kern/55164: net/ndp/t_ndp:ndp_rtm test case fails again

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         55164
>Category:       kern
>Synopsis:       net/ndp/t_ndp:ndp_rtm test case fails again
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 11 12:00:00 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2020.04.02.21.36.03
>Organization:

>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

The net/ndp/t_ndp:ndp_rtm test case is failing since these commits:

  2020.04.02.17.40.33 christos src/usr.bin/kdump/ioctlprint.1 1.3
  2020.04.02.17.40.33 christos src/usr.bin/kdump/kdump.c 1.134
  2020.04.02.17.40.33 christos src/usr.bin/kdump/mkioctls 1.54
  2020.04.02.17.41.33 christos src/usr.bin/ktrace/ktrace.h 1.21
  2020.04.02.17.41.34 christos src/usr.bin/kdump/ioctlprint.1 1.4
  2020.04.02.17.41.34 christos src/usr.bin/kdump/kdump.c 1.135
  2020.04.02.17.41.34 christos src/usr.bin/kdump/mkioctls 1.55
  2020.04.02.18.32.31 christos src/sbin/route/prog_ops.h 1.4
  2020.04.02.18.32.31 christos src/sbin/route/route.c 1.168
  2020.04.02.18.32.31 christos src/sbin/route/route_hostops.c 1.2
  2020.04.02.18.32.31 christos src/sbin/route/route_rumpops.c 1.2
  2020.04.02.20.57.20 roy src/share/man/man7/groups.7 1.8
  2020.04.02.20.57.20 roy src/share/man/man7/users.7 1.5
  2020.04.02.21.36.03 christos src/usr.bin/kdump/mkioctls 1.56

An earlier failure of the same test was reported in PR 55074; that one
was fixed, but it's now failing again.

Logs:

  http://releng.netbsd.org/b5reports/i386/commits-2020.04.html#2020.04.02.21.36.03
  http://releng.netbsd.org/b5reports/i386/2020/2020.04.09.18.20.40/test.html#net_ndp_t_ndp_ndp_rtm

It also fails on amd64, on real hardware:

  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/2020/2020.04.10.21.03.20/test.html#net_ndp_t_ndp_ndp_rtm

>How-To-Repeat:

>Fix: