On Wed, 19 Jan 2011 20:18:23 +0100
Jiri Bohac <[email protected]> wrote:

> Hi,
> 
> 
> The commit (29ba5fed1bbd09c2cba890798c8f9eaab251401d) causes
> another regression:
> 
> Prior to the commit, on a freshly booted system, when I do:
>       sysctl net.ipv6.conf.all.disable_ipv6=1
> Then any attempt to connect to ::1 will fail immediately with
> "Network is unreachable" (e.g. "ping6 ::1" or "telnet ::1 22".
> 
> After the commit, doing
>       sysctl net.ipv6.conf.all.disable_ipv6=1
> makes connection attempts to ::1 wait for a long time before they fail.
> 
> This is caused by the local route which is now left configured. 
> "ip -6 r l table all" has an additional line in its output:
>       local ::1 via :: dev lo  table local  proto none  metric 0  mtu 16436 
> rtt 40ms rttvar 40ms cwnd 3 advmss 16376 hoplimit 0
> 
> With both ::1 and 127.0.0.1 specified for localhost in
> /etc/hosts, disabling ipv6 now breaks many applications
> connecting to localhost. Deleting the local route manually solves
> the problems.
> 
> Could this be reverted, please?
> 
> I have the feeling that Eric's patch is the safest solution we
> have so far:
> 
> > Finding the real bug is beyond me right now, but fixing the regression
> > in disable_ipv6 is simple.  We can just delete ::1 when we bring down
> > the loopback interface, and it will be restored automatically when we
> > bring the loopback interface back up.
> > 
> > Signed-off-by: "Eric W. Biederman" <[email protected]>
> > ---
> > Index: linux-2.6.37-rc5.x86_64/net/ipv6/addrconf.c
> > ===================================================================
> > --- linux-2.6.37-rc5.x86_64.orig/net/ipv6/addrconf.c
> > +++ linux-2.6.37-rc5.x86_64/net/ipv6/addrconf.c
> > @@ -2727,6 +2727,7 @@ static int addrconf_ifdown(struct net_de
> >             /* If just doing link down, and address is permanent
> >                and not link-local, then retain it. */
> >             if (!how &&
> > +               !ipv6_addr_loopback(&ifa->addr) &&
> >                 (ifa->flags&IFA_F_PERMANENT) &&
> >                 !(ipv6_addr_type(&ifa->addr) & IPV6_ADDR_LINKLOCAL)) {
> >                     list_move_tail(&ifa->if_list, &keep_list);
> 

Eric's patch has other regressions, see the discussion.

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