On Wed, Jan 22, 2025 at 06:09 PM +08, Jiayuan Chen wrote: > 'sk->copied_seq' was updated 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. > > It 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 duplicate > 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. > > We do not want to add new proto_ops to implement a new version of > tcp_read_sock, as this would introduce code complexity [1]. > > We could have added noack and copied_seq to desc, and then called > ops->read_sock. However, unfortunately, other modules didn’t fully > initialize desc to zero. So, for now, we are directly calling > tcp_read_sock_noack() in tcp_bpf.c. > > [1]: https://lore.kernel.org/bpf/20241218053408.437295-1-mr...@163.com > Fixes: e5c6de5fa025 ("bpf, sockmap: Incorrectly handling copied_seq") > Suggested-by: Jakub Sitnicki <ja...@cloudflare.com> > Signed-off-by: Jiayuan Chen <mr...@163.com> > ---
I'm happy with how this turned out, but let's run it by Eric. Reviewed-by: Jakub Sitnicki <ja...@cloudflare.com>
