associola.c

在linux环境下的流控制传输协议（sctp）的源代码

	sctp_association_hold(asoc);
	while (NULL != (chunk = sctp_inq_pop(inqueue))) {
		state = asoc->state;
		subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);

		/* SCTP-AUTH, Section 6.3:
		 *    The receiver has a list of chunk types which it expects
		 *    to be received only after an AUTH-chunk.  This list has
		 *    been sent to the peer during the association setup.  It
		 *    MUST silently discard these chunks if they are not placed
		 *    after an AUTH chunk in the packet.
		 */
		if (sctp_auth_recv_cid(subtype.chunk, asoc) && !chunk->auth)
			continue;

		/* Remember where the last DATA chunk came from so we
		 * know where to send the SACK.
		 */
		if (sctp_chunk_is_data(chunk))
			asoc->peer.last_data_from = chunk->transport;
		else
			SCTP_INC_STATS(SCTP_MIB_INCTRLCHUNKS);

		if (chunk->transport)
			chunk->transport->last_time_heard = jiffies;

		/* Run through the state machine. */
		error = sctp_do_sm(SCTP_EVENT_T_CHUNK, subtype,
				   state, ep, asoc, chunk, GFP_ATOMIC);

		/* Check to see if the association is freed in response to
		 * the incoming chunk.  If so, get out of the while loop.
		 */
		if (asoc->base.dead)
			break;

		/* If there is an error on chunk, discard this packet. */
		if (error && chunk)
			chunk->pdiscard = 1;
	}
	sctp_association_put(asoc);
}

/* This routine moves an association from its old sk to a new sk.  */
void sctp_assoc_migrate(struct sctp_association *assoc, struct sock *newsk)
{
	struct sctp_sock *newsp = sctp_sk(newsk);
	struct sock *oldsk = assoc->base.sk;

	/* Delete the association from the old endpoint's list of
	 * associations.
	 */
	list_del_init(&assoc->asocs);

	/* Decrement the backlog value for a TCP-style socket. */
	if (sctp_style(oldsk, TCP))
		oldsk->sk_ack_backlog--;

	/* Release references to the old endpoint and the sock.  */
	sctp_endpoint_put(assoc->ep);
	sock_put(assoc->base.sk);

	/* Get a reference to the new endpoint.  */
	assoc->ep = newsp->ep;
	sctp_endpoint_hold(assoc->ep);

	/* Get a reference to the new sock.  */
	assoc->base.sk = newsk;
	sock_hold(assoc->base.sk);

	/* Add the association to the new endpoint's list of associations.  */
	sctp_endpoint_add_asoc(newsp->ep, assoc);
}

/* Update an association (possibly from unexpected COOKIE-ECHO processing).  */
void sctp_assoc_update(struct sctp_association *asoc,
		       struct sctp_association *new)
{
	struct sctp_transport *trans;
	struct list_head *pos, *temp;

	/* Copy in new parameters of peer. */
	asoc->c = new->c;
	asoc->peer.rwnd = new->peer.rwnd;
	asoc->peer.sack_needed = new->peer.sack_needed;
	asoc->peer.i = new->peer.i;
	sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_SIZE,
			 asoc->peer.i.initial_tsn);

	/* Remove any peer addresses not present in the new association. */
	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
		trans = list_entry(pos, struct sctp_transport, transports);
		if (!sctp_assoc_lookup_paddr(new, &trans->ipaddr))
			sctp_assoc_del_peer(asoc, &trans->ipaddr);

		if (asoc->state >= SCTP_STATE_ESTABLISHED)
			sctp_transport_reset(trans);
	}

	/* If the case is A (association restart), use
	 * initial_tsn as next_tsn. If the case is B, use
	 * current next_tsn in case data sent to peer
	 * has been discarded and needs retransmission.
	 */
	if (asoc->state >= SCTP_STATE_ESTABLISHED) {
		asoc->next_tsn = new->next_tsn;
		asoc->ctsn_ack_point = new->ctsn_ack_point;
		asoc->adv_peer_ack_point = new->adv_peer_ack_point;

		/* Reinitialize SSN for both local streams
		 * and peer's streams.
		 */
		sctp_ssnmap_clear(asoc->ssnmap);

		/* Flush the ULP reassembly and ordered queue.
		 * Any data there will now be stale and will
		 * cause problems.
		 */
		sctp_ulpq_flush(&asoc->ulpq);

		/* reset the overall association error count so
		 * that the restarted association doesn't get torn
		 * down on the next retransmission timer.
		 */
		asoc->overall_error_count = 0;

	} else {
		/* Add any peer addresses from the new association. */
		list_for_each(pos, &new->peer.transport_addr_list) {
			trans = list_entry(pos, struct sctp_transport,
					   transports);
			if (!sctp_assoc_lookup_paddr(asoc, &trans->ipaddr))
				sctp_assoc_add_peer(asoc, &trans->ipaddr,
						    GFP_ATOMIC, trans->state);
		}

		asoc->ctsn_ack_point = asoc->next_tsn - 1;
		asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
		if (!asoc->ssnmap) {
			/* Move the ssnmap. */
			asoc->ssnmap = new->ssnmap;
			new->ssnmap = NULL;
		}

		if (!asoc->assoc_id) {
			/* get a new association id since we don't have one
			 * yet.
			 */
			sctp_assoc_set_id(asoc, GFP_ATOMIC);
		}
	}

	/* SCTP-AUTH: Save the peer parameters from the new assocaitions
	 * and also move the association shared keys over
	 */
	kfree(asoc->peer.peer_random);
	asoc->peer.peer_random = new->peer.peer_random;
	new->peer.peer_random = NULL;

	kfree(asoc->peer.peer_chunks);
	asoc->peer.peer_chunks = new->peer.peer_chunks;
	new->peer.peer_chunks = NULL;

	kfree(asoc->peer.peer_hmacs);
	asoc->peer.peer_hmacs = new->peer.peer_hmacs;
	new->peer.peer_hmacs = NULL;

	sctp_auth_key_put(asoc->asoc_shared_key);
	sctp_auth_asoc_init_active_key(asoc, GFP_ATOMIC);
}

/* Update the retran path for sending a retransmitted packet.
 * Round-robin through the active transports, else round-robin
 * through the inactive transports as this is the next best thing
 * we can try.
 */
void sctp_assoc_update_retran_path(struct sctp_association *asoc)
{
	struct sctp_transport *t, *next;
	struct list_head *head = &asoc->peer.transport_addr_list;
	struct list_head *pos;

	/* Find the next transport in a round-robin fashion. */
	t = asoc->peer.retran_path;
	pos = &t->transports;
	next = NULL;

	while (1) {
		/* Skip the head. */
		if (pos->next == head)
			pos = head->next;
		else
			pos = pos->next;

		t = list_entry(pos, struct sctp_transport, transports);

		/* Try to find an active transport. */

		if ((t->state == SCTP_ACTIVE) ||
		    (t->state == SCTP_UNKNOWN)) {
			break;
		} else {
			/* Keep track of the next transport in case
			 * we don't find any active transport.
			 */
			if (!next)
				next = t;
		}

		/* We have exhausted the list, but didn't find any
		 * other active transports.  If so, use the next
		 * transport.
		 */
		if (t == asoc->peer.retran_path) {
			t = next;
			break;
		}
	}

	asoc->peer.retran_path = t;

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

/* Choose the transport for sending a INIT packet.  */
struct sctp_transport *sctp_assoc_choose_init_transport(
	struct sctp_association *asoc)
{
	struct sctp_transport *t;

	/* Use the retran path. If the last INIT was sent over the
	 * retran path, update the retran path and use it.
	 */
	if (!asoc->init_last_sent_to) {
		t = asoc->peer.active_path;
	} else {
		if (asoc->init_last_sent_to == asoc->peer.retran_path)
			sctp_assoc_update_retran_path(asoc);
		t = asoc->peer.retran_path;
	}

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

	return t;
}

/* Choose the transport for sending a SHUTDOWN packet.  */
struct sctp_transport *sctp_assoc_choose_shutdown_transport(
	struct sctp_association *asoc)
{
	/* If this is the first time SHUTDOWN is sent, use the active path,
	 * else use the retran path. If the last SHUTDOWN was sent over the
	 * retran path, update the retran path and use it.
	 */
	if (!asoc->shutdown_last_sent_to)
		return asoc->peer.active_path;
	else {
		if (asoc->shutdown_last_sent_to == asoc->peer.retran_path)
			sctp_assoc_update_retran_path(asoc);
		return asoc->peer.retran_path;
	}

}

/* Update the association's pmtu and frag_point by going through all the
 * transports. This routine is called when a transport's PMTU has changed.
 */
void sctp_assoc_sync_pmtu(struct sctp_association *asoc)
{
	struct sctp_transport *t;
	struct list_head *pos;
	__u32 pmtu = 0;

	if (!asoc)
		return;

	/* Get the lowest pmtu of all the transports. */
	list_for_each(pos, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);
		if (t->pmtu_pending && t->dst) {
			sctp_transport_update_pmtu(t, dst_mtu(t->dst));
			t->pmtu_pending = 0;
		}
		if (!pmtu || (t->pathmtu < pmtu))
			pmtu = t->pathmtu;
	}

	if (pmtu) {
		struct sctp_sock *sp = sctp_sk(asoc->base.sk);
		asoc->pathmtu = pmtu;
		asoc->frag_point = sctp_frag_point(sp, pmtu);
	}

	SCTP_DEBUG_PRINTK("%s: asoc:%p, pmtu:%d, frag_point:%d\n",
			  __FUNCTION__, asoc, asoc->pathmtu, asoc->frag_point);
}

/* Should we send a SACK to update our peer? */
static inline int sctp_peer_needs_update(struct sctp_association *asoc)
{
	switch (asoc->state) {
	case SCTP_STATE_ESTABLISHED:
	case SCTP_STATE_SHUTDOWN_PENDING:
	case SCTP_STATE_SHUTDOWN_RECEIVED:
	case SCTP_STATE_SHUTDOWN_SENT:
		if ((asoc->rwnd > asoc->a_rwnd) &&
		    ((asoc->rwnd - asoc->a_rwnd) >=
		     min_t(__u32, (asoc->base.sk->sk_rcvbuf >> 1), asoc->pathmtu)))
			return 1;
		break;
	default:
		break;
	}
	return 0;
}

/* Increase asoc's rwnd by len and send any window update SACK if needed. */
void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned len)
{
	struct sctp_chunk *sack;
	struct timer_list *timer;

	if (asoc->rwnd_over) {
		if (asoc->rwnd_over >= len) {
			asoc->rwnd_over -= len;
		} else {
			asoc->rwnd += (len - asoc->rwnd_over);
			asoc->rwnd_over = 0;
		}
	} else {
		asoc->rwnd += len;
	}

	SCTP_DEBUG_PRINTK("%s: asoc %p rwnd increased by %d to (%u, %u) "
			  "- %u\n", __FUNCTION__, asoc, len, asoc->rwnd,
			  asoc->rwnd_over, asoc->a_rwnd);

	/* Send a window update SACK if the rwnd has increased by at least the
	 * minimum of the association's PMTU and half of the receive buffer.
	 * The algorithm used is similar to the one described in
	 * Section 4.2.3.3 of RFC 1122.
	 */
	if (sctp_peer_needs_update(asoc)) {
		asoc->a_rwnd = asoc->rwnd;
		SCTP_DEBUG_PRINTK("%s: Sending window update SACK- asoc: %p "
				  "rwnd: %u a_rwnd: %u\n", __FUNCTION__,
				  asoc, asoc->rwnd, asoc->a_rwnd);
		sack = sctp_make_sack(asoc);
		if (!sack)
			return;

		asoc->peer.sack_needed = 0;

		sctp_outq_tail(&asoc->outqueue, sack);

		/* Stop the SACK timer.  */
		timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
		if (timer_pending(timer) && del_timer(timer))
			sctp_association_put(asoc);
	}
}

/* Decrease asoc's rwnd by len. */
void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned len)
{
	SCTP_ASSERT(asoc->rwnd, "rwnd zero", return);
	SCTP_ASSERT(!asoc->rwnd_over, "rwnd_over not zero", return);
	if (asoc->rwnd >= len) {
		asoc->rwnd -= len;
	} else {
		asoc->rwnd_over = len - asoc->rwnd;
		asoc->rwnd = 0;
	}
	SCTP_DEBUG_PRINTK("%s: asoc %p rwnd decreased by %d to (%u, %u)\n",
			  __FUNCTION__, asoc, len, asoc->rwnd,
			  asoc->rwnd_over);
}

/* Build the bind address list for the association based on info from the
 * local endpoint and the remote peer.
 */
int sctp_assoc_set_bind_addr_from_ep(struct sctp_association *asoc,
				     gfp_t gfp)
{
	sctp_scope_t scope;
	int flags;

	/* Use scoping rules to determine the subset of addresses from
	 * the endpoint.
	 */
	scope = sctp_scope(&asoc->peer.active_path->ipaddr);
	flags = (PF_INET6 == asoc->base.sk->sk_family) ? SCTP_ADDR6_ALLOWED : 0;
	if (asoc->peer.ipv4_address)
		flags |= SCTP_ADDR4_PEERSUPP;
	if (asoc->peer.ipv6_address)
		flags |= SCTP_ADDR6_PEERSUPP;

	return sctp_bind_addr_copy(&asoc->base.bind_addr,
				   &asoc->ep->base.bind_addr,
				   scope, gfp, flags);
}

/* Build the association's bind address list from the cookie.  */
int sctp_assoc_set_bind_addr_from_cookie(struct sctp_association *asoc,
					 struct sctp_cookie *cookie,
					 gfp_t gfp)
{
	int var_size2 = ntohs(cookie->peer_init->chunk_hdr.length);
	int var_size3 = cookie->raw_addr_list_len;
	__u8 *raw = (__u8 *)cookie->peer_init + var_size2;

	return sctp_raw_to_bind_addrs(&asoc->base.bind_addr, raw, var_size3,
				      asoc->ep->base.bind_addr.port, gfp);
}

/* Lookup laddr in the bind address list of an association. */
int sctp_assoc_lookup_laddr(struct sctp_association *asoc,
			    const union sctp_addr *laddr)
{
	int found = 0;

	if ((asoc->base.bind_addr.port == ntohs(laddr->v4.sin_port)) &&
	    sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
				 sctp_sk(asoc->base.sk)))
		found = 1;

	return found;
}

/* Set an association id for a given association */
int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp)
{
	int assoc_id;
	int error = 0;
retry:
	if (unlikely(!idr_pre_get(&sctp_assocs_id, gfp)))
		return -ENOMEM;

	spin_lock_bh(&sctp_assocs_id_lock);
	error = idr_get_new_above(&sctp_assocs_id, (void *)asoc,
				    1, &assoc_id);
	spin_unlock_bh(&sctp_assocs_id_lock);
	if (error == -EAGAIN)
		goto retry;
	else if (error)
		return error;

	asoc->assoc_id = (sctp_assoc_t) assoc_id;
	return error;
}

/* Free asconf_ack cache */
static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc)
{
	struct sctp_chunk *ack;
	struct sctp_chunk *tmp;

	list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
				transmitted_list) {
		list_del_init(&ack->transmitted_list);
		sctp_chunk_free(ack);
	}
}

/* Clean up the ASCONF_ACK queue */
void sctp_assoc_clean_asconf_ack_cache(const struct sctp_association *asoc)
{
	struct sctp_chunk *ack;
	struct sctp_chunk *tmp;

	/* We can remove all the entries from the queue upto
	 * the "Peer-Sequence-Number".
	 */
	list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
				transmitted_list) {
		if (ack->subh.addip_hdr->serial ==
				htonl(asoc->peer.addip_serial))
			break;

		list_del_init(&ack->transmitted_list);
		sctp_chunk_free(ack);
	}
}

/* Find the ASCONF_ACK whose serial number matches ASCONF */
struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
					const struct sctp_association *asoc,
					__be32 serial)
{
	struct sctp_chunk *ack;

	/* Walk through the list of cached ASCONF-ACKs and find the
	 * ack chunk whose serial number matches that of the request.
	 */
	list_for_each_entry(ack, &asoc->asconf_ack_list, transmitted_list) {
		if (ack->subh.addip_hdr->serial == serial) {
			sctp_chunk_hold(ack);
			return ack;
		}
	}

	return NULL;
}