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SubjectRe: [ 150/184] ipv4: check rt_genid in dst_check
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On Tue, 2013-06-04 at 19:24 +0200, Willy Tarreau wrote:
> 2.6.32-longterm review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Benjamin LaHaise <bcrl@kvack.org>
>
> commit d11a4dc18bf41719c9f0d7ed494d295dd2973b92
> Author: Timo Ters <timo.teras@iki.fi>
> Date: Thu Mar 18 23:20:20 2010 +0000
>
> ipv4: check rt_genid in dst_check
>
> Xfrm_dst keeps a reference to ipv4 rtable entries on each
> cached bundle. The only way to renew xfrm_dst when the underlying
> route has changed, is to implement dst_check for this. This is
> what ipv6 side does too.
>
> The problems started after 87c1e12b5eeb7b30b4b41291bef8e0b41fc3dde9
> ("ipsec: Fix bogus bundle flowi") which fixed a bug causing xfrm_dst
> to not get reused, until that all lookups always generated new
> xfrm_dst with new route reference and path mtu worked. But after the
> fix, the old routes started to get reused even after they were expired
> causing pmtu to break (well it would occationally work if the rtable
> gc had run recently and marked the route obsolete causing dst_check to
> get called).
>
> Signed-off-by: Timo Teras <timo.teras@iki.fi>
> Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
> Signed-off-by: David S. Miller <davem@davemloft.net>
>
> This commit is based on the above, with the addition of verifying blackhole
> routes in the same manner.

That addition doesn't seem to correspond to anything in mainline. Why
should 2.6.32 differ?

Ben.

> Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
> net/ipv4/route.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 58f141b..f16d19b 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -1412,7 +1412,7 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
> dev_hold(rt->u.dst.dev);
> if (rt->idev)
> in_dev_hold(rt->idev);
> - rt->u.dst.obsolete = 0;
> + rt->u.dst.obsolete = -1;
> rt->u.dst.lastuse = jiffies;
> rt->u.dst.path = &rt->u.dst;
> rt->u.dst.neighbour = NULL;
> @@ -1477,7 +1477,7 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
> struct dst_entry *ret = dst;
>
> if (rt) {
> - if (dst->obsolete) {
> + if (dst->obsolete > 0) {
> ip_rt_put(rt);
> ret = NULL;
> } else if ((rt->rt_flags & RTCF_REDIRECTED) ||
> @@ -1700,7 +1700,9 @@ static void ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
>
> static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie)
> {
> - return NULL;
> + if (rt_is_expired((struct rtable *)dst))
> + return NULL;
> + return dst;
> }
>
> static void ipv4_dst_destroy(struct dst_entry *dst)
> @@ -1862,7 +1864,8 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
> if (!rth)
> goto e_nobufs;
>
> - rth->u.dst.output= ip_rt_bug;
> + rth->u.dst.output = ip_rt_bug;
> + rth->u.dst.obsolete = -1;
>
> atomic_set(&rth->u.dst.__refcnt, 1);
> rth->u.dst.flags= DST_HOST;
> @@ -2023,6 +2026,7 @@ static int __mkroute_input(struct sk_buff *skb,
> rth->fl.oif = 0;
> rth->rt_spec_dst= spec_dst;
>
> + rth->u.dst.obsolete = -1;
> rth->u.dst.input = ip_forward;
> rth->u.dst.output = ip_output;
> rth->rt_genid = rt_genid(dev_net(rth->u.dst.dev));
> @@ -2187,6 +2191,7 @@ local_input:
> goto e_nobufs;
>
> rth->u.dst.output= ip_rt_bug;
> + rth->u.dst.obsolete = -1;
> rth->rt_genid = rt_genid(net);
>
> atomic_set(&rth->u.dst.__refcnt, 1);
> @@ -2411,7 +2416,8 @@ static int __mkroute_output(struct rtable **result,
> rth->rt_gateway = fl->fl4_dst;
> rth->rt_spec_dst= fl->fl4_src;
>
> - rth->u.dst.output=ip_output;
> + rth->u.dst.output = ip_output;
> + rth->u.dst.obsolete = -1;
> rth->rt_genid = rt_genid(dev_net(dev_out));
>
> RT_CACHE_STAT_INC(out_slow_tot);
> @@ -2741,6 +2747,7 @@ static int ipv4_dst_blackhole(struct net *net, struct rtable **rp, struct flowi
> if (rt) {
> struct dst_entry *new = &rt->u.dst;
>
> + new->obsolete = -1;
> atomic_set(&new->__refcnt, 1);
> new->__use = 1;
> new->input = dst_discard;

--
Ben Hutchings
Theory and practice are closer in theory than in practice.
- John Levine, moderator of comp.compilers
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