[bpf,v4,0/3] bpf: fix wrong copied_seq calculation

Message

Jiayuan Chen Jan. 9, 2025, 3:40 a.m. UTC

A previous commit described in this topic
http://lore.kernel.org/bpf/[e-mail]
directly updated 'sk->copied_seq' in the tcp_eat_skb() function when the
action of a BPF program was SK_REDIRECT. For other actions, like SK_PASS,
the update logic for 'sk->copied_seq' was moved to
tcp_bpf_recvmsg_parser() to ensure the accuracy of the 'fionread' feature.

That commit works for a single stream_verdict scenario, as it also
modified 'sk_data_ready->sk_psock_verdict_data_ready->tcp_read_skb'
to remove updating 'sk->copied_seq'.

However, for programs where both stream_parser and stream_verdict are
active(strparser purpose), tcp_read_sock() was used instead of
tcp_read_skb() (sk_data_ready->strp_data_ready->tcp_read_sock)
tcp_read_sock() now still update 'sk->copied_seq', leading to duplicated
updates.

In summary, for strparser + SK_PASS, copied_seq is redundantly calculated
in both tcp_read_sock() and tcp_bpf_recvmsg_parser().

The issue causes incorrect copied_seq calculations, which prevent
correct data reads from the recv() interface in user-land.

Also we added test cases for bpf + strparser and separated them from
sockmap_basic, as strparser has more encapsulation and parsing
capabilities compared to sockmap.

Fixes: e5c6de5fa025 ("bpf, sockmap: Incorrectly handling copied_seq")

---
V3 -> v4:
https://lore.kernel.org/bpf/[e-mail]/
Avoid introducing new proto_ops. (Daniel Borkmann).
Add more edge test cases for strparser + bpf.
Fix patchwork fail of test cases code.

V1 -> V3:
https://lore.kernel.org/bpf/[e-mail]/
Fix patchwork fail by adding Fixes tag.
Save skb data offset for ENOMEM. (John Fastabend)
---

Jiayuan Chen (3):
  bpf: fix wrong copied_seq calculation
  selftests/bpf: add strparser test for bpf
  bpf, strparser, docs: Add new callback for bpf

 Documentation/networking/strparser.rst        |  11 +-
 include/linux/skmsg.h                         |   2 +
 include/net/strparser.h                       |   2 +
 include/net/tcp.h                             |   3 +
 net/core/skmsg.c                              |  42 ++
 net/ipv4/tcp.c                                |  31 +-
 net/strparser/strparser.c                     |  11 +-
 .../selftests/bpf/prog_tests/sockmap_basic.c  |  53 --
 .../selftests/bpf/prog_tests/sockmap_strp.c   | 452 ++++++++++++++++++
 .../selftests/bpf/progs/test_sockmap_strp.c   |  53 ++
 10 files changed, 599 insertions(+), 61 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sockmap_strp.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_strp.c