ipv6 and magically vanishing routes via gif0

[Stefan `Sec` Zehl]

Hi,

I just upgraded from FreeBSD-5 to -6, and now my default route via gif0
vanishes after 7 seconds.

| ice:~#ifconfig gif0
| gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
|         tunnel inet 194.77.85.2 --> 193.149.44.208
|         inet6 fe80::20e:a6ff:fe04:ea37%gif0 prefixlen 64 scopeid 0x14
|         inet6 2001:608:9::1 prefixlen 128
| 
| ice:~#route add -inet6 default -interface gif0
| add net default: gateway gif0
| 
| ice:~#ping6 www.kame.net
| PING6(56=40+8+8 bytes) 2001:608:9::1 --> 2001:200:0:8002:203:47ff:fea5:3085
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=0 hlim=42 time=343.451 ms
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=1 hlim=45 time=349.477 ms
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=2 hlim=45 time=349.689 ms
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=3 hlim=42 time=342.212 ms
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=5 hlim=42 time=342.123 ms
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=6 hlim=45 time=348.703 ms
| 16 bytes from 2001:200:0:8002:203:47ff:fea5:3085, icmp_seq=7 hlim=45 time=348.479 ms
| ping6: sendmsg: No route to host
| ping6: wrote www.kame.net 16 chars, ret=-1

In fact, any route '-interface gif0' will vanish 7 seconds after the
first packet via that link.

After some wild guesses, I found out, that ndp seems to be the culprit
here. -- If I disable ndp on gif0 with 

| ice:~#ndp -i gif0 -- -nud
| linkmtu=0, maxmtu=1280, curhlim=64, basereachable=30s0ms, reachable=18s, retrans=1s0ms
| Flags: accept_rtadv

Then the routing table stays as it should.

The question is, am I missing something here? Can anybody reproduce that
problem?

It seems wrong that the kernel would delete static routes without even a
single log message.  Furthermore I find it kind of strange that there is
neighbour discovery happening at all on an tunnel interface.

My v6 relevant config:

| ipv6_enable="YES"
| ipv6_network_interfaces="vr0 lo0 gif0"
| ipv6_ifconfig_vr0="2001:608:9:42:: eui64"
| ipv6_ifconfig_vr0_alias0="2001:608:9::42/128"
| ipv6_ifconfig_vr0_alias0="fec0::35/128" # Site-local DNS
| ipv6_ifconfig_gif0="2001:608:9::1/128"
| 
| ipv6_defaultrouter="-interface gif0"
| 
| ipv6_gateway_enable="YES"
| rtadvd_enable="YES"
| rtadvd_interfaces="vr0"
| 
| myhostip="194.77.85.2"
| gif_interfaces="gif0"
| gifconfig_gif0="$myhostip 193.149.44.208"

CU,
    Sec
-- 
The facts, although interesting, are irrelevant.