netdev - Re: [PATCH v2] ipv6: ip6_append_data_mtu do not handle the mtu of the second fragment properly

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Message-ID: <20140317190534.GE12291@order.stressinduktion.org>
Date:	Mon, 17 Mar 2014 20:05:34 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Xin Long <lucien.xin@...il.com>
Cc:	network dev <netdev@...r.kernel.org>,
	Gao feng <gaofeng@...fujitsu.com>
Subject: Re: [PATCH v2] ipv6: ip6_append_data_mtu do not handle the mtu of the second fragment properly

On Mon, Mar 17, 2014 at 12:51:01PM +0800, Xin Long wrote:
> In ip6_append_data_mtu(), when the xfrm mode is not tunnel(such as
> transport),the ipsec header need to be added in the first fragment, so the mtu
> will decrease to reserve space for it, then the second fragment come, the mtu
> should be turn back, as the commit 0c1833797a5a6ec23ea9261d979aa18078720b74
> said.  however, in the commit a493e60ac4bbe2e977e7129d6d8cbb0dd236be, it use
> *mtu = min(*mtu, ...) to change the mtu, which lead to the new mtu is alway
> equal with the first fragment's. and cannot turn back.
> 
> when I test through  ping6 -c1 -s5000 $ip (mtu=1280):
> ...frag (0|1232) ESP(spi=0x00002000,seq=0xb), length 1232
> ...frag (1232|1216)
> ...frag (2448|1216)
> ...frag (3664|1216)
> ...frag (4880|164)
> 
> which should be:
> ...frag (0|1232) ESP(spi=0x00001000,seq=0x1), length 1232
> ...frag (1232|1232)
> ...frag (2464|1232)
> ...frag (3696|1232)
> ...frag (4928|116)
> 
> so delete the min() when change back the mtu.
> 
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Fixes: 75a493e60ac4bb ("ipv6: ip6_append_data_mtu did not care about pmtudisc and frag_size")
Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Thank you!

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