Nicolas Dichtel [off-list ref] writes:

With this patch, a user can define an id for a peer netns by providing a FD or a
PID. These ids are local to netns (ie valid only into one netns).

This will be useful for netlink messages when a x-netns interface is
dumped.

You have a "id -> struct net *" table but you don't have a 
"struct net * -> id" table which looks like it will impact the
performance of peernet2id at scale.

Eric