netdev - Re: [PATCH 2/3] ipv4: Fix packet size calculation for IPsec packets in __ip_append

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Date:	Tue, 07 Jun 2011 07:06:57 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Steffen Klassert <steffen.klassert@...unet.com>
Cc:	David Miller <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 2/3] ipv4: Fix packet size calculation for IPsec
 packets in __ip_append_data

Le lundi 06 juin 2011 à 10:52 +0200, Steffen Klassert a écrit :
> On Mon, Jun 06, 2011 at 09:38:19AM +0200, Eric Dumazet wrote:
> > 
> > Woh, I am afraid I wont have time in following days to check your
> > assertion.
> 
> My test setup was the following:
> 
> I use an IPsec tunnel with tunnel endpoints 192.168.1.1 and 192.168.1.2
> 
> Then I do at 192.168.1.2
> 
> ping -c1 -M do -s 1410 192.168.1.1
> 
> PING 192.168.1.1 (192.168.1.1) 1410(1438) bytes of data.
> From 192.168.1.2 icmp_seq=1 Frag needed and DF set (mtu = 1438)
> 
> --- 192.168.1.1 ping statistics ---
> 0 packets transmitted, 0 received, +1 errors
> 
> So the packet matches the mtu but it is not send.
> I used a kernel with your patch as head commit.
> 
> Reverting your patch (going one commit deeper in the history):
> 
> ping -c1 -M do -s 1410 192.168.1.1
> 
> PING 192.168.1.1 (192.168.1.1) 1410(1438) bytes of data.
> 1418 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=3.01 ms
> 
> --- 192.168.1.1 ping statistics ---
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> rtt min/avg/max/mdev = 3.014/3.014/3.014/0.000 ms
> 
> > 
> > What about original problem then, how should we fix it ?
> > 
> 
> Hm, I don't know. I'll try to reproduce it here.
> 
> > We do have some cases where at least one fragment (the last one) is
> > oversized.
> 
> trailer_len is used only on IPsec so the poroblem exists only when
> using IPsec, right?
> 
> > 
> > I remember I used Nick Bowler scripts at that time, I might find them
> > again...
> 
> Would be nice if you could provide these scripts and some informations
> on how to reproduce the problem.
> 

Nick mail was :

http://www.spinics.net/lists/netdev/msg141308.html

Unfortunatly I could not find on my machines where I put my own
scripts...

Not a big deal, I suspect we can revert my commit if you say it added a
regression :)

Thanks


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