
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index 096625242475..3d0b65e6dea7 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -633,6 +633,8 @@ class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct iphdr',
+            'struct ipv6hdr',
     ]
     known_types = {
             '...',
@@ -682,6 +684,8 @@ class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct iphdr',
+            'struct ipv6hdr',
     }
     mapped_types = {
             'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 34afdd27d0bf..f2f7c8c7058d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5131,6 +5131,92 @@ union bpf_attr {
  *		The **hash_algo** is returned on success,
  *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *		invalid arguments are passed.
+ *
+ * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th, u32 th_len)
+ *	Description
+ *		Try to issue a SYN cookie for the packet with corresponding
+ *		IPv4/TCP headers, *iph* and *th*, without depending on a
+ *		listening socket.
+ *
+ *		*iph* points to the IPv4 header.
+ *
+ *		*th* points to the start of the TCP header, while *th_len*
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
+ *	Return
+ *		On success, lower 32 bits hold the generated SYN cookie in
+ *		followed by 16 bits which hold the MSS value for that cookie,
+ *		and the top 16 bits are unused.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EINVAL** if *th_len* is invalid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ * s64 bpf_tcp_raw_gen_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th, u32 th_len)
+ *	Description
+ *		Try to issue a SYN cookie for the packet with corresponding
+ *		IPv6/TCP headers, *iph* and *th*, without depending on a
+ *		listening socket.
+ *
+ *		*iph* points to the IPv6 header.
+ *
+ *		*th* points to the start of the TCP header, while *th_len*
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
+ *	Return
+ *		On success, lower 32 bits hold the generated SYN cookie in
+ *		followed by 16 bits which hold the MSS value for that cookie,
+ *		and the top 16 bits are unused.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EINVAL** if *th_len* is invalid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ *		**-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
+ *
+ * int bpf_tcp_raw_check_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th)
+ *	Description
+ *		Check whether *iph* and *th* contain a valid SYN cookie ACK
+ *		without depending on a listening socket.
+ *
+ *		*iph* points to the IPv4 header.
+ *
+ *		*th* points to the TCP header.
+ *	Return
+ *		0 if *iph* and *th* are a valid SYN cookie ACK.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EACCES** if the SYN cookie is not valid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ * int bpf_tcp_raw_check_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th)
+ *	Description
+ *		Check whether *iph* and *th* contain a valid SYN cookie ACK
+ *		without depending on a listening socket.
+ *
+ *		*iph* points to the IPv6 header.
+ *
+ *		*th* points to the TCP header.
+ *	Return
+ *		0 if *iph* and *th* are a valid SYN cookie ACK.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EACCES** if the SYN cookie is not valid.
+ *
+ *		**-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ *		cookies (CONFIG_SYN_COOKIES is off).
+ *
+ *		**-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5327,6 +5413,10 @@ union bpf_attr {
 	FN(copy_from_user_task),	\
 	FN(skb_set_tstamp),		\
 	FN(ima_file_hash),		\
+	FN(tcp_raw_gen_syncookie_ipv4),	\
+	FN(tcp_raw_gen_syncookie_ipv6),	\
+	FN(tcp_raw_check_syncookie_ipv4),	\
+	FN(tcp_raw_check_syncookie_ipv6),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.30.2

[PATCH bpf-next v4 5/5] bpf: Add selftests for raw syncookie helpers

[Maxim Mikityanskiy]

This commit adds selftests for the new BPF helpers:
bpf_tcp_raw_{gen,check}_syncookie_ipv{4,6}.

xdp_synproxy_kern.c is a BPF program that generates SYN cookies on
allowed TCP ports and sends SYNACKs to clients, accelerating synproxy
iptables module.

xdp_synproxy.c is a userspace control application that allows to
configure the following options in runtime: list of allowed ports, MSS,
window scale, TTL.

A selftest is added to prog_tests that leverages the above programs to
test the functionality of the new helpers.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
---
 tools/testing/selftests/bpf/.gitignore        |   1 +
 tools/testing/selftests/bpf/Makefile          |   2 +-
 .../selftests/bpf/prog_tests/xdp_synproxy.c   | 101 +++
 .../selftests/bpf/progs/xdp_synproxy_kern.c   | 750 ++++++++++++++++++
 tools/testing/selftests/bpf/xdp_synproxy.c    | 418 ++++++++++
 5 files changed, 1271 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_synproxy.c
 create mode 100644 tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
 create mode 100644 tools/testing/selftests/bpf/xdp_synproxy.c

diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
index a7eead8820a0..b8a3a3d3c353 100644
--- a/tools/testing/selftests/bpf/.gitignore
+++ b/tools/testing/selftests/bpf/.gitignore
@@ -42,3 +42,4 @@ test_cpp
 *.tmp
 xdpxceiver
 xdp_redirect_multi
+xdp_synproxy
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index fe12b4f5fe20..95baf29e8418 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -82,7 +82,7 @@ TEST_PROGS_EXTENDED := with_addr.sh \
 TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
 	flow_dissector_load test_flow_dissector test_tcp_check_syncookie_user \
 	test_lirc_mode2_user xdping test_cpp runqslower bench bpf_testmod.ko \
-	xdpxceiver xdp_redirect_multi
+	xdpxceiver xdp_redirect_multi xdp_synproxy
 
 TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
 
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_synproxy.c b/tools/testing/selftests/bpf/prog_tests/xdp_synproxy.c
new file mode 100644
index 000000000000..4ed41845338b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_synproxy.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#define SYS(cmd) ({ \
+	if (!ASSERT_OK(system(cmd), (cmd))) \
+		goto out; \
+})
+
+#define SYS_OUT(cmd) ({ \
+	FILE *f = popen((cmd), "r"); \
+	if (!ASSERT_OK_PTR(f, (cmd))) \
+		goto out; \
+	f; \
+})
+
+void test_xdp_synproxy(void)
+{
+	int server_fd = -1, client_fd = -1, accept_fd = -1;
+	struct nstoken *ns = NULL;
+	FILE *ctrl_file = NULL;
+	char buf[1024];
+	size_t size;
+
+	SYS("ip netns add synproxy");
+
+	SYS("ip link add tmp0 type veth peer name tmp1");
+	SYS("ip link set tmp1 netns synproxy");
+	SYS("ip link set tmp0 up");
+	SYS("ip addr replace 198.18.0.1/24 dev tmp0");
+
+	// When checksum offload is enabled, the XDP program sees wrong
+	// checksums and drops packets.
+	SYS("ethtool -K tmp0 tx off");
+	// Workaround required for veth.
+	SYS("ip link set tmp0 xdp object xdp_dummy.o section xdp 2> /dev/null");
+
+	ns = open_netns("synproxy");
+	if (!ASSERT_OK_PTR(ns, "setns"))
+		goto out;
+
+	SYS("ip link set lo up");
+	SYS("ip link set tmp1 up");
+	SYS("ip addr replace 198.18.0.2/24 dev tmp1");
+	SYS("sysctl -w net.ipv4.tcp_syncookies=2");
+	SYS("sysctl -w net.ipv4.tcp_timestamps=1");
+	SYS("sysctl -w net.netfilter.nf_conntrack_tcp_loose=0");
+	SYS("iptables -t raw -I PREROUTING \
+	    -i tmp1 -p tcp -m tcp --syn --dport 8080 -j CT --notrack");
+	SYS("iptables -t filter -A INPUT \
+	    -i tmp1 -p tcp -m tcp --dport 8080 -m state --state INVALID,UNTRACKED \
+	    -j SYNPROXY --sack-perm --timestamp --wscale 7 --mss 1460");
+	SYS("iptables -t filter -A INPUT \
+	    -i tmp1 -m state --state INVALID -j DROP");
+
+	ctrl_file = SYS_OUT("./xdp_synproxy --iface tmp1 --ports 8080 --single \
+			    --mss4 1460 --mss6 1460 --wscale 7 --ttl 64");
+	size = fread(buf, 1, sizeof(buf), ctrl_file);
+	fclose(ctrl_file);
+	if (!ASSERT_OK(memcmp(buf, "Total SYNACKs generated: 0\n", size),
+		       "initial SYNACKs"))
+		goto out;
+
+	server_fd = start_server(AF_INET, SOCK_STREAM, "198.18.0.2", 8080, 0);
+	if (!ASSERT_GE(server_fd, 0, "start_server"))
+		goto out;
+
+	close_netns(ns);
+	ns = NULL;
+
+	client_fd = connect_to_fd(server_fd, 10000);
+	if (!ASSERT_GE(client_fd, 0, "connect_to_fd"))
+		goto out;
+
+	accept_fd = accept(server_fd, NULL, NULL);
+	if (!ASSERT_GE(accept_fd, 0, "accept"))
+		goto out;
+
+	ns = open_netns("synproxy");
+	if (!ASSERT_OK_PTR(ns, "setns"))
+		goto out;
+
+	ctrl_file = SYS_OUT("./xdp_synproxy --iface tmp1 --single");
+	size = fread(buf, 1, sizeof(buf), ctrl_file);
+	fclose(ctrl_file);
+	if (!ASSERT_OK(memcmp(buf, "Total SYNACKs generated: 1\n", size),
+		       "SYNACKs after connection"))
+		goto out;
+
+out:
+	if (accept_fd >= 0)
+		close(accept_fd);
+	if (client_fd >= 0)
+		close(client_fd);
+	if (server_fd >= 0)
+		close(server_fd);
+	if (ns)
+		close_netns(ns);
+
+	system("ip netns del synproxy");
+}
diff --git a/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c b/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
new file mode 100644
index 000000000000..7bebec6f2627
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
@@ -0,0 +1,750 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/* Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+#include <asm/errno.h>
+
+#define NSEC_PER_SEC 1000000000L
+
+#define ETH_ALEN 6
+#define ETH_P_IP 0x0800
+#define ETH_P_IPV6 0x86DD
+
+#define tcp_flag_word(tp) (((union tcp_word_hdr *)(tp))->words[3])
+
+#define IP_DF 0x4000
+#define IP_MF 0x2000
+#define IP_OFFSET 0x1fff
+
+#define NEXTHDR_TCP 6
+
+#define TCPOPT_NOP 1
+#define TCPOPT_EOL 0
+#define TCPOPT_MSS 2
+#define TCPOPT_WINDOW 3
+#define TCPOPT_SACK_PERM 4
+#define TCPOPT_TIMESTAMP 8
+
+#define TCPOLEN_MSS 4
+#define TCPOLEN_WINDOW 3
+#define TCPOLEN_SACK_PERM 2
+#define TCPOLEN_TIMESTAMP 10
+
+#define TCP_TS_HZ 1000
+#define TS_OPT_WSCALE_MASK 0xf
+#define TS_OPT_SACK (1 << 4)
+#define TS_OPT_ECN (1 << 5)
+#define TSBITS 6
+#define TSMASK (((__u32)1 << TSBITS) - 1)
+#define TCP_MAX_WSCALE 14U
+
+#define IPV4_MAXLEN 60
+#define TCP_MAXLEN 60
+
+#define DEFAULT_MSS4 1460
+#define DEFAULT_MSS6 1440
+#define DEFAULT_WSCALE 7
+#define DEFAULT_TTL 64
+#define MAX_ALLOWED_PORTS 8
+
+#define swap(a, b) \
+	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+
+#define __get_unaligned_t(type, ptr) ({						\
+	const struct { type x; } __attribute__((__packed__)) *__pptr = (typeof(__pptr))(ptr); \
+	__pptr->x;								\
+})
+
+#define get_unaligned(ptr) __get_unaligned_t(typeof(*(ptr)), (ptr))
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, __u32);
+	__type(value, __u64);
+	__uint(max_entries, 2);
+} values SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, __u32);
+	__type(value, __u16);
+	__uint(max_entries, MAX_ALLOWED_PORTS);
+} allowed_ports SEC(".maps");
+
+extern struct nf_conn *bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx,
+					 struct bpf_sock_tuple *bpf_tuple,
+					 __u32 len_tuple,
+					 struct bpf_ct_opts *opts,
+					 __u32 len_opts) __ksym;
+
+extern void bpf_ct_release(struct nf_conn *ct) __ksym;
+
+static __always_inline void swap_eth_addr(__u8 *a, __u8 *b)
+{
+	__u8 tmp[ETH_ALEN];
+
+	__builtin_memcpy(tmp, a, ETH_ALEN);
+	__builtin_memcpy(a, b, ETH_ALEN);
+	__builtin_memcpy(b, tmp, ETH_ALEN);
+}
+
+static __always_inline __u16 csum_fold(__u32 csum)
+{
+	csum = (csum & 0xffff) + (csum >> 16);
+	csum = (csum & 0xffff) + (csum >> 16);
+	return (__u16)~csum;
+}
+
+static __always_inline __u16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
+					       __u32 len, __u8 proto,
+					       __u32 csum)
+{
+	__u64 s = csum;
+
+	s += (__u32)saddr;
+	s += (__u32)daddr;
+#if defined(__BIG_ENDIAN__)
+	s += proto + len;
+#elif defined(__LITTLE_ENDIAN__)
+	s += (proto + len) << 8;
+#else
+#error Unknown endian
+#endif
+	s = (s & 0xffffffff) + (s >> 32);
+	s = (s & 0xffffffff) + (s >> 32);
+
+	return csum_fold((__u32)s);
+}
+
+static __always_inline __u16 csum_ipv6_magic(const struct in6_addr *saddr,
+					     const struct in6_addr *daddr,
+					     __u32 len, __u8 proto, __u32 csum)
+{
+	__u64 sum = csum;
+	int i;
+
+#pragma unroll
+	for (i = 0; i < 4; i++)
+		sum += (__u32)saddr->in6_u.u6_addr32[i];
+
+#pragma unroll
+	for (i = 0; i < 4; i++)
+		sum += (__u32)daddr->in6_u.u6_addr32[i];
+
+	// Don't combine additions to avoid 32-bit overflow.
+	sum += bpf_htonl(len);
+	sum += bpf_htonl(proto);
+
+	sum = (sum & 0xffffffff) + (sum >> 32);
+	sum = (sum & 0xffffffff) + (sum >> 32);
+
+	return csum_fold((__u32)sum);
+}
+
+static __always_inline __u64 tcp_clock_ns(void)
+{
+	return bpf_ktime_get_ns();
+}
+
+static __always_inline __u32 tcp_ns_to_ts(__u64 ns)
+{
+	return ns / (NSEC_PER_SEC / TCP_TS_HZ);
+}
+
+static __always_inline __u32 tcp_time_stamp_raw(void)
+{
+	return tcp_ns_to_ts(tcp_clock_ns());
+}
+
+struct tcpopt_context {
+	__u8 *ptr;
+	__u8 *end;
+	void *data_end;
+	__be32 *tsecr;
+	__u8 wscale;
+	bool option_timestamp;
+	bool option_sack;
+};
+
+static int tscookie_tcpopt_parse(struct tcpopt_context *ctx)
+{
+	__u8 opcode, opsize;
+
+	if (ctx->ptr >= ctx->end)
+		return 1;
+	if (ctx->ptr >= ctx->data_end)
+		return 1;
+
+	opcode = ctx->ptr[0];
+
+	if (opcode == TCPOPT_EOL)
+		return 1;
+	if (opcode == TCPOPT_NOP) {
+		++ctx->ptr;
+		return 0;
+	}
+
+	if (ctx->ptr + 1 >= ctx->end)
+		return 1;
+	if (ctx->ptr + 1 >= ctx->data_end)
+		return 1;
+	opsize = ctx->ptr[1];
+	if (opsize < 2)
+		return 1;
+
+	if (ctx->ptr + opsize > ctx->end)
+		return 1;
+
+	switch (opcode) {
+	case TCPOPT_WINDOW:
+		if (opsize == TCPOLEN_WINDOW && ctx->ptr + TCPOLEN_WINDOW <= ctx->data_end)
+			ctx->wscale = ctx->ptr[2] < TCP_MAX_WSCALE ? ctx->ptr[2] : TCP_MAX_WSCALE;
+		break;
+	case TCPOPT_TIMESTAMP:
+		if (opsize == TCPOLEN_TIMESTAMP && ctx->ptr + TCPOLEN_TIMESTAMP <= ctx->data_end) {
+			ctx->option_timestamp = true;
+			/* Client's tsval becomes our tsecr. */
+			*ctx->tsecr = get_unaligned((__be32 *)(ctx->ptr + 2));
+		}
+		break;
+	case TCPOPT_SACK_PERM:
+		if (opsize == TCPOLEN_SACK_PERM)
+			ctx->option_sack = true;
+		break;
+	}
+
+	ctx->ptr += opsize;
+
+	return 0;
+}
+
+static int tscookie_tcpopt_parse_batch(__u32 index, void *context)
+{
+	int i;
+
+	for (i = 0; i < 7; i++)
+		if (tscookie_tcpopt_parse(context))
+			return 1;
+	return 0;
+}
+
+static __always_inline bool tscookie_init(struct tcphdr *tcp_header,
+					  __u16 tcp_len, __be32 *tsval,
+					  __be32 *tsecr, void *data_end)
+{
+	struct tcpopt_context loop_ctx = {
+		.ptr = (__u8 *)(tcp_header + 1),
+		.end = (__u8 *)tcp_header + tcp_len,
+		.data_end = data_end,
+		.tsecr = tsecr,
+		.wscale = TS_OPT_WSCALE_MASK,
+		.option_timestamp = false,
+		.option_sack = false,
+	};
+	u32 cookie;
+
+	bpf_loop(6, tscookie_tcpopt_parse_batch, &loop_ctx, 0);
+
+	if (!loop_ctx.option_timestamp)
+		return false;
+
+	cookie = tcp_time_stamp_raw() & ~TSMASK;
+	cookie |= loop_ctx.wscale & TS_OPT_WSCALE_MASK;
+	if (loop_ctx.option_sack)
+		cookie |= TS_OPT_SACK;
+	if (tcp_header->ece && tcp_header->cwr)
+		cookie |= TS_OPT_ECN;
+	*tsval = bpf_htonl(cookie);
+
+	return true;
+}
+
+static __always_inline void values_get_tcpipopts(__u16 *mss, __u8 *wscale,
+						 __u8 *ttl, bool ipv6)
+{
+	__u32 key = 0;
+	__u64 *value;
+
+	value = bpf_map_lookup_elem(&values, &key);
+	if (value && *value != 0) {
+		if (ipv6)
+			*mss = (*value >> 32) & 0xffff;
+		else
+			*mss = *value & 0xffff;
+		*wscale = (*value >> 16) & 0xf;
+		*ttl = (*value >> 24) & 0xff;
+		return;
+	}
+
+	*mss = ipv6 ? DEFAULT_MSS6 : DEFAULT_MSS4;
+	*wscale = DEFAULT_WSCALE;
+	*ttl = DEFAULT_TTL;
+}
+
+static __always_inline void values_inc_synacks(void)
+{
+	__u32 key = 1;
+	__u32 *value;
+
+	value = bpf_map_lookup_elem(&values, &key);
+	if (value)
+		__sync_fetch_and_add(value, 1);
+}
+
+static __always_inline bool check_port_allowed(__u16 port)
+{
+	__u32 i;
+
+	for (i = 0; i < MAX_ALLOWED_PORTS; i++) {
+		__u32 key = i;
+		__u16 *value;
+
+		value = bpf_map_lookup_elem(&allowed_ports, &key);
+
+		if (!value)
+			break;
+		// 0 is a terminator value. Check it first to avoid matching on
+		// a forbidden port == 0 and returning true.
+		if (*value == 0)
+			break;
+
+		if (*value == port)
+			return true;
+	}
+
+	return false;
+}
+
+struct header_pointers {
+	struct ethhdr *eth;
+	struct iphdr *ipv4;
+	struct ipv6hdr *ipv6;
+	struct tcphdr *tcp;
+	__u16 tcp_len;
+};
+
+static __always_inline int tcp_dissect(void *data, void *data_end,
+				       struct header_pointers *hdr)
+{
+	hdr->eth = data;
+	if (hdr->eth + 1 > data_end)
+		return XDP_DROP;
+
+	switch (bpf_ntohs(hdr->eth->h_proto)) {
+	case ETH_P_IP:
+		hdr->ipv6 = NULL;
+
+		hdr->ipv4 = (void *)hdr->eth + sizeof(*hdr->eth);
+		if (hdr->ipv4 + 1 > data_end)
+			return XDP_DROP;
+		if (hdr->ipv4->ihl * 4 < sizeof(*hdr->ipv4))
+			return XDP_DROP;
+		if (hdr->ipv4->version != 4)
+			return XDP_DROP;
+
+		if (hdr->ipv4->protocol != IPPROTO_TCP)
+			return XDP_PASS;
+
+		hdr->tcp = (void *)hdr->ipv4 + hdr->ipv4->ihl * 4;
+		break;
+	case ETH_P_IPV6:
+		hdr->ipv4 = NULL;
+
+		hdr->ipv6 = (void *)hdr->eth + sizeof(*hdr->eth);
+		if (hdr->ipv6 + 1 > data_end)
+			return XDP_DROP;
+		if (hdr->ipv6->version != 6)
+			return XDP_DROP;
+
+		// XXX: Extension headers are not supported and could circumvent
+		// XDP SYN flood protection.
+		if (hdr->ipv6->nexthdr != NEXTHDR_TCP)
+			return XDP_PASS;
+
+		hdr->tcp = (void *)hdr->ipv6 + sizeof(*hdr->ipv6);
+		break;
+	default:
+		// XXX: VLANs will circumvent XDP SYN flood protection.
+		return XDP_PASS;
+	}
+
+	if (hdr->tcp + 1 > data_end)
+		return XDP_DROP;
+	hdr->tcp_len = hdr->tcp->doff * 4;
+	if (hdr->tcp_len < sizeof(*hdr->tcp))
+		return XDP_DROP;
+
+	return XDP_TX;
+}
+
+static __always_inline int tcp_lookup(struct xdp_md *ctx, struct header_pointers *hdr)
+{
+	struct bpf_ct_opts ct_lookup_opts = {
+		.netns_id = BPF_F_CURRENT_NETNS,
+		.l4proto = IPPROTO_TCP,
+	};
+	struct bpf_sock_tuple tup = {};
+	struct nf_conn *ct;
+	__u32 tup_size;
+
+	if (hdr->ipv4) {
+		// TCP doesn't normally use fragments, and XDP can't reassemble them.
+		if ((hdr->ipv4->frag_off & bpf_htons(IP_DF | IP_MF | IP_OFFSET)) != bpf_htons(IP_DF))
+			return XDP_DROP;
+
+		tup.ipv4.saddr = hdr->ipv4->saddr;
+		tup.ipv4.daddr = hdr->ipv4->daddr;
+		tup.ipv4.sport = hdr->tcp->source;
+		tup.ipv4.dport = hdr->tcp->dest;
+		tup_size = sizeof(tup.ipv4);
+	} else if (hdr->ipv6) {
+		__builtin_memcpy(tup.ipv6.saddr, &hdr->ipv6->saddr, sizeof(tup.ipv6.saddr));
+		__builtin_memcpy(tup.ipv6.daddr, &hdr->ipv6->daddr, sizeof(tup.ipv6.daddr));
+		tup.ipv6.sport = hdr->tcp->source;
+		tup.ipv6.dport = hdr->tcp->dest;
+		tup_size = sizeof(tup.ipv6);
+	} else {
+		// The verifier can't track that either ipv4 or ipv6 is not NULL.
+		return XDP_ABORTED;
+	}
+	ct = bpf_xdp_ct_lookup(ctx, &tup, tup_size, &ct_lookup_opts, sizeof(ct_lookup_opts));
+	if (ct) {
+		unsigned long status = ct->status;
+
+		bpf_ct_release(ct);
+		if (status & IPS_CONFIRMED_BIT)
+			return XDP_PASS;
+	} else if (ct_lookup_opts.error != -ENOENT) {
+		return XDP_ABORTED;
+	}
+
+	// error == -ENOENT || !(status & IPS_CONFIRMED_BIT)
+	return XDP_TX;
+}
+
+static __always_inline __u8 tcp_mkoptions(__be32 *buf, __be32 *tsopt, __u16 mss,
+					  __u8 wscale)
+{
+	__be32 *start = buf;
+
+	*buf++ = bpf_htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | mss);
+
+	if (!tsopt)
+		return buf - start;
+
+	if (tsopt[0] & bpf_htonl(1 << 4))
+		*buf++ = bpf_htonl((TCPOPT_SACK_PERM << 24) |
+				   (TCPOLEN_SACK_PERM << 16) |
+				   (TCPOPT_TIMESTAMP << 8) |
+				   TCPOLEN_TIMESTAMP);
+	else
+		*buf++ = bpf_htonl((TCPOPT_NOP << 24) |
+				   (TCPOPT_NOP << 16) |
+				   (TCPOPT_TIMESTAMP << 8) |
+				   TCPOLEN_TIMESTAMP);
+	*buf++ = tsopt[0];
+	*buf++ = tsopt[1];
+
+	if ((tsopt[0] & bpf_htonl(0xf)) != bpf_htonl(0xf))
+		*buf++ = bpf_htonl((TCPOPT_NOP << 24) |
+				   (TCPOPT_WINDOW << 16) |
+				   (TCPOLEN_WINDOW << 8) |
+				   wscale);
+
+	return buf - start;
+}
+
+static __always_inline void tcp_gen_synack(struct tcphdr *tcp_header,
+					   __u32 cookie, __be32 *tsopt,
+					   __u16 mss, __u8 wscale)
+{
+	void *tcp_options;
+
+	tcp_flag_word(tcp_header) = TCP_FLAG_SYN | TCP_FLAG_ACK;
+	if (tsopt && (tsopt[0] & bpf_htonl(1 << 5)))
+		tcp_flag_word(tcp_header) |= TCP_FLAG_ECE;
+	tcp_header->doff = 5; // doff is part of tcp_flag_word.
+	swap(tcp_header->source, tcp_header->dest);
+	tcp_header->ack_seq = bpf_htonl(bpf_ntohl(tcp_header->seq) + 1);
+	tcp_header->seq = bpf_htonl(cookie);
+	tcp_header->window = 0;
+	tcp_header->urg_ptr = 0;
+	tcp_header->check = 0; // Rely on hardware checksum offload.
+
+	tcp_options = (void *)(tcp_header + 1);
+	tcp_header->doff += tcp_mkoptions(tcp_options, tsopt, mss, wscale);
+}
+
+static __always_inline void tcpv4_gen_synack(struct header_pointers *hdr,
+					     __u32 cookie, __be32 *tsopt)
+{
+	__u8 wscale;
+	__u16 mss;
+	__u8 ttl;
+
+	values_get_tcpipopts(&mss, &wscale, &ttl, false);
+
+	swap_eth_addr(hdr->eth->h_source, hdr->eth->h_dest);
+
+	swap(hdr->ipv4->saddr, hdr->ipv4->daddr);
+	hdr->ipv4->check = 0; // Rely on hardware checksum offload.
+	hdr->ipv4->tos = 0;
+	hdr->ipv4->id = 0;
+	hdr->ipv4->ttl = ttl;
+
+	tcp_gen_synack(hdr->tcp, cookie, tsopt, mss, wscale);
+
+	hdr->tcp_len = hdr->tcp->doff * 4;
+	hdr->ipv4->tot_len = bpf_htons(sizeof(*hdr->ipv4) + hdr->tcp_len);
+}
+
+static __always_inline void tcpv6_gen_synack(struct header_pointers *hdr,
+					     __u32 cookie, __be32 *tsopt)
+{
+	__u8 wscale;
+	__u16 mss;
+	__u8 ttl;
+
+	values_get_tcpipopts(&mss, &wscale, &ttl, true);
+
+	swap_eth_addr(hdr->eth->h_source, hdr->eth->h_dest);
+
+	swap(hdr->ipv6->saddr, hdr->ipv6->daddr);
+	*(__be32 *)hdr->ipv6 = bpf_htonl(0x60000000);
+	hdr->ipv6->hop_limit = ttl;
+
+	tcp_gen_synack(hdr->tcp, cookie, tsopt, mss, wscale);
+
+	hdr->tcp_len = hdr->tcp->doff * 4;
+	hdr->ipv6->payload_len = bpf_htons(hdr->tcp_len);
+}
+
+static __always_inline int syncookie_handle_syn(struct header_pointers *hdr,
+						struct xdp_md *ctx,
+						void *data, void *data_end)
+{
+	__u32 old_pkt_size, new_pkt_size;
+	// Unlike clang 10, clang 11 and 12 generate code that doesn't pass the
+	// BPF verifier if tsopt is not volatile. Volatile forces it to store
+	// the pointer value and use it directly, otherwise tcp_mkoptions is
+	// (mis)compiled like this:
+	//   if (!tsopt)
+	//       return buf - start;
+	//   reg = stored_return_value_of_tscookie_init;
+	//   if (reg)
+	//       tsopt = tsopt_buf;
+	//   else
+	//       tsopt = NULL;
+	//   ...
+	//   *buf++ = tsopt[1];
+	// It creates a dead branch where tsopt is assigned NULL, but the
+	// verifier can't prove it's dead and blocks the program.
+	__be32 * volatile tsopt = NULL;
+	__be32 tsopt_buf[2] = {};
+	__u16 ip_len;
+	__u32 cookie;
+	__s64 value;
+
+	// Checksum is not yet verified, but both checksum failure and TCP
+	// header checks return XDP_DROP, so the order doesn't matter.
+	if (hdr->tcp->fin || hdr->tcp->rst)
+		return XDP_DROP;
+
+	// Issue SYN cookies on allowed ports, drop SYN packets on blocked
+	// ports.
+	if (!check_port_allowed(bpf_ntohs(hdr->tcp->dest)))
+		return XDP_DROP;
+
+	if (hdr->ipv4) {
+		// Check the IPv4 and TCP checksums before creating a SYNACK.
+		value = bpf_csum_diff(0, 0, (void *)hdr->ipv4, hdr->ipv4->ihl * 4, 0);
+		if (value < 0)
+			return XDP_ABORTED;
+		if (csum_fold(value) != 0)
+			return XDP_DROP; // Bad IPv4 checksum.
+
+		value = bpf_csum_diff(0, 0, (void *)hdr->tcp, hdr->tcp_len, 0);
+		if (value < 0)
+			return XDP_ABORTED;
+		if (csum_tcpudp_magic(hdr->ipv4->saddr, hdr->ipv4->daddr,
+				      hdr->tcp_len, IPPROTO_TCP, value) != 0)
+			return XDP_DROP; // Bad TCP checksum.
+
+		ip_len = sizeof(*hdr->ipv4);
+
+		value = bpf_tcp_raw_gen_syncookie_ipv4(hdr->ipv4, hdr->tcp,
+						       hdr->tcp_len);
+	} else if (hdr->ipv6) {
+		// Check the TCP checksum before creating a SYNACK.
+		value = bpf_csum_diff(0, 0, (void *)hdr->tcp, hdr->tcp_len, 0);
+		if (value < 0)
+			return XDP_ABORTED;
+		if (csum_ipv6_magic(&hdr->ipv6->saddr, &hdr->ipv6->daddr,
+				    hdr->tcp_len, IPPROTO_TCP, value) != 0)
+			return XDP_DROP; // Bad TCP checksum.
+
+		ip_len = sizeof(*hdr->ipv6);
+
+		value = bpf_tcp_raw_gen_syncookie_ipv6(hdr->ipv6, hdr->tcp,
+						       hdr->tcp_len);
+	} else {
+		return XDP_ABORTED;
+	}
+
+	if (value < 0)
+		return XDP_ABORTED;
+	cookie = (__u32)value;
+
+	if (tscookie_init((void *)hdr->tcp, hdr->tcp_len,
+			  &tsopt_buf[0], &tsopt_buf[1], data_end))
+		tsopt = tsopt_buf;
+
+	// Check that there is enough space for a SYNACK. It also covers
+	// the check that the destination of the __builtin_memmove below
+	// doesn't overflow.
+	if (data + sizeof(*hdr->eth) + ip_len + TCP_MAXLEN > data_end)
+		return XDP_ABORTED;
+
+	if (hdr->ipv4) {
+		if (hdr->ipv4->ihl * 4 > sizeof(*hdr->ipv4)) {
+			struct tcphdr *new_tcp_header;
+
+			new_tcp_header = data + sizeof(*hdr->eth) + sizeof(*hdr->ipv4);
+			__builtin_memmove(new_tcp_header, hdr->tcp, sizeof(*hdr->tcp));
+			hdr->tcp = new_tcp_header;
+
+			hdr->ipv4->ihl = sizeof(*hdr->ipv4) / 4;
+		}
+
+		tcpv4_gen_synack(hdr, cookie, tsopt);
+	} else if (hdr->ipv6) {
+		tcpv6_gen_synack(hdr, cookie, tsopt);
+	} else {
+		return XDP_ABORTED;
+	}
+
+	// Recalculate checksums.
+	hdr->tcp->check = 0;
+	value = bpf_csum_diff(0, 0, (void *)hdr->tcp, hdr->tcp_len, 0);
+	if (value < 0)
+		return XDP_ABORTED;
+	if (hdr->ipv4) {
+		hdr->tcp->check = csum_tcpudp_magic(hdr->ipv4->saddr,
+						    hdr->ipv4->daddr,
+						    hdr->tcp_len,
+						    IPPROTO_TCP,
+						    value);
+
+		hdr->ipv4->check = 0;
+		value = bpf_csum_diff(0, 0, (void *)hdr->ipv4, sizeof(*hdr->ipv4), 0);
+		if (value < 0)
+			return XDP_ABORTED;
+		hdr->ipv4->check = csum_fold(value);
+	} else if (hdr->ipv6) {
+		hdr->tcp->check = csum_ipv6_magic(&hdr->ipv6->saddr,
+						  &hdr->ipv6->daddr,
+						  hdr->tcp_len,
+						  IPPROTO_TCP,
+						  value);
+	} else {
+		return XDP_ABORTED;
+	}
+
+	// Set the new packet size.
+	old_pkt_size = data_end - data;
+	new_pkt_size = sizeof(*hdr->eth) + ip_len + hdr->tcp->doff * 4;
+	if (bpf_xdp_adjust_tail(ctx, new_pkt_size - old_pkt_size))
+		return XDP_ABORTED;
+
+	values_inc_synacks();
+
+	return XDP_TX;
+}
+
+static __always_inline int syncookie_handle_ack(struct header_pointers *hdr)
+{
+	int err;
+
+	if (hdr->tcp->rst)
+		return XDP_DROP;
+
+	if (hdr->ipv4)
+		err = bpf_tcp_raw_check_syncookie_ipv4(hdr->ipv4, hdr->tcp);
+	else if (hdr->ipv6)
+		err = bpf_tcp_raw_check_syncookie_ipv6(hdr->ipv6, hdr->tcp);
+	else
+		return XDP_ABORTED;
+	if (err)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
+
+SEC("xdp/syncookie")
+int syncookie_xdp(struct xdp_md *ctx)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data = (void *)(long)ctx->data;
+	struct header_pointers hdr;
+	__s64 value;
+	int ret;
+
+	struct bpf_ct_opts ct_lookup_opts = {
+		.netns_id = BPF_F_CURRENT_NETNS,
+		.l4proto = IPPROTO_TCP,
+	};
+
+	ret = tcp_dissect(data, data_end, &hdr);
+	if (ret != XDP_TX)
+		return ret;
+
+	ret = tcp_lookup(ctx, &hdr);
+	if (ret != XDP_TX)
+		return ret;
+
+	// Packet is TCP and doesn't belong to an established connection.
+
+	if ((hdr.tcp->syn ^ hdr.tcp->ack) != 1)
+		return XDP_DROP;
+
+	// Grow the TCP header to TCP_MAXLEN to be able to pass any hdr.tcp_len
+	// to bpf_tcp_raw_gen_syncookie_ipv{4,6} and pass the verifier.
+	if (bpf_xdp_adjust_tail(ctx, TCP_MAXLEN - hdr.tcp_len))
+		return XDP_ABORTED;
+
+	data_end = (void *)(long)ctx->data_end;
+	data = (void *)(long)ctx->data;
+
+	if (hdr.ipv4) {
+		hdr.eth = data;
+		hdr.ipv4 = (void *)hdr.eth + sizeof(*hdr.eth);
+		// IPV4_MAXLEN is needed when calculating checksum.
+		// At least sizeof(struct iphdr) is needed here to access ihl.
+		if ((void *)hdr.ipv4 + IPV4_MAXLEN > data_end)
+			return XDP_ABORTED;
+		hdr.tcp = (void *)hdr.ipv4 + hdr.ipv4->ihl * 4;
+	} else if (hdr.ipv6) {
+		hdr.eth = data;
+		hdr.ipv6 = (void *)hdr.eth + sizeof(*hdr.eth);
+		hdr.tcp = (void *)hdr.ipv6 + sizeof(*hdr.ipv6);
+	} else {
+		return XDP_ABORTED;
+	}
+
+	if ((void *)hdr.tcp + TCP_MAXLEN > data_end)
+		return XDP_ABORTED;
+
+	// We run out of registers, tcp_len gets spilled to the stack, and the
+	// verifier forgets its min and max values checked above in tcp_dissect.
+	hdr.tcp_len = hdr.tcp->doff * 4;
+	if (hdr.tcp_len < sizeof(*hdr.tcp))
+		return XDP_ABORTED;
+
+	return hdr.tcp->syn ? syncookie_handle_syn(&hdr, ctx, data, data_end) :
+			      syncookie_handle_ack(&hdr);
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/xdp_synproxy.c b/tools/testing/selftests/bpf/xdp_synproxy.c
new file mode 100644
index 000000000000..2b9585f2bc00
--- /dev/null
+++ b/tools/testing/selftests/bpf/xdp_synproxy.c
@@ -0,0 +1,418 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
+
+#include <stdnoreturn.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <getopt.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+#include <net/if.h>
+#include <linux/if_link.h>
+#include <linux/limits.h>
+
+static unsigned int ifindex;
+static __u32 attached_prog_id;
+
+static void noreturn cleanup(int sig)
+{
+	DECLARE_LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
+	int prog_fd;
+	int err;
+
+	if (attached_prog_id == 0)
+		exit(0);
+
+	prog_fd = bpf_prog_get_fd_by_id(attached_prog_id);
+	if (prog_fd < 0) {
+		fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
+		err = bpf_xdp_attach(ifindex, -1, 0, NULL);
+		if (err < 0) {
+			fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n", strerror(-err));
+			fprintf(stderr, "Failed to detach XDP program\n");
+			exit(1);
+		}
+	} else {
+		opts.old_prog_fd = prog_fd;
+		err = bpf_xdp_attach(ifindex, -1, XDP_FLAGS_REPLACE, &opts);
+		close(prog_fd);
+		if (err < 0) {
+			fprintf(stderr, "Error: bpf_set_link_xdp_fd_opts: %s\n", strerror(-err));
+			// Not an error if already replaced by someone else.
+			if (err != -EEXIST) {
+				fprintf(stderr, "Failed to detach XDP program\n");
+				exit(1);
+			}
+		}
+	}
+	exit(0);
+}
+
+static noreturn void usage(const char *progname)
+{
+	fprintf(stderr, "Usage: %s [--iface <iface>|--prog <prog_id>] [--mss4 <mss ipv4> --mss6 <mss ipv6> --wscale <wscale> --ttl <ttl>] [--ports <port1>,<port2>,...] [--single]\n",
+		progname);
+	exit(1);
+}
+
+static unsigned long parse_arg_ul(const char *progname, const char *arg, unsigned long limit)
+{
+	unsigned long res;
+	char *endptr;
+
+	errno = 0;
+	res = strtoul(arg, &endptr, 10);
+	if (errno != 0 || *endptr != '\0' || arg[0] == '\0' || res > limit)
+		usage(progname);
+
+	return res;
+}
+
+static void parse_options(int argc, char *argv[], unsigned int *ifindex, __u32 *prog_id,
+			  __u64 *tcpipopts, char **ports, bool *single)
+{
+	static struct option long_options[] = {
+		{ "help", no_argument, NULL, 'h' },
+		{ "iface", required_argument, NULL, 'i' },
+		{ "prog", required_argument, NULL, 'x' },
+		{ "mss4", required_argument, NULL, 4 },
+		{ "mss6", required_argument, NULL, 6 },
+		{ "wscale", required_argument, NULL, 'w' },
+		{ "ttl", required_argument, NULL, 't' },
+		{ "ports", required_argument, NULL, 'p' },
+		{ "single", no_argument, NULL, 's' },
+		{ NULL, 0, NULL, 0 },
+	};
+	unsigned long mss4, mss6, wscale, ttl;
+	unsigned int tcpipopts_mask = 0;
+
+	if (argc < 2)
+		usage(argv[0]);
+
+	*ifindex = 0;
+	*prog_id = 0;
+	*tcpipopts = 0;
+	*ports = NULL;
+	*single = false;
+
+	while (true) {
+		int opt;
+
+		opt = getopt_long(argc, argv, "", long_options, NULL);
+		if (opt == -1)
+			break;
+
+		switch (opt) {
+		case 'h':
+			usage(argv[0]);
+			break;
+		case 'i':
+			*ifindex = if_nametoindex(optarg);
+			if (*ifindex == 0)
+				usage(argv[0]);
+			break;
+		case 'x':
+			*prog_id = parse_arg_ul(argv[0], optarg, UINT32_MAX);
+			if (*prog_id == 0)
+				usage(argv[0]);
+			break;
+		case 4:
+			mss4 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
+			tcpipopts_mask |= 1 << 0;
+			break;
+		case 6:
+			mss6 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
+			tcpipopts_mask |= 1 << 1;
+			break;
+		case 'w':
+			wscale = parse_arg_ul(argv[0], optarg, 14);
+			tcpipopts_mask |= 1 << 2;
+			break;
+		case 't':
+			ttl = parse_arg_ul(argv[0], optarg, UINT8_MAX);
+			tcpipopts_mask |= 1 << 3;
+			break;
+		case 'p':
+			*ports = optarg;
+			break;
+		case 's':
+			*single = true;
+			break;
+		default:
+			usage(argv[0]);
+		}
+	}
+	if (optind < argc)
+		usage(argv[0]);
+
+	if (tcpipopts_mask == 0xf) {
+		if (mss4 == 0 || mss6 == 0 || wscale == 0 || ttl == 0)
+			usage(argv[0]);
+		*tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
+	} else if (tcpipopts_mask != 0) {
+		usage(argv[0]);
+	}
+
+	if (*ifindex != 0 && *prog_id != 0)
+		usage(argv[0]);
+	if (*ifindex == 0 && *prog_id == 0)
+		usage(argv[0]);
+}
+
+static int syncookie_attach(const char *argv0, unsigned int ifindex)
+{
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
+	char xdp_filename[PATH_MAX];
+	struct bpf_program *prog;
+	struct bpf_object *obj;
+	int prog_fd;
+	int err;
+
+	snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.o", argv0);
+	obj = bpf_object__open_file(xdp_filename, NULL);
+	err = libbpf_get_error(obj);
+	if (err < 0) {
+		fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
+		return err;
+	}
+
+	err = bpf_object__load(obj);
+	if (err < 0) {
+		fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
+		return err;
+	}
+
+	prog = bpf_object__find_program_by_name(obj, "syncookie_xdp");
+	if (!prog) {
+		fprintf(stderr, "Error: bpf_object__find_program_by_name: program syncookie_xdp was not found\n");
+		return -ENOENT;
+	}
+
+	prog_fd = bpf_program__fd(prog);
+
+	err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
+	if (err < 0) {
+		fprintf(stderr, "Error: bpf_obj_get_info_by_fd: %s\n", strerror(-err));
+		goto out;
+	}
+	attached_prog_id = info.id;
+	signal(SIGINT, cleanup);
+	signal(SIGTERM, cleanup);
+	err = bpf_xdp_attach(ifindex, prog_fd, XDP_FLAGS_UPDATE_IF_NOEXIST, NULL);
+	if (err < 0) {
+		fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n", strerror(-err));
+		signal(SIGINT, SIG_DFL);
+		signal(SIGTERM, SIG_DFL);
+		attached_prog_id = 0;
+		goto out;
+	}
+	err = 0;
+out:
+	bpf_object__close(obj);
+	return err;
+}
+
+static int syncookie_open_bpf_maps(__u32 prog_id, int *values_map_fd, int *ports_map_fd)
+{
+	struct bpf_prog_info prog_info;
+	__u32 map_ids[8];
+	__u32 info_len;
+	int prog_fd;
+	int err;
+	int i;
+
+	*values_map_fd = -1;
+	*ports_map_fd = -1;
+
+	prog_fd = bpf_prog_get_fd_by_id(prog_id);
+	if (prog_fd < 0) {
+		fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
+		return prog_fd;
+	}
+
+	prog_info = (struct bpf_prog_info) {
+		.nr_map_ids = 8,
+		.map_ids = (__u64)map_ids,
+	};
+	info_len = sizeof(prog_info);
+
+	err = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &info_len);
+	if (err != 0) {
+		fprintf(stderr, "Error: bpf_obj_get_info_by_fd: %s\n", strerror(-err));
+		goto out;
+	}
+
+	if (prog_info.type != BPF_PROG_TYPE_XDP) {
+		fprintf(stderr, "Error: BPF prog type is not BPF_PROG_TYPE_XDP\n");
+		err = -ENOENT;
+		goto out;
+	}
+	if (prog_info.nr_map_ids < 2) {
+		fprintf(stderr, "Error: Found %u BPF maps, expected at least 2\n",
+			prog_info.nr_map_ids);
+		err = -ENOENT;
+		goto out;
+	}
+
+	for (i = 0; i < prog_info.nr_map_ids; i++) {
+		struct bpf_map_info map_info = {};
+		int map_fd;
+
+		err = bpf_map_get_fd_by_id(map_ids[i]);
+		if (err < 0) {
+			fprintf(stderr, "Error: bpf_map_get_fd_by_id: %s\n", strerror(-err));
+			goto err_close_map_fds;
+		}
+		map_fd = err;
+
+		info_len = sizeof(map_info);
+		err = bpf_obj_get_info_by_fd(map_fd, &map_info, &info_len);
+		if (err != 0) {
+			fprintf(stderr, "Error: bpf_obj_get_info_by_fd: %s\n", strerror(-err));
+			close(map_fd);
+			goto err_close_map_fds;
+		}
+		if (strcmp(map_info.name, "values") == 0) {
+			*values_map_fd = map_fd;
+			continue;
+		}
+		if (strcmp(map_info.name, "allowed_ports") == 0) {
+			*ports_map_fd = map_fd;
+			continue;
+		}
+		close(map_fd);
+	}
+
+	if (*values_map_fd != -1 && *ports_map_fd != -1) {
+		err = 0;
+		goto out;
+	}
+
+	err = -ENOENT;
+
+err_close_map_fds:
+	if (*values_map_fd != -1)
+		close(*values_map_fd);
+	if (*ports_map_fd != -1)
+		close(*ports_map_fd);
+	*values_map_fd = -1;
+	*ports_map_fd = -1;
+
+out:
+	close(prog_fd);
+	return err;
+}
+
+int main(int argc, char *argv[])
+{
+	int values_map_fd, ports_map_fd;
+	__u64 tcpipopts;
+	bool firstiter;
+	__u64 prevcnt;
+	__u32 prog_id;
+	char *ports;
+	bool single;
+	int err = 0;
+
+	parse_options(argc, argv, &ifindex, &prog_id, &tcpipopts, &ports, &single);
+
+	if (prog_id == 0) {
+		err = bpf_xdp_query_id(ifindex, 0, &prog_id);
+		if (err < 0) {
+			fprintf(stderr, "Error: bpf_get_link_xdp_id: %s\n", strerror(-err));
+			goto out;
+		}
+		if (prog_id == 0) {
+			err = syncookie_attach(argv[0], ifindex);
+			if (err < 0)
+				goto out;
+			prog_id = attached_prog_id;
+		}
+	}
+
+	err = syncookie_open_bpf_maps(prog_id, &values_map_fd, &ports_map_fd);
+	if (err < 0)
+		goto out;
+
+	if (ports) {
+		__u16 port_last = 0;
+		__u32 port_idx = 0;
+		char *p = ports;
+
+		fprintf(stderr, "Replacing allowed ports\n");
+
+		while (p && *p != '\0') {
+			char *token = strsep(&p, ",");
+			__u16 port;
+
+			port = parse_arg_ul(argv[0], token, UINT16_MAX);
+			err = bpf_map_update_elem(ports_map_fd, &port_idx, &port, BPF_ANY);
+			if (err != 0) {
+				fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
+				fprintf(stderr, "Failed to add port %u (index %u)\n",
+					port, port_idx);
+				goto out_close_maps;
+			}
+			fprintf(stderr, "Added port %u\n", port);
+			port_idx++;
+		}
+		err = bpf_map_update_elem(ports_map_fd, &port_idx, &port_last, BPF_ANY);
+		if (err != 0) {
+			fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
+			fprintf(stderr, "Failed to add the terminator value 0 (index %u)\n",
+				port_idx);
+			goto out_close_maps;
+		}
+	}
+
+	if (tcpipopts) {
+		__u32 key = 0;
+
+		fprintf(stderr, "Replacing TCP/IP options\n");
+
+		err = bpf_map_update_elem(values_map_fd, &key, &tcpipopts, BPF_ANY);
+		if (err != 0) {
+			fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
+			goto out_close_maps;
+		}
+	}
+
+	if ((ports || tcpipopts) && attached_prog_id == 0 && !single)
+		goto out_close_maps;
+
+	prevcnt = 0;
+	firstiter = true;
+	while (true) {
+		__u32 key = 1;
+		__u64 value;
+
+		err = bpf_map_lookup_elem(values_map_fd, &key, &value);
+		if (err != 0) {
+			fprintf(stderr, "Error: bpf_map_lookup_elem: %s\n", strerror(-err));
+			goto out_close_maps;
+		}
+		if (firstiter) {
+			prevcnt = value;
+			firstiter = false;
+		}
+		if (single) {
+			printf("Total SYNACKs generated: %llu\n", value);
+			break;
+		}
+		printf("SYNACKs generated: %llu (total %llu)\n", value - prevcnt, value);
+		prevcnt = value;
+		sleep(1);
+	}
+
+out_close_maps:
+	close(values_map_fd);
+	close(ports_map_fd);
+out:
+	return err == 0 ? 0 : 1;
+}
-- 
2.30.2