Re: [PATCHi next] veth: advertise peer link relationship for both devices
From: David Miller <davem@davemloft.net>
Date: 2016-06-11 22:43:41
From: Lance Richardson <redacted> Date: Fri, 10 Jun 2016 12:32:19 -0400
Currently, when creating a veth pair, notfications to user
space only include link peer for one end of the veth pair:
# ip monitor link &
# ip link add dev vm1 type veth peer name vm2
30: vm2@NONE: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN
link/ether be:e3:b7:0e:14:52 brd ff:ff:ff:ff:ff:ff
31: vm1@vm2: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN
link/ether da:e6:a6:c5:42:54 brd ff:ff:ff:ff:ff:ff
With this change, netlink notifications are sent with complete
information for both interfaces of the veth pair:
# 3: vm2@NONE: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN
link/ether e2:94:54:8a:ac:f5 brd ff:ff:ff:ff:ff:ff
4: vm1@vm2: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN
link/ether b2:05:70:e0:fc:35 brd ff:ff:ff:ff:ff:ff
3: vm2@vm1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN
link/ether e2:94:54:8a:ac:f5 brd ff:ff:ff:ff:ff:ff
Signed-off-by: Lance Richardson <redacted>I don't know about this. First of all, those notifications you get above tell you everything you need to know in order to figure out what both ends of the veth pair are. In fact, I would say that the vm1@vm2 notification #31 above is the _only_ one you absolutely need.
quoted hunk ↗ jump to hunk
@@ -466,8 +466,16 @@ static int veth_newlink(struct net *src_net, struct net_device *dev, priv = netdev_priv(peer); rcu_assign_pointer(priv->peer, dev); + + err = rtnl_configure_link(dev, NULL); + if (err < 0) + goto err_configure_dev; + + rtmsg_ifinfo(RTM_NEWLINK, peer, 0, GFP_KERNEL); return 0; +err_configure_dev: + /* nothing to do */ err_register_dev: /* nothing to do */ err_configure_peer:
If you're registering the peer here explicitly, this means a link configure somewhere else is now superfluous. I really don't like this change at all, both from a necessity perspective as well as from it's implementation.