Re: IPv6 default route flapping

[Jan Schaumann <jschauma%netmeister.org@localhost>]

Martin Husemann <martin%duskware.de@localhost> wrote:

> Well, adding -v or -vv would help here, especially to show the RA lifetime.

RA lifetime is 1800s:

IP6 (hlim 255, next-header ICMPv6 (58) payload length: 56) fe80::caa:49ff:feaf:1
815 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 56
        hop limit 255, Flags [managed], pref medium, router lifetime 1800s, reachable time 0ms, retrans timer 0ms
          source link-address option (1), length 8 (1): 0e:aa:49:af:18:15
            0x0000:  0eaa 49af 1815
          prefix info option (3), length 32 (4): 2600:1f18:400c:b800::/64, Flags [onlink], valid time infinity, pref. time infinity
            0x0000:  4080 ffff ffff ffff ffff 0000 0000 2600
            0x0010:  1f18 400c b800 0000 0000 0000 0000

> But more interesting is what happens on the routing socket, as that is
> where dhcpcd gets the idea of reachability from.
> 
> You can see that with: route monitor

got message of size 168 on Tue Apr 20 14:21:51 2021
RTM_MISS: Lookup failed on this address: len 168, pid 0, seq 0, errno 0, flags: 0x40<DONE>
locks: 0 inits: 0
sockaddrs: 0x3<DST,GATEWAY>
 fe80::caa:49ff:feaf:1815%xennet0 link#1
got message of size 168 on Tue Apr 20 14:21:54 2021
RTM_MISS: Lookup failed on this address: len 168, pid 0, seq 0, errno 0, flags: 0x40<DONE>
locks: 0 inits: 0
sockaddrs: 0x3<DST,GATEWAY>
 fe80::caa:49ff:feaf:1815%xennet0 link#1
got message of size 200 on Tue Apr 20 14:21:57 2021
RTM_MISS: Lookup failed on this address: len 200, pid 0, seq 0, errno 0, flags: 0x40<DONE>
locks: 0 inits: 0
sockaddrs: 0x43<DST,GATEWAY,AUTHOR>
 fe80::caa:49ff:feaf:1815%xennet0 link#1
2600:1f18:400c:b800:bc3c:63cc:7e5d:1f96
got message of size 168 on Tue Apr 20 14:22:03 2021
RTM_CHANGE: Change Metrics, Flags or Gateway: len 168, pid 0, seq 0, errno 0, flags: 0x2445<UP,HOST,DONE,LLINFO,CLONED>
locks: 0 inits: 0
sockaddrs: 0x3<DST,GATEWAY>
 fe80::caa:49ff:feaf:1815%xennet0 0e:aa:49:af:18:15
got message of size 168 on Tue Apr 20 14:22:11 2021
RTM_MISS: Lookup failed on this address: len 168, pid 0, seq 0, errno 0, flags: 0x40<DONE>
locks: 0 inits: 0
sockaddrs: 0x3<DST,GATEWAY>
 fe80::caa:49ff:feaf:1815%xennet0 link#1
got message of size 168 on Tue Apr 20 14:22:14 2021
RTM_MISS: Lookup failed on this address: len 168, pid 0, seq 0, errno 0, flags: 0x40<DONE>
locks: 0 inits: 0
sockaddrs: 0x3<DST,GATEWAY>
 fe80::caa:49ff:feaf:1815%xennet0 link#1
got message of size 200 on Tue Apr 20 14:22:17 2021
RTM_MISS: Lookup failed on this address: len 200, pid 0, seq 0, errno 0, flags: 0x40<DONE>
locks: 0 inits: 0
sockaddrs: 0x43<DST,GATEWAY,AUTHOR>
 fe80::caa:49ff:feaf:1815%xennet0 link#1
2600:1f18:400c:b800:bc3c:63cc:7e5d:1f96
got message of size 168 on Tue Apr 20 14:22:23 2021
RTM_CHANGE: Change Metrics, Flags or Gateway: len 168, pid 0, seq 0, errno 0, flags:
0x2445<UP,HOST,DONE,LLINFO,CLONED>
locks: 0 inits: 0
sockaddrs: 0x3<DST,GATEWAY>
 fe80::caa:49ff:feaf:1815%xennet0 0e:aa:49:af:18:15

and so on.

-Jan