Merge remote-tracking branch 'asoc/fix/omap' into asoc-linus

[mirror_ubuntu-zesty-kernel.git] / include / net / sctp / 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/ktime.h>
#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 <linux/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 net      *net;
};

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 {
        /* 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;

        /* Flag to indicate whether computing and verifying checksum
         * is disabled. */
        bool checksum_disable;
} sctp_globals;

#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_checksum_disable           (sctp_globals.checksum_disable)

/* 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;
        char *sctp_hmac_alg;

        /* 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;
        struct list_head auto_asconf_list;
        int do_auto_asconf;
};

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 IS_ENABLED(CONFIG_IPV6)
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? */
        ktime_t 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;
};

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;
};

#define SCTP_ADDRESS_TICK_DELAY 500

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 */
};

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;

        /* Has this transport moved the ctsn since we last sacked */
        __u32 sack_generation;

        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 the SCTP_SET_PEER_ADDR_PARAMS socket option.
         */
        __u16 pathmaxrxt;

        /* This is the partially failed retrans value for the transport
         * and will be initialized from the assocs value.  This can be changed
         * using the SCTP_PEER_ADDR_THLDS socket option
         */
        int pf_retrans;
        /* 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]
         */
        struct timer_list T3_rtx_timer;

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

        /* Timer to handle ICMP proto unreachable envets */
        struct timer_list proto_unreach_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;

        /* 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 rcu_head rcu;
};

struct sctp_transport *sctp_transport_new(struct net *, 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 *, struct sock *sk);
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);
void sctp_transport_burst_limited(struct sctp_transport *);
void sctp_transport_burst_reset(struct sctp_transport *);
unsigned long sctp_transport_timeout(struct sctp_transport *);
void sctp_transport_reset(struct sctp_transport *);
void sctp_transport_update_pmtu(struct sock *, struct sctp_transport *, u32);
void sctp_transport_immediate_rtx(struct sctp_transport *);


/* 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;
};

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

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

        /* Are we doing fast-rtx on this queue */
        char fast_rtx;

        /* Corked? */
        char cork;

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

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_sack(struct sctp_outq *, struct sctp_chunk *);
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;
};

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 net *net, 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 addr_state, 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 *);
int sctp_bind_addr_conflict(struct sctp_bind_addr *, const union sctp_addr *,
                         struct sctp_sock *, struct sctp_sock *);
int sctp_bind_addr_state(const struct sctp_bind_addr *bp,
                         const union sctp_addr *addr);
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(struct net *net, const union sctp_addr *addr, const sctp_scope_t scope);
int sctp_is_any(struct sock *sk, const union sctp_addr *addr);
int sctp_addr_is_valid(const union sctp_addr *addr);
int sctp_is_ep_boundall(struct sock *sk);


/* 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.
         */
        atomic_t    refcnt;
        bool        dead;

        /* 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_SECRET_SIZE];

        /* 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 *,
                                        struct net *, const union sctp_addr *);
int sctp_has_association(struct net *net, const union sctp_addr *laddr,
                         const union sctp_addr *paddr);

int sctp_verify_init(struct net *net, 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 *, struct sctp_chunk *chunk,
                      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;
};

/* SCTP_GET_ASSOC_STATS counters */
struct sctp_priv_assoc_stats {
        /* Maximum observed rto in the association during subsequent
         * observations. Value is set to 0 if no RTO measurement took place
         * The transport where the max_rto was observed is returned in
         * obs_rto_ipaddr
         */
        struct sockaddr_storage obs_rto_ipaddr;
        __u64 max_obs_rto;
        /* Total In and Out SACKs received and sent */
        __u64 isacks;
        __u64 osacks;
        /* Total In and Out packets received and sent */
        __u64 opackets;
        __u64 ipackets;
        /* Total retransmitted chunks */
        __u64 rtxchunks;
        /* TSN received > next expected */
        __u64 outofseqtsns;
        /* Duplicate Chunks received */
        __u64 idupchunks;
        /* Gap Ack Blocks received */
        __u64 gapcnt;
        /* Unordered data chunks sent and received */
        __u64 ouodchunks;
        __u64 iuodchunks;
        /* Ordered data chunks sent and received */
        __u64 oodchunks;
        __u64 iodchunks;
        /* Control chunks sent and received */
        __u64 octrlchunks;
        __u64 ictrlchunks;
};

/* 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;

                /* 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? */
                __u32   sack_cnt;
                __u32   sack_generation;

                /* These are capabilities which our peer advertised.  */
                __u8    ecn_capable:1,      /* Can peer do ECN? */
                        ipv4_address:1,     /* Peer understands IPv4 addresses? */
                        ipv6_address:1,     /* Peer understands IPv6 addresses? */
                        hostname_address:1, /* Peer understands DNS addresses? */
                        asconf_capable:1,   /* Does peer support ADDIP? */
                        prsctp_capable:1,   /* Can peer do PR-SCTP? */
                        auth_capable:1;     /* 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.  */
        ktime_t 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;

        /* This is the partially failed retrans value for the transport
         * and will be initialized from the assocs value.  This can be
         * changed using the SCTP_PEER_ADDR_THLDS socket option
         */
        int pf_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;
        __u32 sackfreq;


        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;

        /* How many times have we resent a SHUTDOWN */
        int shutdown_retries;

        /* 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;

        /* TSN marking the fast recovery exit point */
        __u32 fast_recovery_exit;

        /* Flag to track the current fast recovery state */
        __u8 fast_recovery;

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

        /* The total number of data chunks that we've had to retransmit
         * as the result of a T3 timer expiration
         */
        __u32 rtx_data_chunks;

        /* 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;

        /* Keeps treack of rwnd pressure.  This happens when we have
         * a window, but not recevie buffer (i.e small packets).  This one
         * is releases slowly (1 PMTU at a time ).
         */
        __u32 rwnd_press;

        /* 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;
        __u32 user_frag;

        /* 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 5.2 Upon reception of an ASCONF Chunk.
         *
         * This is needed to implement itmes E1 - E4 of the updated
         * spec.  Here is the justification:
         *
         * Since the peer may bundle multiple ASCONF chunks toward us,
         * we now need the ability to cache multiple ACKs.  The section
         * describes in detail how they are cached and cleaned up.
         */
        struct list_head asconf_ack_list;

        /* 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;
        union sctp_addr *asconf_addr_del_pending;
        int src_out_of_asoc_ok;
        struct sctp_transport *new_transport;

        /* 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;

        __u8 need_ecne:1,       /* Need to send an ECNE Chunk? */
             temp:1;            /* Is it a temporary association? */

        struct sctp_priv_assoc_stats stats;
};


/* 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_alter_transport(
        struct sctp_association *, struct sctp_transport *);
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 *,
                                           struct net *,
                                           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 sock *, struct sctp_association *);
void sctp_assoc_rwnd_increase(struct sctp_association *, unsigned int);
void sctp_assoc_rwnd_decrease(struct sctp_association *, unsigned int);
void sctp_assoc_set_primary(struct sctp_association *,
                            struct sctp_transport *);
void sctp_assoc_del_nonprimary_peers(struct sctp_association *,
                                    struct sctp_transport *);
int sctp_assoc_set_bind_addr_from_ep(struct sctp_association *,
                                     sctp_scope_t, 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);
void sctp_assoc_clean_asconf_ack_cache(const struct sctp_association *asoc);
struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
                                        const struct sctp_association *asoc,
                                        __be32 serial);
void sctp_asconf_queue_teardown(struct sctp_association *asoc);

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__ */