Disable Path MTU discovery

This seems to be a failed concept and causes issues with transferring
large packets through an IPsec tunnel connection.

This configures the kernel to still respond to PMTU ICMP discovery
messages, but will not try this on its own.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

config/etc/sysctl.conf

@@ -1,6 +1,9 @@
 net.ipv4.ip_forward = 1
 net.ipv4.ip_dynaddr = 1
 
+# Disable Path MTU Discovery
+net.ipv4.ip_no_pmtu_disc = 1
+
 net.ipv4.icmp_echo_ignore_broadcasts = 1
 net.ipv4.icmp_ignore_bogus_error_responses = 1
 net.ipv4.icmp_ratelimit = 1000

config/rootfiles/core/120/filelists/files

@@ -1,5 +1,6 @@
 etc/system-release
 etc/issue
+etc/sysctl.conf
 etc/fcron.daily/openvpn-crl-updater
 etc/rc.d/init.d/dhcp
 srv/web/ipfire/cgi-bin/ovpnmain.cgi