Re: IPv6 nexthop for IPv4

On Thu, Mar 26, 2015 at 9:16 AM, Bjørnar Ness [off-list ref] wrote:

Hello, hope this is the right place to ask.

Does anyone know if there is work beeing done in natively supporting
IPv6 nexthops for IPv4?

What problem are you trying to solve? Do you want to tunnel your
ipv4 packet through IPv6? there are a number of tunneling mechanisms
in linux for this.

I know that "some" Linux switch software company is working on this, but
I am afraid the functionality will be more of a "hack".

The benefit of this is stateless configuration (rfc5549), using IPv6 link-local
neighbor address as IPv4 nexthop, beeing able to do for example:

ip route add 10.0.0.0/16 via fe80::225:90ff:fed3:bfb4/64 dev sfp0

Trying to understand what the desired behavior is, for the route
above: if I send a packet from 10.0.0.1 to 10.0.0.2, you want the dst-mac
to be the mac address of e80::225:90ff:fed3:bfb4???
how do you know that fe80::225:90ff:fed3:bfb4 supports ipv4
forwarding on the receiving interface (and if it does, why didn't it
advertise itself as an IPv4 router on that interface)?

This is somehow possible now by exploiting static arp entries and
"unused" IPv4 addresses for nexthop, but is far from ideal.

Hope someone will be able to provide some insight on what is planned
in this area, and weather this direct functionality will ever make it
into the kernel.