[CRIU] Debugging the process to restore veth in a namespace

[Pavel Emelyanov]

On 08/16/2015 10:12 PM, Hui Kang wrote:
> Hi, Pavel
> I used "--veth-pair veth101=veth100" when dumping and restoring a process. veth101 is the 
> device name in the process net namespace, veth100 is the other end which is in the criu host.
> 
> After restore, I can see the ip address of veth101 is restored. However, the veth end in the
> host (veth100) is not successfully restored. By "not success", I mean the veth100 link is
> created, however, its state is DOWN and no IP is assigned to the restore link. Only I manually
> set the link state to UP and assigne IP, the two ends can talk to each other.

Yup, this is the host-side of the link. CRIU only manages the container side. If you need
to do some configuration of the host-side part before the resume, you can hook in to the
post-restore action script.

> Moreover, the link index of veth100 is not the same as when I dump the process. For example
> the index for veth101 and veth100 is 15 and 16 when I dump the process. After restore, 
> veth100's index becomes 17. Is this a bug in CRIU? Thanks.

No, it's not a bug. The problem is that when you do the host-side link restore the index
of it can be busy, so we don't even try to preserve it. Even if we do the "best-effort"
attempt, it will succeed only in trivial cases.

-- Pavel