svn commit: r359487 - in head: share/man/man4 sys/netinet sys/netinet/tcp_stacks
Michael Tuexen
tuexen at FreeBSD.org
Tue Mar 31 16:00:56 UTC 2020
Author: tuexen
Date: Tue Mar 31 15:54:54 2020
New Revision: 359487
URL: https://svnweb.freebsd.org/changeset/base/359487
Log:
Allow the TCP backhole detection to be disabled at all, enabled only
for IPv4, enabled only for IPv6, and enabled for IPv4 and IPv6.
The current blackhole detection might classify a temporary outage as
an MTU issue and reduces permanently the MSS. Since the consequences of
such a reduction due to a misclassification are much more drastically
for IPv4 than for IPv6, allow the administrator to enable it for IPv6 only.
Reviewed by: bcr@ (man page), Richard Scheffenegger
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D24219
Modified:
head/share/man/man4/tcp.4
head/sys/netinet/tcp_stacks/bbr.c
head/sys/netinet/tcp_stacks/rack.c
head/sys/netinet/tcp_timer.c
Modified: head/share/man/man4/tcp.4
==============================================================================
--- head/share/man/man4/tcp.4 Tue Mar 31 15:47:55 2020 (r359486)
+++ head/share/man/man4/tcp.4 Tue Mar 31 15:54:54 2020 (r359487)
@@ -34,7 +34,7 @@
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
-.Dd March 29, 2020
+.Dd March 31, 2020
.Dt TCP 4
.Os
.Sh NAME
@@ -628,21 +628,31 @@ specific connection.
This is needed to help with connection establishment
when a broken firewall is in the network path.
.It Va pmtud_blackhole_detection
-Turn on automatic path MTU blackhole detection.
-In case of retransmits OS will
-lower the MSS to check if it's MTU problem.
-If current MSS is greater than
-configured value to try
+Enable automatic path MTU blackhole detection.
+In case of retransmits of MSS sized segments,
+the OS will lower the MSS to check if it's an MTU problem.
+If the current MSS is greater than the configured value to try
.Po Va net.inet.tcp.pmtud_blackhole_mss
and
.Va net.inet.tcp.v6pmtud_blackhole_mss
.Pc ,
it will be set to this value, otherwise,
-MSS will be set to default values
+the MSS will be set to the default values
.Po Va net.inet.tcp.mssdflt
and
.Va net.inet.tcp.v6mssdflt
.Pc .
+Settings:
+.Bl -tag -compact
+.It 0
+Disable path MTU blackhole detection.
+.It 1
+Enable path MTU blackhole detection for IPv4 and IPv6.
+.It 2
+Enable path MTU blackhole detection only for IPv4.
+.It 3
+Enable path MTU blackhole detection only for IPv6.
+.El
.It Va pmtud_blackhole_mss
MSS to try for IPv4 if PMTU blackhole detection is turned on.
.It Va v6pmtud_blackhole_mss
Modified: head/sys/netinet/tcp_stacks/bbr.c
==============================================================================
--- head/sys/netinet/tcp_stacks/bbr.c Tue Mar 31 15:47:55 2020 (r359486)
+++ head/sys/netinet/tcp_stacks/bbr.c Tue Mar 31 15:54:54 2020 (r359487)
@@ -5041,6 +5041,7 @@ bbr_timeout_rxt(struct tcpcb *tp, struct tcp_bbr *bbr,
{
int32_t rexmt;
int32_t retval = 0;
+ bool isipv6;
bbr->r_ctl.rc_hpts_flags &= ~PACE_TMR_RXT;
if (bbr->rc_all_timers_stopped) {
@@ -5127,11 +5128,16 @@ bbr_timeout_rxt(struct tcpcb *tp, struct tcp_bbr *bbr,
* of packets and process straight to FIN. In that case we won't
* catch ESTABLISHED state.
*/
- if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
- || (tp->t_state == TCPS_FIN_WAIT_1))) {
#ifdef INET6
- int32_t isipv6;
+ isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? true : false;
+#else
+ isipv6 = false;
#endif
+ if (((V_tcp_pmtud_blackhole_detect == 1) ||
+ (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
+ (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
+ ((tp->t_state == TCPS_ESTABLISHED) ||
+ (tp->t_state == TCPS_FIN_WAIT_1))) {
/*
* Idea here is that at each stage of mtu probe (usually,
Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c Tue Mar 31 15:47:55 2020 (r359486)
+++ head/sys/netinet/tcp_stacks/rack.c Tue Mar 31 15:54:54 2020 (r359487)
@@ -3123,6 +3123,7 @@ rack_timeout_rxt(struct tcpcb *tp, struct tcp_rack *ra
int32_t rexmt;
struct inpcb *inp;
int32_t retval = 0;
+ bool isipv6;
inp = tp->t_inpcb;
if (tp->t_timers->tt_flags & TT_STOPPED) {
@@ -3209,11 +3210,16 @@ rack_timeout_rxt(struct tcpcb *tp, struct tcp_rack *ra
* of packets and process straight to FIN. In that case we won't
* catch ESTABLISHED state.
*/
- if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
- || (tp->t_state == TCPS_FIN_WAIT_1))) {
#ifdef INET6
- int32_t isipv6;
+ isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? true : false;
+#else
+ isipv6 = false;
#endif
+ if (((V_tcp_pmtud_blackhole_detect == 1) ||
+ (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
+ (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
+ ((tp->t_state == TCPS_ESTABLISHED) ||
+ (tp->t_state == TCPS_FIN_WAIT_1))) {
/*
* Idea here is that at each stage of mtu probe (usually,
@@ -3243,7 +3249,6 @@ rack_timeout_rxt(struct tcpcb *tp, struct tcp_rack *ra
* default in an attempt to retransmit.
*/
#ifdef INET6
- isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
if (isipv6 &&
tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
/* Use the sysctl tuneable blackhole MSS. */
Modified: head/sys/netinet/tcp_timer.c
==============================================================================
--- head/sys/netinet/tcp_timer.c Tue Mar 31 15:47:55 2020 (r359486)
+++ head/sys/netinet/tcp_timer.c Tue Mar 31 15:54:54 2020 (r359487)
@@ -614,6 +614,7 @@ tcp_timer_rexmt(void * xtp)
int rexmt;
struct inpcb *inp;
struct epoch_tracker et;
+ bool isipv6;
#ifdef TCPDEBUG
int ostate;
@@ -712,12 +713,16 @@ tcp_timer_rexmt(void * xtp)
* packets and process straight to FIN. In that case we won't catch
* ESTABLISHED state.
*/
- if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
- || (tp->t_state == TCPS_FIN_WAIT_1))) {
#ifdef INET6
- int isipv6;
+ isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? true : false;
+#else
+ isipv6 = false;
#endif
-
+ if (((V_tcp_pmtud_blackhole_detect == 1) ||
+ (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
+ (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
+ ((tp->t_state == TCPS_ESTABLISHED) ||
+ (tp->t_state == TCPS_FIN_WAIT_1))) {
/*
* Idea here is that at each stage of mtu probe (usually, 1448
* -> 1188 -> 524) should be given 2 chances to recover before
@@ -746,7 +751,6 @@ tcp_timer_rexmt(void * xtp)
* in an attempt to retransmit.
*/
#ifdef INET6
- isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
if (isipv6 &&
tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
/* Use the sysctl tuneable blackhole MSS. */
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