Disappearing IPv6 default route

[Matthew Seaman]

Dear list,

I've had IPv6 connectivity for some years via an IPv6 in IPv4 gif tunnel
courtesy of my ISP.  However, about a week ago, when I upgraded to
6.2-PRERELEASE, I noticed it had mysteriously stopped working.  (It may have
died before last week though; but that is the probable time) So this
weekend I set out to find out why.

After much head scratching, I discovered that the IPv6 default route
was not present on the system.  If I added it back manually, voilà: IPv6
connectivity back again ... for a few seconds.

This is completely reproducible:

happy-idiot-talk:~:% sudo route add -inet6 default -interface gif0 ; ping6 clueless.aaisp.net.uk
add net default: gateway gif0
PING6(56=40+8+8 bytes) 2001:8b0:151:1::1 --> 2001:8b0:0:81::51bb:5115
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=0 hlim=61 time=32.221 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=1 hlim=61 time=29.856 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=2 hlim=61 time=29.560 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=3 hlim=61 time=30.348 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=4 hlim=61 time=28.957 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=5 hlim=61 time=30.626 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=6 hlim=61 time=29.384 ms
16 bytes from 2001:8b0:0:81::51bb:5115, icmp_seq=7 hlim=61 time=31.815 ms
ping6: sendmsg: No route to host
ping6: wrote clueless.aaisp.net.uk 16 chars, ret=-1
ping6: sendmsg: No route to host
ping6: wrote clueless.aaisp.net.uk 16 chars, ret=-1
ping6: sendmsg: No route to host
ping6: wrote clueless.aaisp.net.uk 16 chars, ret=-1
ping6: sendmsg: No route to host
ping6: wrote clueless.aaisp.net.uk 16 chars, ret=-1
ping6: sendmsg: No route to host
ping6: wrote clueless.aaisp.net.uk 16 chars, ret=-1
^C
--- clueless.aaisp.net.uk ping6 statistics ---
13 packets transmitted, 8 packets received, 38.5% packet loss
round-trip min/avg/max/std-dev = 28.957/30.346/32.221/1.088 ms

After 8 pings, the default route disappears.  tcpdump shows no other traffic
to/from the tunnel end-point than the pings and responses.  I can't find anything
similar reported elsewhere on the 'net.  Any clues gratefully received.

OS Version:

happy-idiot-talk:~:% uname -a 
FreeBSD happy-idiot-talk.infracaninophile.co.uk 6.2-PRERELEASE FreeBSD 6.2-PRERELEASE #9: Fri Sep 29 01:08:43 BST 2006     root at happy-idiot-talk.infracaninophile.co.uk:/usr/obj/usr/src/sys/HAPPY-IDIOT-TALK  i386

IPv6 related stuff from rc.conf:

gif_interfaces="gif0"
gifconfig_gif0="81.187.76.162 81.187.81.6"

ipv6_enable="YES"
ipv6_defaultrouter="-interface gif0"
ipv6_default_interface="gif0"
ipv6_ifconfig_gif0="2001:08b0:0151:0001::1 prefixlen 64"
ipv6_gateway_enable="YES"

happy-idiot-talk:~:% ifconfig gif0 
gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
        tunnel inet 81.187.76.162 --> 81.187.81.6
        inet6 fe80::240:5ff:fea5:8db7%gif0 prefixlen 64 scopeid 0x3 
        inet6 2001:8b0:151:1::1 prefixlen 64 

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       7 Priory Courtyard
                                                      Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey         Ramsgate
                                                      Kent, CT11 9PW

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