Date: Mon, 8 Jan 2024 18:39:57 GMT From: Richard Scheffenegger <rscheff@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: f4574e2dc5a4 - main - tcp: prevent spurious empty segments and fix uncommon panic Message-ID: <202401081839.408Idvbr023938@gitrepo.freebsd.org>
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The branch main has been updated by rscheff: URL: https://cgit.FreeBSD.org/src/commit/?id=f4574e2dc5a4719379496338257526aba484751b commit f4574e2dc5a4719379496338257526aba484751b Author: Richard Scheffenegger <rscheff@FreeBSD.org> AuthorDate: 2024-01-08 08:25:39 +0000 Commit: Richard Scheffenegger <rscheff@FreeBSD.org> CommitDate: 2024-01-08 09:52:49 +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: fengdreamer@126.com Reviewed by: cc, tuexen, #transport MFC after: 1 week Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D43343 --- 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 4a6100fc969b..0014c11d9daa 100644 --- a/sys/netinet/tcp_input.c +++ b/sys/netinet/tcp_input.c @@ -1866,7 +1866,13 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th, tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 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) tcp_output(tp); goto check_delack; } @@ -2033,6 +2039,8 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th, 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.
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