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authorTim Small <tim@buttersideup.com>2009-10-16 20:00:04 +0100
committerHarald Welte <laforge@gnumonks.org>2009-10-25 10:58:23 +0100
commit22bdd6966f2c3ccded984a37ba0b97470bcf9323 (patch)
tree67837effd91fc49bb45733c2f84c481edf627503 /extensions
parent94aa2ea67d7b8a669e8541f094661a1dc89722a3 (diff)
doc: update TCPMSS manpage with Linux 2.6.25 changes
References: http://bugs.debian.org/551272 [j.eng: modified --set-mss option description to be understandable] Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Diffstat (limited to 'extensions')
-rw-r--r--extensions/libxt_TCPMSS.man10
1 files changed, 9 insertions, 1 deletions
diff --git a/extensions/libxt_TCPMSS.man b/extensions/libxt_TCPMSS.man
index dbab918d..b5cb455f 100644
--- a/extensions/libxt_TCPMSS.man
+++ b/extensions/libxt_TCPMSS.man
@@ -34,9 +34,17 @@ configuration like:
\-j TCPMSS \-\-clamp\-mss\-to\-pmtu
.TP
\fB\-\-set\-mss\fP \fIvalue\fP
-Explicitly set MSS option to specified value.
+Explicitly sets MSS option to specified value. If the MSS of the packet is
+already lower than \fIvalue\fP, it will \fBnot\fP be increased (from Linux
+2.6.25 onwards) to avoid more problems with hosts relying on a proper MSS.
.TP
\fB\-\-clamp\-mss\-to\-pmtu\fP
Automatically clamp MSS value to (path_MTU \- 40 for IPv4; \-60 for IPv6).
+This may not function as desired where asymmetric routes with differing
+path MTU exist \(em the kernel uses the path MTU which it would use to send
+packets from itself to the source and destination IP addresses. Prior to
+Linux 2.6.25, only the path MTU to the destination IP address was
+considered by this option; subsequent kernels also consider the path MTU
+to the source IP address.
.PP
These options are mutually exclusive.