The default route a guest obtains via NDP has an
expiry. We set this
to the maximum allowed, 65535s (about 18 hours). We missed, however,
that after that expiry, the guest won't send a new Router
Solicitation. Instead it expects an unsolicited Router Advertisement
to have come at some point before the expiry. This means that on an
IPv6 setup, the default will disappear after 18 hours.
Correct this by sending unsolicited Router Advertisements as required
by RFC 4861. Along the way we make a number of small cleanups to the
NDP code.
Link:
https://github.com/kubevirt/kubevirt/issues/13191
v2:
* Some minor stylistic fixes
* Use srandom()
* Better explanation of the random requirements for the RAs