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tcp: fix forever orphan socket caused by tcp_abort

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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@google.com/
Fixes: c1e64e298b ("net: diag: Support destroying TCP sockets.")
Signed-off-by: Xueming Feng <kuro@kuroa.me>
Tested-by: Lorenzo Colitti <lorenzo@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20240826102327.1461482-1-kuro@kuroa.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Xueming Feng 2024-08-26 18:23:27 +08:00 committed by Jakub Kicinski
parent defd8b3c37
commit bac76cf898
1 changed files with 11 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
net/ipv4/tcp.c
View File

@ -4637,6 +4637,13 @@ int tcp_abort(struct sock *sk, int err)
/* Don't race with userspace socket closes such as tcp_close. */
lock_sock(sk);
/* Avoid closing the same socket twice. */
if (sk->sk_state == TCP_CLOSE) {
if (!has_current_bpf_ctx())
release_sock(sk);
return -ENOENT;
}
if (sk->sk_state == TCP_LISTEN) {
tcp_set_state(sk, TCP_CLOSE);
inet_csk_listen_stop(sk);
@ -4646,16 +4653,13 @@ int tcp_abort(struct sock *sk, int err)
local_bh_disable();
bh_lock_sock(sk);
if (!sock_flag(sk, SOCK_DEAD)) {
if (tcp_need_reset(sk->sk_state))
tcp_send_active_reset(sk, GFP_ATOMIC,
SK_RST_REASON_NOT_SPECIFIED);
tcp_done_with_error(sk, err);
}
if (tcp_need_reset(sk->sk_state))
tcp_send_active_reset(sk, GFP_ATOMIC,
SK_RST_REASON_NOT_SPECIFIED);
tcp_done_with_error(sk, err);
bh_unlock_sock(sk);
local_bh_enable();
tcp_write_queue_purge(sk);
if (!has_current_bpf_ctx())
release_sock(sk);
return 0;