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Annotation of kernel/bsd/netinet/tcp_var.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
        !            26: /*
        !            27:  * Copyright (c) 1982, 1986, 1993, 1994, 1995
        !            28:  *     The Regents of the University of California.  All rights reserved.
        !            29:  *
        !            30:  * Redistribution and use in source and binary forms, with or without
        !            31:  * modification, are permitted provided that the following conditions
        !            32:  * are met:
        !            33:  * 1. Redistributions of source code must retain the above copyright
        !            34:  *    notice, this list of conditions and the following disclaimer.
        !            35:  * 2. Redistributions in binary form must reproduce the above copyright
        !            36:  *    notice, this list of conditions and the following disclaimer in the
        !            37:  *    documentation and/or other materials provided with the distribution.
        !            38:  * 3. All advertising materials mentioning features or use of this software
        !            39:  *    must display the following acknowledgement:
        !            40:  *     This product includes software developed by the University of
        !            41:  *     California, Berkeley and its contributors.
        !            42:  * 4. Neither the name of the University nor the names of its contributors
        !            43:  *    may be used to endorse or promote products derived from this software
        !            44:  *    without specific prior written permission.
        !            45:  *
        !            46:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            47:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            48:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            49:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            50:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            51:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            52:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            53:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            54:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            55:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            56:  * SUCH DAMAGE.
        !            57:  *
        !            58:  *     @(#)tcp_var.h   8.4 (Berkeley) 5/24/95
        !            59:  */
        !            60: 
        !            61: /*
        !            62:  * Kernel variables for tcp.
        !            63:  */
        !            64: 
        !            65: #define N_TIME_WAIT_SLOTS      120
        !            66: 
        !            67: #define N_TCP_HASH_ELEMENTS    (8 * 1024)         /* must be power of 2 */
        !            68: #define TCP_HASH_MASK           (N_TCP_HASH_ELEMENTS - 1)
        !            69: #define N_TCP_LPORT_HASH_ELEMENTS      (1024)
        !            70: #define TCP_LPORT_HASH_MASK            (N_TCP_LPORT_HASH_ELEMENTS - 1)
        !            71: 
        !            72: /*
        !            73:  * The macro below takes a value from 0 - 8192 and sets a corresponding bit in the
        !            74:  * 1024 byte delack_bitmask array. Each bit represents represents one of the
        !            75:  * hash-queue entries in the TCP hash queue array.
        !            76:  */
        !            77: 
        !            78: #define TCP_DELACK_BITSET(hash_elem)   \
        !            79:                        delack_bitmask[((hash_elem) >> 5)] |= 1 << ((hash_elem) & 0x1F)
        !            80: 
        !            81: #define DELACK_BITMASK_ON      1
        !            82: #define DELACK_BITMASK_THRESH  300
        !            83: 
        !            84: 
        !            85: /*
        !            86:  * Tcp control block, one per tcp; fields:
        !            87:  */
        !            88: struct tcpcb {
        !            89:        struct  tcpiphdr *seg_next;     /* sequencing queue */
        !            90:        struct  tcpiphdr *seg_prev;
        !            91:        short   t_state;                /* state of this connection */
        !            92:        short   t_timer[TCPT_NTIMERS];  /* tcp timers */
        !            93:        short   t_rxtshift;             /* log(2) of rexmt exp. backoff */
        !            94:        short   t_rxtcur;               /* current retransmit value */
        !            95:        short   t_dupacks;              /* consecutive dup acks recd */
        !            96:        u_short t_maxseg;               /* maximum segment size */
        !            97:        char    t_force;                /* 1 if forcing out a byte */
        !            98:        u_short t_flags;
        !            99: #define        TF_ACKNOW       0x0001          /* ack peer immediately */
        !           100: #define        TF_DELACK       0x0002          /* ack, but try to delay it */
        !           101: #define        TF_NODELAY      0x0004          /* don't delay packets to coalesce */
        !           102: #define        TF_NOOPT        0x0008          /* don't use tcp options */
        !           103: #define        TF_SENTFIN      0x0010          /* have sent FIN */
        !           104: #define        TF_REQ_SCALE    0x0020          /* have/will request window scaling */
        !           105: #define        TF_RCVD_SCALE   0x0040          /* other side has requested scaling */
        !           106: #define        TF_REQ_TSTMP    0x0080          /* have/will request timestamps */
        !           107: #define        TF_RCVD_TSTMP   0x0100          /* a timestamp was received in SYN */
        !           108: #define        TF_SACK_PERMIT  0x0200          /* other side said I could SACK */
        !           109: 
        !           110:        struct  tcpiphdr *t_template;   /* skeletal packet for transmit */
        !           111:        struct  inpcb *t_inpcb;         /* back pointer to internet pcb */
        !           112: /*
        !           113:  * The following fields are used as in the protocol specification.
        !           114:  * See RFC783, Dec. 1981, page 21.
        !           115:  */
        !           116: /* send sequence variables */
        !           117:        tcp_seq snd_una;                /* send unacknowledged */
        !           118:        tcp_seq snd_nxt;                /* send next */
        !           119:        tcp_seq snd_up;                 /* send urgent pointer */
        !           120:        tcp_seq snd_wl1;                /* window update seg seq number */
        !           121:        tcp_seq snd_wl2;                /* window update seg ack number */
        !           122:        tcp_seq iss;                    /* initial send sequence number */
        !           123:        u_long  snd_wnd;                /* send window */
        !           124: /* receive sequence variables */
        !           125:        u_long  rcv_wnd;                /* receive window */
        !           126:        tcp_seq rcv_nxt;                /* receive next */
        !           127:        tcp_seq rcv_up;                 /* receive urgent pointer */
        !           128:        tcp_seq irs;                    /* initial receive sequence number */
        !           129: /*
        !           130:  * Additional variables for this implementation.
        !           131:  */
        !           132: /* receive variables */
        !           133:        tcp_seq rcv_adv;                /* advertised window */
        !           134: /* retransmit variables */
        !           135:        tcp_seq snd_max;                /* highest sequence number sent;
        !           136:                                         * used to recognize retransmits
        !           137:                                         */
        !           138: /* congestion control (for slow start, source quench, retransmit after loss) */
        !           139:        u_long  snd_cwnd;               /* congestion-controlled window */
        !           140:        u_long  snd_ssthresh;           /* snd_cwnd size threshhold for
        !           141:                                         * for slow start exponential to
        !           142:                                         * linear switch
        !           143:                                         */
        !           144: /*
        !           145:  * transmit timing stuff.  See below for scale of srtt and rttvar.
        !           146:  * "Variance" is actually smoothed difference.
        !           147:  */
        !           148:        u_short t_idle;                 /* inactivity time */
        !           149:        short   t_rtt;                  /* round trip time */
        !           150:        tcp_seq t_rtseq;                /* sequence number being timed */
        !           151:        short   t_srtt;                 /* smoothed round-trip time */
        !           152:        short   t_rttvar;               /* variance in round-trip time */
        !           153:        u_short t_rttmin;               /* minimum rtt allowed */
        !           154:        u_long  max_sndwnd;             /* largest window peer has offered */
        !           155: 
        !           156: /* out-of-band data */
        !           157:        char    t_oobflags;             /* have some */
        !           158:        char    t_iobc;                 /* input character */
        !           159: #define        TCPOOB_HAVEDATA 0x01
        !           160: #define        TCPOOB_HADDATA  0x02
        !           161:        short   t_softerror;            /* possible error not yet reported */
        !           162: 
        !           163: /* RFC 1323 variables */
        !           164:        u_char  snd_scale;              /* window scaling for send window */
        !           165:        u_char  rcv_scale;              /* window scaling for recv window */
        !           166:        u_char  request_r_scale;        /* pending window scaling */
        !           167:        u_char  requested_s_scale;
        !           168:        u_long  ts_recent;              /* timestamp echo data */
        !           169:        u_long  ts_recent_age;          /* when last updated */
        !           170:        tcp_seq last_ack_sent;
        !           171: 
        !           172: /* TUBA stuff */
        !           173:        caddr_t t_tuba_pcb;             /* next level down pcb for TCP over z */
        !           174: };
        !           175: 
        !           176: 
        !           177: 
        !           178: 
        !           179: #define        intotcpcb(ip)   ((struct tcpcb *)(ip)->inp_ppcb)
        !           180: #define        sototcpcb(so)   (intotcpcb(sotoinpcb(so)))
        !           181: 
        !           182: /*
        !           183:  * The smoothed round-trip time and estimated variance
        !           184:  * are stored as fixed point numbers scaled by the values below.
        !           185:  * For convenience, these scales are also used in smoothing the average
        !           186:  * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).
        !           187:  * With these scales, srtt has 3 bits to the right of the binary point,
        !           188:  * and thus an "ALPHA" of 0.875.  rttvar has 2 bits to the right of the
        !           189:  * binary point, and is smoothed with an ALPHA of 0.75.
        !           190:  */
        !           191: #define        TCP_RTT_SCALE           8       /* multiplier for srtt; 3 bits frac. */
        !           192: #define        TCP_RTT_SHIFT           3       /* shift for srtt; 3 bits frac. */
        !           193: #define        TCP_RTTVAR_SCALE        4       /* multiplier for rttvar; 2 bits */
        !           194: #define        TCP_RTTVAR_SHIFT        2       /* multiplier for rttvar; 2 bits */
        !           195: 
        !           196: /*
        !           197:  * The initial retransmission should happen at rtt + 4 * rttvar.
        !           198:  * Because of the way we do the smoothing, srtt and rttvar
        !           199:  * will each average +1/2 tick of bias.  When we compute
        !           200:  * the retransmit timer, we want 1/2 tick of rounding and
        !           201:  * 1 extra tick because of +-1/2 tick uncertainty in the
        !           202:  * firing of the timer.  The bias will give us exactly the
        !           203:  * 1.5 tick we need.  But, because the bias is
        !           204:  * statistical, we have to test that we don't drop below
        !           205:  * the minimum feasible timer (which is 2 ticks).
        !           206:  * This macro assumes that the value of TCP_RTTVAR_SCALE
        !           207:  * is the same as the multiplier for rttvar.
        !           208:  */
        !           209: #define        TCP_REXMTVAL(tp) \
        !           210:        (((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar)
        !           211: 
        !           212: /* XXX
        !           213:  * We want to avoid doing m_pullup on incoming packets but that
        !           214:  * means avoiding dtom on the tcp reassembly code.  That in turn means
        !           215:  * keeping an mbuf pointer in the reassembly queue (since we might
        !           216:  * have a cluster).  As a quick hack, the source & destination
        !           217:  * port numbers (which are no longer needed once we've located the
        !           218:  * tcpcb) are overlayed with an mbuf pointer.
        !           219:  */
        !           220: #define REASS_MBUF(ti) (*(struct mbuf **)&((ti)->ti_t))
        !           221: 
        !           222: /*
        !           223:  * TCP statistics.
        !           224:  * Many of these should be kept per connection,
        !           225:  * but that's inconvenient at the moment.
        !           226:  */
        !           227: struct tcpstat {
        !           228:        u_long  tcps_connattempt;       /* connections initiated */
        !           229:        u_long  tcps_accepts;           /* connections accepted */
        !           230:        u_long  tcps_connects;          /* connections established */
        !           231:        u_long  tcps_drops;             /* connections dropped */
        !           232:        u_long  tcps_conndrops;         /* embryonic connections dropped */
        !           233:        u_long  tcps_closed;            /* conn. closed (includes drops) */
        !           234:        u_long  tcps_segstimed;         /* segs where we tried to get rtt */
        !           235:        u_long  tcps_rttupdated;        /* times we succeeded */
        !           236:        u_long  tcps_delack;            /* delayed acks sent */
        !           237:        u_long  tcps_timeoutdrop;       /* conn. dropped in rxmt timeout */
        !           238:        u_long  tcps_rexmttimeo;        /* retransmit timeouts */
        !           239:        u_long  tcps_persisttimeo;      /* persist timeouts */
        !           240:        u_long  tcps_keeptimeo;         /* keepalive timeouts */
        !           241:        u_long  tcps_keepprobe;         /* keepalive probes sent */
        !           242:        u_long  tcps_keepdrops;         /* connections dropped in keepalive */
        !           243: 
        !           244:        u_long  tcps_sndtotal;          /* total packets sent */
        !           245:        u_long  tcps_sndpack;           /* data packets sent */
        !           246:        u_long  tcps_sndbyte;           /* data bytes sent */
        !           247:        u_long  tcps_sndrexmitpack;     /* data packets retransmitted */
        !           248:        u_long  tcps_sndrexmitbyte;     /* data bytes retransmitted */
        !           249:        u_long  tcps_sndacks;           /* ack-only packets sent */
        !           250:        u_long  tcps_sndprobe;          /* window probes sent */
        !           251:        u_long  tcps_sndurg;            /* packets sent with URG only */
        !           252:        u_long  tcps_sndwinup;          /* window update-only packets sent */
        !           253:        u_long  tcps_sndctrl;           /* control (SYN|FIN|RST) packets sent */
        !           254: 
        !           255:        u_long  tcps_rcvtotal;          /* total packets received */
        !           256:        u_long  tcps_rcvpack;           /* packets received in sequence */
        !           257:        u_long  tcps_rcvbyte;           /* bytes received in sequence */
        !           258:        u_long  tcps_rcvbadsum;         /* packets received with ccksum errs */
        !           259:        u_long  tcps_rcvbadoff;         /* packets received with bad offset */
        !           260:        u_long  tcps_rcvshort;          /* packets received too short */
        !           261:        u_long  tcps_rcvduppack;        /* duplicate-only packets received */
        !           262:        u_long  tcps_rcvdupbyte;        /* duplicate-only bytes received */
        !           263:        u_long  tcps_rcvpartduppack;    /* packets with some duplicate data */
        !           264:        u_long  tcps_rcvpartdupbyte;    /* dup. bytes in part-dup. packets */
        !           265:        u_long  tcps_rcvoopack;         /* out-of-order packets received */
        !           266:        u_long  tcps_rcvoobyte;         /* out-of-order bytes received */
        !           267:        u_long  tcps_rcvpackafterwin;   /* packets with data after window */
        !           268:        u_long  tcps_rcvbyteafterwin;   /* bytes rcvd after window */
        !           269:        u_long  tcps_rcvafterclose;     /* packets rcvd after "close" */
        !           270:        u_long  tcps_rcvwinprobe;       /* rcvd window probe packets */
        !           271:        u_long  tcps_rcvdupack;         /* rcvd duplicate acks */
        !           272:        u_long  tcps_rcvacktoomuch;     /* rcvd acks for unsent data */
        !           273:        u_long  tcps_rcvackpack;        /* rcvd ack packets */
        !           274:        u_long  tcps_rcvackbyte;        /* bytes acked by rcvd acks */
        !           275:        u_long  tcps_rcvwinupd;         /* rcvd window update packets */
        !           276:        u_long  tcps_pawsdrop;          /* segments dropped due to PAWS */
        !           277:        u_long  tcps_predack;           /* times hdr predict ok for acks */
        !           278:        u_long  tcps_preddat;           /* times hdr predict ok for data pkts */
        !           279:        u_long  tcps_pcbcachemiss;      /* tcp pcb cache misses - no longer used */
        !           280:        u_long  tcps_persistdrop;       /* timeout in persist state */
        !           281:        u_long  tcps_badsyn;            /* bogus SYN, e.g. premature ACK */
        !           282: };
        !           283: 
        !           284: #ifdef _KERNEL
        !           285: extern struct  inpcb tcb;              /* head of queue of active tcpcb's */
        !           286: extern struct  tcpstat tcpstat;        /* tcp statistics */
        !           287: extern u_long  tcp_now;                /* for RFC 1323 timestamps */
        !           288: 
        !           289: int     tcp_attach __P((struct socket *));
        !           290: void    tcp_canceltimers __P((struct tcpcb *));
        !           291: struct tcpcb *
        !           292:         tcp_close __P((struct tcpcb *));
        !           293: void    tcp_ctlinput __P((int, struct sockaddr *, struct ip *));
        !           294: int     tcp_ctloutput __P((int, struct socket *, int, int, struct mbuf **));
        !           295: struct tcpcb *
        !           296:         tcp_disconnect __P((struct tcpcb *));
        !           297: struct tcpcb *
        !           298:         tcp_drop __P((struct tcpcb *, int));
        !           299: void    tcp_dooptions __P((struct tcpcb *,
        !           300:            u_char *, int, struct tcpiphdr *, int *, u_long *, u_long *));
        !           301: void    tcp_drain __P((void));
        !           302: void    tcp_fasttimo __P((void));
        !           303: void    tcp_init __P((void));
        !           304: void    tcp_input __P((struct mbuf *, int));
        !           305: int     tcp_mss __P((struct tcpcb *, u_int));
        !           306: struct tcpcb *
        !           307:         tcp_newtcpcb __P((struct inpcb *));
        !           308: void    tcp_notify __P((struct inpcb *, int));
        !           309: int     tcp_output __P((struct tcpcb *));
        !           310: void    tcp_pulloutofband __P((struct socket *,
        !           311:            struct tcpiphdr *, struct mbuf *));
        !           312: void    tcp_quench __P((struct inpcb *, int));
        !           313: int     tcp_reass __P((struct tcpcb *, struct tcpiphdr *, struct mbuf *));
        !           314: void    tcp_respond __P((struct tcpcb *,
        !           315:            struct tcpiphdr *, struct mbuf *, u_long, u_long, int));
        !           316: void    tcp_setpersist __P((struct tcpcb *));
        !           317: void    tcp_slowtimo __P((void));
        !           318: struct tcpiphdr *
        !           319:         tcp_template __P((struct tcpcb *));
        !           320: struct tcpcb *
        !           321:         tcp_timers __P((struct tcpcb *, int));
        !           322: void    tcp_trace __P((int, int, struct tcpcb *, struct tcpiphdr *, int));
        !           323: struct tcpcb *
        !           324:         tcp_usrclosed __P((struct tcpcb *));
        !           325: int     tcp_usrreq __P((struct socket *,
        !           326:            int, struct mbuf *, struct mbuf *, struct mbuf *));
        !           327: void    tcp_xmit_timer __P((struct tcpcb *, int));
        !           328: #endif

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