Short form:
I'm using rad to update local machines with the IPv6 address prefix
currently assigned by Verizon. It runs on my firewall/external router.
The router advertisement destructively changes the route and interface
of an address on that machine.
dhcpcd gets <prefix>/56 from Verizon fiber service.
manually ifconfig interface1 inet6 <prefix>::9/56
netstat -rn -f inet6 shows
<prefix/56>:: and <prefix>::9 routed via interface1
everything works.
rad message sent out from interface1:
<prefix>/56 valid 1000 preferred 10000
netstat now shows
<prefix/56> routed via lo0
<prefix>::9 is still on interface1
That address is now (mostly) unusable
Other addresses assigned to that interface work.
Is this expected?
Possible workarounds:
blocking loopback of router advertisements (preferred)
dhcp6 server for guest machines & fixed assignments
for servers/test machine (inconvenient or worse)
Monitor prefix for changes - hope that's not often
I have to assume the mechanism which processes RAs follows the
RFC and uses the link level address of the sender.
I hypothesize it sees lo0 as the sender
and Bad Things happen.
ding:236$ doas ifconfig cnmac0 inet6 2600:4040:xxxx:xxxx:7 prefixlen 56
ding:237$ netstat -rn -f inet6
2600:4040:xxxx:xxxx::/56 2600:4040:xxxx:xxx::7 UCn
0 0 - 4 cnmac0
2600:4040:xxxx:xxxx::7 f0:9f:c2:cf:9e:e7 UHLl
0 0 - 1 cnmac0
------- rad message
22:06:10.869060 fe80::f29f:c2ff:fecf:9ee7 > ff02::1: icmp6: router
advertisement
(chlim=64, pref=medium, router_ltime=1800, reachable_time=0,
retrans_time=0)
(prefix info: LA valid_ltime=7200, preferred_ltime=7200,
prefix=2600:4040:xxxx:xxx::/56)
(prefix info: LA valid_ltime=2592000, preferred_ltime=604800,
prefix=fde3:3eec:4f3c:29dc::/64)
(rdnss: lifetime=2000s, addr=fde3:3eec:4f3c:29dc::7)(dnssl:
opt_len=3) [icmp6 cksum ok] (len 128, hlim 255)
2600:4040:xxxx:xxx::/56 ::1 UGR 0 718 32768 56
lo0
2600:4040:xxxx:xxx::7 f0:9f:c2:cf:9e:e7 UHLl 0
16 - 1 cnmac0
There's a off-by-4 in RAD display in tcpdump. Will post that later.
I added the extra detail in that as well - will post if anyone things
it's useful.
geoff steckel
