structs.h

/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001 Intel Corp.
 *
 * This file is part of the SCTP kernel implementation
 *
 * This SCTP implementation is free software;
 * you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This SCTP implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *		   ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email addresses:
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    Randall Stewart	    <randall@sctp.chicago.il.us>
 *    Ken Morneau	    <kmorneau@cisco.com>
 *    Qiaobing Xie	    <qxie1@email.mot.com>
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson	    <karl@athena.chicago.il.us>
 *    Jon Grimm		    <jgrimm@us.ibm.com>
 *    Xingang Guo	    <xingang.guo@intel.com>
 *    Hui Huang		    <hui.huang@nokia.com>
 *    Sridhar Samudrala	    <sri@us.ibm.com>
 *    Daisy Chang	    <daisyc@us.ibm.com>
 *    Dajiang Zhang	    <dajiang.zhang@nokia.com>
 *    Ardelle Fan	    <ardelle.fan@intel.com>
 *    Ryan Layer	    <rmlayer@us.ibm.com>
 *    Anup Pemmaiah	    <pemmaiah@cc.usu.edu>
 *    Kevin Gao             <kevin.gao@intel.com>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#ifndef __sctp_structs_h__
#define __sctp_structs_h__

#include <linux/time.h>		/* We get struct timespec.    */
#include <linux/socket.h>	/* linux/in.h needs this!!    */
#include <linux/in.h>		/* We get struct sockaddr_in. */
#include <linux/in6.h>		/* We get struct in6_addr     */
#include <linux/ipv6.h>
#include <asm/param.h>		/* We get MAXHOSTNAMELEN.     */
#include <asm/atomic.h>		/* This gets us atomic counters.  */
#include <linux/skbuff.h>	/* We need sk_buff_head. */
#include <linux/workqueue.h>	/* We need tq_struct.	 */
#include <linux/sctp.h>		/* We need sctp* header structs.  */
#include <net/sctp/auth.h>	/* We need auth specific structs */

/* A convenience structure for handling sockaddr structures.
 * We should wean ourselves off this.
 */
union sctp_addr {
	struct sockaddr_in v4;
	struct sockaddr_in6 v6;
	struct sockaddr sa;
};

/* Forward declarations for data structures. */
struct sctp_globals;
struct sctp_endpoint;
struct sctp_association;
struct sctp_transport;
struct sctp_packet;
struct sctp_chunk;
struct sctp_inq;
struct sctp_outq;
struct sctp_bind_addr;
struct sctp_ulpq;
struct sctp_ep_common;
struct sctp_ssnmap;
struct crypto_hash;


#include <net/sctp/tsnmap.h>
#include <net/sctp/ulpevent.h>
#include <net/sctp/ulpqueue.h>

/* Structures useful for managing bind/connect. */

struct sctp_bind_bucket {
	unsigned short	port;
	unsigned short	fastreuse;
	struct hlist_node	node;
	struct hlist_head	owner;
};

struct sctp_bind_hashbucket {
	spinlock_t	lock;
	struct hlist_head	chain;
};

/* Used for hashing all associations.  */
struct sctp_hashbucket {
	rwlock_t	lock;
	struct hlist_head	chain;
} __attribute__((__aligned__(8)));


/* The SCTP globals structure. */
extern struct sctp_globals {
	/* RFC2960 Section 14. Suggested SCTP Protocol Parameter Values
	 *
	 * The following protocol parameters are RECOMMENDED:
	 *
	 * RTO.Initial		    - 3	 seconds
	 * RTO.Min		    - 1	 second
	 * RTO.Max		   -  60 seconds
	 * RTO.Alpha		    - 1/8  (3 when converted to right shifts.)
	 * RTO.Beta		    - 1/4  (2 when converted to right shifts.)
	 */
	unsigned int rto_initial;
	unsigned int rto_min;
	unsigned int rto_max;

	/* Note: rto_alpha and rto_beta are really defined as inverse
	 * powers of two to facilitate integer operations.
	 */
	int rto_alpha;
	int rto_beta;

	/* Max.Burst		    - 4 */
	int max_burst;

	/* Whether Cookie Preservative is enabled(1) or not(0) */
	int cookie_preserve_enable;

	/* Valid.Cookie.Life	    - 60  seconds  */
	unsigned int valid_cookie_life;

	/* Delayed SACK timeout  200ms default*/
	unsigned int sack_timeout;

	/* HB.interval		    - 30 seconds  */
	unsigned int hb_interval;

	/* Association.Max.Retrans  - 10 attempts
	 * Path.Max.Retrans	    - 5	 attempts (per destination address)
	 * Max.Init.Retransmits	    - 8	 attempts
	 */
	int max_retrans_association;
	int max_retrans_path;
	int max_retrans_init;

	/*
	 * Policy for preforming sctp/socket accounting
	 * 0   - do socket level accounting, all assocs share sk_sndbuf
	 * 1   - do sctp accounting, each asoc may use sk_sndbuf bytes
	 */
	int sndbuf_policy;

	/*
	 * Policy for preforming sctp/socket accounting
	 * 0   - do socket level accounting, all assocs share sk_rcvbuf
	 * 1   - do sctp accounting, each asoc may use sk_rcvbuf bytes
	 */
	int rcvbuf_policy;

	/* The following variables are implementation specific.	 */

	/* Default initialization values to be applied to new associations. */
	__u16 max_instreams;
	__u16 max_outstreams;

	/* This is a list of groups of functions for each address
	 * family that we support.
	 */
	struct list_head address_families;

	/* This is the hash of all endpoints. */
	int ep_hashsize;
	struct sctp_hashbucket *ep_hashtable;

	/* This is the hash of all associations. */
	int assoc_hashsize;
	struct sctp_hashbucket *assoc_hashtable;

	/* This is the sctp port control hash.	*/
	int port_hashsize;
	struct sctp_bind_hashbucket *port_hashtable;

	/* This is the global local address list.
	 * We actively maintain this complete list of addresses on
	 * the system by catching address add/delete events.
	 *
	 * It is a list of sctp_sockaddr_entry.
	 */
	struct list_head local_addr_list;

	/* Lock that protects the local_addr_list writers */
	spinlock_t addr_list_lock;
	
	/* Flag to indicate if addip is enabled. */
	int addip_enable;
	int addip_noauth_enable;

	/* Flag to indicate if PR-SCTP is enabled. */
	int prsctp_enable;

	/* Flag to idicate if SCTP-AUTH is enabled */
	int auth_enable;

	/*
	 * Policy to control SCTP IPv4 address scoping
	 * 0   - Disable IPv4 address scoping
	 * 1   - Enable IPv4 address scoping
	 * 2   - Selectively allow only IPv4 private addresses
	 * 3   - Selectively allow only IPv4 link local address
	 */
	int ipv4_scope_policy;

	/* Flag to indicate whether computing and verifying checksum
	 * is disabled. */
        int checksum_disable;

	/* Threshold for rwnd update SACKS.  Receive buffer shifted this many
	 * bits is an indicator of when to send and window update SACK.
	 */
	int rwnd_update_shift;
} sctp_globals;

#define sctp_rto_initial		(sctp_globals.rto_initial)
#define sctp_rto_min			(sctp_globals.rto_min)
#define sctp_rto_max			(sctp_globals.rto_max)
#define sctp_rto_alpha			(sctp_globals.rto_alpha)
#define sctp_rto_beta			(sctp_globals.rto_beta)
#define sctp_max_burst			(sctp_globals.max_burst)
#define sctp_valid_cookie_life		(sctp_globals.valid_cookie_life)
#define sctp_cookie_preserve_enable	(sctp_globals.cookie_preserve_enable)
#define sctp_max_retrans_association	(sctp_globals.max_retrans_association)
#define sctp_sndbuf_policy	 	(sctp_globals.sndbuf_policy)
#define sctp_rcvbuf_policy	 	(sctp_globals.rcvbuf_policy)
#define sctp_max_retrans_path		(sctp_globals.max_retrans_path)
#define sctp_max_retrans_init		(sctp_globals.max_retrans_init)
#define sctp_sack_timeout		(sctp_globals.sack_timeout)
#define sctp_hb_interval		(sctp_globals.hb_interval)
#define sctp_max_instreams		(sctp_globals.max_instreams)
#define sctp_max_outstreams		(sctp_globals.max_outstreams)
#define sctp_address_families		(sctp_globals.address_families)
#define sctp_ep_hashsize		(sctp_globals.ep_hashsize)
#define sctp_ep_hashtable		(sctp_globals.ep_hashtable)
#define sctp_assoc_hashsize		(sctp_globals.assoc_hashsize)
#define sctp_assoc_hashtable		(sctp_globals.assoc_hashtable)
#define sctp_port_hashsize		(sctp_globals.port_hashsize)
#define sctp_port_hashtable		(sctp_globals.port_hashtable)
#define sctp_local_addr_list		(sctp_globals.local_addr_list)
#define sctp_local_addr_lock		(sctp_globals.addr_list_lock)
#define sctp_scope_policy		(sctp_globals.ipv4_scope_policy)
#define sctp_addip_enable		(sctp_globals.addip_enable)
#define sctp_addip_noauth		(sctp_globals.addip_noauth_enable)
#define sctp_prsctp_enable		(sctp_globals.prsctp_enable)
#define sctp_auth_enable		(sctp_globals.auth_enable)
#define sctp_checksum_disable		(sctp_globals.checksum_disable)
#define sctp_rwnd_upd_shift		(sctp_globals.rwnd_update_shift)

/* SCTP Socket type: UDP or TCP style. */
typedef enum {
	SCTP_SOCKET_UDP = 0,
	SCTP_SOCKET_UDP_HIGH_BANDWIDTH,
	SCTP_SOCKET_TCP
} sctp_socket_type_t;

/* Per socket SCTP information. */
struct sctp_sock {
	/* inet_sock has to be the first member of sctp_sock */
	struct inet_sock inet;
	/* What kind of a socket is this? */
	sctp_socket_type_t type;

	/* PF_ family specific functions.  */
	struct sctp_pf *pf;

	/* Access to HMAC transform. */
	struct crypto_hash *hmac;

	/* What is our base endpointer? */
	struct sctp_endpoint *ep;

	struct sctp_bind_bucket *bind_hash;
	/* Various Socket Options.  */
	__u16 default_stream;
	__u32 default_ppid;
	__u16 default_flags;
	__u32 default_context;
	__u32 default_timetolive;
	__u32 default_rcv_context;
	int max_burst;

	/* Heartbeat interval: The endpoint sends out a Heartbeat chunk to
	 * the destination address every heartbeat interval. This value
	 * will be inherited by all new associations.
	 */
	__u32 hbinterval;

	/* This is the max_retrans value for new associations. */
	__u16 pathmaxrxt;

	/* The initial Path MTU to use for new associations. */
	__u32 pathmtu;

	/* The default SACK delay timeout for new associations. */
	__u32 sackdelay;
	__u32 sackfreq;

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

	struct sctp_initmsg initmsg;
	struct sctp_rtoinfo rtoinfo;
	struct sctp_paddrparams paddrparam;
	struct sctp_event_subscribe subscribe;
	struct sctp_assocparams assocparams;
	int user_frag;
	__u32 autoclose;
	__u8 nodelay;
	__u8 disable_fragments;
	__u8 v4mapped;
	__u8 frag_interleave;
	__u32 adaptation_ind;
	__u32 pd_point;

	atomic_t pd_mode;
	/* Receive to here while partial delivery is in effect. */
	struct sk_buff_head pd_lobby;
};

static inline struct sctp_sock *sctp_sk(const struct sock *sk)
{
       return (struct sctp_sock *)sk;
}

static inline struct sock *sctp_opt2sk(const struct sctp_sock *sp)
{
       return (struct sock *)sp;
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
struct sctp6_sock {
       struct sctp_sock  sctp;
       struct ipv6_pinfo inet6;
};
#endif /* CONFIG_IPV6 */


/* This is our APPLICATION-SPECIFIC state cookie.
 * THIS IS NOT DICTATED BY THE SPECIFICATION.
 */
/* These are the parts of an association which we send in the cookie.
 * Most of these are straight out of:
 * RFC2960 12.2 Parameters necessary per association (i.e. the TCB)
 *
 */

struct sctp_cookie {

	/* My	       : Tag expected in every inbound packet and sent
	 * Verification: in the INIT or INIT ACK chunk.
	 * Tag	       :
	 */
	__u32 my_vtag;

	/* Peer's      : Tag expected in every outbound packet except
	 * Verification: in the INIT chunk.
	 * Tag	       :
	 */
	__u32 peer_vtag;

	/* The rest of these are not from the spec, but really need to
	 * be in the cookie.
	 */

	/* My Tie Tag  : Assist in discovering a restarting association. */
	__u32 my_ttag;

	/* Peer's Tie Tag: Assist in discovering a restarting association. */
	__u32 peer_ttag;

	/* When does this cookie expire? */
	struct timeval expiration;

	/* Number of inbound/outbound streams which are set
	 * and negotiated during the INIT process.
	 */
	__u16 sinit_num_ostreams;
	__u16 sinit_max_instreams;

	/* This is the first sequence number I used.  */
	__u32 initial_tsn;

	/* This holds the originating address of the INIT packet.  */
	union sctp_addr peer_addr;

	/* IG Section 2.35.3 
	 * Include the source port of the INIT-ACK
	 */
	__u16		my_port;

	__u8 prsctp_capable;

	/* Padding for future use */
	__u8 padding;  		

	__u32 adaptation_ind;

	__u8 auth_random[sizeof(sctp_paramhdr_t) + SCTP_AUTH_RANDOM_LENGTH];
	__u8 auth_hmacs[SCTP_AUTH_NUM_HMACS * sizeof(__u16) + 2];
	__u8 auth_chunks[sizeof(sctp_paramhdr_t) + SCTP_AUTH_MAX_CHUNKS];

	/* This is a shim for my peer's INIT packet, followed by
	 * a copy of the raw address list of the association.
	 * The length of the raw address list is saved in the
	 * raw_addr_list_len field, which will be used at the time when
	 * the association TCB is re-constructed from the cookie.
	 */
	__u32 raw_addr_list_len;
	struct sctp_init_chunk peer_init[0];
};


/* The format of our cookie that we send to our peer. */
struct sctp_signed_cookie {
	__u8 signature[SCTP_SECRET_SIZE];
	__u32 __pad;		/* force sctp_cookie alignment to 64 bits */
	struct sctp_cookie c;
} __packed;

/* This is another convenience type to allocate memory for address
 * params for the maximum size and pass such structures around
 * internally.
 */
union sctp_addr_param {
	struct sctp_paramhdr p;
	struct sctp_ipv4addr_param v4;
	struct sctp_ipv6addr_param v6;
};

/* A convenience type to allow walking through the various
 * parameters and avoid casting all over the place.
 */
union sctp_params {
	void *v;
	struct sctp_paramhdr *p;
	struct sctp_cookie_preserve_param *life;
	struct sctp_hostname_param *dns;
	struct sctp_cookie_param *cookie;
	struct sctp_supported_addrs_param *sat;
	struct sctp_ipv4addr_param *v4;
	struct sctp_ipv6addr_param *v6;
	union sctp_addr_param *addr;
	struct sctp_adaptation_ind_param *aind;
	struct sctp_supported_ext_param *ext;
	struct sctp_random_param *random;
	struct sctp_chunks_param *chunks;
	struct sctp_hmac_algo_param *hmac_algo;
	struct sctp_addip_param *addip;
};

/* RFC 2960.  Section 3.3.5 Heartbeat.
 *    Heartbeat Information: variable length
 *    The Sender-specific Heartbeat Info field should normally include
 *    information about the sender's current time when this HEARTBEAT
 *    chunk is sent and the destination transport address to which this
 *    HEARTBEAT is sent (see Section 8.3).
 */
typedef struct sctp_sender_hb_info {
	struct sctp_paramhdr param_hdr;
	union sctp_addr daddr;
	unsigned long sent_at;
	__u64 hb_nonce;
} __packed sctp_sender_hb_info_t;

/*
 *  RFC 2960 1.3.2 Sequenced Delivery within Streams
 *
 *  The term "stream" is used in SCTP to refer to a sequence of user
 *  messages that are to be delivered to the upper-layer protocol in
 *  order with respect to other messages within the same stream.  This is
 *  in contrast to its usage in TCP, where it refers to a sequence of
 *  bytes (in this document a byte is assumed to be eight bits).
 *  ...
 *
 *  This is the structure we use to track both our outbound and inbound
 *  SSN, or Stream Sequence Numbers.
 */

struct sctp_stream {
	__u16 *ssn;
	unsigned int len;
};

struct sctp_ssnmap {
	struct sctp_stream in;
	struct sctp_stream out;
	int malloced;
};

struct sctp_ssnmap *sctp_ssnmap_new(__u16 in, __u16 out,
				    gfp_t gfp);
void sctp_ssnmap_free(struct sctp_ssnmap *map);
void sctp_ssnmap_clear(struct sctp_ssnmap *map);

/* What is the current SSN number for this stream? */
static inline __u16 sctp_ssn_peek(struct sctp_stream *stream, __u16 id)
{
	return stream->ssn[id];
}

/* Return the next SSN number for this stream.	*/
static inline __u16 sctp_ssn_next(struct sctp_stream *stream, __u16 id)
{
	return stream->ssn[id]++;
}

/* Skip over this ssn and all below. */
static inline void sctp_ssn_skip(struct sctp_stream *stream, __u16 id, 
				 __u16 ssn)
{
	stream->ssn[id] = ssn+1;
}
              
/*
 * Pointers to address related SCTP functions.
 * (i.e. things that depend on the address family.)
 */
struct sctp_af {
	int		(*sctp_xmit)	(struct sk_buff *skb,
					 struct sctp_transport *);
	int		(*setsockopt)	(struct sock *sk,
					 int level,
					 int optname,
					 char __user *optval,
					 unsigned int optlen);
	int		(*getsockopt)	(struct sock *sk,
					 int level,
					 int optname,
					 char __user *optval,
					 int __user *optlen);
	int		(*compat_setsockopt)	(struct sock *sk,
					 int level,
					 int optname,
					 char __user *optval,
					 unsigned int optlen);
	int		(*compat_getsockopt)	(struct sock *sk,
					 int level,
					 int optname,
					 char __user *optval,
					 int __user *optlen);
	void		(*get_dst)	(struct sctp_transport *t,
					 union sctp_addr *saddr,
					 struct flowi *fl,
					 struct sock *sk);
	void		(*get_saddr)	(struct sctp_sock *sk,
					 struct sctp_transport *t,
					 struct flowi *fl);
	void		(*copy_addrlist) (struct list_head *,
					  struct net_device *);
	int		(*cmp_addr)	(const union sctp_addr *addr1,
					 const union sctp_addr *addr2);
	void		(*addr_copy)	(union sctp_addr *dst,
					 union sctp_addr *src);
	void		(*from_skb)	(union sctp_addr *,
					 struct sk_buff *skb,
					 int saddr);
	void		(*from_sk)	(union sctp_addr *,
					 struct sock *sk);
	void		(*to_sk_saddr)	(union sctp_addr *,
					 struct sock *sk);
	void		(*to_sk_daddr)	(union sctp_addr *,
					 struct sock *sk);
	void		(*from_addr_param) (union sctp_addr *,
					    union sctp_addr_param *,
					    __be16 port, int iif);
	int		(*to_addr_param) (const union sctp_addr *,
					  union sctp_addr_param *); 
	int		(*addr_valid)	(union sctp_addr *,
					 struct sctp_sock *,
					 const struct sk_buff *);
	sctp_scope_t	(*scope) (union sctp_addr *);
	void		(*inaddr_any)	(union sctp_addr *, __be16);
	int		(*is_any)	(const union sctp_addr *);
	int		(*available)	(union sctp_addr *,
					 struct sctp_sock *);
	int		(*skb_iif)	(const struct sk_buff *sk);
	int		(*is_ce)	(const struct sk_buff *sk);
	void		(*seq_dump_addr)(struct seq_file *seq,
					 union sctp_addr *addr);
	void		(*ecn_capable)(struct sock *sk);
	__u16		net_header_len;
	int		sockaddr_len;
	sa_family_t	sa_family;
	struct list_head list;
};

struct sctp_af *sctp_get_af_specific(sa_family_t);
int sctp_register_af(struct sctp_af *);

/* Protocol family functions. */
struct sctp_pf {
	void (*event_msgname)(struct sctp_ulpevent *, char *, int *);
	void (*skb_msgname)  (struct sk_buff *, char *, int *);
	int  (*af_supported) (sa_family_t, struct sctp_sock *);
	int  (*cmp_addr) (const union sctp_addr *,
			  const union sctp_addr *,
			  struct sctp_sock *);
	int  (*bind_verify) (struct sctp_sock *, union sctp_addr *);
	int  (*send_verify) (struct sctp_sock *, union sctp_addr *);
	int  (*supported_addrs)(const struct sctp_sock *, __be16 *);
	struct sock *(*create_accept_sk) (struct sock *sk,
					  struct sctp_association *asoc);
	void (*addr_v4map) (struct sctp_sock *, union sctp_addr *);
	struct sctp_af *af;
};


/* Structure to track chunk fragments that have been acked, but peer
 * fragments of the same message have not.
 */
struct sctp_datamsg {
	/* Chunks waiting to be submitted to lower layer. */
	struct list_head chunks;
	/* Reference counting. */
	atomic_t refcnt;
	/* When is this message no longer interesting to the peer? */
	unsigned long expires_at;
	/* Did the messenge fail to send? */
	int send_error;
	u8 send_failed:1,
	   can_abandon:1,   /* can chunks from this message can be abandoned. */
	   can_delay;	    /* should this message be Nagle delayed */
};

struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *,
					    struct sctp_sndrcvinfo *,
					    struct msghdr *, int len);
void sctp_datamsg_free(struct sctp_datamsg *);
void sctp_datamsg_put(struct sctp_datamsg *);
void sctp_chunk_fail(struct sctp_chunk *, int error);
int sctp_chunk_abandoned(struct sctp_chunk *);

/* RFC2960 1.4 Key Terms
 *
 * o Chunk: A unit of information within an SCTP packet, consisting of
 * a chunk header and chunk-specific content.
 *
 * As a matter of convenience, we remember the SCTP common header for
 * each chunk as well as a few other header pointers...
 */
struct sctp_chunk {
	struct list_head list;

	atomic_t refcnt;

	/* This is our link to the per-transport transmitted list.  */
	struct list_head transmitted_list;

	/* This field is used by chunks that hold fragmented data.
	 * For the first fragment this is the list that holds the rest of
	 * fragments. For the remaining fragments, this is the link to the
	 * frag_list maintained in the first fragment.
	 */
	struct list_head frag_list;

	/* This points to the sk_buff containing the actual data.  */
	struct sk_buff *skb;

	/* These are the SCTP headers by reverse order in a packet.
	 * Note that some of these may happen more than once.  In that
	 * case, we point at the "current" one, whatever that means
	 * for that level of header.
	 */

	/* We point this at the FIRST TLV parameter to chunk_hdr.  */
	union sctp_params param_hdr;
	union {
		__u8 *v;
		struct sctp_datahdr *data_hdr;
		struct sctp_inithdr *init_hdr;
		struct sctp_sackhdr *sack_hdr;
		struct sctp_heartbeathdr *hb_hdr;
		struct sctp_sender_hb_info *hbs_hdr;
		struct sctp_shutdownhdr *shutdown_hdr;
		struct sctp_signed_cookie *cookie_hdr;
		struct sctp_ecnehdr *ecne_hdr;
		struct sctp_cwrhdr *ecn_cwr_hdr;
		struct sctp_errhdr *err_hdr;
		struct sctp_addiphdr *addip_hdr;
		struct sctp_fwdtsn_hdr *fwdtsn_hdr;
		struct sctp_authhdr *auth_hdr;
	} subh;

	__u8 *chunk_end;

	struct sctp_chunkhdr *chunk_hdr;
	struct sctphdr *sctp_hdr;

	/* This needs to be recoverable for SCTP_SEND_FAILED events. */
	struct sctp_sndrcvinfo sinfo;

	/* Which association does this belong to?  */
	struct sctp_association *asoc;

	/* What endpoint received this chunk? */
	struct sctp_ep_common *rcvr;

	/* We fill this in if we are calculating RTT. */
	unsigned long sent_at;

	/* What is the origin IP address for this chunk?  */
	union sctp_addr source;
	/* Destination address for this chunk. */
	union sctp_addr dest;

	/* For outbound message, track all fragments for SEND_FAILED. */
	struct sctp_datamsg *msg;

	/* For an inbound chunk, this tells us where it came from.
	 * For an outbound chunk, it tells us where we'd like it to
	 * go.	It is NULL if we have no preference.
	 */
	struct sctp_transport *transport;

	/* SCTP-AUTH:  For the special case inbound processing of COOKIE-ECHO
	 * we need save a pointer to the AUTH chunk, since the SCTP-AUTH
	 * spec violates the principle premis that all chunks are processed
	 * in order.
	 */
	struct sk_buff *auth_chunk;

#define SCTP_CAN_FRTX 0x0
#define SCTP_NEED_FRTX 0x1
#define SCTP_DONT_FRTX 0x2
	__u16	rtt_in_progress:1,	/* This chunk used for RTT calc? */
		has_tsn:1,		/* Does this chunk have a TSN yet? */
		has_ssn:1,		/* Does this chunk have a SSN yet? */
		singleton:1,		/* Only chunk in the packet? */
		end_of_packet:1,	/* Last chunk in the packet? */
		ecn_ce_done:1,		/* Have we processed the ECN CE bit? */
		pdiscard:1,		/* Discard the whole packet now? */
		tsn_gap_acked:1,	/* Is this chunk acked by a GAP ACK? */
		data_accepted:1,	/* At least 1 chunk accepted */
		auth:1,			/* IN: was auth'ed | OUT: needs auth */
		has_asconf:1,		/* IN: have seen an asconf before */
		tsn_missing_report:2,	/* Data chunk missing counter. */
		fast_retransmit:2;	/* Is this chunk fast retransmitted? */
};

void sctp_chunk_hold(struct sctp_chunk *);
void sctp_chunk_put(struct sctp_chunk *);
int sctp_user_addto_chunk(struct sctp_chunk *chunk, int off, int len,
			  struct iovec *data);
void sctp_chunk_free(struct sctp_chunk *);
void  *sctp_addto_chunk(struct sctp_chunk *, int len, const void *data);
void  *sctp_addto_chunk_fixed(struct sctp_chunk *, int len, const void *data);
struct sctp_chunk *sctp_chunkify(struct sk_buff *,
				 const struct sctp_association *,
				 struct sock *);
void sctp_init_addrs(struct sctp_chunk *, union sctp_addr *,
		     union sctp_addr *);
const union sctp_addr *sctp_source(const struct sctp_chunk *chunk);

enum {
	SCTP_ADDR_NEW,		/* new address added to assoc/ep */
	SCTP_ADDR_SRC,		/* address can be used as source */
	SCTP_ADDR_DEL,		/* address about to be deleted */
};

/* This is a structure for holding either an IPv6 or an IPv4 address.  */
struct sctp_sockaddr_entry {
	struct list_head list;
	struct rcu_head	rcu;
	union sctp_addr a;
	__u8 state;
	__u8 valid;
};

typedef struct sctp_chunk *(sctp_packet_phandler_t)(struct sctp_association *);

/* This structure holds lists of chunks as we are assembling for
 * transmission.
 */
struct sctp_packet {
	/* These are the SCTP header values (host order) for the packet. */
	__u16 source_port;
	__u16 destination_port;
	__u32 vtag;

	/* This contains the payload chunks.  */
	struct list_head chunk_list;

	/* This is the overhead of the sctp and ip headers. */
	size_t overhead;
	/* This is the total size of all chunks INCLUDING padding.  */
	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;

	u8  has_cookie_echo:1,	/* This packet contains a COOKIE-ECHO chunk. */
	    has_sack:1,		/* This packet contains a SACK chunk. */
	    has_auth:1,		/* This packet contains an AUTH chunk */
	    has_data:1,		/* This packet contains at least 1 DATA chunk */
	    ipfragok:1,		/* So let ip fragment this packet */
	    malloced:1;		/* Is it 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 *, int);
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;
	__u32	 dead:1,
		/* 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.
		 */
		 rto_pending:1,

		/*
		 * hb_sent : a flag that signals that we have a pending
		 * heartbeat.
		 */
		hb_sent:1,

		/* Is the Path MTU update pending on this tranport */
		pmtu_pending:1,

		/* Is this structure kfree()able? */
		malloced:1;

	struct flowi fl;

	/* 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;

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

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

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

	/*
	 * 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;

	__u32 burst_limited;	/* Holds old cwnd when max.burst is applied */

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

	/* 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;
	__u32 sackfreq;

	/* 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;

	/* 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_UNKNOWN.
	 */
	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]
	 */