git: 2751e264dfef - releng/13.0 - tcp: improve behaviour when using TCP_NOOPT

[Michael Tuexen]

The branch releng/13.0 has been updated by tuexen:

URL: https://cgit.FreeBSD.org/src/commit/?id=2751e264dfef1e59e9c45d511a2d3ee99839651e

commit 2751e264dfef1e59e9c45d511a2d3ee99839651e
Author:     Michael Tuexen <tuexen at FreeBSD.org>
AuthorDate: 2021-02-14 11:10:31 +0000
Commit:     Michael Tuexen <tuexen at FreeBSD.org>
CommitDate: 2021-03-02 15:17:25 +0000

    tcp: improve behaviour when using TCP_NOOPT
    
    Use ISS for SEG.SEQ when sending a SYN-ACK segment in response to
    an SYN segment received in the SYN-SENT state on a socket having
    the IPPROTO_TCP level socket option TCP_NOOPT enabled.
    
    Approved by:            re (gjb)
    Reviewed by:            rscheff
    Sponsored by:           Netflix, Inc.
    Differential Revision:  https://reviews.freebsd.org/D28656
    
    (cherry picked from commit ed782b9f5a7a05debe944a33b4ac9e5629a95803)
    (cherry picked from commit e949dcc283cd3b19e8e3113d8d3e10a72c2bbe6e)
---
 sys/netinet/tcp_output.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index cacc0c51bd8e..b4c7ab0a1ab7 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -785,6 +785,10 @@ send:
 #endif
 		hdrlen = sizeof (struct tcpiphdr);
 
+	if (flags & TH_SYN) {
+		tp->snd_nxt = tp->iss;
+	}
+
 	/*
 	 * Compute options for segment.
 	 * We only have to care about SYN and established connection
@@ -795,7 +799,6 @@ send:
 	if ((tp->t_flags & TF_NOOPT) == 0) {
 		/* Maximum segment size. */
 		if (flags & TH_SYN) {
-			tp->snd_nxt = tp->iss;
 			to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
 			to.to_flags |= TOF_MSS;