So_bindtodevice

My device has multiple interfaces and supports dynamic ips.
SO_BINDTODEVICE looks like it would be used to specify a device in the
listen statement instead of having to update every IP change.

I see someone submitted a patch years ago that wasn’t accepted and
there was no follow on. Is there any particular reason other than this
probably isn’t a common use case? Is this something that could be
added in the future?

SO_BINDTODEVICE was originally put in to allow the DHCP server to tell
on
which interface a packet had arrived. I don’t see any reason why it
couldn’t be used the way you describe, but I am under the impression
that
it is somewhat deprecated, and that may be why there was no action on
that
patch. Your best bet would be to ask the Linux network folks.