[CRIU] restore of deleted standalone unix sockets

[Pavel Emelyanov]

On 06/22/2016 08:35 PM, Tycho Andersen wrote:
> Hi guys,
> 
> I noticed that restoring of standalone unix sockets in the LISTEN state fails,
> because we don't keep the address during the dump phase, and the kernel expects
> us to bind() to an address before we can listen() on these sockets (see test
> for an example).
> 
> One problem with this patch is that if there are two sockets bound to the same
> path, but one was deleted, we could fail if we restore the non-deleted one
> first. I think there are a few options for this:
> 
> 1. Try to order the sockets so they're always restored in the right order
>    (similar to how the process did it the first time). I'm not aware of any
>    ordering hooks we have in the code to do this.
> 2. Try to bind the socket to some other path; since it is deleted, nobody can
>    connect to it anyway, so it doesn't matter where it's bound.
> 3. Don't care about this case ;)

4. Move the offending path, bind the socket, move the original path back %)

> Anyway, here's a first draft of a set, let me know what you think.

I'd appreciate either of 1, 2 or 4 to get fixed, since AFAIK unlinking of
a socket and binding another one under the same name is standard practice
when restarting daemons, so we will definitely step into this soon. Now
we don't as we just forget the name for unlinked sockets.

-- Pavel