Two interfaces sharing the same IP address: how to change default route's interface on link change?

[Bruce M. Simpson]

Jeremie Le Hen wrote:
> In summary, favor wired connectivity over the wireless one, at any time:
> could this be at boot time or not.
>
> I'm pretty sure I'm not the only one who wants this kind of setup.  So
> how did you achieve this setup?

The forwarding code needs to be changed to support the notion of a 
floating static, regardless.

Recall that in BSD default routes configured statically, whether 
manually or by DHCP, have the RTF_STATIC flg set.

Currently, the BSD behaviour is NOT to update the rt_ifp for an 
RTF_STATUC route when ifadown is called. I believe this to be correct 
and honours the original API contract of RTF_STATIC. It is not what you 
desire in your use case however.

Configuring ifstated to manually replumb addresses and routes is 
probably an easier place to start. Seamless migration is not possible 
yet; generally sockets are tied to the interface where they were 
implicitly bound, also nexthop selection happens purely on the basis of 
destination address.

BMS