Re: [PATCH net] net: core: sock: add AF_PACKET unsupported binding error

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Kuniyuki Iwashima wrote:
> From: "Szpetkowski, Grzegorz" <grzegorz.szpetkowski@intel.com>
> Date: Thu, 11 Jul 2024 13:48:07 +0000
> > Hi All,
> > 
> > Currently, when setsockopt() API with SO_BINDTODEVICE option is
> > called over a raw packet socket, then although the function doesn't
> > return an error, the socket is not bound to a specific interface.
> > 
> > The limitation itself is explicitly stated in man 7 socket, particularly
> > that SO_BINDTODEVICE is "not supported for packet sockets".
> > 
> > The patch below is to align the API, so that it does return failure in
> > case of a packet socket.
> 
> SO_XXX is generic options and can be set to any socket (except for
> SO_ZEROCOPY due to MSG_ZEROCOPY, see 76851d1212c11), and whether it's
> really used or not depends on each socket implementation.
> 
> Otherwise, we need this kind of change for all socket options and
> families.

Making this change now might also break applications that
set it even though it is a noop for them.