2 resolv tests timing out consistently

[Florian Weimer]

* Zack Weinberg:

> resolv/tst-bug18665 and resolv/tst-resolv-search are consistently
> failing for me on my development workstation, which is x86-64 running
> Debian unstable.  The .out files both say the same thing:
>
> warning: could not become root outside namespace (Operation not permitted)
> warning: unshare (CLONE_NEWUTS) failed: Operation not permitted
> warning: could not enter network namespace
> Timed out: killed the child process
> Termination time: 2019-02-18T21:46:18.136967
> Last write to standard output: 2019-02-18T21:45:58.133916
>
> (Debian's default kernel configuration doesn't permit unprivileged
> users to use CLONE_NEWUSER; I think the rest of the warnings are
> fallout from that.)
>
> I don't see anything in either test program that should take a long
> time, or actually _require_ the user/network namespace.  Any ideas?

The network namespace has the side effect of disabling iptables for that
namespace, in particular connection tracking.  It is possible that you
run into a state table overflow.  Check for kernel error messages.

It may be possible to work around that by exempting lo-to-lo traffic
from connection tracking.

Some other tests run into kernel bugs where the kernel does not generate
ICMP messages, but the tests you mentioned are not of these types.

Thanks,
Florian