Subject: Re: [PATCH 1/2] ipv6: avoid blackhole and prohibited entries upon prefix purge [v2]

From: Nicolas Dichtel <[email-masked]>
Date: Mon, 07 Jan 2013 11:25:15 +0100

Le 05/01/2013 22:44, Romain KUNTZ a écrit :
> Mobile IPv6 provokes a kernel Oops since commit 64c6d08e (ipv6:
> del unreachable route when an addr is deleted on lo), because
> ip6_route_lookup() may also return blackhole and prohibited
> entry. However, these entries have a NULL rt6i_table argument,
> which provokes an Oops in __ip6_del_rt() when trying to lock
> rt6i_table->tb6_lock.
>
> Beside, when purging a prefix, blakhole and prohibited entries
> should not be selected because they are not what we are looking
> for.
>
> We fix this by adding two new lookup flags (RT6_LOOKUP_F_NO_BLK_HOLE
> and RT6_LOOKUP_F_NO_PROHIBIT) in order to ensure that such entries
> are skipped during lookup and that the correct entry is returned.
>
> [v2]: use 'goto out;' instead of 'goto again;' to avoid unnecessary
> oprations on rt (as suggested by Eric Dumazet).
>
> Signed-off-by: Romain Kuntz <[email-masked]>
> ---
>   include/net/ip6_route.h |    2 ++
>   net/ipv6/addrconf.c     |    4 +++-
>   net/ipv6/fib6_rules.c   |    4 ++++
>   3 files changed, 9 insertions(+), 1 deletions(-)
>
> diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
> index 27d8318..3c93743 100644
> --- a/include/net/ip6_route.h
> +++ b/include/net/ip6_route.h
> @@ -30,6 +30,8 @@ struct route_info {
>   #define RT6_LOOKUP_F_SRCPREF_TMP	0x00000008
>   #define RT6_LOOKUP_F_SRCPREF_PUBLIC	0x00000010
>   #define RT6_LOOKUP_F_SRCPREF_COA	0x00000020
> +#define RT6_LOOKUP_F_NO_BLK_HOLE	0x00000040
> +#define RT6_LOOKUP_F_NO_PROHIBIT	0x00000080
>
>   /*
>    * rt6_srcprefs2flags() and rt6_flags2srcprefs() translate
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 408cac4a..1891e23 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -948,7 +948,9 @@ static void ipv6_del_addr(struct inet6_ifaddr *ifp)
>   		fl6.flowi6_oif = ifp->idev->dev->ifindex;
>   		fl6.daddr = prefix;
>   		rt = (struct rt6_info *)ip6_route_lookup(net, &fl6,
> -							 RT6_LOOKUP_F_IFACE);
> +						RT6_LOOKUP_F_IFACE |
> +						RT6_LOOKUP_F_NO_BLK_HOLE |
> +						RT6_LOOKUP_F_NO_PROHIBIT);
>
>   		if (rt != net->ipv6.ip6_null_entry &&
Is it not simpler to test the result here (net->ipv6.ip6_blk_hole_entry and
net->ipv6.ip6_prohibit_entry) like for the null_entry?
It will also avoid adding more flags.