From 853fd7a2e39802e46bd3d6476529796ac22412d9 Mon Sep 17 00:00:00 2001 From: Richard Scheffenegger Date: Fri, 19 Feb 2021 13:52:06 +0100 Subject: [PATCH] Ensure cwnd doesn't shrink to zero with PRR Under some circumstances, PRR may end up with a fully collapsed cwnd when finalizing the loss recovery. Reviewed By: #transport, kbowling Reported by: Liang Tian MFC after: 1 week Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D28780 --- sys/netinet/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c index dbe86e4e65c..39039fe5b9a 100644 --- a/sys/netinet/tcp_input.c +++ b/sys/netinet/tcp_input.c @@ -3990,8 +3990,8 @@ tcp_prr_partialack(struct tcpcb *tp, struct tcphdr *th) * If there is going to be a SACK retransmission, adjust snd_cwnd * accordingly. */ - tp->snd_cwnd = tp->snd_nxt - tp->snd_recover + - tp->sackhint.sack_bytes_rexmit + (snd_cnt * maxseg); + tp->snd_cwnd = max(maxseg, (int64_t)tp->snd_nxt - tp->snd_recover + + tp->sackhint.sack_bytes_rexmit + (snd_cnt * maxseg)); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); }