2010-12-12 01:20:22

by Andrei Vagin

Subject: [PATCH] net: delete expired route in ip6_pmtu_deliver

The first big packets sent to a "low-MTU" client correctly
triggers the creation of a temporary route containing the reduced MTU.

But after the temporary route has expired, new ICMP6 "packet too big"
will be sent, rt6_pmtu_discovery will find the previous EXPIRED route
check that its mtu isn't bigger then in icmp packet and do nothing
before the temporary route will not deleted by gc.

I make the simple experiment:
while :; do
time ( dd if=/dev/zero bs=10K count=1 | ssh hostname dd of=/dev/null ) || break;
done

The "time" reports real 0m0.197s if a temporary route isn't expired, but
it reports real 0m52.837s (!!!!) immediately after a temporare route has
expired.

Cc: [email protected]
Signed-off-by: Andrey Vagin <[email protected]>
---
net/ipv6/route.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 96455ffb..7659d6f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1565,11 +1565,16 @@ static void rt6_do_pmtu_disc(struct in6_addr *daddr, struct in6_addr *saddr,
{
struct rt6_info *rt, *nrt;
int allfrag = 0;
-
+again:
rt = rt6_lookup(net, daddr, saddr, ifindex, 0);
if (rt == NULL)
return;

+ if (rt6_check_expired(rt)) {
+ ip6_del_rt(rt);
+ goto again;
+ }
+
if (pmtu >= dst_mtu(&rt->dst))
goto out;

--
1.7.2.1

2010-12-16 20:28:28

by David Miller

Subject: Re: [PATCH] net: delete expired route in ip6_pmtu_deliver

From: Andrey Vagin <[email protected]>
Date: Sun, 12 Dec 2010 04:20:11 +0300

> The first big packets sent to a "low-MTU" client correctly
> triggers the creation of a temporary route containing the reduced MTU.
>
> But after the temporary route has expired, new ICMP6 "packet too big"
> will be sent, rt6_pmtu_discovery will find the previous EXPIRED route
> check that its mtu isn't bigger then in icmp packet and do nothing
> before the temporary route will not deleted by gc.
>
> I make the simple experiment:
> while :; do
> time ( dd if=/dev/zero bs=10K count=1 | ssh hostname dd of=/dev/null ) || break;
> done
>
> The "time" reports real 0m0.197s if a temporary route isn't expired, but
> it reports real 0m52.837s (!!!!) immediately after a temporare route has
> expired.
>
> Signed-off-by: Andrey Vagin <[email protected]>

Applied and queued up for -stable, thanks.