Re: [PATCH bpf v9 0/5] bpf: fix wrong copied_seq calculation and add tests

Jakub Sitnicki
2025-01-26T14:16:51Z

On Wed, Jan 22, 2025 at 06:09 PM +08, Jiayuan Chen wrote:
> A previous commit described in this topic
> http://lore.kernel.org/bpf/20230523025618.113937-9-john.fastabend@gmail.com
> 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 updates '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.
>
> ---
> V8 -> v9
> https://lore.kernel.org/bpf/20250121050707.55523-1-mrpre@163.com/
> Fixed some issues suggested by Jakub Sitnicki.
>
> V7 -> V8
> https://lore.kernel.org/bpf/20250116140531.108636-1-mrpre@163.com/
> Avoid using add read_sock to psock. (Jakub Sitnicki)
> Avoid using warpper function to check whether strparser is supported.
>
> V3 -> V7:
> https://lore.kernel.org/bpf/20250109094402.50838-1-mrpre@163.com/
> https://lore.kernel.org/bpf/20241218053408.437295-1-mrpre@163.com/
> Avoid introducing new proto_ops. (Jakub Sitnicki).
> Add more edge test cases for strparser + bpf.
> Fix patchwork fail of test cases code.
> Fix psock fetch without rcu lock.
> Move code of modifying to tcp_bpf.c.
>
> V1 -> V3:
> https://lore.kernel.org/bpf/20241209152740.281125-1-mrpre@163.com/
> Fix patchwork fail by adding Fixes tag.
> Save skb data offset for ENOMEM. (John Fastabend)
> ---

Thanks for addressing all feedback, Jiayuan. Series LGTM.
Feel free to carry my tags if there is another iteration.

-jkbs