Option to add static routes to the network contextualization

[atodorov-storpool]

It is relatively common practice to have additional static routes to internal private networks that differ from the default gateway without defining a virtual router setup.

The static routes could be defined as a comma-separated list in a custom contextualization variable, and the contextualization could append them to route-<iface>

For example ETH0_STATIC_ROUTES=1.2.3.4/24 via 2.3.4.5 dev eth0,5.6.7.8/22 via 2.3.4.5 dev eth0 could lead to
/etc/sysconfig/network-scripts/route-eth0 containing

1.2.3.4/24 via 2.3.4.5 dev eth0
5.6.7.8/22 via 2.3.4.5 dev eth0

edit: escape < and >

[baby-gnu]

I think the dev eth0 should be automatically added since the device name could be something else.