sctp_disposition_t sctp_sf_t4_timer_expire(
	struct net *net,
	const struct sctp_endpoint *ep,
	const struct sctp_association *asoc,
	const sctp_subtype_t type,
	void *arg,
	sctp_cmd_seq_t *commands)
{
	struct sctp_chunk *chunk = asoc->addip_last_asconf;
	struct sctp_transport *transport = chunk->transport;

	SCTP_INC_STATS(net, SCTP_MIB_T4_RTO_EXPIREDS);

	/* ADDIP 4.1 B1) Increment the error counters and perform path failure
	 * detection on the appropriate destination address as defined in
	 * RFC2960 [5] section 8.1 and 8.2.
	 */
	if (transport)
		sctp_add_cmd_sf(commands, SCTP_CMD_STRIKE,
				SCTP_TRANSPORT(transport));

	/* Reconfig T4 timer and transport. */
	sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T4, SCTP_CHUNK(chunk));

	/* ADDIP 4.1 B2) Increment the association error counters and perform
	 * endpoint failure detection on the association as defined in
	 * RFC2960 [5] section 8.1 and 8.2.
	 * association error counter is incremented in SCTP_CMD_STRIKE.
	 */
	if (asoc->overall_error_count >= asoc->max_retrans) {
		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
				SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
		sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
				SCTP_ERROR(ETIMEDOUT));
		sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
				SCTP_PERR(SCTP_ERROR_NO_ERROR));
		SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
		SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);
		return SCTP_DISPOSITION_ABORT;
	}

	/* ADDIP 4.1 B3) Back-off the destination address RTO value to which
	 * the ASCONF chunk was sent by doubling the RTO timer value.
	 * This is done in SCTP_CMD_STRIKE.
	 */

	/* ADDIP 4.1 B4) Re-transmit the ASCONF Chunk last sent and if possible
	 * choose an alternate destination address (please refer to RFC2960
	 * [5] section 6.4.1). An endpoint MUST NOT add new parameters to this
	 * chunk, it MUST be the same (including its serial number) as the last
	 * ASCONF sent.
	 */
	sctp_chunk_hold(asoc->addip_last_asconf);
	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
			SCTP_CHUNK(asoc->addip_last_asconf));

	/* ADDIP 4.1 B5) Restart the T-4 RTO timer. Note that if a different
	 * destination is selected, then the RTO used will be that of the new
	 * destination address.
	 */
	sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
			SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));

	return SCTP_DISPOSITION_CONSUME;
}

Unknown