sm_make_chunk.c

Linux Kernel 2.6.9 for OMAP1710

 *  RFC 2481 details a specific bit for a sender to send in the header of
 *  its next outbound TCP segment to indicate to its peer that it has
 *  reduced its congestion window.  This is termed the CWR bit.  For
 *  SCTP the same indication is made by including the CWR chunk.
 *  This chunk contains one data element, i.e. the TSN number that
 *  was sent in the ECNE chunk.  This element represents the lowest
 *  TSN number in the datagram that was originally marked with the
 *  CE bit.
 *
 *     0                   1                   2                   3
 *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    | Chunk Type=13 | Flags=00000000|    Chunk Length = 8           |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                      Lowest TSN Number                        |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 *     Note: The CWR is considered a Control chunk.
 */
struct sctp_chunk *sctp_make_cwr(const struct sctp_association *asoc,
			    const __u32 lowest_tsn,
			    const struct sctp_chunk *chunk)
{
	struct sctp_chunk *retval;
	sctp_cwrhdr_t cwr;

	cwr.lowest_tsn = htonl(lowest_tsn);
	retval = sctp_make_chunk(asoc, SCTP_CID_ECN_CWR, 0,
				 sizeof(sctp_cwrhdr_t));

	if (!retval)
		goto nodata;

	retval->subh.ecn_cwr_hdr =
		sctp_addto_chunk(retval, sizeof(cwr), &cwr);

	/* RFC 2960 6.4 Multi-homed SCTP Endpoints
	 *
	 * An endpoint SHOULD transmit reply chunks (e.g., SACK,
	 * HEARTBEAT ACK, * etc.) to the same destination transport
	 * address from which it * received the DATA or control chunk
	 * to which it is replying.
	 *
	 * [Report a reduced congestion window back to where the ECNE
	 * came from.]
	 */
	if (chunk)
		retval->transport = chunk->transport;

nodata:
	return retval;
}

/* Make an ECNE chunk.  This is a congestion experienced report.  */
struct sctp_chunk *sctp_make_ecne(const struct sctp_association *asoc,
			     const __u32 lowest_tsn)
{
	struct sctp_chunk *retval;
	sctp_ecnehdr_t ecne;

	ecne.lowest_tsn = htonl(lowest_tsn);
	retval = sctp_make_chunk(asoc, SCTP_CID_ECN_ECNE, 0,
				 sizeof(sctp_ecnehdr_t));
	if (!retval)
		goto nodata;
	retval->subh.ecne_hdr =
		sctp_addto_chunk(retval, sizeof(ecne), &ecne);

nodata:
	return retval;
}

/* Make a DATA chunk for the given association from the provided
 * parameters.  However, do not populate the data payload.
 */
struct sctp_chunk *sctp_make_datafrag_empty(struct sctp_association *asoc,
				       const struct sctp_sndrcvinfo *sinfo,
				       int data_len, __u8 flags, __u16 ssn)
{
	struct sctp_chunk *retval;
	struct sctp_datahdr dp;
	int chunk_len;

	/* We assign the TSN as LATE as possible, not here when
	 * creating the chunk.
	 */
	dp.tsn = 0;
	dp.stream = htons(sinfo->sinfo_stream);
	dp.ppid   = sinfo->sinfo_ppid;

	/* Set the flags for an unordered send.  */
	if (sinfo->sinfo_flags & MSG_UNORDERED) {
		flags |= SCTP_DATA_UNORDERED;
		dp.ssn = 0;
	} else
		dp.ssn = htons(ssn);

	chunk_len = sizeof(dp) + data_len;
	retval = sctp_make_chunk(asoc, SCTP_CID_DATA, flags, chunk_len);
	if (!retval)
		goto nodata;

	retval->subh.data_hdr = sctp_addto_chunk(retval, sizeof(dp), &dp);
	memcpy(&retval->sinfo, sinfo, sizeof(struct sctp_sndrcvinfo));

nodata:
	return retval;
}

/* Make a DATA chunk for the given association.  Populate the data
 * payload.
 */
struct sctp_chunk *sctp_make_datafrag(struct sctp_association *asoc,
				 const struct sctp_sndrcvinfo *sinfo,
				 int data_len, const __u8 *data,
				 __u8 flags, __u16 ssn)
{
	struct sctp_chunk *retval;

	retval = sctp_make_datafrag_empty(asoc, sinfo, data_len, flags, ssn);
	if (retval)
		sctp_addto_chunk(retval, data_len, data);

	return retval;
}

/* Make a DATA chunk for the given association to ride on stream id
 * 'stream', with a payload id of 'payload', and a body of 'data'.
 */
struct sctp_chunk *sctp_make_data(struct sctp_association *asoc,
			     const struct sctp_sndrcvinfo *sinfo,
			     int data_len, const __u8 *data)
{
	struct sctp_chunk *retval = NULL;

	retval = sctp_make_data_empty(asoc, sinfo, data_len);
	if (retval)
		sctp_addto_chunk(retval, data_len, data);
        return retval;
}

/* Make a DATA chunk for the given association to ride on stream id
 * 'stream', with a payload id of 'payload', and a body big enough to
 * hold 'data_len' octets of data.  We use this version when we need
 * to build the message AFTER allocating memory.
 */
struct sctp_chunk *sctp_make_data_empty(struct sctp_association *asoc,
				   const struct sctp_sndrcvinfo *sinfo,
				   int data_len)
{
	__u8 flags = SCTP_DATA_NOT_FRAG;

	return sctp_make_datafrag_empty(asoc, sinfo, data_len, flags, 0);
}

/* Create a selective ackowledgement (SACK) for the given
 * association.  This reports on which TSN's we've seen to date,
 * including duplicates and gaps.
 */
struct sctp_chunk *sctp_make_sack(const struct sctp_association *asoc)
{
	struct sctp_chunk *retval;
	struct sctp_sackhdr sack;
	int len;
	__u32 ctsn;
	__u16 num_gabs, num_dup_tsns;
	struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;

	ctsn = sctp_tsnmap_get_ctsn(map);
	SCTP_DEBUG_PRINTK("sackCTSNAck sent:  0x%x.\n", ctsn);

	/* How much room is needed in the chunk? */
	num_gabs = sctp_tsnmap_num_gabs(map);
	num_dup_tsns = sctp_tsnmap_num_dups(map);

	/* Initialize the SACK header.  */
	sack.cum_tsn_ack	    = htonl(ctsn);
	sack.a_rwnd 		    = htonl(asoc->a_rwnd);
	sack.num_gap_ack_blocks     = htons(num_gabs);
	sack.num_dup_tsns           = htons(num_dup_tsns);

	len = sizeof(sack)
		+ sizeof(struct sctp_gap_ack_block) * num_gabs
		+ sizeof(__u32) * num_dup_tsns;

	/* Create the chunk.  */
	retval = sctp_make_chunk(asoc, SCTP_CID_SACK, 0, len);
	if (!retval)
		goto nodata;

	/* RFC 2960 6.4 Multi-homed SCTP Endpoints
	 *
	 * An endpoint SHOULD transmit reply chunks (e.g., SACK,
	 * HEARTBEAT ACK, etc.) to the same destination transport
	 * address from which it received the DATA or control chunk to
	 * which it is replying.  This rule should also be followed if
	 * the endpoint is bundling DATA chunks together with the
	 * reply chunk.
	 *
	 * However, when acknowledging multiple DATA chunks received
	 * in packets from different source addresses in a single
	 * SACK, the SACK chunk may be transmitted to one of the
	 * destination transport addresses from which the DATA or
	 * control chunks being acknowledged were received.
	 *
	 * [BUG:  We do not implement the following paragraph.
	 * Perhaps we should remember the last transport we used for a
	 * SACK and avoid that (if possible) if we have seen any
	 * duplicates. --piggy]
	 *
	 * When a receiver of a duplicate DATA chunk sends a SACK to a
	 * multi- homed endpoint it MAY be beneficial to vary the
	 * destination address and not use the source address of the
	 * DATA chunk.  The reason being that receiving a duplicate
	 * from a multi-homed endpoint might indicate that the return
	 * path (as specified in the source address of the DATA chunk)
	 * for the SACK is broken.
	 *
	 * [Send to the address from which we last received a DATA chunk.]
	 */
	retval->transport = asoc->peer.last_data_from;

	retval->subh.sack_hdr =
		sctp_addto_chunk(retval, sizeof(sack), &sack);

	/* Add the gap ack block information.   */
	if (num_gabs)
		sctp_addto_chunk(retval, sizeof(__u32) * num_gabs,
				 sctp_tsnmap_get_gabs(map));

	/* Add the duplicate TSN information.  */
	if (num_dup_tsns)
		sctp_addto_chunk(retval, sizeof(__u32) * num_dup_tsns,
				 sctp_tsnmap_get_dups(map));

nodata:
	return retval;
}

/* Make a SHUTDOWN chunk. */
struct sctp_chunk *sctp_make_shutdown(const struct sctp_association *asoc,
				      const struct sctp_chunk *chunk)
{
	struct sctp_chunk *retval;
	sctp_shutdownhdr_t shut;
	__u32 ctsn;

	ctsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map);
	shut.cum_tsn_ack = htonl(ctsn);

	retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN, 0,
				 sizeof(sctp_shutdownhdr_t));
	if (!retval)
		goto nodata;

	retval->subh.shutdown_hdr =
		sctp_addto_chunk(retval, sizeof(shut), &shut);

	if (chunk)
		retval->transport = chunk->transport;
nodata:
	return retval;
}

struct sctp_chunk *sctp_make_shutdown_ack(const struct sctp_association *asoc,
				     const struct sctp_chunk *chunk)
{
	struct sctp_chunk *retval;

	retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_ACK, 0, 0);

	/* RFC 2960 6.4 Multi-homed SCTP Endpoints
	 *
	 * An endpoint SHOULD transmit reply chunks (e.g., SACK,
	 * HEARTBEAT ACK, * etc.) to the same destination transport
	 * address from which it * received the DATA or control chunk
	 * to which it is replying.
	 *
	 * [ACK back to where the SHUTDOWN came from.]
	 */
	if (retval && chunk)
		retval->transport = chunk->transport;

	return retval;
}

struct sctp_chunk *sctp_make_shutdown_complete(
	const struct sctp_association *asoc,
	const struct sctp_chunk *chunk)
{
	struct sctp_chunk *retval;
	__u8 flags = 0;

	/* Maybe set the T-bit if we have no association. */
	flags |= asoc ? 0 : SCTP_CHUNK_FLAG_T;

	retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_COMPLETE, flags, 0);

	/* RFC 2960 6.4 Multi-homed SCTP Endpoints
	 *
	 * An endpoint SHOULD transmit reply chunks (e.g., SACK,
	 * HEARTBEAT ACK, * etc.) to the same destination transport
	 * address from which it * received the DATA or control chunk
	 * to which it is replying.
	 *
	 * [Report SHUTDOWN COMPLETE back to where the SHUTDOWN ACK
	 * came from.]
	 */
	if (retval && chunk)
		retval->transport = chunk->transport;

        return retval;
}

/* Create an ABORT.  Note that we set the T bit if we have no
 * association.
 */
struct sctp_chunk *sctp_make_abort(const struct sctp_association *asoc,
			      const struct sctp_chunk *chunk,
			      const size_t hint)
{
	struct sctp_chunk *retval;
	__u8 flags = 0;

	/* Maybe set the T-bit if we have no association.  */
	flags |= asoc ? 0 : SCTP_CHUNK_FLAG_T;

	retval = sctp_make_chunk(asoc, SCTP_CID_ABORT, flags, hint);

	/* RFC 2960 6.4 Multi-homed SCTP Endpoints
	 *
	 * An endpoint SHOULD transmit reply chunks (e.g., SACK,
	 * HEARTBEAT ACK, * etc.) to the same destination transport
	 * address from which it * received the DATA or control chunk
	 * to which it is replying.
	 *
	 * [ABORT back to where the offender came from.]
	 */
	if (retval && chunk)
		retval->transport = chunk->transport;

	return retval;
}

/* Helper to create ABORT with a NO_USER_DATA error.  */
struct sctp_chunk *sctp_make_abort_no_data(
	const struct sctp_association *asoc,
	const struct sctp_chunk *chunk, __u32 tsn)
{
	struct sctp_chunk *retval;
	__u32 payload;

	retval = sctp_make_abort(asoc, chunk, sizeof(sctp_errhdr_t)
				 + sizeof(tsn));

	if (!retval)
		goto no_mem;

	/* Put the tsn back into network byte order.  */
	payload = htonl(tsn);
	sctp_init_cause(retval, SCTP_ERROR_NO_DATA, (const void *)&payload,
			sizeof(payload));

	/* RFC 2960 6.4 Multi-homed SCTP Endpoints
	 *
	 * An endpoint SHOULD transmit reply chunks (e.g., SACK,
	 * HEARTBEAT ACK, * etc.) to the same destination transport
	 * address from which it * received the DATA or control chunk
	 * to which it is replying.
	 *
	 * [ABORT back to where the offender came from.]
	 */
	if (chunk)
		retval->transport = chunk->transport;

no_mem:
	return retval;
}

/* Helper to create ABORT with a SCTP_ERROR_USER_ABORT error.  */
struct sctp_chunk *sctp_make_abort_user(const struct sctp_association *asoc,
				   const struct sctp_chunk *chunk,
				   const struct msghdr *msg)
{
	struct sctp_chunk *retval;
	void *payload = NULL, *payoff;
	size_t paylen = 0;
	struct iovec *iov = NULL;
	int iovlen = 0;

	if (msg) {
		iov = msg->msg_iov;
		iovlen = msg->msg_iovlen;
		paylen = get_user_iov_size(iov, iovlen);
	}

	retval = sctp_make_abort(asoc, chunk, sizeof(sctp_errhdr_t) + paylen);
	if (!retval)
		goto err_chunk;

	if (paylen) {
		/* Put the msg_iov together into payload.  */
		payload = kmalloc(paylen, GFP_ATOMIC);
		if (!payload)
			goto err_payload;
		payoff = payload;

		for (; iovlen > 0; --iovlen) {
			if (copy_from_user(payoff, iov->iov_base,iov->iov_len))
				goto err_copy;
			payoff += iov->iov_len;
			iov++;
		}
	}

	sctp_init_cause(retval, SCTP_ERROR_USER_ABORT, payload, paylen);

	if (paylen)
		kfree(payload);

	return retval;

err_copy:
	kfree(payload);
err_payload:
	sctp_chunk_free(retval);
	retval = NULL;
err_chunk:
	return retval;
}

/* Make a HEARTBEAT chunk.  */
struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
				  const struct sctp_transport *transport,
				  const void *payload, const size_t paylen)
{
	struct sctp_chunk *retval = sctp_make_chunk(asoc, SCTP_CID_HEARTBEAT,
						    0, paylen);