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	sctp: implement receiver-side procedures for the SSN/TSN Reset Request Parameter
This patch is to implement Receiver-Side Procedures for the SSN/TSN Reset Request Parameter described in rfc6525 section 6.2.4. The process is kind of complicate, it's wonth having some comments from section 6.2.4 in the codes. Signed-off-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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					 3 changed files with 86 additions and 0 deletions
				
			
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			@ -293,6 +293,10 @@ struct sctp_chunk *sctp_process_strreset_inreq(
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				struct sctp_association *asoc,
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				union sctp_params param,
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				struct sctp_ulpevent **evp);
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struct sctp_chunk *sctp_process_strreset_tsnreq(
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				struct sctp_association *asoc,
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				union sctp_params param,
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				struct sctp_ulpevent **evp);
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/* Prototypes for statetable processing. */
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			@ -3872,6 +3872,9 @@ sctp_disposition_t sctp_sf_do_reconf(struct net *net,
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		else if (param.p->type == SCTP_PARAM_RESET_IN_REQUEST)
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			reply = sctp_process_strreset_inreq(
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				(struct sctp_association *)asoc, param, &ev);
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		else if (param.p->type == SCTP_PARAM_RESET_TSN_REQUEST)
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			reply = sctp_process_strreset_tsnreq(
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				(struct sctp_association *)asoc, param, &ev);
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		/* More handles for other types will be added here, by now it
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		 * just ignores other types.
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		 */
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			@ -477,3 +477,82 @@ struct sctp_chunk *sctp_process_strreset_inreq(
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	return chunk;
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}
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struct sctp_chunk *sctp_process_strreset_tsnreq(
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				struct sctp_association *asoc,
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				union sctp_params param,
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				struct sctp_ulpevent **evp)
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{
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	__u32 init_tsn = 0, next_tsn = 0, max_tsn_seen;
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	struct sctp_strreset_tsnreq *tsnreq = param.v;
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	struct sctp_stream *stream = asoc->stream;
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	__u32 result = SCTP_STRRESET_DENIED;
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	__u32 request_seq;
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	__u16 i;
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	request_seq = ntohl(tsnreq->request_seq);
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	if (request_seq > asoc->strreset_inseq) {
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		result = SCTP_STRRESET_ERR_BAD_SEQNO;
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		goto out;
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	} else if (request_seq == asoc->strreset_inseq) {
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		asoc->strreset_inseq++;
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	}
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	if (!(asoc->strreset_enable & SCTP_ENABLE_RESET_ASSOC_REQ))
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		goto out;
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	if (asoc->strreset_outstanding) {
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		result = SCTP_STRRESET_ERR_IN_PROGRESS;
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		goto out;
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	}
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	/* G3: The same processing as though a SACK chunk with no gap report
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	 *     and a cumulative TSN ACK of the Sender's Next TSN minus 1 were
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	 *     received MUST be performed.
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	 */
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	max_tsn_seen = sctp_tsnmap_get_max_tsn_seen(&asoc->peer.tsn_map);
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	sctp_ulpq_reasm_flushtsn(&asoc->ulpq, max_tsn_seen);
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	sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);
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	/* G1: Compute an appropriate value for the Receiver's Next TSN -- the
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	 *     TSN that the peer should use to send the next DATA chunk.  The
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	 *     value SHOULD be the smallest TSN not acknowledged by the
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	 *     receiver of the request plus 2^31.
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	 */
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	init_tsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map) + (1 << 31);
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	sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
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			 init_tsn, GFP_ATOMIC);
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	/* G4: The same processing as though a FWD-TSN chunk (as defined in
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	 *     [RFC3758]) with all streams affected and a new cumulative TSN
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	 *     ACK of the Receiver's Next TSN minus 1 were received MUST be
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	 *     performed.
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	 */
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	sctp_outq_free(&asoc->outqueue);
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	/* G2: Compute an appropriate value for the local endpoint's next TSN,
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	 *     i.e., the next TSN assigned by the receiver of the SSN/TSN reset
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	 *     chunk.  The value SHOULD be the highest TSN sent by the receiver
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	 *     of the request plus 1.
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	 */
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	next_tsn = asoc->next_tsn;
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	asoc->ctsn_ack_point = next_tsn - 1;
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	asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
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	/* G5:  The next expected and outgoing SSNs MUST be reset to 0 for all
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	 *      incoming and outgoing streams.
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	 */
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	for (i = 0; i < stream->outcnt; i++)
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		stream->out[i].ssn = 0;
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	for (i = 0; i < stream->incnt; i++)
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		stream->in[i].ssn = 0;
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	result = SCTP_STRRESET_PERFORMED;
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	*evp = sctp_ulpevent_make_assoc_reset_event(asoc, 0, init_tsn,
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						    next_tsn, GFP_ATOMIC);
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out:
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	return sctp_make_strreset_tsnresp(asoc, result, request_seq,
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					  next_tsn, init_tsn);
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}
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