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structs.h

/* SCTP kernel reference 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 reference Implementation
 *
 * The SCTP reference 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.
 *
 * The SCTP reference 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;
} 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_rover             (sctp_globals.port_rover)
#define sctp_port_alloc_lock        (sctp_globals.port_alloc_lock)
#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_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)

/* 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;

      /* 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 + 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;
} __attribute__((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;
};

/* 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;
} __attribute__((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 ipfragok);
      int         (*setsockopt)     (struct sock *sk,
                               int level,
                               int optname,
                               char __user *optval,
                               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,
                               int optlen);
      int         (*compat_getsockopt)    (struct sock *sk,
                               int level,
                               int optname,
                               char __user *optval,
                               int __user *optlen);
      struct dst_entry *(*get_dst)  (struct sctp_association *asoc,
                               union sctp_addr *daddr,
                               union sctp_addr *saddr);
      void        (*get_saddr)      (struct sctp_association *asoc,
                               struct dst_entry *dst,
                               union sctp_addr *daddr,
                               union sctp_addr *saddr);
      void        (*copy_addrlist) (struct list_head *,
                                struct net_device *);
      void        (*dst_saddr)      (union sctp_addr *saddr,
                               struct dst_entry *dst,
                               __be16 port);
      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);
      __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;
      /* Chunks that have been transmitted. */
      struct list_head track;
      /* 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;
      char send_failed;
      /* Control whether chunks from this message can be abandoned. */
      char can_abandon;
};

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

      __u8 rtt_in_progress;   /* Is this chunk used for RTT calculation? */
      __u8 resent;            /* Has this chunk ever been retransmitted. */
      __u8 has_tsn;           /* Does this chunk have a TSN yet? */
      __u8 has_ssn;           /* Does this chunk have a SSN yet? */
      __u8 singleton;         /* Was this the only chunk in the packet? */
      __u8 end_of_packet;     /* Was this the last chunk in the packet? */
      __u8 ecn_ce_done; /* Have we processed the ECN CE bit? */
      __u8 pdiscard;          /* Discard the whole packet now? */
      __u8 tsn_gap_acked;     /* Is this chunk acked by a GAP ACK? */
      __s8 fast_retransmit;    /* Is this chunk fast retransmitted? */
      __u8 tsn_missing_report; /* Data chunk missing counter. */
      __u8 data_accepted;     /* At least 1 chunk in this packet accepted */
      __u8 auth;        /* IN: was auth'ed | OUT: needs auth */
};

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);
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);

/* 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 use_as_src;
      __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;

      /* 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?  */
};

void sctp_bind_addr_init(struct sctp_bind_addr *, __u16 port);
void sctp_bind_addr_free(struct sctp_bind_addr *);
int sctp_bind_addr_copy(struct sctp_bind_addr *dest,
                  const struct sctp_bind_addr *src,
                  sctp_scope_t scope, gfp_t gfp,
                  int flags);
int sctp_bind_addr_dup(struct sctp_bind_addr *dest,
                  const struct sctp_bind_addr *src,
                  gfp_t gfp);
int sctp_add_bind_addr(struct sctp_bind_addr *, union sctp_addr *,
                   __u8 use_as_src, gfp_t gfp);
int sctp_del_bind_addr(struct sctp_bind_addr *, union sctp_addr *);
int sctp_bind_addr_match(struct sctp_bind_addr *, const union sctp_addr *,
                   struct sctp_sock *);
union sctp_addr *sctp_find_unmatch_addr(struct sctp_bind_addr     *bp,
                              const union sctp_addr   *addrs,
                              int               addrcnt,
                              struct sctp_sock  *opt);
union sctp_params sctp_bind_addrs_to_raw(const struct sctp_bind_addr *bp,
                               int *addrs_len,
                               gfp_t gfp);
int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw, int len,
                     __u16 port, gfp_t gfp);

sctp_scope_t sctp_scope(const union sctp_addr *);
int sctp_in_scope(const union sctp_addr *addr, const sctp_scope_t scope);
int sctp_is_any(const union sctp_addr *addr);
int sctp_addr_is_valid(const union sctp_addr *addr);


/* What type of endpoint?  */
typedef enum {
      SCTP_EP_TYPE_SOCKET,
      SCTP_EP_TYPE_ASSOCIATION,
} sctp_endpoint_type_t;

/*
 * A common base class to bridge the implmentation view of a
 * socket (usually listening) endpoint versus an association's
 * local endpoint.
 * This common structure is useful for several purposes:
 *   1) Common interface for lookup routines.
 *    a) Subfunctions work for either endpoint or association
 *    b) Single interface to lookup allows hiding the lookup lock rather
 *       than acquiring it externally.
 *   2) Common interface for the inbound chunk handling/state machine.
 *   3) Common object handling routines for reference counting, etc.
 *   4) Disentangle association lookup from endpoint lookup, where we
 *    do not have to find our endpoint to find our association.
 *
 */

struct sctp_ep_common {
      /* Fields to help us manage our entries in the hash tables. */
      struct hlist_node node;
      int hashent;

      /* Runtime type information.  What kind of endpoint is this? */
      sctp_endpoint_type_t type;

      /* Some fields to help us manage this object.
       *   refcnt   - Reference count access to this object.
       *   dead     - Do not attempt to use this object.
       *   malloced - Do we need to kfree this object?
       */
      atomic_t    refcnt;
      char      dead;
      char      malloced;

      /* What socket does this endpoint belong to?  */
      struct sock *sk;

      /* This is where we receive inbound chunks.  */
      struct sctp_inq     inqueue;

      /* This substructure includes the defining parameters of the
       * endpoint:
       * bind_addr.port is our shared port number.
       * bind_addr.address_list is our set of local IP addresses.
       */
      struct sctp_bind_addr bind_addr;
};


/* RFC Section 1.4 Key Terms
 *
 * o SCTP endpoint: The logical sender/receiver of SCTP packets. On a
 *   multi-homed host, an SCTP endpoint is represented to its peers as a
 *   combination of a set of eligible destination transport addresses to
 *   which SCTP packets can be sent and a set of eligible source
 *   transport addresses from which SCTP packets can be received.
 *   All transport addresses used by an SCTP endpoint must use the
 *   same port number, but can use multiple IP addresses. A transport
 *   address used by an SCTP endpoint must not be used by another
 *   SCTP endpoint. In other words, a transport address is unique
 *   to an SCTP endpoint.
 *
 * From an implementation perspective, each socket has one of these.
 * A TCP-style socket will have exactly one association on one of
 * these.  An UDP-style socket will have multiple associations hanging
 * off one of these.
 */

struct sctp_endpoint {
      /* Common substructure for endpoint and association. */
      struct sctp_ep_common base;

      /* Associations: A list of current associations and mappings
       *          to the data consumers for each association. This
       *          may be in the form of a hash table or other
       *          implementation dependent structure. The data
       *          consumers may be process identification
       *          information such as file descriptors, named pipe
       *          pointer, or table pointers dependent on how SCTP
       *          is implemented.
       */
      /* This is really a list of struct sctp_association entries. */
      struct list_head asocs;

      /* Secret Key: A secret key used by this endpoint to compute
       *          the MAC.    This SHOULD be a cryptographic quality
       *          random number with a sufficient length.
       *          Discussion in [RFC1750] can be helpful in
       *          selection of the key.
       */
      __u8 secret_key[SCTP_HOW_MANY_SECRETS][SCTP_SECRET_SIZE];
      int current_key;
      int last_key;
      int key_changed_at;

      /* digest:  This is a digest of the sctp cookie.  This field is
       *        only used on the receive path when we try to validate
       *        that the cookie has not been tampered with.  We put
       *        this here so we pre-allocate this once and can re-use
       *        on every receive.
       */
      __u8 *digest;
 
      /* sendbuf acct. policy.      */
      __u32 sndbuf_policy;

      /* rcvbuf acct. policy. */
      __u32 rcvbuf_policy;

      /* SCTP AUTH: array of the HMACs that will be allocated
       * we need this per association so that we don't serialize
       */
      struct crypto_hash **auth_hmacs;

      /* SCTP-AUTH: hmacs for the endpoint encoded into parameter */
       struct sctp_hmac_algo_param *auth_hmacs_list;

      /* SCTP-AUTH: chunks to authenticate encoded into parameter */
      struct sctp_chunks_param *auth_chunk_list;

      /* SCTP-AUTH: endpoint shared keys */
      struct list_head endpoint_shared_keys;
      __u16 active_key_id;
};

/* Recover the outter endpoint structure. */
static inline struct sctp_endpoint *sctp_ep(struct sctp_ep_common *base)
{
      struct sctp_endpoint *ep;

      ep = container_of(base, struct sctp_endpoint, base);
      return ep;
}

/* These are function signatures for manipulating endpoints.  */
struct sctp_endpoint *sctp_endpoint_new(struct sock *, gfp_t);
void sctp_endpoint_free(struct sctp_endpoint *);
void sctp_endpoint_put(struct sctp_endpoint *);
void sctp_endpoint_hold(struct sctp_endpoint *);
void sctp_endpoint_add_asoc(struct sctp_endpoint *, struct sctp_association *);
struct sctp_association *sctp_endpoint_lookup_assoc(
      const struct sctp_endpoint *ep,
      const union sctp_addr *paddr,
      struct sctp_transport **);
int sctp_endpoint_is_peeled_off(struct sctp_endpoint *,
                        const union sctp_addr *);
struct sctp_endpoint *sctp_endpoint_is_match(struct sctp_endpoint *,
                              const union sctp_addr *);
int sctp_has_association(const union sctp_addr *laddr,
                   const union sctp_addr *paddr);

int sctp_verify_init(const struct sctp_association *asoc, sctp_cid_t,
                 sctp_init_chunk_t *peer_init, struct sctp_chunk *chunk,
                 struct sctp_chunk **err_chunk);
int sctp_process_init(struct sctp_association *, sctp_cid_t cid,
                  const union sctp_addr *peer,
                  sctp_init_chunk_t *init, gfp_t gfp);
__u32 sctp_generate_tag(const struct sctp_endpoint *);
__u32 sctp_generate_tsn(const struct sctp_endpoint *);

struct sctp_inithdr_host {
      __u32 init_tag;
      __u32 a_rwnd;
      __u16 num_outbound_streams;
      __u16 num_inbound_streams;
      __u32 initial_tsn;
};

/* RFC2960
 *
 * 12. Recommended Transmission Control Block (TCB) Parameters
 *
 * This section details a recommended set of parameters that should
 * be contained within the TCB for an implementation. This section is
 * for illustrative purposes and should not be deemed as requirements
 * on an implementation or as an exhaustive list of all parameters
 * inside an SCTP TCB. Each implementation may need its own additional
 * parameters for optimization.
 */


/* Here we have information about each individual association. */
struct sctp_association {

      /* A base structure common to endpoint and association.
       * In this context, it represents the associations's view
       * of the local endpoint of the association.
       */
      struct sctp_ep_common base;

      /* Associations on the same socket. */
      struct list_head asocs;

      /* association id. */
      sctp_assoc_t assoc_id;

      /* This is our parent endpoint.      */
      struct sctp_endpoint *ep;

      /* These are those association elements needed in the cookie.  */
      struct sctp_cookie c;

      /* This is all information about our peer.  */
      struct {
            /* rwnd
             *
             * Peer Rwnd   : Current calculated value of the peer's rwnd.
             */
            __u32 rwnd;

            /* transport_addr_list
             *
             * Peer            : A list of SCTP transport addresses that the
             * Transport   : peer is bound to. This information is derived
             * Address     : from the INIT or INIT ACK and is used to
             * List            : associate an inbound packet with a given
             *           : association. Normally this information is
             *           : hashed or keyed for quick lookup and access
             *           : of the TCB.
             *           : The list is also initialized with the list
             *           : of addresses passed with the sctp_connectx()
             *           : call.
             *
             * It is a list of SCTP_transport's.
             */
            struct list_head transport_addr_list;

            /* transport_count
             *
             * Peer        : A count of the number of peer addresses
             * Transport   : in the Peer Transport Address List.
             * Address     :
             * Count       :
             */
            __u16 transport_count;

            /* port
             *   The transport layer port number.
             */
            __u16 port;

            /* primary_path
             *
             * Primary     : This is the current primary destination
             * Path            : transport address of the peer endpoint.  It
             *           : may also specify a source transport address
             *           : on this endpoint.
             *
             * All of these paths live on transport_addr_list.
             *
             * At the bakeoffs, we discovered that the intent of
             * primaryPath is that it only changes when the ULP
             * asks to have it changed.  We add the activePath to
             * designate the connection we are currently using to
             * transmit new data and most control chunks.
             */
            struct sctp_transport *primary_path;

            /* Cache the primary path address here, when we
             * need a an address for msg_name.
             */
            union sctp_addr primary_addr;

            /* active_path
             *   The path that we are currently using to
             *   transmit new data and most control chunks.
             */
            struct sctp_transport *active_path;

            /* retran_path
             *
             * RFC2960 6.4 Multi-homed SCTP Endpoints
             * ...
             * Furthermore, when its peer is multi-homed, an
             * endpoint SHOULD try to retransmit a chunk to an
             * active destination transport address that is
             * different from the last destination address to
             * which the DATA chunk was sent.
             */
            struct sctp_transport *retran_path;

            /* Pointer to last transport I have sent on.  */
            struct sctp_transport *last_sent_to;

            /* This is the last transport I have received DATA on.      */
            struct sctp_transport *last_data_from;

            /*
             * Mapping  An array of bits or bytes indicating which out of
             * Array    order TSN's have been received (relative to the
             *        Last Rcvd TSN). If no gaps exist, i.e. no out of
             *        order packets have been received, this array
             *        will be set to all zero. This structure may be
             *        in the form of a circular buffer or bit array.
             *
             * Last Rcvd   : This is the last TSN received in
             * TSN             : sequence. This value is set initially by
             *           : taking the peer's Initial TSN, received in
             *           : the INIT or INIT ACK chunk, and subtracting
             *           : one from it.
             *
             * Throughout most of the specification this is called the
             * "Cumulative TSN ACK Point".      In this case, we
             * ignore the advice in 12.2 in favour of the term
             * used in the bulk of the text.  This value is hidden
             * in tsn_map--we get it by calling sctp_tsnmap_get_ctsn().
             */
            struct sctp_tsnmap tsn_map;
            __u8 _map[sctp_tsnmap_storage_size(SCTP_TSN_MAP_SIZE)];

            /* Ack State   : This flag indicates if the next received
             *             : packet is to be responded to with a
             *             : SACK. This is initializedto 0.  When a packet
             *             : is received it is incremented. If this value
             *             : reaches 2 or more, a SACK is sent and the
             *             : value is reset to 0. Note: This is used only
             *             : when no DATA chunks are received out of
             *             : order.  When DATA chunks are out of order,
             *             : SACK's are not delayed (see Section 6).
             */
            __u8    sack_needed;     /* Do we need to sack the peer? */

            /* These are capabilities which our peer advertised.  */
            __u8  ecn_capable;       /* Can peer do ECN? */
            __u8  ipv4_address;      /* Peer understands IPv4 addresses? */
            __u8  ipv6_address;      /* Peer understands IPv6 addresses? */
            __u8  hostname_address;/* Peer understands DNS addresses? */
            __u8    asconf_capable;  /* Does peer support ADDIP? */
            __u8    prsctp_capable;  /* Can peer do PR-SCTP? */
            __u8  auth_capable;      /* Is peer doing SCTP-AUTH? */

            __u32   adaptation_ind;  /* Adaptation Code point. */

            /* This mask is used to disable sending the ASCONF chunk
             * with specified parameter to peer.
             */
            __be16 addip_disabled_mask;

            struct sctp_inithdr_host i;
            int cookie_len;
            void *cookie;

            /* ADDIP Section 4.2 Upon reception of an ASCONF Chunk.
             * C1) ... "Peer-Serial-Number'. This value MUST be initialized to the
             * Initial TSN Value minus 1
             */
            __u32 addip_serial;

            /* SCTP-AUTH: We need to know pears random number, hmac list
             * and authenticated chunk list.  All that is part of the
             * cookie and these are just pointers to those locations
             */
            sctp_random_param_t *peer_random;
            sctp_chunks_param_t *peer_chunks;
            sctp_hmac_algo_param_t *peer_hmacs;
      } peer;

      /* State       : A state variable indicating what state the
       *           : association is in, i.e. COOKIE-WAIT,
       *           : COOKIE-ECHOED, ESTABLISHED, SHUTDOWN-PENDING,
       *           : SHUTDOWN-SENT, SHUTDOWN-RECEIVED, SHUTDOWN-ACK-SENT.
       *
       *          Note: No "CLOSED" state is illustrated since if a
       *          association is "CLOSED" its TCB SHOULD be removed.
       *
       *          In this implementation we DO have a CLOSED
       *          state which is used during initiation and shutdown.
       *
       *          State takes values from SCTP_STATE_*.
       */
      sctp_state_t state;

      /* The cookie life I award for any cookie.  */
      struct timeval cookie_life;

      /* Overall     : The overall association error count.
       * Error Count : [Clear this any time I get something.]
       */
      int overall_error_count;

      /* These are the association's initial, max, and min RTO values.
       * These values will be initialized by system defaults, but can
       * be modified via the SCTP_RTOINFO socket option.
       */
      unsigned long rto_initial;
      unsigned long rto_max;
      unsigned long rto_min;

      /* Maximum number of new data packets that can be sent in a burst.  */
      int max_burst;

      /* This is the max_retrans value for the association.  This value will
       * be initialized initialized from system defaults, but can be
       * modified by the SCTP_ASSOCINFO socket option.
       */
      int max_retrans;

      /* Maximum number of times the endpoint will retransmit INIT  */
      __u16 max_init_attempts;

      /* How many times have we resent an INIT? */
      __u16 init_retries;

      /* The largest timeout or RTO value to use in attempting an INIT */
      unsigned long max_init_timeo;

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

      /* This is the max_retrans value for new transports in the
       * association.
       */
      __u16 pathmaxrxt;

      /* Flag that path mtu update is pending */
      __u8   pmtu_pending;

      /* Association : The smallest PMTU discovered for all of the
       * PMTU            : peer's transport addresses.
       */
      __u32 pathmtu;

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

      /* SACK delay timeout */
      unsigned long sackdelay;


      unsigned long timeouts[SCTP_NUM_TIMEOUT_TYPES];
      struct timer_list timers[SCTP_NUM_TIMEOUT_TYPES];

      /* Transport to which SHUTDOWN chunk was last sent.  */
      struct sctp_transport *shutdown_last_sent_to;

      /* Transport to which INIT chunk was last sent.  */
      struct sctp_transport *init_last_sent_to;

      /* Next TSN    : The next TSN number to be assigned to a new
       *           : DATA chunk.  This is sent in the INIT or INIT
       *           : ACK chunk to the peer and incremented each
       *           : time a DATA chunk is assigned a TSN
       *           : (normally just prior to transmit or during
       *           : fragmentation).
       */
      __u32 next_tsn;

      /*
       * Last Rcvd   : This is the last TSN received in sequence.  This value
       * TSN             : is set initially by taking the peer's Initial TSN,
       *           : received in the INIT or INIT ACK chunk, and
       *           : subtracting one from it.
       *
       * Most of RFC 2960 refers to this as the Cumulative TSN Ack Point.
       */

      __u32 ctsn_ack_point;

      /* PR-SCTP Advanced.Peer.Ack.Point */
      __u32 adv_peer_ack_point;

      /* Highest TSN that is acknowledged by incoming SACKs. */
      __u32 highest_sacked;

      /* The number of unacknowledged data chunks.  Reported through
       * the SCTP_STATUS sockopt.
       */
      __u16 unack_data;

      /* This is the association's receive buffer space.  This value is used
       * to set a_rwnd field in an INIT or a SACK chunk.
       */
      __u32 rwnd;

      /* This is the last advertised value of rwnd over a SACK chunk. */
      __u32 a_rwnd;

      /* Number of bytes by which the rwnd has slopped.  The rwnd is allowed
       * to slop over a maximum of the association's frag_point.
       */
      __u32 rwnd_over;

      /* This is the sndbuf size in use for the association.
       * This corresponds to the sndbuf size for the association,
       * as specified in the sk->sndbuf.
       */
      int sndbuf_used;

      /* This is the amount of memory that this association has allocated
       * in the receive path at any given time.
       */
      atomic_t rmem_alloc;

      /* This is the wait queue head for send requests waiting on
       * the association sndbuf space.
       */
      wait_queue_head_t wait;

      /* The message size at which SCTP fragmentation will occur. */
      __u32 frag_point;

      /* Counter used to count INIT errors. */
      int init_err_counter;

      /* Count the number of INIT cycles (for doubling timeout). */
      int init_cycle;

      /* Default send parameters. */
      __u16 default_stream;
      __u16 default_flags;
      __u32 default_ppid;
      __u32 default_context;
      __u32 default_timetolive;

      /* Default receive parameters */
      __u32 default_rcv_context;

      /* This tracks outbound ssn for a given stream.  */
      struct sctp_ssnmap *ssnmap;

      /* All outbound chunks go through this structure.  */
      struct sctp_outq outqueue;

      /* A smart pipe that will handle reordering and fragmentation,
       * as well as handle passing events up to the ULP.
       */
      struct sctp_ulpq ulpq;

      /* Last TSN that caused an ECNE Chunk to be sent.  */
      __u32 last_ecne_tsn;

      /* Last TSN that caused a CWR Chunk to be sent.  */
      __u32 last_cwr_tsn;

      /* How many duplicated TSNs have we seen?  */
      int numduptsns;

      /* Number of seconds of idle time before an association is closed.
       * In the association context, this is really used as a boolean
       * since the real timeout is stored in the timeouts array
       */
      __u32 autoclose;

      /* These are to support
       * "SCTP Extensions for Dynamic Reconfiguration of IP Addresses
       *  and Enforcement of Flow and Message Limits"
       * <draft-ietf-tsvwg-addip-sctp-02.txt>
       * or "ADDIP" for short.
       */



      /* ADDIP Section 4.1.1 Congestion Control of ASCONF Chunks
       *
       * R1) One and only one ASCONF Chunk MAY be in transit and
       * unacknowledged at any one time.  If a sender, after sending
       * an ASCONF chunk, decides it needs to transfer another
       * ASCONF Chunk, it MUST wait until the ASCONF-ACK Chunk
       * returns from the previous ASCONF Chunk before sending a
       * subsequent ASCONF. Note this restriction binds each side,
       * so at any time two ASCONF may be in-transit on any given
       * association (one sent from each endpoint).
       *
       * [This is our one-and-only-one ASCONF in flight.  If we do
       * not have an ASCONF in flight, this is NULL.]
       */
      struct sctp_chunk *addip_last_asconf;

      /* ADDIP Section 4.2 Upon reception of an ASCONF Chunk.
       *
       * IMPLEMENTATION NOTE: As an optimization a receiver may wish
       * to save the last ASCONF-ACK for some predetermined period
       * of time and instead of re-processing the ASCONF (with the
       * same serial number) it may just re-transmit the
       * ASCONF-ACK. It may wish to use the arrival of a new serial
       * number to discard the previously saved ASCONF-ACK or any
       * other means it may choose to expire the saved ASCONF-ACK.
       *
       * [This is our saved ASCONF-ACK.  We invalidate it when a new
       * ASCONF serial number arrives.]
       */
      struct sctp_chunk *addip_last_asconf_ack;

      /* These ASCONF chunks are waiting to be sent.
       *
       * These chunaks can't be pushed to outqueue until receiving
       * ASCONF_ACK for the previous ASCONF indicated by
       * addip_last_asconf, so as to guarantee that only one ASCONF
       * is in flight at any time.
       *
       * ADDIP Section 4.1.1 Congestion Control of ASCONF Chunks
       *
       * In defining the ASCONF Chunk transfer procedures, it is
       * essential that these transfers MUST NOT cause congestion
       * within the network.  To achieve this, we place these
       * restrictions on the transfer of ASCONF Chunks:
       *
       * R1) One and only one ASCONF Chunk MAY be in transit and
       * unacknowledged at any one time.  If a sender, after sending
       * an ASCONF chunk, decides it needs to transfer another
       * ASCONF Chunk, it MUST wait until the ASCONF-ACK Chunk
       * returns from the previous ASCONF Chunk before sending a
       * subsequent ASCONF. Note this restriction binds each side,
       * so at any time two ASCONF may be in-transit on any given
       * association (one sent from each endpoint).
       *
       *
       * [I really think this is EXACTLY the sort of intelligence
       *  which already resides in sctp_outq.    Please move this
       *  queue and its supporting logic down there.  --piggy]
       */
      struct list_head addip_chunk_list;

      /* ADDIP Section 4.1 ASCONF Chunk Procedures
       *
       * A2) A serial number should be assigned to the Chunk. The
       * serial number SHOULD be a monotonically increasing
       * number. The serial number SHOULD be initialized at
       * the start of the association to the same value as the
       * Initial TSN and every time a new ASCONF chunk is created
       * it is incremented by one after assigning the serial number
       * to the newly created chunk.
       *
       * ADDIP
       * 3.1.1  Address/Stream Configuration Change Chunk (ASCONF)
       *
       * Serial Number : 32 bits (unsigned integer)
       *
       * This value represents a Serial Number for the ASCONF
       * Chunk. The valid range of Serial Number is from 0 to
       * 4294967295 (2^32 - 1).  Serial Numbers wrap back to 0
       * after reaching 4294967295.
       */
      __u32 addip_serial;

      /* SCTP AUTH: list of the endpoint shared keys.  These
       * keys are provided out of band by the user applicaton
       * and can't change during the lifetime of the association
       */
      struct list_head endpoint_shared_keys;

      /* SCTP AUTH:
       * The current generated assocaition shared key (secret)
       */
      struct sctp_auth_bytes *asoc_shared_key;

      /* SCTP AUTH: hmac id of the first peer requested algorithm
       * that we support.
       */
      __u16 default_hmac_id;

      __u16 active_key_id;

      /* Need to send an ECNE Chunk? */
      char need_ecne;

      /* Is it a temporary association? */
      char temp;
};


/* An eyecatcher for determining if we are really looking at an
 * association data structure.
 */
enum {
      SCTP_ASSOC_EYECATCHER = 0xa550c123,
};

/* Recover the outter association structure. */
static inline struct sctp_association *sctp_assoc(struct sctp_ep_common *base)
{
      struct sctp_association *asoc;

      asoc = container_of(base, struct sctp_association, base);
      return asoc;
}

/* These are function signatures for manipulating associations.    */


struct sctp_association *
sctp_association_new(const struct sctp_endpoint *, const struct sock *,
                 sctp_scope_t scope, gfp_t gfp);
void sctp_association_free(struct sctp_association *);
void sctp_association_put(struct sctp_association *);
void sctp_association_hold(struct sctp_association *);

struct sctp_transport *sctp_assoc_choose_init_transport(
      struct sctp_association *);
struct sctp_transport *sctp_assoc_choose_shutdown_transport(
      struct sctp_association *);
void sctp_assoc_update_retran_path(struct sctp_association *);
struct sctp_transport *sctp_assoc_lookup_paddr(const struct sctp_association *,
                                const union sctp_addr *);
int sctp_assoc_lookup_laddr(struct sctp_association *asoc,
                      const union sctp_addr *laddr);
struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *,
                             const union sctp_addr *address,
                             const gfp_t gfp,
                             const int peer_state);
void sctp_assoc_del_peer(struct sctp_association *asoc,
                   const union sctp_addr *addr);
void sctp_assoc_rm_peer(struct sctp_association *asoc,
                   struct sctp_transport *peer);
void sctp_assoc_control_transport(struct sctp_association *,
                          struct sctp_transport *,
                          sctp_transport_cmd_t, sctp_sn_error_t);
struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association *, __u32);
struct sctp_transport *sctp_assoc_is_match(struct sctp_association *,
                                 const union sctp_addr *,
                                 const union sctp_addr *);
void sctp_assoc_migrate(struct sctp_association *, struct sock *);
void sctp_assoc_update(struct sctp_association *old,
                   struct sctp_association *new);

__u32 sctp_association_get_next_tsn(struct sctp_association *);

void sctp_assoc_sync_pmtu(struct sctp_association *);
void sctp_assoc_rwnd_increase(struct sctp_association *, unsigned);
void sctp_assoc_rwnd_decrease(struct sctp_association *, unsigned);
void sctp_assoc_set_primary(struct sctp_association *,
                      struct sctp_transport *);
int sctp_assoc_set_bind_addr_from_ep(struct sctp_association *,
                             gfp_t);
int sctp_assoc_set_bind_addr_from_cookie(struct sctp_association *,
                               struct sctp_cookie*,
                               gfp_t gfp);
int sctp_assoc_set_id(struct sctp_association *, gfp_t);

int sctp_cmp_addr_exact(const union sctp_addr *ss1,
                  const union sctp_addr *ss2);
struct sctp_chunk *sctp_get_ecne_prepend(struct sctp_association *asoc);

/* A convenience structure to parse out SCTP specific CMSGs. */
typedef struct sctp_cmsgs {
      struct sctp_initmsg *init;
      struct sctp_sndrcvinfo *info;
} sctp_cmsgs_t;

/* Structure for tracking memory objects */
typedef struct {
      char *label;
      atomic_t *counter;
} sctp_dbg_objcnt_entry_t;

#endif /* __sctp_structs_h__ */

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