Subject: IPv6 Extension Headers

From: Srinivas Goud <[email-masked]>
Date: Mon, 27 Jun 2005 17:11:01 +0530

Hello All,
I am a beginner and working on IPv6 Extension Headers Implementation for IPSec.
I am confused with freeBSD implementation and RFC2460 specification
for Destination Options.

My interpretation from RFC2460 is that,  If a packet consists of
hop-by-hop and destination extension headers, destination header
should be inserted inside AH.
i.e., hop + AH + dst.

But freeBSD implementation is the other way,
i.e., hop + dst + AH.

which is the correct way of implementation according to RFC2460? Please
let me know, if my interpretation is wrong.

Any help/suggestion is greatly appreciated.

Regards,
Srinivas.

-- 
Srinivas Goud
"Everything is Nicer when shared with a Friend"

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From: Francis Dupont <[email-masked]>
Date: Mon, 27 Jun 2005 14:23:10 +0200

In your previous mail you wrote:

=> RFC 2460 is not complete about positions of destination options

   
=> this is the correct way if (and only if) the destination option
is a home address option.

Regards

[email-masked]

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From: Srinivas Goud <[email-masked]>
Date: Tue, 28 Jun 2005 10:29:31 +0530

Hi Francis,
I have some more queries about RFC2460,  Please let me know the
insertion of AH in the following cases:

from RFC2460: (section 4.1)
   Each extension header should occur at most once, except for the
   Destination Options header which should occur at most twice (once
   before a Routing header and once before the upper-layer header).

1. hop + dst                           (you have clarified in previous mail)
2. hop + dst + route                (let me know AH insertion place)
3. hop + dst + route + dst        (let me know AH insertion place)

from RFC2460: (section 4.1)
   IPv6 nodes must accept and attempt to process extension headers in
   any order and occurring any number of times in the same packet,
   except for the Hop-by-Hop Options header which is restricted to
   appear immediately after an IPv6 header only.  Nonetheless, it is
   strongly advised that sources of IPv6 packets adhere to the above
   recommended order until and unless subsequent specifications revise
   that recommendation.

1. hop + dst + dst                                               (let
me know AH insertion place)
2. hop + dst + dst + route + route                          (let me
know AH insertion place)
3. hop + dst + dst + route + route + dst + dst           (let me know
AH insertion place)
4. hop + dst + route + dst + dst + route + dst + dst   (let me know AH
insertion place)

Regards,
Srinivas.

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From: Francis Dupont <[email-masked]>
Date: Tue, 28 Jun 2005 14:25:48 +0200

Hi Francis,

=> in fact the destination options header can occur three times.

   
=> look at the RFC 3775!

   1. hop + dst + dst                                               (let

=> in fact you have to look at the destination options:
 - if they apply to intermediate destination the header must be before
   the first routing header and after if there is one the hop-by-hop header,
   and AH is always after the last routing header.
 - home address option must be after the last routing header if there is one,
   and before the fragmentation header if there is one. AH is always after
   the fragmentation header.
 - options for the final destination must be after any IPsec header if there
   is one, and before the upper layer and final (i.e., not extension) header.
   So AH is always before this kind of destination options header.
The only case I don't know if it should supported is where options for
intermediate destionations and multiple routing headers are mixed. BTW
this case should not happen with current registered destination options
and routing header types...

Regards

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From: Srinivas Goud <[email-masked]>
Date: Wed, 29 Jun 2005 13:17:33 +0530

Hi Francis, 
Thank you very much for the information.  I am proceeding with the
implementation.
How do we distinguish the destination options? 
(intermediate destination / home address destination / final destination)

As per my understanding intermediate destination is the one which is
coming before routing header and final destination is the one which is
coming after routing header.
Is my understanding correct?  
I am not having clear idea about home address option.

Regards,
Srinivas.