FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_var.h

     /*
      * Copyright (c) 1982, 1986, 1993, 1994, 1995
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)tcp_var.h   8.4 (Berkeley) 5/24/95
     * $FreeBSD: releng/5.2/sys/netinet/tcp_var.h 126496 2004-03-02 17:24:46Z nectar $
     */
    
    #ifndef _NETINET_TCP_VAR_H_
    #define _NETINET_TCP_VAR_H_
    
    #include <netinet/in_pcb.h>             /* needed for in_conninfo, inp_gen_t */
    #include <netinet/tcp.h>
    
    /*
     * Kernel variables for tcp.
     */
    extern int      tcp_do_rfc1323;
    extern int      tcp_do_rfc1644;
    
    /* TCP segment queue entry */
    struct tseg_qent {
            LIST_ENTRY(tseg_qent) tqe_q;
            int     tqe_len;                /* TCP segment data length */
            struct  tcphdr *tqe_th;         /* a pointer to tcp header */
            struct  mbuf    *tqe_m;         /* mbuf contains packet */
    };
    LIST_HEAD(tsegqe_head, tseg_qent);
    extern int      tcp_reass_qsize;
    extern struct uma_zone  *tcp_reass_zone;
    
    struct tcptemp {
            u_char  tt_ipgen[40]; /* the size must be of max ip header, now IPv6 */
            struct  tcphdr tt_t;
    };
    
    #define tcp6cb          tcpcb  /* for KAME src sync over BSD*'s */
    
    /*
     * Tcp control block, one per tcp; fields:
     * Organized for 16 byte cacheline efficiency.
     */
    struct tcpcb {
            struct  tsegqe_head t_segq;
            int     t_dupacks;              /* consecutive dup acks recd */
            struct  tcptemp *unused;        /* unused */
    
            struct  callout *tt_rexmt;      /* retransmit timer */
            struct  callout *tt_persist;    /* retransmit persistence */
            struct  callout *tt_keep;       /* keepalive */
            struct  callout *tt_2msl;       /* 2*msl TIME_WAIT timer */
            struct  callout *tt_delack;     /* delayed ACK timer */
    
            struct  inpcb *t_inpcb;         /* back pointer to internet pcb */
            int     t_state;                /* state of this connection */
            u_int   t_flags;
    #define TF_ACKNOW       0x000001        /* ack peer immediately */
    #define TF_DELACK       0x000002        /* ack, but try to delay it */
    #define TF_NODELAY      0x000004        /* don't delay packets to coalesce */
    #define TF_NOOPT        0x000008        /* don't use tcp options */
    #define TF_SENTFIN      0x000010        /* have sent FIN */
    #define TF_REQ_SCALE    0x000020        /* have/will request window scaling */
    #define TF_RCVD_SCALE   0x000040        /* other side has requested scaling */
    #define TF_REQ_TSTMP    0x000080        /* have/will request timestamps */
    #define TF_RCVD_TSTMP   0x000100        /* a timestamp was received in SYN */
    #define TF_SACK_PERMIT  0x000200        /* other side said I could SACK */
    #define TF_NEEDSYN      0x000400        /* send SYN (implicit state) */
    #define TF_NEEDFIN      0x000800        /* send FIN (implicit state) */
    #define TF_NOPUSH       0x001000        /* don't push */
    #define TF_REQ_CC       0x002000        /* have/will request CC */
    #define TF_RCVD_CC      0x004000        /* a CC was received in SYN */
   #define TF_SENDCCNEW    0x008000        /* send CCnew instead of CC in SYN */
   #define TF_MORETOCOME   0x010000        /* More data to be appended to sock */
   #define TF_LQ_OVERFLOW  0x020000        /* listen queue overflow */
   #define TF_LASTIDLE     0x040000        /* connection was previously idle */
   #define TF_RXWIN0SENT   0x080000        /* sent a receiver win 0 in response */
   #define TF_FASTRECOVERY 0x100000        /* in NewReno Fast Recovery */
   #define TF_WASFRECOVERY 0x200000        /* was in NewReno Fast Recovery */
           int     t_force;                /* 1 if forcing out a byte */
   
           tcp_seq snd_una;                /* send unacknowledged */
           tcp_seq snd_max;                /* highest sequence number sent;
                                            * used to recognize retransmits
                                            */
           tcp_seq snd_nxt;                /* send next */
           tcp_seq snd_up;                 /* send urgent pointer */
   
           tcp_seq snd_wl1;                /* window update seg seq number */
           tcp_seq snd_wl2;                /* window update seg ack number */
           tcp_seq iss;                    /* initial send sequence number */
           tcp_seq irs;                    /* initial receive sequence number */
   
           tcp_seq rcv_nxt;                /* receive next */
           tcp_seq rcv_adv;                /* advertised window */
           u_long  rcv_wnd;                /* receive window */
           tcp_seq rcv_up;                 /* receive urgent pointer */
   
           u_long  snd_wnd;                /* send window */
           u_long  snd_cwnd;               /* congestion-controlled window */
           u_long  snd_bwnd;               /* bandwidth-controlled window */
           u_long  snd_ssthresh;           /* snd_cwnd size threshold for
                                            * for slow start exponential to
                                            * linear switch
                                            */
           u_long  snd_bandwidth;          /* calculated bandwidth or 0 */
           tcp_seq snd_recover;            /* for use in NewReno Fast Recovery */
   
           u_int   t_maxopd;               /* mss plus options */
   
           u_long  t_rcvtime;              /* inactivity time */
           u_long  t_starttime;            /* time connection was established */
           int     t_rtttime;              /* round trip time */
           tcp_seq t_rtseq;                /* sequence number being timed */
   
           int     t_bw_rtttime;           /* used for bandwidth calculation */
           tcp_seq t_bw_rtseq;             /* used for bandwidth calculation */
   
           int     t_rxtcur;               /* current retransmit value (ticks) */
           u_int   t_maxseg;               /* maximum segment size */
           int     t_srtt;                 /* smoothed round-trip time */
           int     t_rttvar;               /* variance in round-trip time */
   
           int     t_rxtshift;             /* log(2) of rexmt exp. backoff */
           u_int   t_rttmin;               /* minimum rtt allowed */
           u_int   t_rttbest;              /* best rtt we've seen */
           u_long  t_rttupdated;           /* number of times rtt sampled */
           u_long  max_sndwnd;             /* largest window peer has offered */
   
           int     t_softerror;            /* possible error not yet reported */
   /* out-of-band data */
           char    t_oobflags;             /* have some */
           char    t_iobc;                 /* input character */
   #define TCPOOB_HAVEDATA 0x01
   #define TCPOOB_HADDATA  0x02
   /* RFC 1323 variables */
           u_char  snd_scale;              /* window scaling for send window */
           u_char  rcv_scale;              /* window scaling for recv window */
           u_char  request_r_scale;        /* pending window scaling */
           u_char  requested_s_scale;
           u_long  ts_recent;              /* timestamp echo data */
   
           u_long  ts_recent_age;          /* when last updated */
           tcp_seq last_ack_sent;
   /* RFC 1644 variables */
           tcp_cc  cc_send;                /* send connection count */
           tcp_cc  cc_recv;                /* receive connection count */
   /* experimental */
           u_long  snd_cwnd_prev;          /* cwnd prior to retransmit */
           u_long  snd_ssthresh_prev;      /* ssthresh prior to retransmit */
           tcp_seq snd_recover_prev;       /* snd_recover prior to retransmit */
           u_long  t_badrxtwin;            /* window for retransmit recovery */
           u_char  snd_limited;            /* segments limited transmitted */
   /* anti DoS counters */
           u_long  rcv_second;             /* start of interval second */
           u_long  rcv_pps;                /* received packets per second */
           u_long  rcv_byps;               /* received bytes per second */
   };
   
   #define IN_FASTRECOVERY(tp)     (tp->t_flags & TF_FASTRECOVERY)
   #define ENTER_FASTRECOVERY(tp)  tp->t_flags |= TF_FASTRECOVERY
   #define EXIT_FASTRECOVERY(tp)   tp->t_flags &= ~TF_FASTRECOVERY
   
   /*
    * Structure to hold TCP options that are only used during segment
    * processing (in tcp_input), but not held in the tcpcb.
    * It's basically used to reduce the number of parameters
    * to tcp_dooptions.
    */
   struct tcpopt {
           u_long          to_flags;       /* which options are present */
   #define TOF_TS          0x0001          /* timestamp */
   #define TOF_CC          0x0002          /* CC and CCnew are exclusive */
   #define TOF_CCNEW       0x0004
   #define TOF_CCECHO      0x0008
   #define TOF_MSS         0x0010
   #define TOF_SCALE       0x0020
           u_int32_t       to_tsval;
           u_int32_t       to_tsecr;
           tcp_cc          to_cc;          /* holds CC or CCnew */
           tcp_cc          to_ccecho;
           u_int16_t       to_mss;
           u_int8_t        to_requested_s_scale;
           u_int8_t        to_pad;
   };
   
   struct syncache {
           inp_gen_t       sc_inp_gencnt;          /* pointer check */
           struct          tcpcb *sc_tp;           /* tcb for listening socket */
           struct          mbuf *sc_ipopts;        /* source route */
           struct          in_conninfo sc_inc;     /* addresses */
           u_int32_t       sc_tsrecent;
           tcp_cc          sc_cc_send;             /* holds CC or CCnew */
           tcp_cc          sc_cc_recv;
           tcp_seq         sc_irs;                 /* seq from peer */
           tcp_seq         sc_iss;                 /* our ISS */
           u_long          sc_rxttime;             /* retransmit time */
           u_int16_t       sc_rxtslot;             /* retransmit counter */
           u_int16_t       sc_peer_mss;            /* peer's MSS */
           u_int16_t       sc_wnd;                 /* advertised window */
           u_int8_t        sc_requested_s_scale:4,
                           sc_request_r_scale:4;
           u_int8_t        sc_flags;
   #define SCF_NOOPT       0x01                    /* no TCP options */
   #define SCF_WINSCALE    0x02                    /* negotiated window scaling */
   #define SCF_TIMESTAMP   0x04                    /* negotiated timestamps */
   #define SCF_CC          0x08                    /* negotiated CC */
   #define SCF_UNREACH     0x10                    /* icmp unreachable received */
           TAILQ_ENTRY(syncache)   sc_hash;
           TAILQ_ENTRY(syncache)   sc_timerq;
   };
   
   struct syncache_head {
           TAILQ_HEAD(, syncache)  sch_bucket;
           u_int           sch_length;
   };
   
   struct hc_metrics_lite {        /* must stay in sync with hc_metrics */
           u_long  rmx_mtu;        /* MTU for this path */
           u_long  rmx_ssthresh;   /* outbound gateway buffer limit */
           u_long  rmx_rtt;        /* estimated round trip time */
           u_long  rmx_rttvar;     /* estimated rtt variance */
           u_long  rmx_bandwidth;  /* estimated bandwidth */
           u_long  rmx_cwnd;       /* congestion window */
           u_long  rmx_sendpipe;   /* outbound delay-bandwidth product */
           u_long  rmx_recvpipe;   /* inbound delay-bandwidth product */
   };
   
   struct tcptw {
           struct inpcb    *tw_inpcb;      /* XXX back pointer to internet pcb */
           tcp_seq         snd_nxt;
           tcp_seq         rcv_nxt;
           tcp_seq         iss;
           tcp_seq         irs;
           tcp_cc          cc_recv;
           tcp_cc          cc_send;
           u_short         last_win;       /* cached window value */
           u_short         tw_so_options;  /* copy of so_options */
           struct ucred    *tw_cred;       /* user credentials */
           u_long          t_recent;
           u_long          t_starttime;
           int             tw_time;
           LIST_ENTRY(tcptw) tw_2msl;
   };
    
   /*
    * The TAO cache entry which is stored in the tcp hostcache.
    */
   struct rmxp_tao {
           tcp_cc  tao_cc;                 /* latest CC in valid SYN */
           tcp_cc  tao_ccsent;             /* latest CC sent to peer */
           u_short tao_mssopt;             /* peer's cached MSS */
   #ifdef notyet
           u_short tao_flags;              /* cache status flags */
   #define TAOF_DONT       0x0001          /* peer doesn't understand rfc1644 */
   #define TAOF_OK         0x0002          /* peer does understand rfc1644 */
   #define TAOF_UNDEF      0               /* we don't know yet */
   #endif /* notyet */
   };
   
   #define intotcpcb(ip)   ((struct tcpcb *)(ip)->inp_ppcb)
   #define intotw(ip)      ((struct tcptw *)(ip)->inp_ppcb)
   #define sototcpcb(so)   (intotcpcb(sotoinpcb(so)))
   
   /*
    * The smoothed round-trip time and estimated variance
    * are stored as fixed point numbers scaled by the values below.
    * For convenience, these scales are also used in smoothing the average
    * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).
    * With these scales, srtt has 3 bits to the right of the binary point,
    * and thus an "ALPHA" of 0.875.  rttvar has 2 bits to the right of the
    * binary point, and is smoothed with an ALPHA of 0.75.
    */
   #define TCP_RTT_SCALE           32      /* multiplier for srtt; 3 bits frac. */
   #define TCP_RTT_SHIFT           5       /* shift for srtt; 3 bits frac. */
   #define TCP_RTTVAR_SCALE        16      /* multiplier for rttvar; 2 bits */
   #define TCP_RTTVAR_SHIFT        4       /* shift for rttvar; 2 bits */
   #define TCP_DELTA_SHIFT         2       /* see tcp_input.c */
   
   /*
    * The initial retransmission should happen at rtt + 4 * rttvar.
    * Because of the way we do the smoothing, srtt and rttvar
    * will each average +1/2 tick of bias.  When we compute
    * the retransmit timer, we want 1/2 tick of rounding and
    * 1 extra tick because of +-1/2 tick uncertainty in the
    * firing of the timer.  The bias will give us exactly the
    * 1.5 tick we need.  But, because the bias is
    * statistical, we have to test that we don't drop below
    * the minimum feasible timer (which is 2 ticks).
    * This version of the macro adapted from a paper by Lawrence
    * Brakmo and Larry Peterson which outlines a problem caused
    * by insufficient precision in the original implementation,
    * which results in inappropriately large RTO values for very
    * fast networks.
    */
   #define TCP_REXMTVAL(tp) \
           max((tp)->t_rttmin, (((tp)->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT))  \
             + (tp)->t_rttvar) >> TCP_DELTA_SHIFT)
   
   /*
    * TCP statistics.
    * Many of these should be kept per connection,
    * but that's inconvenient at the moment.
    */
   struct  tcpstat {
           u_long  tcps_connattempt;       /* connections initiated */
           u_long  tcps_accepts;           /* connections accepted */
           u_long  tcps_connects;          /* connections established */
           u_long  tcps_drops;             /* connections dropped */
           u_long  tcps_conndrops;         /* embryonic connections dropped */
           u_long  tcps_minmssdrops;       /* average minmss too low drops */
           u_long  tcps_closed;            /* conn. closed (includes drops) */
           u_long  tcps_segstimed;         /* segs where we tried to get rtt */
           u_long  tcps_rttupdated;        /* times we succeeded */
           u_long  tcps_delack;            /* delayed acks sent */
           u_long  tcps_timeoutdrop;       /* conn. dropped in rxmt timeout */
           u_long  tcps_rexmttimeo;        /* retransmit timeouts */
           u_long  tcps_persisttimeo;      /* persist timeouts */
           u_long  tcps_keeptimeo;         /* keepalive timeouts */
           u_long  tcps_keepprobe;         /* keepalive probes sent */
           u_long  tcps_keepdrops;         /* connections dropped in keepalive */
   
           u_long  tcps_sndtotal;          /* total packets sent */
           u_long  tcps_sndpack;           /* data packets sent */
           u_long  tcps_sndbyte;           /* data bytes sent */
           u_long  tcps_sndrexmitpack;     /* data packets retransmitted */
           u_long  tcps_sndrexmitbyte;     /* data bytes retransmitted */
           u_long  tcps_sndrexmitbad;      /* unnecessary packet retransmissions */
           u_long  tcps_sndacks;           /* ack-only packets sent */
           u_long  tcps_sndprobe;          /* window probes sent */
           u_long  tcps_sndurg;            /* packets sent with URG only */
           u_long  tcps_sndwinup;          /* window update-only packets sent */
           u_long  tcps_sndctrl;           /* control (SYN|FIN|RST) packets sent */
   
           u_long  tcps_rcvtotal;          /* total packets received */
           u_long  tcps_rcvpack;           /* packets received in sequence */
           u_long  tcps_rcvbyte;           /* bytes received in sequence */
           u_long  tcps_rcvbadsum;         /* packets received with ccksum errs */
           u_long  tcps_rcvbadoff;         /* packets received with bad offset */
           u_long  tcps_rcvmemdrop;        /* packets dropped for lack of memory */
           u_long  tcps_rcvshort;          /* packets received too short */
           u_long  tcps_rcvduppack;        /* duplicate-only packets received */
           u_long  tcps_rcvdupbyte;        /* duplicate-only bytes received */
           u_long  tcps_rcvpartduppack;    /* packets with some duplicate data */
           u_long  tcps_rcvpartdupbyte;    /* dup. bytes in part-dup. packets */
           u_long  tcps_rcvoopack;         /* out-of-order packets received */
           u_long  tcps_rcvoobyte;         /* out-of-order bytes received */
           u_long  tcps_rcvpackafterwin;   /* packets with data after window */
           u_long  tcps_rcvbyteafterwin;   /* bytes rcvd after window */
           u_long  tcps_rcvafterclose;     /* packets rcvd after "close" */
           u_long  tcps_rcvwinprobe;       /* rcvd window probe packets */
           u_long  tcps_rcvdupack;         /* rcvd duplicate acks */
           u_long  tcps_rcvacktoomuch;     /* rcvd acks for unsent data */
           u_long  tcps_rcvackpack;        /* rcvd ack packets */
           u_long  tcps_rcvackbyte;        /* bytes acked by rcvd acks */
           u_long  tcps_rcvwinupd;         /* rcvd window update packets */
           u_long  tcps_pawsdrop;          /* segments dropped due to PAWS */
           u_long  tcps_predack;           /* times hdr predict ok for acks */
           u_long  tcps_preddat;           /* times hdr predict ok for data pkts */
           u_long  tcps_pcbcachemiss;
           u_long  tcps_cachedrtt;         /* times cached RTT in route updated */
           u_long  tcps_cachedrttvar;      /* times cached rttvar updated */
           u_long  tcps_cachedssthresh;    /* times cached ssthresh updated */
           u_long  tcps_usedrtt;           /* times RTT initialized from route */
           u_long  tcps_usedrttvar;        /* times RTTVAR initialized from rt */
           u_long  tcps_usedssthresh;      /* times ssthresh initialized from rt*/
           u_long  tcps_persistdrop;       /* timeout in persist state */
           u_long  tcps_badsyn;            /* bogus SYN, e.g. premature ACK */
           u_long  tcps_mturesent;         /* resends due to MTU discovery */
           u_long  tcps_listendrop;        /* listen queue overflows */
   
           u_long  tcps_sc_added;          /* entry added to syncache */
           u_long  tcps_sc_retransmitted;  /* syncache entry was retransmitted */
           u_long  tcps_sc_dupsyn;         /* duplicate SYN packet */
           u_long  tcps_sc_dropped;        /* could not reply to packet */
           u_long  tcps_sc_completed;      /* successful extraction of entry */
           u_long  tcps_sc_bucketoverflow; /* syncache per-bucket limit hit */
           u_long  tcps_sc_cacheoverflow;  /* syncache cache limit hit */
           u_long  tcps_sc_reset;          /* RST removed entry from syncache */
           u_long  tcps_sc_stale;          /* timed out or listen socket gone */
           u_long  tcps_sc_aborted;        /* syncache entry aborted */
           u_long  tcps_sc_badack;         /* removed due to bad ACK */
           u_long  tcps_sc_unreach;        /* ICMP unreachable received */
           u_long  tcps_sc_zonefail;       /* zalloc() failed */
           u_long  tcps_sc_sendcookie;     /* SYN cookie sent */
           u_long  tcps_sc_recvcookie;     /* SYN cookie received */
   
           u_long  tcps_hc_added;          /* entry added to hostcache */
           u_long  tcps_hc_bucketoverflow; /* hostcache per bucket limit hit */
   };
   
   /*
    * TCB structure exported to user-land via sysctl(3).
    * Evil hack: declare only if in_pcb.h and sys/socketvar.h have been
    * included.  Not all of our clients do.
    */
   #if defined(_NETINET_IN_PCB_H_) && defined(_SYS_SOCKETVAR_H_)
   struct  xtcpcb {
           size_t  xt_len;
           struct  inpcb   xt_inp;
           struct  tcpcb   xt_tp;
           struct  xsocket xt_socket;
           u_quad_t        xt_alignment_hack;
   };
   #endif
   
   /*
    * Names for TCP sysctl objects
    */
   #define TCPCTL_DO_RFC1323       1       /* use RFC-1323 extensions */
   #define TCPCTL_DO_RFC1644       2       /* use RFC-1644 extensions */
   #define TCPCTL_MSSDFLT          3       /* MSS default */
   #define TCPCTL_STATS            4       /* statistics (read-only) */
   #define TCPCTL_RTTDFLT          5       /* default RTT estimate */
   #define TCPCTL_KEEPIDLE         6       /* keepalive idle timer */
   #define TCPCTL_KEEPINTVL        7       /* interval to send keepalives */
   #define TCPCTL_SENDSPACE        8       /* send buffer space */
   #define TCPCTL_RECVSPACE        9       /* receive buffer space */
   #define TCPCTL_KEEPINIT         10      /* timeout for establishing syn */
   #define TCPCTL_PCBLIST          11      /* list of all outstanding PCBs */
   #define TCPCTL_DELACKTIME       12      /* time before sending delayed ACK */
   #define TCPCTL_V6MSSDFLT        13      /* MSS default for IPv6 */
   #define TCPCTL_MAXID            14
   
   #define TCPCTL_NAMES { \
           { 0, 0 }, \
           { "rfc1323", CTLTYPE_INT }, \
           { "rfc1644", CTLTYPE_INT }, \
           { "mssdflt", CTLTYPE_INT }, \
           { "stats", CTLTYPE_STRUCT }, \
           { "rttdflt", CTLTYPE_INT }, \
           { "keepidle", CTLTYPE_INT }, \
           { "keepintvl", CTLTYPE_INT }, \
           { "sendspace", CTLTYPE_INT }, \
           { "recvspace", CTLTYPE_INT }, \
           { "keepinit", CTLTYPE_INT }, \
           { "pcblist", CTLTYPE_STRUCT }, \
           { "delacktime", CTLTYPE_INT }, \
           { "v6mssdflt", CTLTYPE_INT }, \
           { "maxid", CTLTYPE_INT }, \
   }
   
   
   #ifdef _KERNEL
   #ifdef SYSCTL_DECL
   SYSCTL_DECL(_net_inet_tcp);
   #endif
   
   extern  struct inpcbhead tcb;           /* head of queue of active tcpcb's */
   extern  struct inpcbinfo tcbinfo;
   extern  struct tcpstat tcpstat; /* tcp statistics */
   extern  int tcp_mssdflt;        /* XXX */
   extern  int tcp_minmss;
   extern  int tcp_minmssoverload;
   extern  int tcp_delack_enabled;
   extern  int tcp_do_newreno;
   extern  int path_mtu_discovery;
   extern  int ss_fltsz;
   extern  int ss_fltsz_local;
   
   void     tcp_canceltimers(struct tcpcb *);
   struct tcpcb *
            tcp_close(struct tcpcb *);
   void     tcp_twstart(struct tcpcb *);
   int      tcp_twrecycleable(struct tcptw *tw);
   struct tcptw *
            tcp_twclose(struct tcptw *_tw, int _reuse);
   void     tcp_ctlinput(int, struct sockaddr *, void *);
   int      tcp_ctloutput(struct socket *, struct sockopt *);
   struct tcpcb *
            tcp_drop(struct tcpcb *, int);
   void     tcp_drain(void);
   void     tcp_fasttimo(void);
   void     tcp_init(void);
   void     tcp_input(struct mbuf *, int);
   u_long   tcp_maxmtu(struct in_conninfo *);
   u_long   tcp_maxmtu6(struct in_conninfo *);
   void     tcp_mss(struct tcpcb *, int);
   int      tcp_mssopt(struct in_conninfo *);
   struct inpcb *   
            tcp_drop_syn_sent(struct inpcb *, int);
   struct inpcb *
            tcp_mtudisc(struct inpcb *, int);
   struct tcpcb *
            tcp_newtcpcb(struct inpcb *);
   int      tcp_output(struct tcpcb *);
   struct inpcb *
            tcp_quench(struct inpcb *, int);
   void     tcp_reass_init(void);
   void     tcp_respond(struct tcpcb *, void *,
               struct tcphdr *, struct mbuf *, tcp_seq, tcp_seq, int);
   int      tcp_twrespond(struct tcptw *, struct socket *, struct mbuf *, int);
   void     tcp_setpersist(struct tcpcb *);
   void     tcp_slowtimo(void);
   struct tcptemp *
            tcpip_maketemplate(struct inpcb *);
   void     tcpip_fillheaders(struct inpcb *, void *, void *);
   struct tcpcb *
            tcp_timers(struct tcpcb *, int);
   void     tcp_trace(int, int, struct tcpcb *, void *, struct tcphdr *, int);
   void     tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq);
   void     syncache_init(void);
   void     syncache_unreach(struct in_conninfo *, struct tcphdr *);
   int      syncache_expand(struct in_conninfo *, struct tcphdr *,
                struct socket **, struct mbuf *);
   int      syncache_add(struct in_conninfo *, struct tcpopt *,
                struct tcphdr *, struct socket **, struct mbuf *);
   void     syncache_chkrst(struct in_conninfo *, struct tcphdr *);
   void     syncache_badack(struct in_conninfo *);
   /*
    * All tcp_hc_* functions are IPv4 and IPv6 (via in_conninfo)
    */
   void     tcp_hc_init(void);
   void     tcp_hc_get(struct in_conninfo *, struct hc_metrics_lite *);
   u_long   tcp_hc_getmtu(struct in_conninfo *);
   void     tcp_hc_gettao(struct in_conninfo *, struct rmxp_tao *);
   void     tcp_hc_updatemtu(struct in_conninfo *, u_long);
   void     tcp_hc_update(struct in_conninfo *, struct hc_metrics_lite *);
   void     tcp_hc_updatetao(struct in_conninfo *, int, tcp_cc, u_short);
   /* update which tao field */
   #define TCP_HC_TAO_CC           0x1
   #define TCP_HC_TAO_CCSENT       0x2
   #define TCP_HC_TAO_MSSOPT       0x3
   
   extern  struct pr_usrreqs tcp_usrreqs;
   extern  u_long tcp_sendspace;
   extern  u_long tcp_recvspace;
   tcp_seq tcp_new_isn(struct tcpcb *);
   
   #endif /* _KERNEL */
   
   #endif /* _NETINET_TCP_VAR_H_ */

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