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New feature: Set advmss on IPv4 default route

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This ensures that TCP connections terminated through the CLAT gets a sensible
TCP MSS value negotiated. By default, the value is set to the MTU of the
defaultroute minus 40. There should be no reason to change this in the vast
majority of cases, but it can be overridden with the "v4-defaultroute-advmss"
setting.
This commit is contained in:
Tore Anderson
2015-10-22 11:58:19 +02:00
parent 9f1789f34d
commit a80e2f30ab
2 changed files with 17 additions and 1 deletions
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11
README.pod
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@@ -326,6 +326,17 @@ If you know that the IPv6 Path MTU between the host and the PLAT is larger
than 1280, you may increase this, but then you should also recompile TAYGA
with a larger B<ipv6_offlink_mtu> setting in I<conffile.c>.
=item B<v4-defaultroute-advmss=integer> (default: B<v4-defaultroute-mtu> - 40)
The "advmss" value assigned to the the default route potining to the CLAT. This
controls the advertised TCP MSS value for TCP connections made through the
CLAT.
You should normally not need to set this. By default the value is calculated by
taking the value of B<v4-defaultroute-mtu> and substracting 40 (20 bytes for
the IPv4 header + 20 bytes for the TCP header). If B<v4-defaultroute-mtu> is
unset or 0, there is no default.
=back
=head1 LIMITATIONS

7
clatd
View File

@@ -40,6 +40,7 @@ $CFG{"v4-defaultroute-enable"} = 1; # add a v4 defaultroute via the CLAT?
$CFG{"v4-defaultroute-replace"} = 0; # replace existing v4 defaultroute?
$CFG{"v4-defaultroute-metric"} = 2048; # metric for the IPv4 defaultroute
$CFG{"v4-defaultroute-mtu"} = 1260; # MTU for the IPv4 defaultroute
$CFG{"v4-defaultroute-advmss"} = 0; # TCP MSS for the IPv4 defaultroute
#
@@ -868,7 +869,11 @@ if(cfgbool("v4-defaultroute-enable")) {
push(@cmdline, ("metric", cfgint("v4-defaultroute-metric")))
}
if(cfgint("v4-defaultroute-mtu")) {
push(@cmdline, ("mtu", cfgint("v4-defaultroute-mtu")))
push(@cmdline, ("mtu", cfgint("v4-defaultroute-mtu")));
push(@cmdline, ("advmss", cfgint("v4-defaultroute-advmss") ||
cfgint("v4-defaultroute-mtu") - 40));
} elsif(cfgint("v4-defaultroute-advmss")) {
push(@cmdline, ("advmss", cfgint("v4-defaultroute-advmss")));
}
p("Adding IPv4 default route via the CLAT");
cmd(\&err, cfg("cmd-ip"), @cmdline);