[PATCH bpf-next v2 0/9] Introduce unstable CT lookup helpers

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

This series adds unstable conntrack lookup helpers using BPF kfunc support.  The
patch adding the lookup helper is based off of Maxim's recent patch to aid in
rebasing their series on top of this, all adjusted to work with module kfuncs [0].

  [0]: https://lore.kernel.org/bpf/20211019144655.3483197-8-maximmi@nvidia.com

To enable returning a reference to struct nf_conn, the verifier is extended to
support reference tracking for PTR_TO_BTF_ID, and kfunc is extended with support
for working as acquire/release functions, similar to existing BPF helpers. kfunc
returning pointer (limited to PTR_TO_BTF_ID in the kernel) can also return a
PTR_TO_BTF_ID_OR_NULL now, typically needed when acquiring a resource can fail.
kfunc can also receive PTR_TO_CTX and PTR_TO_MEM (with some limitations) as
arguments now. There is also support for passing a mem, len pair as argument
to kfunc now. In such cases, passing pointer to unsized type (void) is also
permitted.

Please see individual commits for details.

Note 1: Patch 1 in this series makes the same change as b12f03104324 ("bpf: Fix
bpf_check_mod_kfunc_call for built-in modules") in bpf tree, so there will be a
conflict if patch 1 is applied against that commit. I incorporated the same diff
change so that testing this set is possible (tests in patch 8 rely on it), but
before applying this, I'll rebase and resend, after bpf tree is merged into
bpf-next.

Note 2: BPF CI needs to add the following to config to test the set. I did
update the selftests config in patch 8, but not sure if that is enough.

	CONFIG_NETFILTER=y
	CONFIG_NF_DEFRAG_IPV4=y
	CONFIG_NF_DEFRAG_IPV6=y
	CONFIG_NF_CONNTRACK=y

Changelog:
----------

RFC v1 -> v2:
v1: https://lore.kernel.org/bpf/20211030144609.263572-1-memxor@gmail.com

 * Limit PTR_TO_MEM support to pointer to scalar, or struct with scalars (Alexei)
 * Use btf_id_set for checking acquire, release, ret type null (Alexei)
 * Introduce opts struct for CT helpers, move int err parameter to it
 * Add l4proto as parameter to CT helper's opts, remove separate tcp/udp helpers
 * Add support for mem, len argument pair to kfunc
 * Allow void * as pointer type for mem, len argument pair
 * Extend selftests to cover new additions to kfuncs
 * Copy ref_obj_id to PTR_TO_BTF_ID dst_reg on btf_struct_access, test it
 * Fix other misc nits, bugs, and expand commit messages

Kumar Kartikeya Dwivedi (9):
  bpf: Refactor bpf_check_mod_kfunc_call
  bpf: Remove DEFINE_KFUNC_BTF_ID_SET
  bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support
  bpf: Introduce mem, size argument pair support for kfunc
  bpf: Add reference tracking support to kfunc
  bpf: Track provenance for pointers formed from referenced
    PTR_TO_BTF_ID
  net/netfilter: Add unstable CT lookup helpers for XDP and TC-BPF
  selftests/bpf: Extend kfunc selftests
  selftests/bpf: Add test for unstable CT lookup API

 include/linux/bpf.h                           |  27 +-
 include/linux/bpf_verifier.h                  |  12 +
 include/linux/btf.h                           |  48 +++-
 kernel/bpf/btf.c                              | 218 ++++++++++++---
 kernel/bpf/verifier.c                         | 232 +++++++++++-----
 net/bpf/test_run.c                            | 147 ++++++++++
 net/core/filter.c                             |  27 ++
 net/core/net_namespace.c                      |   1 +
 net/ipv4/tcp_bbr.c                            |   5 +-
 net/ipv4/tcp_cubic.c                          |   5 +-
 net/ipv4/tcp_dctcp.c                          |   5 +-
 net/netfilter/nf_conntrack_core.c             | 252 ++++++++++++++++++
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |   5 +-
 tools/testing/selftests/bpf/config            |   4 +
 .../testing/selftests/bpf/prog_tests/bpf_nf.c |  48 ++++
 .../selftests/bpf/prog_tests/kfunc_call.c     |  28 ++
 .../selftests/bpf/progs/kfunc_call_test.c     |  52 +++-
 .../bpf/progs/kfunc_call_test_fail1.c         |  16 ++
 .../bpf/progs/kfunc_call_test_fail2.c         |  16 ++
 .../bpf/progs/kfunc_call_test_fail3.c         |  16 ++
 .../bpf/progs/kfunc_call_test_fail4.c         |  16 ++
 .../bpf/progs/kfunc_call_test_fail5.c         |  16 ++
 .../bpf/progs/kfunc_call_test_fail6.c         |  16 ++
 .../bpf/progs/kfunc_call_test_fail7.c         |  24 ++
 .../bpf/progs/kfunc_call_test_fail8.c         |  22 ++
 .../testing/selftests/bpf/progs/test_bpf_nf.c | 113 ++++++++
 26 files changed, 1259 insertions(+), 112 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_nf.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail1.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail2.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail3.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail4.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail5.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail6.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail7.c
 create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_test_fail8.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_bpf_nf.c

-- 
2.34.1