svn commit: r242074 - head/etc/rc.d

[Brian Somers]

On Fri, Oct 26, 2012 at 03:52:15AM +0900, Hiroki Sato wrote:
> Brian Somers <brian at FreeBSD.org> wrote
>   in <20121025171827.GA59432 at thong.lan.Awfulhak.org>:
> 
> br> After upgrading from 8-STABLE to 9-STABLE on Monday, IPv6 routing
> br> advertisments were broken.  Disabling accept (enabling send) appeared
> br> to be necessary to get things up and running.
> br>
> br> As you say, net.inet6.ip6.accept_rtadv is set to zero (off, meaning
> br> that we *can* send advertisments), so I don't now what the issue
> br> is.  Irrespective of this, I think it's useful to explicitly set
> br> the interface to be able to send advertisments when running rtadvd
> br> - just in case the sysctl is set to 1 elsewhere.
> br>
> br> Doing an "ifconfig <interface> inet6 accept_rtadv" after boot doesn't
> br> seem to disable sending advertisments, so I'm finding it difficult
> br> to test this remotely...  testing is awkward when I'm not at home
> br> as this machine is also suffering from the "can't reboot" issue!!
> br>
> br> I'll look into why the sysctl doesn't seem to behave as expected
> br> when I get home this evening.
> 
>  In 9.X and later the meaning of net.inet6.ip6.accept_rtadv has been
>  changed and the flag for whether receiving RAs or not is now in a
>  per-IF basis.  9.0R release note says the following:
> 
>   | The sysctl(8) variable net.inet6.ip6.accept_rtadv has been
>   | changed. It was a system-wide configuration knob which controlled
>   | whether the system accepts ICMPv6 Router Advertisement messages or
>   | not. In FreeBSD 9.0-RELEASE, this knob is converted into a
>   | per-interface inet6 accept_rtadv ifconfig(8) option. Although the
>   | sysctl(8) variable is available still in FreeBSD 9.0-RELEASE, it
>   | now controls whether the per-interface option is set by default or
>   | not. The default value is 0 (not accept the RA messages).
> 
>  So, by default RAs can be sent on any interface even if setting
>  net.inet6.ip6.accept_rtadv=1 manually after a boot because no
>  accept_rtadv per-IF flag is set.  I guess this was a source of the
>  confusion.  I am not sure why setting accept_rtadv flag on an
>  interface did not prevent from sending RAs in your case.  It is not
>  an intended behavior.  If it is reproducible, please let me know.
> 
>  The release notes explains more details of IPv6 configuration
>  migration from 8.X to 9.X.

When I reboot and don't use -accept_rtadv (and leave
net.inet6.ip6.accept_rtadv set to zero), I repeatedly see this in
/var/log/messages:

Oct 26 16:31:26 gw rtadvd[2879]: non-zero lifetime RA on RA receiving interface sk0.  Ignored.
Oct 26 16:31:33 gw rtadvd[2879]: non-zero lifetime RA on RA receiving interface bridge0.  Ignored.
Oct 26 16:31:42 gw rtadvd[2879]: non-zero lifetime RA on RA receiving interface sk0.  Ignored.
Oct 26 16:31:49 gw rtadvd[2879]: non-zero lifetime RA on RA receiving interface bridge0.  Ignored.

This seems to be the problem.  Because check_accept_rtadv() (in
rtadvd) reports the interface as being able to accept RAs (it finds
the ND6_IFF_ACCEPT_RTADV flag), it drops outgoing RAs and nothing
happens.

-- 
Brian Somers                                          <brian at Awfulhak.org>
Don't _EVER_ lose your sense of humour !               <brian at FreeBSD.org>
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