Bug#941026: netcfg_gateway_reachable wrongly rejects IPv6 link-local addresses

[Andrew Kanaber <adk-debianbugs@jump.net.uk>]

On Wed, Oct 02, 2019 at 08:27:34AM +0200, Philipp Kern wrote:
> On 2019-09-23 18:00, Andrew Kanaber wrote:
> > When doing static IP configuration, netcfg will reject a gateway address
> > outside the host's network as defined by the netmask.
> So how does it identify the interface to use in this case? Does the kernel
> have special support to pick the correct one if there is only one
> non-loopback interface? Generally link-local addresses do need to be
> qualified with the interface to be used.

The routing table entry contains both the gateway address and the interface to
use. When the kernel decides to use the route it has everything it needs.

Using a link-local gateway is an entirely standard thing to do. It would have
been reasonable for netcfg to reject link-local addresses entered as the actual
host address - but it doesn't check for that, it just does this netmask check
that happens to reject global unicast host address plus link-local gateway.

Thanks,

Andrew