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 10:53:59 +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

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...

- 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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