On Wed, Jul 17, 2024 at 09:19:53AM +0800, Zhenlei Huang wrote: > > > > On Jul 17, 2024, at 4:04 AM, Mark Johnston <ma...@freebsd.org> wrote: > > > > Hello, > > > > When IPv6 SLAAC is configured for an interface, the kernel will update > > its default router list upon receipt of a router advertisement. In so > > doing it may install a default route; in the kernel this happens in > > defrouter_addreq(). > > > > If one uses "route flush" or "service routing restart" to reset the > > routing tables, the default router list is not purged, so a subsequent > > RA from the original default router does not update the list, and so > > does not re-create the default route, even if one re-runs rtsol(8). > > > > This appears to be a bug, but I'm not sure where best to fix it. Should > > "service routing restart" invoke "ndp -R" to flush the default router > > list? > > That can be a workaround, but not the ideal fix. > > > Should route(8) handle this as part of a flush command? > > No, I do not think so. route(8) should handle the routing / FIB parts. > IPv6 default route list is maintained as a per AF basis. Handling the > default route list via route(8), aka the userland, seems to be more a > HACK. > > > Or > > something else? > > I'd propose that the kernel handle this situation, so that for other cases > such as `route -6 delete default`, or route change event from NETLINK > socket, the IPv6 SLAAC default router feature can also work as expected. > > To be precise, `sys/netinet6/nd6_rtr.c` listen on route events and clear > the `installed` flag on deleting the previously installed default route, or > maybe purge all default route list. Then the next time the kernel receives > a RA it re-installs the default route.
Thank you for the hint. It turns out that the kernel already does this, but a bug was preventing it from working correctly. https://reviews.freebsd.org/D46020 fixes the problem for me. > This IMO may have side effect that user may really want to delete the > default route while not providing an explicit default route. I think for that > case user should disable accepting RA on the interface ( aka > ifconfig em0 inet6 no_radr, or turn on net.inet6.ip6.no_radr globally). That sounds perfectly reasonable. > How about this proposal ? > > > Best regards, > Zhenlei >
