On Wed, May 31, 2017 at 5:27 AM, Harald Welte <lafo...@gnumonks.org> wrote: > Hi Cong, > > On Tue, May 30, 2017 at 04:18:17PM -0700, Cong Wang wrote: >> On Tue, May 30, 2017 at 3:07 PM, Harald Welte <lafo...@gnumonks.org> wrote: >> > But, to the contrary, this doesn't happen. The unshare-created netns is >> > gone, but the netdevice did not get moved back to the root namespace >> > either. The only hack to get back to the "eth0" device is to unload the >> > driver and re-load it. >> >> >> Net namespace simply unregisters all netdevices inside when it is >> gone, no matter where they are from. > > ah, ok. I missed that part. Is there a good piece of documentation on > netwokr namespaces that I should read?
I don't know any doc mentioning this. >> I am pretty sure you can move it back to root-ns if you want, > > Yes, I can explicitly do that, but this of course doesn't work if e.g. > my [single] process in that namespace crashes due to some bug, OOM or > the like. > >> it is a little tricky because you have to give the root-ns a name >> first. > > It's actually not, as you can just identify the root-ns by pid 1, so > "ip link set $DEV netns 1" will move it back. As indicated, I'm worried > about the error paths. > Yeah, using PID works too. Unfortunately the whole namespace is gone too no matter the last process exits normally or not, it is just refcount'ed. >> > What am I missing here? Is this the intended behavior? >> >> Yes it is. > > thanks for your confirmation. Guess I have to get used to it. > >> > Of course I know I could simply do something like "ip link set eth0 >> > netns 1" from within the namespace before leaving. But what if the >> > process is not bash and the process exits abnormally? I'd consider >> > that explicit reassignment more like a hack than a proper solution... >> >> It doesn't make sense to move it back to where it is from, for example, >> what if you move a veth0 from netns1 to netns2 and netns1 is gone >> before netns2? > > for virtual devices, I would agree. For physical devices, I think the > default behavior to unregister them is - from my of course very > subjective point of view - quite questionable. Network namespace does not special-case the physical devices, it treats them all equally as abstract net devices. Hope this helps.
