Re: [PATCH net 4/5] sctp: avoid flushing unsent queue when doing asoc reset

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Sat, Nov 25, 2017 at 09:05:35PM +0800, Xin Long wrote:
> Now when doing asoc reset, it cleans up sacked and abandoned queues
> by calling sctp_outq_free where it also cleans up unsent, retransmit
> and transmitted queues.
> 
> It's safe for the sender of response, as these 3 queues are empty at
> that time. But when the receiver of response is doing the reset, the
> users may already enqueue some chunks into unsent during the time
> waiting the response, and these chunks should not be flushed.
> 
> To void the chunks in it would be removed, it moves the queue into a
> temp list, then gets it back after sctp_outq_free is done.
> 
> The patch also fixes some incorrect comments in
> sctp_process_strreset_tsnreq.
> 
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

> ---
>  net/sctp/stream.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index f3b7d27..9dd5bfe 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -747,9 +747,10 @@ struct sctp_chunk *sctp_process_strreset_tsnreq(
>  		goto out;
>  	}
>  
> -	/* G3: The same processing as though a SACK chunk with no gap report
> -	 *     and a cumulative TSN ACK of the Sender's Next TSN minus 1 were
> -	 *     received MUST be performed.
> +	/* G4: The same processing as though a FWD-TSN chunk (as defined in
> +	 *     [RFC3758]) with all streams affected and a new cumulative TSN
> +	 *     ACK of the Receiver's Next TSN minus 1 were received MUST be
> +	 *     performed.
>  	 */
>  	max_tsn_seen = sctp_tsnmap_get_max_tsn_seen(&asoc->peer.tsn_map);
>  	sctp_ulpq_reasm_flushtsn(&asoc->ulpq, max_tsn_seen);
> @@ -764,10 +765,9 @@ struct sctp_chunk *sctp_process_strreset_tsnreq(
>  	sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
>  			 init_tsn, GFP_ATOMIC);
>  
> -	/* G4: The same processing as though a FWD-TSN chunk (as defined in
> -	 *     [RFC3758]) with all streams affected and a new cumulative TSN
> -	 *     ACK of the Receiver's Next TSN minus 1 were received MUST be
> -	 *     performed.
> +	/* G3: The same processing as though a SACK chunk with no gap report
> +	 *     and a cumulative TSN ACK of the Sender's Next TSN minus 1 were
> +	 *     received MUST be performed.
>  	 */
>  	sctp_outq_free(&asoc->outqueue);
>  
> @@ -1021,6 +1021,7 @@ struct sctp_chunk *sctp_process_strreset_resp(
>  		if (result == SCTP_STRRESET_PERFORMED) {
>  			__u32 mtsn = sctp_tsnmap_get_max_tsn_seen(
>  						&asoc->peer.tsn_map);
> +			LIST_HEAD(temp);
>  
>  			sctp_ulpq_reasm_flushtsn(&asoc->ulpq, mtsn);
>  			sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);
> @@ -1029,7 +1030,13 @@ struct sctp_chunk *sctp_process_strreset_resp(
>  					 SCTP_TSN_MAP_INITIAL,
>  					 stsn, GFP_ATOMIC);
>  
> +			/* Clean up sacked and abandoned queues only. As the
> +			 * out_chunk_list may not be empty, splice it to temp,
> +			 * then get it back after sctp_outq_free is done.
> +			 */
> +			list_splice_init(&asoc->outqueue.out_chunk_list, &temp);
>  			sctp_outq_free(&asoc->outqueue);
> +			list_splice_init(&temp, &asoc->outqueue.out_chunk_list);
>  
>  			asoc->next_tsn = rtsn;
>  			asoc->ctsn_ack_point = asoc->next_tsn - 1;
> -- 
> 2.1.0
> 
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