On Tue, Jan 15, 2019 at 11:30 AM David Herrmann <dh.herrm...@gmail.com> wrote: > > This introduces a new generic SOL_SOCKET-level socket option called > SO_BINDTOIFINDEX. It behaves similar to SO_BINDTODEVICE, but takes a > network interface index as argument, rather than the network interface > name. > > User-space often refers to network-interfaces via their index, but has > to temporarily resolve it to a name for a call into SO_BINDTODEVICE. > This might pose problems when the network-device is renamed > asynchronously by other parts of the system. When this happens, the > SO_BINDTODEVICE might either fail, or worse, it might bind to the wrong > device. > > In most cases user-space only ever operates on devices which they > either manage themselves, or otherwise have a guarantee that the device > name will not change (e.g., devices that are UP cannot be renamed). > However, particularly in libraries this guarantee is non-obvious and it > would be nice if that race-condition would simply not exist. It would > make it easier for those libraries to operate even in situations where > the device-name might change under the hood. > > A real use-case that we recently hit is trying to start the network > stack early in the initrd but make it survive into the real system. > Existing distributions rename network-interfaces during the transition > from initrd into the real system. This, obviously, cannot affect > devices that are up and running (unless you also consider moving them > between network-namespaces). However, the network manager now has to > make sure its management engine for dormant devices will not run in > parallel to these renames. Particularly, when you offload operations > like DHCP into separate processes, these might setup their sockets > early, and thus have to resolve the device-name possibly running into > this race-condition. > > By avoiding a call to resolve the device-name, we no longer depend on > the name and can run network setup of dormant devices in parallel to > the transition off the initrd. The SO_BINDTOIFINDEX ioctl plugs this > race. > > Reviewed-by: Tom Gundersen <t...@jklm.no> > Signed-off-by: David Herrmann <dh.herrm...@gmail.com>
This looks great to me, thanks. For the series Acked-by: Willem de Bruijn <will...@google.com>
