[NETFILTER]: add IPv6-capable TCPMSS target

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 614c92c1783..748f7f00909 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -395,6 +395,32 @@ config NETFILTER_XT_TARGET_CONNSECMARK
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NETFILTER_XT_TARGET_TCPMSS
+	tristate '"TCPMSS" target support'
+	depends on NETFILTER_XTABLES && (IPV6 || IPV6=n)
+	---help---
+	  This option adds a `TCPMSS' target, which allows you to alter the
+	  MSS value of TCP SYN packets, to control the maximum size for that
+	  connection (usually limiting it to your outgoing interface's MTU
+	  minus 40).
+
+	  This is used to overcome criminally braindead ISPs or servers which
+	  block ICMP Fragmentation Needed packets.  The symptoms of this
+	  problem are that everything works fine from your Linux
+	  firewall/router, but machines behind it can never exchange large
+	  packets:
+	        1) Web browsers connect, then hang with no data received.
+	        2) Small mail works fine, but large emails hang.
+	        3) ssh works fine, but scp hangs after initial handshaking.
+
+	  Workaround: activate this option and add a rule to your firewall
+	  configuration like:
+
+	  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN \
+	                 -j TCPMSS --clamp-mss-to-pmtu
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_MATCH_COMMENT
 	tristate  '"comment" match support'
 	depends on NETFILTER_XTABLES