PATCH: IO: Avoid calling SO_BINDTODEVICE if not needed

[Christian Svensson]

Hi Alexander,

On Sat, Jul 27, 2024 at 2:05 PM Alexander Zubkov <green at qrator.net> wrote:
> I wonder if it is necessary at all to set a vrf on an accepted connection? It seems to me that setting or checking vrf should be avoided instead for an accepted connection. What do you think?

Indeed, this is what I set out to do in the beginning and is, if you
boil this patch down, the actual implication when using VRFs.

The reason I chose to implement the patch as a get+set rather than a
conditional set was that the existing code structure assumes that
sk_setup is called on multiple types of sockets and I wasn't sure
exactly how to guard for specifically sockets that are connected.
In addition I tried to find a reference in the kernel to where exactly
it inherits the bound interface when a new socket is created from
accept() but I could not. It is evident from my experiments that it is
inherited, and that is the only way accept() on a VRF bind() would
make sense.
Doing a get+set seems like the least risky change that I felt safe to propose.

That said, if you believe it is better implemented as a conditional
and are able to nudge me how you'd want a check for the particular
socket type to look, I'd be happy to do a v2 patch.

Regards,