This patch adds path of mtu discovery for sit tunnel.
To enable/disable DiscoverPathMTU is introduced.
Example configuration
file: sit.netdev
[NetDev]
Name=sit-tun
Kind=sit
MTUBytes=1480
[Tunnel]
DiscoverPathMTU=1
Local=X.X.X.X
Remote=X.X.X.X
By default pmtudisc is turned on , if DiscoverPathMTU
is missing from the config. To turn it off
DiscoverPathMTU=0 needs to be set.