vrf: add a runtime check before playing with netns

This patch adds a runtime check to determine if netns are available. Some
systems like OpenWRT have the system call setns() but don't have the kernel
option CONFIG_NET_NS enabled.

Reported-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Tested-by: Christian Franke <chris@opensourcerouting.org>
1 file changed