On Thu, 22 Oct 2015 16:52:13 +0200, Nicolas Dichtel wrote: > With the proposed scenario: > 1. create netns 'new_netns' > 2. in root netns, move the interface with ifindex 2 to new_netns > 3. in new_netns, delete the interface with ifindex 2 > 4. in new_netns, create an interface - it will get ifindex 2 > > Operation 2 and 4 are done by dev_change_net_namespace() under rtnl_lock(). > RTM_DELLINK(root netns) and RTM_NEWLINK(new_netns) are sent by this function. > It means that operation 3 has been done before and that RTM_DELLINK(new_netns) > has been sent before.
Imagine the application trying to configure the interface with ifindex 2 after your step 2. It constructs a netlink message and sends it to the kernel; but while doing so, steps 3 and 4 happen. Now the application ends up configuring a different interface than it intended to. After that, it polls the netlink socket and receives the notifications about interface disappearing and a new one appearing. I don't see any way the user space application can prevent this. There will always be a race between receiving netlink notifications and sending config requests. I guess Thomas Haller can elaborate more as he ran into this. Jiri -- Jiri Benc -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
