Subject: Re: [mobile-ip] Coexistence with other uses for routing header

From: "Charles E. Perkins" <[email-masked]>
Date: Mon, 24 Sep 2001 10:10:13 -0700

Hello Francis,

Francis Dupont wrote:
> 
>  In your previous mail you wrote:
> 
>    > PS: you have a similar issue when the source route is reversed,
>    > the last (becomes the first) intermediate hop (i.e. the care-of address)
>    > SHOULD be removed. If it is not, the first hop is the sender node
>    > and if policy is to disable forwarding of source routed packet on hosts
>    > (cf. a current thread in the IPv6 WG mailing list) one is in trouble.
> 
>    But the routing header does NOT require source route reversal,
>    as best I understand it.
> 
> => RFC 2460 uses the word "permitted" but in fact reversing is done
> if and only if there is a (valid) AH.
> 
>    If this isn't clear, then I think it
>    should be made clear in the Mobile IPv6 text.
> 
> => I agree, this must be made clear in the Mobile IPv6 text.

I checked, and I think the handling for Routing Headers is pretty
clear in the text.  The mobile node doesn't put its care-of address
in a routing header for the correspondent node, and the correspondent
node checks its Binding Cache before putting in the care-of address
into a Routing Header.  These cases are not in the danger zone of
reversing "unauthorized" Routing Headers.

Regards,
Charlie P.

---

From: Francis Dupont <[email-masked]>
Date: Tue, 25 Sep 2001 10:04:46 +0200

=> the issue is not in reversing "unauthorized" RHs, the issue is in
reversing "authorized" RHs from the correspondent node and keeping
the care-of address in them (the CoA is the last intermediate in
received RHs and in careless reversing the CoA becomes the first one).
 "Authorized" RHs are managed through reversing using the property than
reverse o reverse = Id, if the mobility adds something in the RH, the
other end SHOULD removes it. BTW your proposed text should avoid
spurious multiple additions of the CoA in RHs by the correspondent
if the mobile node doesn't apply my idea.

Thanks

[email-masked]

PS: this is very easy to implement and changes are only in
the mobile node code.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Tue, 25 Sep 2001 11:16:05 -0700

> if the mobile node doesn't apply my idea.

O.K.  Now I see the point, and remember that this point has been
raised in the past.  The mobile node should use natural route
table selection when sending packets to the correspondent node,
not route reversal of a source route from the correspondent node.
But there is already text in the draft that says what you want,
in section 10.3:

   In addition, the general procedures defined by IPv6 for Routing
   headers suggest that a received Routing header MAY be automatically 
   "reversed" to construct a Routing header for use in any response
   packets sent by upper-layer protocols, if the received packet is
   authenticated [6].  If this is done for upper-layer protocol response
   packets sent by a mobile node while away from home, the mobile
   node SHOULD NOT include its own care-of address, which appears in  
   the Routing header of the received packet, in the reversed route
   for the response packet.            ...........

Is there more to do?

Regards,
Charlie P.