sm_make_chunk.c

在linux环境下的流控制传输协议（sctp）的源代码

			  struct iovec *data)
{
	__u8 *target;
	int err = 0;

	/* Make room in chunk for data.  */
	target = skb_put(chunk->skb, len);

	/* Copy data (whole iovec) into chunk */
	if ((err = memcpy_fromiovecend(target, data, off, len)))
		goto out;

	/* Adjust the chunk length field.  */
	chunk->chunk_hdr->length =
		htons(ntohs(chunk->chunk_hdr->length) + len);
	chunk->chunk_end = skb_tail_pointer(chunk->skb);

out:
	return err;
}

/* Helper function to assign a TSN if needed.  This assumes that both
 * the data_hdr and association have already been assigned.
 */
void sctp_chunk_assign_ssn(struct sctp_chunk *chunk)
{
	struct sctp_datamsg *msg;
	struct sctp_chunk *lchunk;
	struct sctp_stream *stream;
	__u16 ssn;
	__u16 sid;

	if (chunk->has_ssn)
		return;

	/* All fragments will be on the same stream */
	sid = ntohs(chunk->subh.data_hdr->stream);
	stream = &chunk->asoc->ssnmap->out;

	/* Now assign the sequence number to the entire message.
	 * All fragments must have the same stream sequence number.
	 */
	msg = chunk->msg;
	list_for_each_entry(lchunk, &msg->chunks, frag_list) {
		if (lchunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) {
			ssn = 0;
		} else {
			if (lchunk->chunk_hdr->flags & SCTP_DATA_LAST_FRAG)
				ssn = sctp_ssn_next(stream, sid);
			else
				ssn = sctp_ssn_peek(stream, sid);
		}

		lchunk->subh.data_hdr->ssn = htons(ssn);
		lchunk->has_ssn = 1;
	}
}

/* Helper function to assign a TSN if needed.  This assumes that both
 * the data_hdr and association have already been assigned.
 */
void sctp_chunk_assign_tsn(struct sctp_chunk *chunk)
{
	if (!chunk->has_tsn) {
		/* This is the last possible instant to
		 * assign a TSN.
		 */
		chunk->subh.data_hdr->tsn =
			htonl(sctp_association_get_next_tsn(chunk->asoc));
		chunk->has_tsn = 1;
	}
}

/* Create a CLOSED association to use with an incoming packet.  */
struct sctp_association *sctp_make_temp_asoc(const struct sctp_endpoint *ep,
					struct sctp_chunk *chunk,
					gfp_t gfp)
{
	struct sctp_association *asoc;
	struct sk_buff *skb;
	sctp_scope_t scope;
	struct sctp_af *af;

	/* Create the bare association.  */
	scope = sctp_scope(sctp_source(chunk));
	asoc = sctp_association_new(ep, ep->base.sk, scope, gfp);
	if (!asoc)
		goto nodata;
	asoc->temp = 1;
	skb = chunk->skb;
	/* Create an entry for the source address of the packet.  */
	af = sctp_get_af_specific(ipver2af(ip_hdr(skb)->version));
	if (unlikely(!af))
		goto fail;
	af->from_skb(&asoc->c.peer_addr, skb, 1);
nodata:
	return asoc;

fail:
	sctp_association_free(asoc);
	return NULL;
}

/* Build a cookie representing asoc.
 * This INCLUDES the param header needed to put the cookie in the INIT ACK.
 */
static sctp_cookie_param_t *sctp_pack_cookie(const struct sctp_endpoint *ep,
				      const struct sctp_association *asoc,
				      const struct sctp_chunk *init_chunk,
				      int *cookie_len,
				      const __u8 *raw_addrs, int addrs_len)
{
	sctp_cookie_param_t *retval;
	struct sctp_signed_cookie *cookie;
	struct scatterlist sg;
	int headersize, bodysize;
	unsigned int keylen;
	char *key;

	/* Header size is static data prior to the actual cookie, including
	 * any padding.
	 */
	headersize = sizeof(sctp_paramhdr_t) +
		     (sizeof(struct sctp_signed_cookie) -
		      sizeof(struct sctp_cookie));
	bodysize = sizeof(struct sctp_cookie)
		+ ntohs(init_chunk->chunk_hdr->length) + addrs_len;

	/* Pad out the cookie to a multiple to make the signature
	 * functions simpler to write.
	 */
	if (bodysize % SCTP_COOKIE_MULTIPLE)
		bodysize += SCTP_COOKIE_MULTIPLE
			- (bodysize % SCTP_COOKIE_MULTIPLE);
	*cookie_len = headersize + bodysize;

	/* Clear this memory since we are sending this data structure
	 * out on the network.
	 */
	retval = kzalloc(*cookie_len, GFP_ATOMIC);
	if (!retval)
		goto nodata;

	cookie = (struct sctp_signed_cookie *) retval->body;

	/* Set up the parameter header.  */
	retval->p.type = SCTP_PARAM_STATE_COOKIE;
	retval->p.length = htons(*cookie_len);

	/* Copy the cookie part of the association itself.  */
	cookie->c = asoc->c;
	/* Save the raw address list length in the cookie. */
	cookie->c.raw_addr_list_len = addrs_len;

	/* Remember PR-SCTP capability. */
	cookie->c.prsctp_capable = asoc->peer.prsctp_capable;

	/* Save adaptation indication in the cookie. */
	cookie->c.adaptation_ind = asoc->peer.adaptation_ind;

	/* Set an expiration time for the cookie.  */
	do_gettimeofday(&cookie->c.expiration);
	TIMEVAL_ADD(asoc->cookie_life, cookie->c.expiration);

	/* Copy the peer's init packet.  */
	memcpy(&cookie->c.peer_init[0], init_chunk->chunk_hdr,
	       ntohs(init_chunk->chunk_hdr->length));

	/* Copy the raw local address list of the association. */
	memcpy((__u8 *)&cookie->c.peer_init[0] +
	       ntohs(init_chunk->chunk_hdr->length), raw_addrs, addrs_len);

	if (sctp_sk(ep->base.sk)->hmac) {
		struct hash_desc desc;

		/* Sign the message.  */
		sg_init_one(&sg, &cookie->c, bodysize);
		keylen = SCTP_SECRET_SIZE;
		key = (char *)ep->secret_key[ep->current_key];
		desc.tfm = sctp_sk(ep->base.sk)->hmac;
		desc.flags = 0;

		if (crypto_hash_setkey(desc.tfm, key, keylen) ||
		    crypto_hash_digest(&desc, &sg, bodysize, cookie->signature))
			goto free_cookie;
	}

	return retval;

free_cookie:
	kfree(retval);
nodata:
	*cookie_len = 0;
	return NULL;
}

/* Unpack the cookie from COOKIE ECHO chunk, recreating the association.  */
struct sctp_association *sctp_unpack_cookie(
	const struct sctp_endpoint *ep,
	const struct sctp_association *asoc,
	struct sctp_chunk *chunk, gfp_t gfp,
	int *error, struct sctp_chunk **errp)
{
	struct sctp_association *retval = NULL;
	struct sctp_signed_cookie *cookie;
	struct sctp_cookie *bear_cookie;
	int headersize, bodysize, fixed_size;
	__u8 *digest = ep->digest;
	struct scatterlist sg;
	unsigned int keylen, len;
	char *key;
	sctp_scope_t scope;
	struct sk_buff *skb = chunk->skb;
	struct timeval tv;
	struct hash_desc desc;

	/* Header size is static data prior to the actual cookie, including
	 * any padding.
	 */
	headersize = sizeof(sctp_chunkhdr_t) +
		     (sizeof(struct sctp_signed_cookie) -
		      sizeof(struct sctp_cookie));
	bodysize = ntohs(chunk->chunk_hdr->length) - headersize;
	fixed_size = headersize + sizeof(struct sctp_cookie);

	/* Verify that the chunk looks like it even has a cookie.
	 * There must be enough room for our cookie and our peer's
	 * INIT chunk.
	 */
	len = ntohs(chunk->chunk_hdr->length);
	if (len < fixed_size + sizeof(struct sctp_chunkhdr))
		goto malformed;

	/* Verify that the cookie has been padded out. */
	if (bodysize % SCTP_COOKIE_MULTIPLE)
		goto malformed;

	/* Process the cookie.  */
	cookie = chunk->subh.cookie_hdr;
	bear_cookie = &cookie->c;

	if (!sctp_sk(ep->base.sk)->hmac)
		goto no_hmac;

	/* Check the signature.  */
	keylen = SCTP_SECRET_SIZE;
	sg_init_one(&sg, bear_cookie, bodysize);
	key = (char *)ep->secret_key[ep->current_key];
	desc.tfm = sctp_sk(ep->base.sk)->hmac;
	desc.flags = 0;

	memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
	if (crypto_hash_setkey(desc.tfm, key, keylen) ||
	    crypto_hash_digest(&desc, &sg, bodysize, digest)) {
		*error = -SCTP_IERROR_NOMEM;
		goto fail;
	}

	if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
		/* Try the previous key. */
		key = (char *)ep->secret_key[ep->last_key];
		memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
		if (crypto_hash_setkey(desc.tfm, key, keylen) ||
		    crypto_hash_digest(&desc, &sg, bodysize, digest)) {
			*error = -SCTP_IERROR_NOMEM;
			goto fail;
		}

		if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
			/* Yikes!  Still bad signature! */
			*error = -SCTP_IERROR_BAD_SIG;
			goto fail;
		}
	}

no_hmac:
	/* IG Section 2.35.2:
	 *  3) Compare the port numbers and the verification tag contained
	 *     within the COOKIE ECHO chunk to the actual port numbers and the
	 *     verification tag within the SCTP common header of the received
	 *     packet. If these values do not match the packet MUST be silently
	 *     discarded,
	 */
	if (ntohl(chunk->sctp_hdr->vtag) != bear_cookie->my_vtag) {
		*error = -SCTP_IERROR_BAD_TAG;
		goto fail;
	}

	if (chunk->sctp_hdr->source != bear_cookie->peer_addr.v4.sin_port ||
	    ntohs(chunk->sctp_hdr->dest) != bear_cookie->my_port) {
		*error = -SCTP_IERROR_BAD_PORTS;
		goto fail;
	}

	/* Check to see if the cookie is stale.  If there is already
	 * an association, there is no need to check cookie's expiration
	 * for init collision case of lost COOKIE ACK.
	 * If skb has been timestamped, then use the stamp, otherwise
	 * use current time.  This introduces a small possibility that
	 * that a cookie may be considered expired, but his would only slow
	 * down the new association establishment instead of every packet.
	 */
	if (sock_flag(ep->base.sk, SOCK_TIMESTAMP))
		skb_get_timestamp(skb, &tv);
	else
		do_gettimeofday(&tv);

	if (!asoc && tv_lt(bear_cookie->expiration, tv)) {
		/*
		 * Section 3.3.10.3 Stale Cookie Error (3)
		 *
		 * Cause of error
		 * ---------------
		 * Stale Cookie Error:  Indicates the receipt of a valid State
		 * Cookie that has expired.
		 */
		len = ntohs(chunk->chunk_hdr->length);
		*errp = sctp_make_op_error_space(asoc, chunk, len);
		if (*errp) {
			suseconds_t usecs = (tv.tv_sec -
				bear_cookie->expiration.tv_sec) * 1000000L +
				tv.tv_usec - bear_cookie->expiration.tv_usec;
			__be32 n = htonl(usecs);

			sctp_init_cause(*errp, SCTP_ERROR_STALE_COOKIE,
					sizeof(n));
			sctp_addto_chunk(*errp, sizeof(n), &n);
			*error = -SCTP_IERROR_STALE_COOKIE;
		} else
			*error = -SCTP_IERROR_NOMEM;

		goto fail;
	}

	/* Make a new base association.  */
	scope = sctp_scope(sctp_source(chunk));
	retval = sctp_association_new(ep, ep->base.sk, scope, gfp);
	if (!retval) {
		*error = -SCTP_IERROR_NOMEM;
		goto fail;
	}

	/* Set up our peer's port number.  */
	retval->peer.port = ntohs(chunk->sctp_hdr->source);

	/* Populate the association from the cookie.  */
	memcpy(&retval->c, bear_cookie, sizeof(*bear_cookie));

	if (sctp_assoc_set_bind_addr_from_cookie(retval, bear_cookie,
						 GFP_ATOMIC) < 0) {
		*error = -SCTP_IERROR_NOMEM;
		goto fail;
	}

	/* Also, add the destination address. */
	if (list_empty(&retval->base.bind_addr.address_list)) {
		sctp_add_bind_addr(&retval->base.bind_addr, &chunk->dest,
				SCTP_ADDR_SRC, GFP_ATOMIC);
	}

	retval->next_tsn = retval->c.initial_tsn;
	retval->ctsn_ack_point = retval->next_tsn - 1;
	retval->addip_serial = retval->c.initial_tsn;
	retval->adv_peer_ack_point = retval->ctsn_ack_point;
	retval->peer.prsctp_capable = retval->c.prsctp_capable;
	retval->peer.adaptation_ind = retval->c.adaptation_ind;

	/* The INIT stuff will be done by the side effects.  */
	return retval;

fail:
	if (retval)
		sctp_association_free(retval);

	return NULL;

malformed:
	/* Yikes!  The packet is either corrupt or deliberately
	 * malformed.
	 */
	*error = -SCTP_IERROR_MALFORMED;
	goto fail;
}

/********************************************************************
 * 3rd Level Abstractions
 ********************************************************************/

struct __sctp_missing {
	__be32 num_missing;
	__be16 type;
}  __attribute__((packed));

/*
 * Report a missing mandatory parameter.
 */
static int sctp_process_missing_param(const struct sctp_association *asoc,
				      sctp_param_t paramtype,
				      struct sctp_chunk *chunk,
				      struct sctp_chunk **errp)
{
	struct __sctp_missing report;
	__u16 len;

	len = WORD_ROUND(sizeof(report));

	/* Make an ERROR chunk, preparing enough room for
	 * returning multiple unknown parameters.
	 */
	if (!*errp)
		*errp = sctp_make_op_error_space(asoc, chunk, len);

	if (*errp) {
		report.num_missing = htonl(1);
		report.type = paramtype;
		sctp_init_cause(*errp, SCTP_ERROR_MISS_PARAM,
				sizeof(report));
		sctp_addto_chunk(*errp, sizeof(report), &report);
	}

	/* Stop processing this chunk. */
	return 0;
}

/* Report an Invalid Mandatory Parameter.  */
static int sctp_process_inv_mandatory(const struct sctp_association *asoc,
				      struct sctp_chunk *chunk,
				      struct sctp_chunk **errp)
{
	/* Invalid Mandatory Parameter Error has no payload. */

	if (!*errp)
		*errp = sctp_make_op_error_space(asoc, chunk, 0);

	if (*errp)
		sctp_init_cause(*errp, SCTP_ERROR_INV_PARAM, 0);

	/* Stop processing this chunk. */
	return 0;
}

static int sctp_process_inv_paramlength(const struct sctp_association *asoc,
					struct sctp_paramhdr *param,
					const struct sctp_chunk *chunk,
					struct sctp_chunk **errp)
{