On Mon, Aug 26, 2024 at 12:23 PM Xueming Feng <kuro@xxxxxxxx> wrote: > > We have some problem closing zero-window fin-wait-1 tcp sockets in our > environment. This patch come from the investigation. > > Previously tcp_abort only sends out reset and calls tcp_done when the > socket is not SOCK_DEAD, aka orphan. For orphan socket, it will only > purging the write queue, but not close the socket and left it to the > timer. > > While purging the write queue, tp->packets_out and sk->sk_write_queue > is cleared along the way. However tcp_retransmit_timer have early > return based on !tp->packets_out and tcp_probe_timer have early > return based on !sk->sk_write_queue. > > This caused ICSK_TIME_RETRANS and ICSK_TIME_PROBE0 not being resched > and socket not being killed by the timers, converting a zero-windowed > orphan into a forever orphan. > > This patch removes the SOCK_DEAD check in tcp_abort, making it send > reset to peer and close the socket accordingly. Preventing the > timer-less orphan from happening. > > According to Lorenzo's email in the v1 thread, the check was there to > prevent force-closing the same socket twice. That situation is handled > by testing for TCP_CLOSE inside lock, and returning -ENOENT if it is > already closed. > > The -ENOENT code comes from the associate patch Lorenzo made for > iproute2-ss; link attached below, which also conform to RFC 9293. > > At the end of the patch, tcp_write_queue_purge(sk) is removed because it > was already called in tcp_done_with_error(). > > p.s. This is the same patch with v2. Resent due to mis-labeled "changes > requested" on patchwork.kernel.org. > > Link: https://patchwork.ozlabs.org/project/netdev/patch/1450773094-7978-3-git-send-email-lorenzo@xxxxxxxxxx/ > Fixes: c1e64e298b8c ("net: diag: Support destroying TCP sockets.") > Signed-off-by: Xueming Feng <kuro@xxxxxxxx> > Tested-by: Lorenzo Colitti <lorenzo@xxxxxxxxxx> > Reviewed-by: Jason Xing <kerneljasonxing@xxxxxxxxx> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
