associola.c

在linux环境下的流控制传输协议（sctp）的源代码

/* Remove a transport from an association.  */
void sctp_assoc_rm_peer(struct sctp_association *asoc,
			struct sctp_transport *peer)
{
	struct list_head	*pos;
	struct sctp_transport	*transport;

	SCTP_DEBUG_PRINTK_IPADDR("sctp_assoc_rm_peer:association %p addr: ",
				 " port: %d\n",
				 asoc,
				 (&peer->ipaddr),
				 ntohs(peer->ipaddr.v4.sin_port));

	/* If we are to remove the current retran_path, update it
	 * to the next peer before removing this peer from the list.
	 */
	if (asoc->peer.retran_path == peer)
		sctp_assoc_update_retran_path(asoc);

	/* Remove this peer from the list. */
	list_del(&peer->transports);

	/* Get the first transport of asoc. */
	pos = asoc->peer.transport_addr_list.next;
	transport = list_entry(pos, struct sctp_transport, transports);

	/* Update any entries that match the peer to be deleted. */
	if (asoc->peer.primary_path == peer)
		sctp_assoc_set_primary(asoc, transport);
	if (asoc->peer.active_path == peer)
		asoc->peer.active_path = transport;
	if (asoc->peer.last_data_from == peer)
		asoc->peer.last_data_from = transport;

	/* If we remove the transport an INIT was last sent to, set it to
	 * NULL. Combined with the update of the retran path above, this
	 * will cause the next INIT to be sent to the next available
	 * transport, maintaining the cycle.
	 */
	if (asoc->init_last_sent_to == peer)
		asoc->init_last_sent_to = NULL;

	asoc->peer.transport_count--;

	sctp_transport_free(peer);
}

/* Add a transport address to an association.  */
struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
					   const union sctp_addr *addr,
					   const gfp_t gfp,
					   const int peer_state)
{
	struct sctp_transport *peer;
	struct sctp_sock *sp;
	unsigned short port;

	sp = sctp_sk(asoc->base.sk);

	/* AF_INET and AF_INET6 share common port field. */
	port = ntohs(addr->v4.sin_port);

	SCTP_DEBUG_PRINTK_IPADDR("sctp_assoc_add_peer:association %p addr: ",
				 " port: %d state:%d\n",
				 asoc,
				 addr,
				 port,
				 peer_state);

	/* Set the port if it has not been set yet.  */
	if (0 == asoc->peer.port)
		asoc->peer.port = port;

	/* Check to see if this is a duplicate. */
	peer = sctp_assoc_lookup_paddr(asoc, addr);
	if (peer) {
		if (peer->state == SCTP_UNKNOWN) {
			if (peer_state == SCTP_ACTIVE)
				peer->state = SCTP_ACTIVE;
			if (peer_state == SCTP_UNCONFIRMED)
				peer->state = SCTP_UNCONFIRMED;
		}
		return peer;
	}

	peer = sctp_transport_new(addr, gfp);
	if (!peer)
		return NULL;

	sctp_transport_set_owner(peer, asoc);

	/* Initialize the peer's heartbeat interval based on the
	 * association configured value.
	 */
	peer->hbinterval = asoc->hbinterval;

	/* Set the path max_retrans.  */
	peer->pathmaxrxt = asoc->pathmaxrxt;

	/* Initialize the peer's SACK delay timeout based on the
	 * association configured value.
	 */
	peer->sackdelay = asoc->sackdelay;

	/* Enable/disable heartbeat, SACK delay, and path MTU discovery
	 * based on association setting.
	 */
	peer->param_flags = asoc->param_flags;

	/* Initialize the pmtu of the transport. */
	if (peer->param_flags & SPP_PMTUD_ENABLE)
		sctp_transport_pmtu(peer);
	else if (asoc->pathmtu)
		peer->pathmtu = asoc->pathmtu;
	else
		peer->pathmtu = SCTP_DEFAULT_MAXSEGMENT;

	/* If this is the first transport addr on this association,
	 * initialize the association PMTU to the peer's PMTU.
	 * If not and the current association PMTU is higher than the new
	 * peer's PMTU, reset the association PMTU to the new peer's PMTU.
	 */
	if (asoc->pathmtu)
		asoc->pathmtu = min_t(int, peer->pathmtu, asoc->pathmtu);
	else
		asoc->pathmtu = peer->pathmtu;

	SCTP_DEBUG_PRINTK("sctp_assoc_add_peer:association %p PMTU set to "
			  "%d\n", asoc, asoc->pathmtu);

	asoc->frag_point = sctp_frag_point(sp, asoc->pathmtu);

	/* The asoc->peer.port might not be meaningful yet, but
	 * initialize the packet structure anyway.
	 */
	sctp_packet_init(&peer->packet, peer, asoc->base.bind_addr.port,
			 asoc->peer.port);

	/* 7.2.1 Slow-Start
	 *
	 * o The initial cwnd before DATA transmission or after a sufficiently
	 *   long idle period MUST be set to
	 *      min(4*MTU, max(2*MTU, 4380 bytes))
	 *
	 * o The initial value of ssthresh MAY be arbitrarily high
	 *   (for example, implementations MAY use the size of the
	 *   receiver advertised window).
	 */
	peer->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));

	/* At this point, we may not have the receiver's advertised window,
	 * so initialize ssthresh to the default value and it will be set
	 * later when we process the INIT.
	 */
	peer->ssthresh = SCTP_DEFAULT_MAXWINDOW;

	peer->partial_bytes_acked = 0;
	peer->flight_size = 0;

	/* Set the transport's RTO.initial value */
	peer->rto = asoc->rto_initial;

	/* Set the peer's active state. */
	peer->state = peer_state;

	/* Attach the remote transport to our asoc.  */
	list_add_tail(&peer->transports, &asoc->peer.transport_addr_list);
	asoc->peer.transport_count++;

	/* If we do not yet have a primary path, set one.  */
	if (!asoc->peer.primary_path) {
		sctp_assoc_set_primary(asoc, peer);
		asoc->peer.retran_path = peer;
	}

	if (asoc->peer.active_path == asoc->peer.retran_path) {
		asoc->peer.retran_path = peer;
	}

	return peer;
}

/* Delete a transport address from an association.  */
void sctp_assoc_del_peer(struct sctp_association *asoc,
			 const union sctp_addr *addr)
{
	struct list_head	*pos;
	struct list_head	*temp;
	struct sctp_transport	*transport;

	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
		transport = list_entry(pos, struct sctp_transport, transports);
		if (sctp_cmp_addr_exact(addr, &transport->ipaddr)) {
			/* Do book keeping for removing the peer and free it. */
			sctp_assoc_rm_peer(asoc, transport);
			break;
		}
	}
}

/* Lookup a transport by address. */
struct sctp_transport *sctp_assoc_lookup_paddr(
					const struct sctp_association *asoc,
					const union sctp_addr *address)
{
	struct sctp_transport *t;
	struct list_head *pos;

	/* Cycle through all transports searching for a peer address. */

	list_for_each(pos, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);
		if (sctp_cmp_addr_exact(address, &t->ipaddr))
			return t;
	}

	return NULL;
}

/* Remove all transports except a give one */
void sctp_assoc_del_nonprimary_peers(struct sctp_association *asoc,
				     struct sctp_transport *primary)
{
	struct sctp_transport	*temp;
	struct sctp_transport	*t;

	list_for_each_entry_safe(t, temp, &asoc->peer.transport_addr_list,
				 transports) {
		/* if the current transport is not the primary one, delete it */
		if (t != primary)
			sctp_assoc_rm_peer(asoc, t);
	}

	return;
}

/* Engage in transport control operations.
 * Mark the transport up or down and send a notification to the user.
 * Select and update the new active and retran paths.
 */
void sctp_assoc_control_transport(struct sctp_association *asoc,
				  struct sctp_transport *transport,
				  sctp_transport_cmd_t command,
				  sctp_sn_error_t error)
{
	struct sctp_transport *t = NULL;
	struct sctp_transport *first;
	struct sctp_transport *second;
	struct sctp_ulpevent *event;
	struct sockaddr_storage addr;
	struct list_head *pos;
	int spc_state = 0;

	/* Record the transition on the transport.  */
	switch (command) {
	case SCTP_TRANSPORT_UP:
		/* If we are moving from UNCONFIRMED state due
		 * to heartbeat success, report the SCTP_ADDR_CONFIRMED
		 * state to the user, otherwise report SCTP_ADDR_AVAILABLE.
		 */
		if (SCTP_UNCONFIRMED == transport->state &&
		    SCTP_HEARTBEAT_SUCCESS == error)
			spc_state = SCTP_ADDR_CONFIRMED;
		else
			spc_state = SCTP_ADDR_AVAILABLE;
		transport->state = SCTP_ACTIVE;
		break;

	case SCTP_TRANSPORT_DOWN:
		/* if the transort was never confirmed, do not transition it
		 * to inactive state.
		 */
		if (transport->state != SCTP_UNCONFIRMED)
			transport->state = SCTP_INACTIVE;

		spc_state = SCTP_ADDR_UNREACHABLE;
		break;

	default:
		return;
	}

	/* Generate and send a SCTP_PEER_ADDR_CHANGE notification to the
	 * user.
	 */
	memset(&addr, 0, sizeof(struct sockaddr_storage));
	memcpy(&addr, &transport->ipaddr, transport->af_specific->sockaddr_len);
	event = sctp_ulpevent_make_peer_addr_change(asoc, &addr,
				0, spc_state, error, GFP_ATOMIC);
	if (event)
		sctp_ulpq_tail_event(&asoc->ulpq, event);

	/* Select new active and retran paths. */

	/* Look for the two most recently used active transports.
	 *
	 * This code produces the wrong ordering whenever jiffies
	 * rolls over, but we still get usable transports, so we don't
	 * worry about it.
	 */
	first = NULL; second = NULL;

	list_for_each(pos, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);

		if ((t->state == SCTP_INACTIVE) ||
		    (t->state == SCTP_UNCONFIRMED))
			continue;
		if (!first || t->last_time_heard > first->last_time_heard) {
			second = first;
			first = t;
		}
		if (!second || t->last_time_heard > second->last_time_heard)
			second = t;
	}

	/* RFC 2960 6.4 Multi-Homed SCTP Endpoints
	 *
	 * By default, an endpoint should always transmit to the
	 * primary path, unless the SCTP user explicitly specifies the
	 * destination transport address (and possibly source
	 * transport address) to use.
	 *
	 * [If the primary is active but not most recent, bump the most
	 * recently used transport.]
	 */
	if (((asoc->peer.primary_path->state == SCTP_ACTIVE) ||
	     (asoc->peer.primary_path->state == SCTP_UNKNOWN)) &&
	    first != asoc->peer.primary_path) {
		second = first;
		first = asoc->peer.primary_path;
	}

	/* If we failed to find a usable transport, just camp on the
	 * primary, even if it is inactive.
	 */
	if (!first) {
		first = asoc->peer.primary_path;
		second = asoc->peer.primary_path;
	}

	/* Set the active and retran transports.  */
	asoc->peer.active_path = first;
	asoc->peer.retran_path = second;
}

/* Hold a reference to an association. */
void sctp_association_hold(struct sctp_association *asoc)
{
	atomic_inc(&asoc->base.refcnt);
}

/* Release a reference to an association and cleanup
 * if there are no more references.
 */
void sctp_association_put(struct sctp_association *asoc)
{
	if (atomic_dec_and_test(&asoc->base.refcnt))
		sctp_association_destroy(asoc);
}

/* Allocate the next TSN, Transmission Sequence Number, for the given
 * association.
 */
__u32 sctp_association_get_next_tsn(struct sctp_association *asoc)
{
	/* From Section 1.6 Serial Number Arithmetic:
	 * Transmission Sequence Numbers wrap around when they reach
	 * 2**32 - 1.  That is, the next TSN a DATA chunk MUST use
	 * after transmitting TSN = 2*32 - 1 is TSN = 0.
	 */
	__u32 retval = asoc->next_tsn;
	asoc->next_tsn++;
	asoc->unack_data++;

	return retval;
}

/* Compare two addresses to see if they match.  Wildcard addresses
 * only match themselves.
 */
int sctp_cmp_addr_exact(const union sctp_addr *ss1,
			const union sctp_addr *ss2)
{
	struct sctp_af *af;

	af = sctp_get_af_specific(ss1->sa.sa_family);
	if (unlikely(!af))
		return 0;

	return af->cmp_addr(ss1, ss2);
}

/* Return an ecne chunk to get prepended to a packet.
 * Note:  We are sly and return a shared, prealloced chunk.  FIXME:
 * No we don't, but we could/should.
 */
struct sctp_chunk *sctp_get_ecne_prepend(struct sctp_association *asoc)
{
	struct sctp_chunk *chunk;

	/* Send ECNE if needed.
	 * Not being able to allocate a chunk here is not deadly.
	 */
	if (asoc->need_ecne)
		chunk = sctp_make_ecne(asoc, asoc->last_ecne_tsn);
	else
		chunk = NULL;

	return chunk;
}

/*
 * Find which transport this TSN was sent on.
 */
struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association *asoc,
					     __u32 tsn)
{
	struct sctp_transport *active;
	struct sctp_transport *match;
	struct list_head *entry, *pos;
	struct sctp_transport *transport;
	struct sctp_chunk *chunk;
	__be32 key = htonl(tsn);

	match = NULL;

	/*
	 * FIXME: In general, find a more efficient data structure for
	 * searching.
	 */

	/*
	 * The general strategy is to search each transport's transmitted
	 * list.   Return which transport this TSN lives on.
	 *
	 * Let's be hopeful and check the active_path first.
	 * Another optimization would be to know if there is only one
	 * outbound path and not have to look for the TSN at all.
	 *
	 */

	active = asoc->peer.active_path;

	list_for_each(entry, &active->transmitted) {
		chunk = list_entry(entry, struct sctp_chunk, transmitted_list);

		if (key == chunk->subh.data_hdr->tsn) {
			match = active;
			goto out;
		}
	}

	/* If not found, go search all the other transports. */
	list_for_each(pos, &asoc->peer.transport_addr_list) {
		transport = list_entry(pos, struct sctp_transport, transports);

		if (transport == active)
			break;
		list_for_each(entry, &transport->transmitted) {
			chunk = list_entry(entry, struct sctp_chunk,
					   transmitted_list);
			if (key == chunk->subh.data_hdr->tsn) {
				match = transport;
				goto out;
			}
		}
	}
out:
	return match;
}

/* Is this the association we are looking for? */
struct sctp_transport *sctp_assoc_is_match(struct sctp_association *asoc,
					   const union sctp_addr *laddr,
					   const union sctp_addr *paddr)
{
	struct sctp_transport *transport;

	if ((htons(asoc->base.bind_addr.port) == laddr->v4.sin_port) &&
	    (htons(asoc->peer.port) == paddr->v4.sin_port)) {
		transport = sctp_assoc_lookup_paddr(asoc, paddr);
		if (!transport)
			goto out;

		if (sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
					 sctp_sk(asoc->base.sk)))
			goto out;
	}
	transport = NULL;

out:
	return transport;
}

/* Do delayed input processing.  This is scheduled by sctp_rcv(). */
static void sctp_assoc_bh_rcv(struct work_struct *work)
{
	struct sctp_association *asoc =
		container_of(work, struct sctp_association,
			     base.inqueue.immediate);
	struct sctp_endpoint *ep;
	struct sctp_chunk *chunk;
	struct sock *sk;
	struct sctp_inq *inqueue;
	int state;
	sctp_subtype_t subtype;
	int error = 0;

	/* The association should be held so we should be safe. */
	ep = asoc->ep;
	sk = asoc->base.sk;

	inqueue = &asoc->base.inqueue;