sctp: refactor sctp_outq_teardown to insure proper re-initalization

Jamie Parsons reported a problem recently, in which the re-initalization of an
association (The duplicate init case), resulted in a loss of receive window
space.  He tracked down the root cause to sctp_outq_teardown, which discarded
all the data on an outq during a re-initalization of the corresponding
association, but never reset the outq->outstanding_data field to zero.  I wrote,
and he tested this fix, which does a proper full re-initalization of the outq,
fixing this problem, and hopefully future proofing us from simmilar issues down
the road.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Jamie Parsons <Jamie.Parsons@metaswitch.com>
Tested-by: Jamie Parsons <Jamie.Parsons@metaswitch.com>
CC: Jamie Parsons <Jamie.Parsons@metaswitch.com>
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: netdev@vger.kernel.org
---
 net/sctp/outqueue.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

On 01/17/2013 04:15 PM, Neil Horman wrote:
> Jamie Parsons reported a problem recently, in which the re-initalization of an
> association (The duplicate init case), resulted in a loss of receive window
> space.  He tracked down the root cause to sctp_outq_teardown, which discarded
> all the data on an outq during a re-initalization of the corresponding
> association, but never reset the outq->outstanding_data field to zero.  I wrote,
> and he tested this fix, which does a proper full re-initalization of the outq,
> fixing this problem, and hopefully future proofing us from simmilar issues down
> the road.
>

Good find.

Acked-by: Vlad Yasevich <vyasevich@gmail.com>

-vlad

> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> Reported-by: Jamie Parsons <Jamie.Parsons@metaswitch.com>
> Tested-by: Jamie Parsons <Jamie.Parsons@metaswitch.com>
> CC: Jamie Parsons <Jamie.Parsons@metaswitch.com>
> CC: Vlad Yasevich <vyasevich@gmail.com>
> CC: "David S. Miller" <davem@davemloft.net>
> CC: netdev@vger.kernel.org
> ---
>   net/sctp/outqueue.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
> index 379c81d..9bcdbd0 100644
> --- a/net/sctp/outqueue.c
> +++ b/net/sctp/outqueue.c
> @@ -224,7 +224,7 @@ void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
>
>   /* Free the outqueue structure and any related pending chunks.
>    */
> -void sctp_outq_teardown(struct sctp_outq *q)
> +static void __sctp_outq_teardown(struct sctp_outq *q)
>   {
>   	struct sctp_transport *transport;
>   	struct list_head *lchunk, *temp;
> @@ -277,8 +277,6 @@ void sctp_outq_teardown(struct sctp_outq *q)
>   		sctp_chunk_free(chunk);
>   	}
>
> -	q->error = 0;
> -
>   	/* Throw away any leftover control chunks. */
>   	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
>   		list_del_init(&chunk->list);
> @@ -286,11 +284,17 @@ void sctp_outq_teardown(struct sctp_outq *q)
>   	}
>   }
>
> +void sctp_outq_teardown(struct sctp_outq *q)
> +{
> +	__sctp_outq_teardown(q);
> +	sctp_outq_init(q->asoc, q);
> +}
> +
>   /* Free the outqueue structure and any related pending chunks.  */
>   void sctp_outq_free(struct sctp_outq *q)
>   {
>   	/* Throw away leftover chunks. */
> -	sctp_outq_teardown(q);
> +	__sctp_outq_teardown(q);
>
>   	/* If we were kmalloc()'d, free the memory.  */
>   	if (q->malloced)
>

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From: Vlad Yasevich <vyasevich@gmail.com>
Date: Thu, 17 Jan 2013 17:48:20 -0500

> On 01/17/2013 04:15 PM, Neil Horman wrote:
>> Jamie Parsons reported a problem recently, in which the
>> re-initalization of an
>> association (The duplicate init case), resulted in a loss of receive
>> window
>> space.  He tracked down the root cause to sctp_outq_teardown, which
>> discarded
>> all the data on an outq during a re-initalization of the corresponding
>> association, but never reset the outq->outstanding_data field to zero.
>> I wrote,
>> and he tested this fix, which does a proper full re-initalization of
>> the outq,
>> fixing this problem, and hopefully future proofing us from simmilar
>> issues down
>> the road.
>>
> 
> Good find.
> 
> Acked-by: Vlad Yasevich <vyasevich@gmail.com>

Applied and queued up for -stable, thanks everyone.
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