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Date:      Mon, 09 Jul 2001 01:51:10 +0900 (JST)
From:      Motonori Shindo <mshindo@mshindo.net>
To:        freebsd-net@FreeBSD.ORG
Subject:   Tunnel Mode AH
Message-ID:  <20010709.015110.52175108.mshindo@mshindo.net>

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Hi,

I have a question regarding IPsec tunnel mode AH processing.

ipsec(4) says:

  AH tunnel may not work as you might expect.  If you configure ``require''
  policy against AH tunnel for inbound, tunneled packets will be rejected.
  This is because AH authenticates encapsulating (outer) packet, not the
  encapsulated (inner) packet.

I am seeing exactly what is explained in this paragraph; IKE (racoon)
successfully establishes IPsec SA for both directions and packets get
properly encapsulated (tunnel-mode AH) and sent to the peer but the
peer looks rejecting the packet. If I change the parameter in the
policy setting from 'required' to 'use', it works just fine.

setkey(8) also says that: 

  require means SA is required whenever the kernel deals with the
  packet. 

Even if the policy is specified as "required", it looks (at least, to
me) that SA (destination address, Security Protocol(AH/ESP), and SPI)
is properly established. I don't see anything that can prevent it from
working if the policy is specified as 'require'. 

Will anybody here help me understand this?

Regards,

=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=
 +----+----+     
 |.. .|    |     Motonori Shindo
 |_~__|    |     
 | .. |~~_~|     Sr. Systems Engineer
 | .  |    |     CoSine Communications Inc.
 +----+----+     
 C o S i n e     e-mail:  mshindo@cosinecom.com 
Communications
=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=



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