Quoting Daniel P. Berrange (berrange@xxxxxxxxxx): > Another feature I'd like to provide in libvirt LXC is "hotplug" of NIC > devices to containers. > > eg, I have a NIC eth1 in the host and I want to make it appear as eth0 > in the container. There are two ways I can do this > > # ip link set eth1 name eth0 > # ip link set eth0 ns $PID > > Or > > # ip link set eth1 ns $PID > # setns --net $PID (assume it opens /proc/$PID/ns/net & does setns(fd)) > # ip link set eth1 name eth0 > > > Both these approaches suffer from flaws though. The first approach fails > on step one, if there is already another NIC in the host, that has the > same name as the target we want to use in the container. The second > approach fails on step 1 if there is already a NIC in the container > which has the same name as the original device on the host. > > To get around this, we'd basically need to temporarily use a completely > random NIC name eg > > # ip link set eth1 name $RANDOMNAME > # ip link set $RANDOMNAME ns $PID > # setns --net $PID (assume it opens /proc/$PID/ns/net & does setns(fd)) > # ip link set $RANDOMNAME name eth0 > > This is workable, but feels slightly unpleasant. So IMHO if would be Yes, it feels racy. I assume 'ip' will give a helpful error if RANDOMNAME happens to be already taken though. > desirable if the kernel allowed us to atomically change the NIC device > name and namespace at the same time. eg > > # ip link set eth1 name eth0 ns $PID An alternative would be to encode the above logic in the ip program itself, but not the kernel. I think that's the way to go. We don't want every user of this to have to do the ugly steps, but I don't know that this quite justifies kernel help. > Although that 'ip' CLI syntax is allowed, it appears to implement it in > two steps, doing the rename first and then setting the namespace, so you > still hit the NIC name clash problem. > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| > _______________________________________________ > Containers mailing list > Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx > https://lists.linuxfoundation.org/mailman/listinfo/containers _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
