Re: [shim6] AD review of draft-ietf-shim6-multihome-shim-api

Miika Komu <mkomu@cs.hut.fi> Wed, 13 October 2010 04:57 UTC

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Date: Wed, 13 Oct 2010 07:59:56 +0300
From: Miika Komu <mkomu@cs.hut.fi>
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Cc: shim6 <shim6@ietf.org>, "kristian.slavov@ericsson.com" <kristian.slavov@ericsson.com>
Subject: Re: [shim6] AD review of draft-ietf-shim6-multihome-shim-api
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Hi,

On 12/10/10 20:54, Henderson, Thomas R wrote:

>> -----Original Message----- From: Miika Komu
>> [mailto:mkomu@cs.hut.fi] Sent: Friday, October 08, 2010 4:35 AM To:
>> Jari Arkko Cc: Shinta Sugimoto; shim6;
>> kristian.slavov@ericsson.com; Henderson, Thomas R Subject: Re:
>> [shim6] AD review of draft-ietf-shim6-multihome-shim-api
>>
> <snip>
>
>>> However, IIRC in HIP you cannot propose a locator for the other
>>> side, only for yourself. Or is your plan that you move the
>> session to
>>> another locator and that if that node happens to be the
>> wrong one, then
>>> it cannot decrypt the traffic anyway, so there's no damage?
>>
>> (There has to be a successful return routability check before any
>> traffic is transported)
>>
>> There's two use cases:
>>
>> 1. No HIP session (i.e. SHIM context) yet and application knows the
>> IP address of the peer. 2. An existing HIP session, connectivity
>> lost but the application (with the assistance from the user) can
>> help to rediscover the peer.
>>
>> Now remembering this "unknown" part again, I think the MAY was
>> referring to the first case described above. It should be ok for
>> the application give a hint especially in the absence of better
>> knowledge from the SHIM.
>
> I agree; that was my understanding of the main intent of this clause
> (to allow the application to provide the shim with a hint of the
> binding to IP address).
>
> However, in reviewing section 6.2, it seems like this would fail
> since there is no shim context for the socket.  If I'm not mistaken,
> the draft seems to forbid applications running in opportunistic HIP
> mode because this API requires that shim context be associated with
> the socket for the ancillary data to be accepted.

right:

http://tools.ietf.org/html/draft-ietf-hip-native-api-12#section-4.6

"Another use case is to use the opportunistic mode.."

>> Regarding to the case two, it is true that RFC5206 basically
>> assumes that the peer has to announce it's locator set before the
>> local host can use them. I believe the peer can refuse to answer if
>> the local host triggers a return routability check to an
>> unannounced locator of the peer. However, the situation may be
>> changing in RFC5206-bis due to the recent advancements in IPv4-IPv6
>> handovers [1] which are not yet included in RFC5206.
>>
>> Tom, care to comment if I am too proactive here?
>>
>> [1] Secure and efficient IPv4/IPv6 handovers using host-based
>> identifier-locator Split, Samu Varjonen et al, 2009
>
> The paper does point out a use case for sending data to a previously
> unknown locator-- however, it seems to be slightly different than the
> use case here.  In the paper, the node learns of the address change
> and it seems that the HIP daemon sends an Echo request-- I take this
> to mean that the HIP daemon does this proactively.  Here, we are
> talking about applications triggering this directly and using this
> API to do so since they may have learned of the address out of band?

I stand corrected, setting the destination address should be possible 
only in the beginning of HIP communications between two hosts.