71 lines
2.4 KiB
Diff
71 lines
2.4 KiB
Diff
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From d2311b4517beebda22c76f82a120f7b1f765a79d Mon Sep 17 00:00:00 2001
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From: csalinezh <csalinezh@gmail.com>
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Date: Thu, 5 Jan 2023 22:38:31 +0200
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Subject: [PATCH] tracepath: restore the MTU probing behaviour since release
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20071127
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Since 81d0f03 (tracepath: fix IP{V6,}_PMTUDISC_DO values), tracepath
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shows the PMTU for a target only at the first hop but not the hop where
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MTU is reduced, if that data has been cached in kernel FIB by previous
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probing attempts.
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IP_PMTUDISC_PROBE instructs the kernel to set the Don't Fragment flag
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while bypassing PMTU checks. Usage of IP_PMTUDISC_PROBE in tracepath was
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introduced in 37bd60c and mentioned in the release note of 20071127
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(1d83610) as a feature.
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As previously identified in 81d0f03 (appeared in release 20190709), the
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definition of these options became incorrect during a copy refactoring in
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d3028f1 (in release 20100418). The value for IP_PMTUDISC_PROBE continued
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to be used until 81d0f03 when the correct definition of IP_PMTUDISC_DO was
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adopted, thus causing a regression.
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This commit resotres the previous behaviour by adopting IP_PMTUDISC_PROBE.
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Fixes: d3028f1, 81d0f03
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Signed-off-by: Charles Zhang <csalinezh@gmail.com>
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---
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iputils_common.h | 6 ++++++
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tracepath.c | 4 ++--
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2 files changed, 8 insertions(+), 2 deletions(-)
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diff --git a/iputils_common.h b/iputils_common.h
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index 67b495ef..49e790d8 100644
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--- a/iputils_common.h
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+++ b/iputils_common.h
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@@ -55,6 +55,12 @@
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#ifndef IPV6_PMTUDISC_DO
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# define IPV6_PMTUDISC_DO 2
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#endif
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+#ifndef IP_PMTUDISC_PROBE
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+# define IP_PMTUDISC_PROBE 3
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+#endif
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+#ifndef IPV6_PMTUDISC_PROBE
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+# define IPV6_PMTUDISC_PROBE 3
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+#endif
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#ifdef HAVE_ERROR_H
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# include <error.h>
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diff --git a/tracepath.c b/tracepath.c
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index 4d2a9acf..ebb7f72f 100644
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--- a/tracepath.c
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+++ b/tracepath.c
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@@ -532,7 +532,7 @@ int main(int argc, char **argv)
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if (ctl.mtu <= ctl.overhead)
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goto pktlen_error;
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- on = IPV6_PMTUDISC_DO;
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+ on = IPV6_PMTUDISC_PROBE;
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if (setsockopt(ctl.socket_fd, SOL_IPV6, IPV6_MTU_DISCOVER, &on, sizeof(on)) &&
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(on = IPV6_PMTUDISC_DO, setsockopt(ctl.socket_fd, SOL_IPV6,
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IPV6_MTU_DISCOVER, &on, sizeof(on))))
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@@ -557,7 +557,7 @@ int main(int argc, char **argv)
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if (ctl.mtu <= ctl.overhead)
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goto pktlen_error;
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- on = IP_PMTUDISC_DO;
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+ on = IP_PMTUDISC_PROBE;
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if (setsockopt(ctl.socket_fd, SOL_IP, IP_MTU_DISCOVER, &on, sizeof(on)))
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error(1, errno, "IP_MTU_DISCOVER");
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on = 1;
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