git: cc3c34859eab - main - tcp: fix handling of TCP RST segments missing timestamps

[Michael Tuexen]

The branch main has been updated by tuexen:

URL: https://cgit.FreeBSD.org/src/commit/?id=cc3c34859eab1b317d0f38731355b53f7d978c97

commit cc3c34859eab1b317d0f38731355b53f7d978c97
Author:     Michael Tuexen <tuexen at FreeBSD.org>
AuthorDate: 2021-01-13 22:43:40 +0000
Commit:     Michael Tuexen <tuexen at FreeBSD.org>
CommitDate: 2021-01-14 13:39:35 +0000

    tcp: fix handling of TCP RST segments missing timestamps
    
    A TCP RST segment should be processed even it is missing TCP
    timestamps.
    
    Reported by:            dmgk@, kevans@
    Reviewed by:            rscheff@, dmgk@
    Sponsored by:           Netflix, Inc.
    MFC after:              3 days
    Differential Revision:  https://reviews.freebsd.org/D28143
---
 sys/netinet/tcp_input.c       | 21 +++++++++++++++------
 sys/netinet/tcp_stacks/bbr.c  |  5 +++--
 sys/netinet/tcp_stacks/rack.c |  5 +++--
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 7746ccf24073..dda37d4795c9 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1692,16 +1692,25 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
 	/*
 	 * If timestamps were negotiated during SYN/ACK and a
 	 * segment without a timestamp is received, silently drop
-	 * the segment.
+	 * the segment, unless it is a RST segment.
 	 * See section 3.2 of RFC 7323.
 	 */
 	if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
-		if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
-			log(LOG_DEBUG, "%s; %s: Timestamp missing, "
-			    "segment silently dropped\n", s, __func__);
-			free(s, M_TCPLOG);
+		if ((thflags & TH_RST) != 0) {
+			if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
+				log(LOG_DEBUG, "%s; %s: Timestamp missing, "
+				    "segment processed normally\n",
+				    s, __func__);
+				free(s, M_TCPLOG);
+			}
+		} else {
+			if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
+				log(LOG_DEBUG, "%s; %s: Timestamp missing, "
+				    "segment silently dropped\n", s, __func__);
+				free(s, M_TCPLOG);
+			}
+			goto drop;
 		}
-		goto drop;
 	}
 	/*
 	 * If timestamps were not negotiated during SYN/ACK and a
diff --git a/sys/netinet/tcp_stacks/bbr.c b/sys/netinet/tcp_stacks/bbr.c
index ccf138f70719..e59d9b9ff168 100644
--- a/sys/netinet/tcp_stacks/bbr.c
+++ b/sys/netinet/tcp_stacks/bbr.c
@@ -11463,10 +11463,11 @@ bbr_do_segment_nounlock(struct mbuf *m, struct tcphdr *th, struct socket *so,
 	/*
 	 * If timestamps were negotiated during SYN/ACK and a
 	 * segment without a timestamp is received, silently drop
-	 * the segment.
+	 * the segment, unless it is a RST segment.
 	 * See section 3.2 of RFC 7323.
 	 */
-	if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
+	if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS) &&
+	    ((thflags & TH_RST) == 0)) {
 		retval = 0;
 		goto done_with_input;
 	}
diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c
index c225377807ba..7c81e8b3a2bc 100644
--- a/sys/netinet/tcp_stacks/rack.c
+++ b/sys/netinet/tcp_stacks/rack.c
@@ -10879,10 +10879,11 @@ rack_do_segment_nounlock(struct mbuf *m, struct tcphdr *th, struct socket *so,
 	/*
 	 * If timestamps were negotiated during SYN/ACK and a
 	 * segment without a timestamp is received, silently drop
-	 * the segment.
+	 * the segment, unless it is a RST segment.
 	 * See section 3.2 of RFC 7323.
 	 */
-	if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
+	if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS) &&
+	    ((thflags & TH_RST) == 0)) {
 		way_out = 5;
 		retval = 0;
 		goto done_with_input;