netdev - Re: [PATCH net-next-2.6 v4 4/5] sctp: Add ASCONF operation on the single-homed host

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Date:	Mon, 25 Apr 2011 11:29:56 +0900
From:	Michio Honda <micchie@....wide.ad.jp>
To:	Wei Yongjun <yjwei@...fujitsu.com>
Cc:	netdev@...r.kernel.org, lksctp-developers@...ts.sourceforge.net
Subject: Re: [PATCH net-next-2.6 v4 4/5] sctp: Add ASCONF operation on the single-homed host

Yes, I think the association cannot be kept, if the single-homed ASCONF receiver moves to the new network before sending ASCONF-ACK.  
Am I missing?

Thanks,
- Michio

On Apr 25, 2011, at 11:02 , Wei Yongjun wrote:

> 
>> Hi, 
>> 
>> Such operation would not be supported by specification, in Sec.5.3 in RFC 5061:
>>   F1)  When adding an IP address to an association, the IP address is
>>        NOT considered fully added to the association until the ASCONF-
>>        ACK arrives.  This means that until such time as the ASCONF
>>        containing the add is acknowledged, the sender MUST NOT use the
>>        new IP address as a source for ANY SCTP packet except on
>>        carrying an ASCONF Chunk. 
>> 
>> I think this means we cannot send ASCONF-ACK from the new address even if it bundles ASCONF...
> 
> If so, both side do not have valid address to send the such
> ASCONF-ACK, and can not recv ASCONF-ACK.
> 
>> - Michio
>> 
>> On Apr 25, 2011, at 9:57 , Wei Yongjun wrote:
>> 
>>>> On Apr 22, 2011, at 13:10 , Wei Yongjun wrote:
>>>> 
>>>>>> Since the sender MUST NOT use the  new IP address as a source for ANY SCTP
>>>>>> packet except on  carrying an ASCONF Chunk. And ASCONF chunk can be bundled.
>>>>>> How about this change. If so, you do not need change to sctp_outq_tail();
>>>>>> 
>>>>>> diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
>>>>>> index 1c88c89..bd6cc9c 100644
>>>>>> --- a/net/sctp/outqueue.c
>>>>>> +++ b/net/sctp/outqueue.c
>>>>>> @@ -754,6 +754,13 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
>>>>>> 	 */
>>>>>> 
>>>>>> 	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
>>>>>> +		/* RFC 5061, 5.3
>>>>>> +		 * F1) This ...
>>>>>> +		 */
>>>>>> +		if (q->asoc->src_out_of_asoc_ok &&
>>>>>> +		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
>>>>> SCTP_CID_ASCONF_ACK should be also allowed, the peer may
>>>>> send ASCONF to do the same thing at the same time.
>>>> Sorry for my bad understanding, 
>>>> Do you mean the situation: "the peer (ASCONF receiver) may send ASCONF-ACK to the unconfirmed destination"?
>>>> Or do you mean following situation?
>>>> 1. the pear sends ADD/DEL ASCONF to me, 
>>>> 2. I receive it, 
>>>> 3. I migrate to the other network and get new address, 
>>>> 4. I send ASCONF-ACK to the peer from the new address
>>> Yes, If both side send ADD/DEL ASCONF to del the last one
>>> address at the same time like this:
>>> 
>>> ASCONF  -----    ------ASCONF
>>> (ADD/DEL)    \  /     (ADD/DEL)
>>>             \/        
>>>             /\
>>>       <----/  \----->
>>> ASCONF-ACK---\  /------ASCONF-ACK
>>>             \/
>>>             /\
>>>       <----/  \----->
>>> 
>>> But I do not test for it. Not sure we need to do this, can you
>>> check this before commit your new patchset?
>>> 
>>> 
>>>>>> +			continue;
>>>>>> +
>>>>>> 		list_del_init(&chunk->list);
>>>>>> 
>>>>>> 		/* Pick the right transport to use. */
>>>>>> @@ -881,6 +888,9 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
>>>>>> 		}
>>>>>> 	}
>>>>>> 
>>>>>> +	if (q->asoc->src_out_of_asoc_ok)
>>>>>> +		goto sctp_flush_out;
>>>>>> +
>>>>>> 	/* Is it OK to send data chunks?  */
>>>>>> 	switch (asoc->state) {
>>>>>> 	case SCTP_STATE_COOKIE_ECHOED:
>>>>>> 
>>>>>> 
>>>>>> 
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