kern/53644: pppoe tests failing since Aug 24

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

>Number:         53644
>Category:       kern
>Synopsis:       pppoe tests failing since Aug 24
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Sep 30 09:05:00 +0000 2018
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2018.08.24.17.06.29
>Organization:
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

Since maxv's commit of src/sys/net/if_pppoe.c 1.143 on CVS source date
2018.08.24.17.06.29, the following pppoe tests are failing in every
run on i386 and sparc, but not on amd64:

  net/if_pppoe/t_pppoe/pppoe_chap
  net/if_pppoe/t_pppoe/pppoe6_pap
  net/if_pppoe/t_pppoe/pppoe6_chap
  net/if_pppoe/t_pppoe/pppoe_pap

An automated report about the issue was sent to current-users
on Aug 25:

  https://mail-index.netbsd.org/current-users/2018/08/25/msg034117.html

This listed only one of the failing tests, probably because the others
had recently shown random failures.  The pppoe tests have been failing
occasionally for a long time, but this PR is specifically about them
now failing every time.

Log output from a recent set of test failures is at:

  http://releng.netbsd.org/b5reports/i386/2018/2018.09.29.13.19.38/test.html#net_if_pppoe_t_pppoe_pppoe6_chap

>How-To-Repeat:

>Fix: