netdev - Re: [PATCH] ipv6: don't call addrconf_dst

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140108080528.GD9007@order.stressinduktion.org>
Date:	Wed, 8 Jan 2014 09:05:28 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Gao feng <gaofeng@...fujitsu.com>
Cc:	chenweilong <chenweilong@...wei.com>,
	David Miller <davem@...emloft.net>, kumaran.4353@...il.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv6: don't call addrconf_dst_alloc again when enable lo

On Wed, Jan 08, 2014 at 03:50:09PM +0800, Gao feng wrote:
> On 01/03/2014 02:53 PM, Hannes Frederic Sowa wrote:
> > On Thu, Jan 02, 2014 at 05:33:15PM +0800, chenweilong wrote:
> >> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> >> index 62d1799..d2f8c0a 100644
> >> --- a/net/ipv6/addrconf.c
> >> +++ b/net/ipv6/addrconf.c
> >> @@ -2422,8 +2422,9 @@ static void init_loopback(struct net_device *dev)
> >>  			if (sp_ifa->flags & (IFA_F_DADFAILED | IFA_F_TENTATIVE))
> >>  				continue;
> >>
> >> -			if (sp_ifa->rt)
> >> -				continue;
> >> +			if (sp_ifa->rt && sp_ifa->rt->dst.dev == dev) {
> >> +				ip6_del_rt(sp_ifa->rt);
> >> +			}
> >>
> >>  			sp_rt = addrconf_dst_alloc(idev, &sp_ifa->addr, 0);
> >>
> > 
> > Maybe this change would not be that bad after all, as those ifa attached dsts
> > are already dead and queued up for gc and should not get inserted back.
> 
> I like this idea, maybe the below patch is better. we only need to delete this
> route when it has been added to garbage list.
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 1a341f7..4dca886 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -2610,8 +2610,16 @@ static void init_loopback(struct net_device *dev)
>                         if (sp_ifa->flags & (IFA_F_DADFAILED | IFA_F_TENTATIVE))
>                                 continue;
> 
> -                       if (sp_ifa->rt)
> -                               continue;
> +                       if (sp_ifa->rt) {
> +                               /* This dst has been added to garbage list when
> +                                * lo device down, delete this obsolete dst and
> +                                * reallocate new router for ifa. */
> +                               if (sp_ifa->rt->dst.obsolete > 0) {
> +                                       ip6_del_rt(sp_ifa->rt);
> +                                       sp_ifa->rt = NULL;
> +                               } else
> +                                       continue;
> +                       }
> 
>                         sp_rt = addrconf_dst_alloc(idev, &sp_ifa->addr, false);

It looks like it can work but I don't know if we should just fix this the
clean way (see below).

> > I'll try to just disable routes without removing them at all when we set an
> > interface to down at the weekend.
> > 
> 
> How do you decide which route should be disabled?  use rt6_flags? I don't know
> if your way will cause miscarriage.

What I did so far is that I added a new function next to rt6_ifdown that
only gets called if interface gets shutdown but not unregistered (from
addrconf_ifdown).

fib6_clean_all then iterates over the whole routing table with a new predicate
function which checks in the same way like fib6_ifdown, if it is a matching route
(the interfaces match up) and if so, toggles a new "DEAD" flag in rt6i_flags.

When bringing up the interface I distinguish between up and register and just
clear this death flag from the routes on bringing it up.

fib lookup code then does not honour those routes.

I had no time to test this thoroughly at the weekend and still have some code
paths were I am unsure. Do you see any problems with this so far? We could
then delete the special cases on loopback interface init.

Thanks,

  Hannes

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html