From: Steffen Klassert <steffen.klassert@secunet•com>
To: David Miller <davem@davemloft•net>
Cc: netdev@vger•kernel.org
Subject: Re: [PATCH 1/4] ipv4: Fix pmtu propagating
Date: Thu, 13 Oct 2011 12:09:50 +0200 [thread overview]
Message-ID: <20111013100950.GO1830@secunet.com> (raw)
In-Reply-To: <20111012.170218.279202034199478303.davem@davemloft.net>
On Wed, Oct 12, 2011 at 05:02:18PM -0400, David Miller wrote:
>
> This dst_check() call will only do something if dst->obsolete is non-zero.
>
> If dst->obsolete can be set in these circumstances, that's a bug. The
> caller is responsible for providing either a freshly looked up route
> or a cached route which has had dst_check() or sk_dst_check() invoked
> upon it.
dst->obsolete was -1 in all cases I observed, regardless if connected or not.
>
> I am pretty sure these rules are followed by the current code.
>
> Again, there are only two scenerios:
>
> 1) 'rt' is just looked up by caller (f.e. udp_sendmsg() in rt == NULL case),
> here dst->obsolete is very unlikely to be non-zero.
>
> 2) Connected case, and we use cached route from the socket, but here
> we'll use sk_dst_check() to validate the route. sk_dst_check()
> makes the necessary dst->ops->check() call if dst->obsolete is
> non-zero, and in fact that is it's one and only job.
>
At least it seems that raw_sendmsg() and ping_sendmsg() don't use
a cached route, they do the route lookup in any case. I don't see
where we check if we learned a new pmtu in this cases.
I added some debugging output and saw that peer->pmtu_learned
has the correct pmtu value, but it never ends up in the metric
of the dst_entry.
With a ping -s 1400 to a destination where the pmtu is 1000
I get for each packet 'Frag needed and DF set (mtu = 1000)'.
That's how I noticed that something changed.
With the dst_check() in ip_setup_cork() I get
'Frag needed and DF set (mtu = 1000)' for the first packet and
all further packets reach the destination, as it was before
commmit 2c8cec5c.
next prev parent reply other threads:[~2011-10-13 10:09 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-11 11:08 [PATCH net 0/4] ipv4: various pmtu discovery fixes Steffen Klassert
2011-10-11 11:09 ` [PATCH 1/4] ipv4: Fix pmtu propagating Steffen Klassert
2011-10-12 21:02 ` David Miller
2011-10-13 10:09 ` Steffen Klassert [this message]
2011-10-13 17:58 ` David Miller
2011-10-14 5:54 ` Steffen Klassert
2011-10-17 12:18 ` Steffen Klassert
2011-10-19 9:07 ` Gao feng
2011-10-19 19:32 ` David Miller
2011-11-08 19:19 ` David Miller
2011-11-08 19:33 ` David Miller
2011-11-09 12:08 ` Steffen Klassert
2011-11-21 7:56 ` Steffen Klassert
2011-12-01 18:40 ` David Miller
2011-10-11 11:10 ` [PATCH 2/4] ipv4: Update pmtu informations on inetpeer only for output routes Steffen Klassert
2011-10-12 21:08 ` David Miller
2011-10-14 6:34 ` Steffen Klassert
2011-11-08 19:36 ` David Miller
2011-11-09 12:11 ` Steffen Klassert
2011-11-14 10:12 ` Steffen Klassert
2011-11-14 19:33 ` David Miller
2011-11-15 10:00 ` Steffen Klassert
2011-11-22 13:20 ` Steffen Klassert
2011-10-11 11:11 ` [PATCH 3/4] ipv4: Fix inetpeer expiration handling Steffen Klassert
2011-10-20 6:24 ` Gao feng
2011-11-08 19:38 ` David Miller
2011-11-09 12:47 ` Steffen Klassert
2011-10-11 11:12 ` [PATCH 4/4] ipv4: Fix inetpeer expire time information Steffen Klassert
2011-10-11 19:54 ` [PATCH net 0/4] ipv4: various pmtu discovery fixes David Miller
2011-11-08 19:41 ` David Miller
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