The branch stable/13 has been updated by rscheff:
URL:
https://cgit.FreeBSD.org/src/commit/?id=04719681ba76a0756492b42313ea744503b78358
commit 04719681ba76a0756492b42313ea744503b78358
Author: Richard Scheffenegger <rsch...@freebsd.org>
AuthorDate: 2024-01-08 08:25:39 +0000
Commit: Richard Scheffenegger <rsch...@freebsd.org>
CommitDate: 2024-01-15 05:22:17 +0000
tcp: prevent spurious empty segments and fix uncommon panic
Only try sending more data on pure ACKs when there is
more data available in the send buffer.
In the case of a retransmitted SYN not being sent due to
an internal error, the snd_una/snd_nxt accounting could
be off, leading to a panic. Pulling snd_nxt up to snd_una
prevents this from happening.
Reported by: fengdrea...@126.com
Reviewed by: cc, tuexen, #transport
MFC after: 1 week
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D43343
(cherry picked from commit f4574e2dc5a4719379496338257526aba484751b)
---
sys/netinet/tcp_input.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 262e95d08071..af6afbd271bb 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1943,7 +1943,13 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct
socket *so,
tcp_timer_activate(tp, TT_REXMT,
tp->t_rxtcur);
sowwakeup(so);
- if (sbavail(&so->so_snd))
+ /*
+ * Only call tcp_output when there
+ * is new data available to be sent
+ * or we need to send an ACK.
+ */
+ if (SEQ_GT(tp->snd_una + sbavail(&so->so_snd),
+ tp->snd_max) || tp->t_flags & TF_ACKNOW)
(void) tp->t_fb->tfb_tcp_output(tp);
goto check_delack;
}
@@ -2112,6 +2118,8 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct
socket *so,
tp->rcv_adv += min(tp->rcv_wnd,
TCP_MAXWIN << tp->rcv_scale);
tp->snd_una++; /* SYN is acked */
+ if (SEQ_LT(tp->snd_nxt, tp->snd_una))
+ tp->snd_nxt = tp->snd_una;
/*
* If not all the data that was sent in the TFO SYN
* has been acked, resend the remainder right away.
