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

Miika Komu <mkomu@cs.hut.fi> Sat, 16 October 2010 10:46 UTC

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Date: Sat, 16 Oct 2010 13:47:47 +0300
From: Miika Komu <mkomu@cs.hut.fi>
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Subject: Re: [shim6] AD review of draft-ietf-shim6-multihome-shim-api
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Hi Shinta,

On 10/15/2010 07:41 AM, Shinta Sugimoto wrote:
> Hi Miika,
>
> Miika Komu wrote:
>> Hi,
>>
>> On 10/14/2010 08:29 AM, Shinta Sugimoto wrote:
>>> Hi Miika and Thomas,
>>>
>>> Henderson, Thomas wrote:
>>>>
>>>>> -----Original Message-----
>>>>> From: Miika Komu [mailto:mkomu@cs.hut.fi]
>>>>> Sent: Wednesday, October 13, 2010 9:35 PM
>>>>> To: Henderson, Thomas R
>>>>> Cc: shim6; kristian.slavov@ericsson.com
>>>>> Subject: Re: [shim6] AD review of draft-ietf-shim6-multihome-shim-api
>>>>>
>>>>> Hi,
>>>>>
>>>>> On 13/10/10 17:23, Henderson, Thomas R wrote:
>>>>>
>>>>>> Yes, but the HIP native API draft does not say anything about
>>>>>> overriding the rules in the shim6 API specification concerning
>>>>>> the need for shim context. Maybe that should be clarified in
>>>>>> the HIP API draft.
>>>>> I think it would have been simpler to keep the exception in the SHIM6
>>>>> draft rather than changing the HIP draft which is in editor queue
>>>>> (blocked by the SHIM6 draft)?
>>>>>
>>>>
>>>> You raise a good procedural point; I would also be fine with editing
>>>> the shim6 draft if Shinta is OK with it.
>>>
>>> I see.
>>>
>>> I would like to keep the socket option (to specify the initial locator,
>>> i.e., where to send I1 message) separate from SHIM_LOC_PEER_SEND because
>>> they are semantically different. Are you fine with adding a socket
>>> option something like SHIM_INITIAL_PEER_LOCATOR in the multihome shim
>>> API document (this one)?
>>
>> procedurally, I'm not really fine with this because then we have to
>> change anyway the native HIP API. It is already referring to
>> SHIM_LOC_PEER_PREF, SHIM_LOCLIST_PEER and SHIM_LOC_PEER_SEND:
>>
>> http://tools.ietf.org/html/draft-ietf-hip-native-api-12#section-4.6
>
> Ok, I read section 4.6 of the HIP Native API document.
>
>> Technically, I am not convinced if having a separate constant for
>> initial locator is really needed.
>
> Well, the feature is the same. But the requirements and pre-requisites
> are different. Anyway, let's resolve this.
>
>> It seems that we have the following options:
>>
>> 1. Override the statement in the native HIP API draft
>> 2. Remove the statement in the SHIM API
>> 3. Cross-reference the native HIP API draft
>> 4. Document the exception for HIP in the SHIM API
>>
>> I would be in favor of 2 and perhaps 3. What about others?
>
> By 2, you mean updating the texts in the SHIM API document, correct?

yes, by removing the statement:

    If the shim sub-layer turns out to be HIP, the HIP implementation MAY
    accept the request for using unknown destination locator.

> What about updating the texts for Section 13.1.2 (replacing the second
> paragraph) as follows:
>
> If the shim sub-layer turns out to be HIP, the HIP implementation MUST
> reject the request (SHIM_LOC_PEER_SEND as cmsg_type) for using a unknown
> destination locator. There is, however, an exceptional case where the
> HIP implementation SHOULD accept the request provided that the message
> to be sent by sendmsg() contains an I1 packet. In this exceptional case,
> the kernel SHOULD accept the request even if there is no shim context
> associated with the socket.
>
> Does this sound reasonable?

It does, except why do we need to restrict to sendmsg()? I would also 
suggest the following changes:

* s/implementation/layer/
* s/kernel/HIP layer/
* s/constains an I1 packet/would be used to initiate a key exchange by 
the HIP layer/