structs.h

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	size_t size;

	/* The packet is destined for this transport address.
	 * The function we finally use to pass down to the next lower
	 * layer lives in the transport structure.
	 */
	struct sctp_transport *transport;

	/* pointer to the auth chunk for this packet */
	struct sctp_chunk *auth;

	/* This packet contains a COOKIE-ECHO chunk. */
	__u8 has_cookie_echo;

	/* This packet contains a SACK chunk. */
	__u8 has_sack;

	/* This packet contains an AUTH chunk */
	__u8 has_auth;

	/* This packet contains at least 1 DATA chunk */
	__u8 has_data;

	/* SCTP cannot fragment this packet. So let ip fragment it. */
	__u8 ipfragok;

	__u8 malloced;
};

struct sctp_packet *sctp_packet_init(struct sctp_packet *,
				     struct sctp_transport *,
				     __u16 sport, __u16 dport);
struct sctp_packet *sctp_packet_config(struct sctp_packet *, __u32 vtag, int);
sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *,
                                       struct sctp_chunk *);
sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *,
                                     struct sctp_chunk *);
int sctp_packet_transmit(struct sctp_packet *);
void sctp_packet_free(struct sctp_packet *);

static inline int sctp_packet_empty(struct sctp_packet *packet)
{
	return (packet->size == packet->overhead);
}

/* This represents a remote transport address.
 * For local transport addresses, we just use union sctp_addr.
 *
 * RFC2960 Section 1.4 Key Terms
 *
 *   o	Transport address:  A Transport Address is traditionally defined
 *	by Network Layer address, Transport Layer protocol and Transport
 *	Layer port number.  In the case of SCTP running over IP, a
 *	transport address is defined by the combination of an IP address
 *	and an SCTP port number (where SCTP is the Transport protocol).
 *
 * RFC2960 Section 7.1 SCTP Differences from TCP Congestion control
 *
 *   o	The sender keeps a separate congestion control parameter set for
 *	each of the destination addresses it can send to (not each
 *	source-destination pair but for each destination).  The parameters
 *	should decay if the address is not used for a long enough time
 *	period.
 *
 */
struct sctp_transport {
	/* A list of transports. */
	struct list_head transports;

	/* Reference counting. */
	atomic_t refcnt;
	int	 dead;

	/* This is the peer's IP address and port. */
	union sctp_addr ipaddr;

	/* These are the functions we call to handle LLP stuff.	 */
	struct sctp_af *af_specific;

	/* Which association do we belong to?  */
	struct sctp_association *asoc;

	/* RFC2960
	 *
	 * 12.3 Per Transport Address Data
	 *
	 * For each destination transport address in the peer's
	 * address list derived from the INIT or INIT ACK chunk, a
	 * number of data elements needs to be maintained including:
	 */
	/* RTO	       : The current retransmission timeout value.  */
	unsigned long rto;
	unsigned long last_rto;

	__u32 rtt;		/* This is the most recent RTT.	 */

	/* RTTVAR      : The current RTT variation.  */
	__u32 rttvar;

	/* SRTT	       : The current smoothed round trip time.	*/
	__u32 srtt;

	/* RTO-Pending : A flag used to track if one of the DATA
	 *		chunks sent to this address is currently being
	 *		used to compute a RTT. If this flag is 0,
	 *		the next DATA chunk sent to this destination
	 *		should be used to compute a RTT and this flag
	 *		should be set. Every time the RTT
	 *		calculation completes (i.e. the DATA chunk
	 *		is SACK'd) clear this flag.
	 */
	int rto_pending;

	/*
	 * These are the congestion stats.
	 */
	/* cwnd	       : The current congestion window.	 */
	__u32 cwnd;		  /* This is the actual cwnd.  */

	/* ssthresh    : The current slow start threshold value.  */
	__u32 ssthresh;

	/* partial     : The tracking method for increase of cwnd when in
	 * bytes acked : congestion avoidance mode (see Section 6.2.2)
	 */
	__u32 partial_bytes_acked;

	/* Data that has been sent, but not acknowledged. */
	__u32 flight_size;

	/* Destination */
	struct dst_entry *dst;
	/* Source address. */
	union sctp_addr saddr;

	/* When was the last time(in jiffies) that a data packet was sent on
	 * this transport?  This is used to adjust the cwnd when the transport
	 * becomes inactive.
	 */
	unsigned long last_time_used;

	/* Heartbeat interval: The endpoint sends out a Heartbeat chunk to
	 * the destination address every heartbeat interval.
	 */
	unsigned long hbinterval;

	/* SACK delay timeout */
	unsigned long sackdelay;

	/* When was the last time (in jiffies) that we heard from this
	 * transport?  We use this to pick new active and retran paths.
	 */
	unsigned long last_time_heard;

	/* Last time(in jiffies) when cwnd is reduced due to the congestion
	 * indication based on ECNE chunk.
	 */
	unsigned long last_time_ecne_reduced;

	/* This is the max_retrans value for the transport and will
	 * be initialized from the assocs value.  This can be changed
	 * using SCTP_SET_PEER_ADDR_PARAMS socket option.
	 */
	__u16 pathmaxrxt;

	/* is the Path MTU update pending on this tranport */
	__u8 pmtu_pending;

	/* PMTU	      : The current known path MTU.  */
	__u32 pathmtu;

	/* Flags controlling Heartbeat, SACK delay, and Path MTU Discovery. */
	__u32 param_flags;

	/* The number of times INIT has been sent on this transport. */
	int init_sent_count;

	/* state       : The current state of this destination,
	 *             : i.e. SCTP_ACTIVE, SCTP_INACTIVE, SCTP_UNKOWN.
	 */
	int state;

	/* These are the error stats for this destination.  */

	/* Error count : The current error count for this destination.	*/
	unsigned short error_count;

	/* Per	       : A timer used by each destination.
	 * Destination :
	 * Timer       :
	 *
	 * [Everywhere else in the text this is called T3-rtx. -ed]
	 */
	struct timer_list T3_rtx_timer;

	/* Heartbeat timer is per destination. */
	struct timer_list hb_timer;

	/* Since we're using per-destination retransmission timers
	 * (see above), we're also using per-destination "transmitted"
	 * queues.  This probably ought to be a private struct
	 * accessible only within the outqueue, but it's not, yet.
	 */
	struct list_head transmitted;

	/* We build bundle-able packets for this transport here.  */
	struct sctp_packet packet;

	/* This is the list of transports that have chunks to send.  */
	struct list_head send_ready;

	int malloced; /* Is this structure kfree()able? */

	/* State information saved for SFR_CACC algorithm. The key
	 * idea in SFR_CACC is to maintain state at the sender on a
	 * per-destination basis when a changeover happens.
	 *	char changeover_active;
	 *	char cycling_changeover;
	 *	__u32 next_tsn_at_change;
	 *	char cacc_saw_newack;
	 */
	struct {
		/* An unsigned integer, which stores the next TSN to be
		 * used by the sender, at the moment of changeover.
		 */
		__u32 next_tsn_at_change;

		/* A flag which indicates the occurrence of a changeover */
		char changeover_active;

		/* A flag which indicates whether the change of primary is
		 * the first switch to this destination address during an
		 * active switch.
		 */
		char cycling_changeover;

		/* A temporary flag, which is used during the processing of
		 * a SACK to estimate the causative TSN(s)'s group.
		 */
		char cacc_saw_newack;
	} cacc;

	/* 64-bit random number sent with heartbeat. */
	__u64 hb_nonce;
};

struct sctp_transport *sctp_transport_new(const union sctp_addr *,
					  gfp_t);
void sctp_transport_set_owner(struct sctp_transport *,
			      struct sctp_association *);
void sctp_transport_route(struct sctp_transport *, union sctp_addr *,
			  struct sctp_sock *);
void sctp_transport_pmtu(struct sctp_transport *);
void sctp_transport_free(struct sctp_transport *);
void sctp_transport_reset_timers(struct sctp_transport *);
void sctp_transport_hold(struct sctp_transport *);
void sctp_transport_put(struct sctp_transport *);
void sctp_transport_update_rto(struct sctp_transport *, __u32);
void sctp_transport_raise_cwnd(struct sctp_transport *, __u32, __u32);
void sctp_transport_lower_cwnd(struct sctp_transport *, sctp_lower_cwnd_t);
unsigned long sctp_transport_timeout(struct sctp_transport *);
void sctp_transport_reset(struct sctp_transport *);
void sctp_transport_update_pmtu(struct sctp_transport *, u32);


/* This is the structure we use to queue packets as they come into
 * SCTP.  We write packets to it and read chunks from it.
 */
struct sctp_inq {
	/* This is actually a queue of sctp_chunk each
	 * containing a partially decoded packet.
	 */
	struct list_head in_chunk_list;
	/* This is the packet which is currently off the in queue and is
	 * being worked on through the inbound chunk processing.
	 */
	struct sctp_chunk *in_progress;

	/* This is the delayed task to finish delivering inbound
	 * messages.
	 */
	struct work_struct immediate;

	int malloced;	     /* Is this structure kfree()able?	*/
};

void sctp_inq_init(struct sctp_inq *);
void sctp_inq_free(struct sctp_inq *);
void sctp_inq_push(struct sctp_inq *, struct sctp_chunk *packet);
struct sctp_chunk *sctp_inq_pop(struct sctp_inq *);
struct sctp_chunkhdr *sctp_inq_peek(struct sctp_inq *);
void sctp_inq_set_th_handler(struct sctp_inq *, work_func_t);

/* This is the structure we use to hold outbound chunks.  You push
 * chunks in and they automatically pop out the other end as bundled
 * packets (it calls (*output_handler)()).
 *
 * This structure covers sections 6.3, 6.4, 6.7, 6.8, 6.10, 7., 8.1,
 * and 8.2 of the v13 draft.
 *
 * It handles retransmissions.	The connection to the timeout portion
 * of the state machine is through sctp_..._timeout() and timeout_handler.
 *
 * If you feed it SACKs, it will eat them.
 *
 * If you give it big chunks, it will fragment them.
 *
 * It assigns TSN's to data chunks.  This happens at the last possible
 * instant before transmission.
 *
 * When free()'d, it empties itself out via output_handler().
 */
struct sctp_outq {
	struct sctp_association *asoc;

	/* Data pending that has never been transmitted.  */
	struct list_head out_chunk_list;

	unsigned out_qlen;	/* Total length of queued data chunks. */

	/* Error of send failed, may used in SCTP_SEND_FAILED event. */
	unsigned error;

	/* These are control chunks we want to send.  */
	struct list_head control_chunk_list;

	/* These are chunks that have been sacked but are above the
	 * CTSN, or cumulative tsn ack point.
	 */
	struct list_head sacked;

	/* Put chunks on this list to schedule them for
	 * retransmission.
	 */
	struct list_head retransmit;

	/* Put chunks on this list to save them for FWD TSN processing as
	 * they were abandoned.
	 */
	struct list_head abandoned;

	/* How many unackd bytes do we have in-flight?	*/
	__u32 outstanding_bytes;

	/* Corked? */
	char cork;

	/* Is this structure empty?  */
	char empty;

	/* Are we kfree()able? */
	char malloced;
};

void sctp_outq_init(struct sctp_association *, struct sctp_outq *);
void sctp_outq_teardown(struct sctp_outq *);
void sctp_outq_free(struct sctp_outq*);
int sctp_outq_tail(struct sctp_outq *, struct sctp_chunk *chunk);
int sctp_outq_flush(struct sctp_outq *, int);
int sctp_outq_sack(struct sctp_outq *, struct sctp_sackhdr *);
int sctp_outq_is_empty(const struct sctp_outq *);
void sctp_outq_restart(struct sctp_outq *);

void sctp_retransmit(struct sctp_outq *, struct sctp_transport *,
		     sctp_retransmit_reason_t);
void sctp_retransmit_mark(struct sctp_outq *, struct sctp_transport *, __u8);
int sctp_outq_uncork(struct sctp_outq *);
/* Uncork and flush an outqueue.  */
static inline void sctp_outq_cork(struct sctp_outq *q)
{
	q->cork = 1;
}

/* These bind address data fields common between endpoints and associations */
struct sctp_bind_addr {

	/* RFC 2960 12.1 Parameters necessary for the SCTP instance
	 *
	 * SCTP Port:	The local SCTP port number the endpoint is
	 *		bound to.
	 */
	__u16 port;

	/* RFC 2960 12.1 Parameters necessary for the SCTP instance
	 *
	 * Address List: The list of IP addresses that this instance
	 *	has bound.  This information is passed to one's
	 *	peer(s) in INIT and INIT ACK chunks.
	 */
	struct list_head address_list;

	int malloced;	     /* Are we kfree()able?  */
};