Re: [PATCH] sctp: Make "Invalid Stream Identifier" ERROR follows SACK when bundling

[David Miller <davem@davemloft.net>]

From: <xufengzhang.main@gmail.com>
Date: Thu, 19 Jul 2012 13:57:30 +0800

> When "Invalid Stream Identifier" ERROR happens after process the
> received DATA chunks, this ERROR chunk is enqueued into outqueue
> before SACK chunk, so when bundling ERROR chunk with SACK chunk,
> the ERROR chunk is always placed first in the packet because of
> the chunk's position in the outqueue.
> This violates sctp specification:
>     RFC 4960 6.5. Stream Identifier and Stream Sequence Number
>     ...The endpoint may bundle the ERROR chunk in the same
>     packet as the SACK as long as the ERROR follows the SACK.
> So we must place SACK first when bundling "Invalid Stream Identifier"
> ERROR and SACK in one packet.
> Although we can do that by enqueue SACK chunk into outqueue before
> ERROR chunk, it will violate the side-effect interpreter processing.
> It's easy to do this job when dequeue chunks from the outqueue,
> by this way, we introduce a flag 'has_isi_err' which indicate
> whether or not the "Invalid Stream Identifier" ERROR happens.
> 
> Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>

Can some SCTP experts please review this?