kern/50031: PPPoE server fails to work on -7

[roy%marples.name@localhost]

>Number:         50031
>Category:       kern
>Synopsis:       PPPoE server fails to work on -7
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jul 04 08:50:00 +0000 2015
>Originator:     Roy Marples
>Release:        NetBSD-7.0_RC1
>Organization:
>Environment:
NetBSD erlite.marples.name 7.99.18 NetBSD 7.99.18 (ERLITE) #3: Tue Jun 16 13:47:35 BST 2015  roy%uberlaptop2.marples.name@localhost:/home/roy/obj/src-evbmips/sys/arch/evbmips/compile/ERLITE evbmips
>Description:
PPPoE server fails to work on -7 and -current.
95% sure the same config worked on -6.
tcpdump reports PADI packets arrive, but nothing is returned and no diagnostic is logged.

>How-To-Repeat:
1) Setup a PPPoE server as noted here:
http://www.netbsd.org/docs/network/pppoe/#pppoe-server

2) Note it fails to work.

Here are some configs:

erlite$ strings /boot/netbsd.elf32 | grep PPPOE
_KERNEL_OPT_NPPPOE
_KERNEL_OPT_PPPOE_SERVER
_KERNEL_OPT_PPPOE_TERM_UNKNOWN_SESSIONS

erlite$ sudo cat /etc/ifconfig.pppoe1
create
# Server
link0
! /sbin/pppoectl -e cnmac2 $int
! /sbin/pppoectl $int hisauthproto=pap hisauthname='foobar%baz.com@localhost' hisauthsecret='oink' myauthproto=none
10.3.3.1 10.3.3.3 up

erlite$ sudo pppoectl -v pppoe1
pppoe1: phase=dead
        hisauthproto=pap hisauthname="foobar%baz.com@localhost"
        lcp timeout: 1.000 s
        idle timeout = disabled
        max-auth-failure = 5
        max-noreceive = 15 seconds
        max-alive-missed = 3 unanswered echo requests

erlite$ ifconfig pppoe1
pppoe1: flags=9811<UP,POINTOPOINT,SIMPLEX,LINK0,MULTICAST> mtu 1492
        inet 10.3.3.1 -> 10.3.3.3 netmask 0xff000000
        inet6 fe80::618:d6ff:fef0:2cb%pppoe1 ->  prefixlen 64 scopeid 0x8

erlite$ ifconfig cnmac2
cnmac2: flags=8a43<UP,BROADCAST,RUNNING,ALLMULTI,SIMPLEX,MULTICAST> mtu 1500
        capabilities=15500<IP4CSUM_Rx,TCP4CSUM_Rx,UDP4CSUM_Rx,TCP6CSUM_Rx>
        capabilities=15500<UDP6CSUM_Rx>
        enabled=0
        address: 04:18:d6:f0:02:cd
        media: Ethernet autoselect (100baseTX full-duplex,flowcontrol,rxpause,txpause)
        status: active
        inet 10.73.3.1 netmask 0xffffff00 broadcast 10.73.3.255


>Fix: