kern/50588: ATF tests fail with "rump.ping6: failed to get receiving hop limit"

[ozaki-r%netbsd.org@localhost]

>Number:         50588
>Category:       kern
>Synopsis:       ATF tests fail with "rump.ping6: failed to get receiving hop limit"
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Dec 24 08:45:00 +0000 2015
>Originator:     Ryota Ozaki
>Release:        NetBSD-current
>Organization:
>Environment:
NetBSD rangeley 7.99.24 NetBSD 7.99.24 (GENERIC) #216: Thu Dec 17 11:33:13 JST 2015  ozaki-r@rangeley:(hidden) amd6
>Description:
ATF tests using rump.ping6 fail with "rump.ping6: failed to get receiving hop limit".
The error means that rump.ping6 sets IPV6_RECVHOPLIMIT to a socket, however,
it cannot get a hop limit value from a packet being received on the socket via
ancillary data (CMSG_DATA(3)).

It rarely fails only on rump_server in ATF tests. I have never seen the error on
baremetal machines.
>How-To-Repeat:
Run ATF tests using rump.ping6, e.g., t_gif, many times.
Or see results of ATF tests on anita: http://releng.netbsd.org/test-results.html

It's known that if we limit rump_server's memory (e.g., -r 1m), we can reproduce it
in smaller number of trials.
>Fix:
N/A