Linux: gre tunnels cannot be added in a namespace

Publication date: 2019-05-08

Issue: gre tunnels cannot be added in a namespace if net/core/fb_tunnels_only_for_init_net=1 is set

"fb_tunnels_only_for_init_net" is a parameter that disables creation of fallback tunnel interfaces in namespace. This avoids unnecessary overhead since most of the time these are not needed.

Solution: Create fallback tunnel manually first

The fallback tunnel (gre0) needs to be created manually in a namespace before other gre tunnels can be created in that namespace. To do this invoke within the namespace:

ip link add name gre0 type gre local 0.0.0.0 remote 0.0.0.0