Hello,
AS57335 operates a 49 node anycast instance exclusively running OpenBSD. All
instances are hosted virtual machines (aka "VPS" instances) and all are
running a recent snapshot (kern.version=OpenBSD 6.4-current (GENERIC.MP) #381:
Mon Oct 22 22:18:48 MDT 2018). Eleven of these nodes exhibit strange ndp(8)
behavior causing IPv6 BGP sessions to flap at inconsistent intervals.
All eleven instances have the following in common:
vio(4) network interface
netmask of /64
do not use autoconf
Linux KVM hypervisor hosts (hw.vendor=QEMU & pvbus0 at mainbus0: KVM)
kern.timecounter.hardware=acpihpet0
v6 gateway is Cisco (based on OUI lookup)
no pf(4) rules
BGP session traffic is the only regular/recurring v6 traffic on the nodes.
Running a `ping6 google.com` in the background will occasionally allow BGP
sessions to stay alive for 6-12 hours (in some cases, one to two days).
>From looking at `ndp -nA 1` output, the gateway address state will change to
Delay with an expiry of ~45 seconds then set to Stale with an expiry of 24h.
When set Stale with 24h expiry, a link-local address with the gateway
linklayer in it (ex. fe80::e25f:b9ff:fed1:527f%vio0) is added with a state of
Delay and an expiry of 5 seconds. Once expiry reaches 1 second remaining, the
link-local entry begins three attempts at Probe, and at the first attempt the
gateway address expiry goes from 23h59m55s to 5s. After three Probe attempts,
the link-local entry is removed, and the gateway address expiry goes to 45s or
sometimes a bit less (38s is the lowest I've caught).
I admit of all the RFCs I've read, NDP is not any of them; nor have I gone
spelunking in the code base at all (I peeked once; and would need a buddy to
have a useful look again).
I am happy to add a pubkey to any and all systems exhibiting this behavior;
and of course provide any additional detail that might be useful.
Thanks
(please cc me as I am not subscribed to this list)
