Append a default route to the CNI reply if there's a gateway advertised.
Append a default route to the CNI reply if there's a gateway advertised.

Classless static routes (DHCP option 121) are now processed first.
If CSRs exist, static routes (DHCP option 33) and the gateway default
route are ignored as per RFC 3442.

containernetworking/plugins,containernetworking/plugins