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Date:      Tue, 23 Feb 2010 13:21:27 +0100
From:      VANHULLEBUS Yvan <vanhu@FreeBSD.org>
To:        Denis Antrushin <DAntrushin@mail.ru>
Cc:        "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, freebsd-net@freebsd.org
Subject:   Re:  IPSec connection troubles
Message-ID:  <20100223122127.GA45649@zeninc.net>
In-Reply-To: <4B83B79F.102@mail.ru>
References:  <4B73E902.6050301@mail.ru> <20100211124756.GA9528@zeninc.net> <20100211125420.G27327@maildrop.int.zabbadoz.net> <4B83B79F.102@mail.ru>

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On Tue, Feb 23, 2010 at 02:10:23PM +0300, Denis Antrushin wrote:
[...]
> ipsec-tools understand NAT-OA payload in IKE exchange, but then simply
> discard it and do not send this information to kernel.
> In ipsec-tool mailing list archives I found mention that linux does not
> need this OA info, because it simply recomputes/ignore TCP checksums.

Userland part is the most simple to do, as PFKey extension for NAT-OA
already exists, it haven't been done so far because it's useless until
someone does the big part of the kob on a kernel...


> Can we do the same or this is unacceptable for FreeBSD and we want
> NAT-OA communicated to kernel by IKEd?
> I made a simple patch to ipsec_common_input_cb() to ignore TCP/UDP
> checksums of ESP-protected packets and I happily can connect to
> Solaris VPN server from behind the NAT device (after working around
> some security policy matching issues).

Just adding some code to always ignore such checksums sounds like a
bad idea for me.....

But maybe we could have at least a sysctl (disabled by default) to
ignore them.....



Yvan.



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