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Annotation of 43BSDReno/sys/netinet/tcp_subr.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution is only permitted until one year after the first shipment
        !             6:  * of 4.4BSD by the Regents.  Otherwise, redistribution and use in source and
        !             7:  * binary forms are permitted provided that: (1) source distributions retain
        !             8:  * this entire copyright notice and comment, and (2) distributions including
        !             9:  * binaries display the following acknowledgement:  This product includes
        !            10:  * software developed by the University of California, Berkeley and its
        !            11:  * contributors'' in the documentation or other materials provided with the
        !            12:  * distribution and in all advertising materials mentioning features or use
        !            13:  * of this software.  Neither the name of the University nor the names of
        !            14:  * its contributors may be used to endorse or promote products derived from
        !            15:  * this software without specific prior written permission.
        !            16:  * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            17:  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            18:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            19:  *
        !            20:  *     @(#)tcp_subr.c  7.19 (Berkeley) 7/25/90
        !            21:  */
        !            22: 
        !            23: #include "param.h"
        !            24: #include "systm.h"
        !            25: #include "malloc.h"
        !            26: #include "mbuf.h"
        !            27: #include "socket.h"
        !            28: #include "socketvar.h"
        !            29: #include "protosw.h"
        !            30: #include "errno.h"
        !            31: 
        !            32: #include "../net/route.h"
        !            33: #include "../net/if.h"
        !            34: 
        !            35: #include "in.h"
        !            36: #include "in_systm.h"
        !            37: #include "ip.h"
        !            38: #include "in_pcb.h"
        !            39: #include "ip_var.h"
        !            40: #include "ip_icmp.h"
        !            41: #include "tcp.h"
        !            42: #include "tcp_fsm.h"
        !            43: #include "tcp_seq.h"
        !            44: #include "tcp_timer.h"
        !            45: #include "tcp_var.h"
        !            46: #include "tcpip.h"
        !            47: 
        !            48: /* patchable/settable parameters for tcp */
        !            49: int    tcp_ttl = TCP_TTL;
        !            50: int    tcp_mssdflt = TCP_MSS;
        !            51: int    tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
        !            52: 
        !            53: extern struct inpcb *tcp_last_inpcb;
        !            54: 
        !            55: /*
        !            56:  * Tcp initialization
        !            57:  */
        !            58: tcp_init()
        !            59: {
        !            60: 
        !            61:        tcp_iss = 1;            /* wrong */
        !            62:        tcb.inp_next = tcb.inp_prev = &tcb;
        !            63:        if (max_protohdr < sizeof(struct tcpiphdr))
        !            64:                max_protohdr = sizeof(struct tcpiphdr);
        !            65:        if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN)
        !            66:                panic("tcp_init");
        !            67: }
        !            68: 
        !            69: /*
        !            70:  * Create template to be used to send tcp packets on a connection.
        !            71:  * Call after host entry created, allocates an mbuf and fills
        !            72:  * in a skeletal tcp/ip header, minimizing the amount of work
        !            73:  * necessary when the connection is used.
        !            74:  */
        !            75: struct tcpiphdr *
        !            76: tcp_template(tp)
        !            77:        struct tcpcb *tp;
        !            78: {
        !            79:        register struct inpcb *inp = tp->t_inpcb;
        !            80:        register struct mbuf *m;
        !            81:        register struct tcpiphdr *n;
        !            82: 
        !            83:        if ((n = tp->t_template) == 0) {
        !            84:                m = m_get(M_DONTWAIT, MT_HEADER);
        !            85:                if (m == NULL)
        !            86:                        return (0);
        !            87:                m->m_len = sizeof (struct tcpiphdr);
        !            88:                n = mtod(m, struct tcpiphdr *);
        !            89:        }
        !            90:        n->ti_next = n->ti_prev = 0;
        !            91:        n->ti_x1 = 0;
        !            92:        n->ti_pr = IPPROTO_TCP;
        !            93:        n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));
        !            94:        n->ti_src = inp->inp_laddr;
        !            95:        n->ti_dst = inp->inp_faddr;
        !            96:        n->ti_sport = inp->inp_lport;
        !            97:        n->ti_dport = inp->inp_fport;
        !            98:        n->ti_seq = 0;
        !            99:        n->ti_ack = 0;
        !           100:        n->ti_x2 = 0;
        !           101:        n->ti_off = 5;
        !           102:        n->ti_flags = 0;
        !           103:        n->ti_win = 0;
        !           104:        n->ti_sum = 0;
        !           105:        n->ti_urp = 0;
        !           106:        return (n);
        !           107: }
        !           108: 
        !           109: /*
        !           110:  * Send a single message to the TCP at address specified by
        !           111:  * the given TCP/IP header.  If m == 0, then we make a copy
        !           112:  * of the tcpiphdr at ti and send directly to the addressed host.
        !           113:  * This is used to force keep alive messages out using the TCP
        !           114:  * template for a connection tp->t_template.  If flags are given
        !           115:  * then we send a message back to the TCP which originated the
        !           116:  * segment ti, and discard the mbuf containing it and any other
        !           117:  * attached mbufs.
        !           118:  *
        !           119:  * In any case the ack and sequence number of the transmitted
        !           120:  * segment are as specified by the parameters.
        !           121:  */
        !           122: tcp_respond(tp, ti, m, ack, seq, flags)
        !           123:        struct tcpcb *tp;
        !           124:        register struct tcpiphdr *ti;
        !           125:        register struct mbuf *m;
        !           126:        tcp_seq ack, seq;
        !           127:        int flags;
        !           128: {
        !           129:        register int tlen;
        !           130:        int win = 0;
        !           131:        struct route *ro = 0;
        !           132: 
        !           133:        if (tp) {
        !           134:                win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);
        !           135:                ro = &tp->t_inpcb->inp_route;
        !           136:        }
        !           137:        if (m == 0) {
        !           138:                m = m_gethdr(M_DONTWAIT, MT_HEADER);
        !           139:                if (m == NULL)
        !           140:                        return;
        !           141: #ifdef TCP_COMPAT_42
        !           142:                tlen = 1;
        !           143: #else
        !           144:                tlen = 0;
        !           145: #endif
        !           146:                m->m_data += max_linkhdr;
        !           147:                *mtod(m, struct tcpiphdr *) = *ti;
        !           148:                ti = mtod(m, struct tcpiphdr *);
        !           149:                flags = TH_ACK;
        !           150:        } else {
        !           151:                m_freem(m->m_next);
        !           152:                m->m_next = 0;
        !           153:                m->m_data = (caddr_t)ti;
        !           154:                m->m_len = sizeof (struct tcpiphdr);
        !           155:                tlen = 0;
        !           156: #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
        !           157:                xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long);
        !           158:                xchg(ti->ti_dport, ti->ti_sport, u_short);
        !           159: #undef xchg
        !           160:        }
        !           161:        ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen));
        !           162:        tlen += sizeof (struct tcpiphdr);
        !           163:        m->m_len = tlen;
        !           164:        m->m_pkthdr.len = tlen;
        !           165:        m->m_pkthdr.rcvif = (struct ifnet *) 0;
        !           166:        ti->ti_next = ti->ti_prev = 0;
        !           167:        ti->ti_x1 = 0;
        !           168:        ti->ti_seq = htonl(seq);
        !           169:        ti->ti_ack = htonl(ack);
        !           170:        ti->ti_x2 = 0;
        !           171:        ti->ti_off = sizeof (struct tcphdr) >> 2;
        !           172:        ti->ti_flags = flags;
        !           173:        ti->ti_win = htons((u_short)win);
        !           174:        ti->ti_urp = 0;
        !           175:        ti->ti_sum = in_cksum(m, tlen);
        !           176:        ((struct ip *)ti)->ip_len = tlen;
        !           177:        ((struct ip *)ti)->ip_ttl = tcp_ttl;
        !           178:        (void) ip_output(m, (struct mbuf *)0, ro, 0);
        !           179: }
        !           180: 
        !           181: /*
        !           182:  * Create a new TCP control block, making an
        !           183:  * empty reassembly queue and hooking it to the argument
        !           184:  * protocol control block.
        !           185:  */
        !           186: struct tcpcb *
        !           187: tcp_newtcpcb(inp)
        !           188:        struct inpcb *inp;
        !           189: {
        !           190:        struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB);
        !           191:        register struct tcpcb *tp;
        !           192: 
        !           193:        if (m == NULL)
        !           194:                return ((struct tcpcb *)0);
        !           195:        tp = mtod(m, struct tcpcb *);
        !           196:        tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp;
        !           197:        tp->t_maxseg = tcp_mssdflt;
        !           198: 
        !           199:        tp->t_flags = 0;                /* sends options! */
        !           200:        tp->t_inpcb = inp;
        !           201:        /*
        !           202:         * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
        !           203:         * rtt estimate.  Set rttvar so that srtt + 2 * rttvar gives
        !           204:         * reasonable initial retransmit time.
        !           205:         */
        !           206:        tp->t_srtt = TCPTV_SRTTBASE;
        !           207:        tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << 2;
        !           208:        tp->t_rttmin = TCPTV_MIN;
        !           209:        TCPT_RANGESET(tp->t_rxtcur, 
        !           210:            ((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1,
        !           211:            TCPTV_MIN, TCPTV_REXMTMAX);
        !           212:        tp->snd_cwnd = TCP_MAXWIN;
        !           213:        tp->snd_ssthresh = TCP_MAXWIN;
        !           214:        inp->inp_ip.ip_ttl = tcp_ttl;
        !           215:        inp->inp_ppcb = (caddr_t)tp;
        !           216:        return (tp);
        !           217: }
        !           218: 
        !           219: /*
        !           220:  * Drop a TCP connection, reporting
        !           221:  * the specified error.  If connection is synchronized,
        !           222:  * then send a RST to peer.
        !           223:  */
        !           224: struct tcpcb *
        !           225: tcp_drop(tp, errno)
        !           226:        register struct tcpcb *tp;
        !           227:        int errno;
        !           228: {
        !           229:        struct socket *so = tp->t_inpcb->inp_socket;
        !           230: 
        !           231:        if (TCPS_HAVERCVDSYN(tp->t_state)) {
        !           232:                tp->t_state = TCPS_CLOSED;
        !           233:                (void) tcp_output(tp);
        !           234:                tcpstat.tcps_drops++;
        !           235:        } else
        !           236:                tcpstat.tcps_conndrops++;
        !           237:        if (errno == ETIMEDOUT && tp->t_softerror)
        !           238:                errno = tp->t_softerror;
        !           239:        so->so_error = errno;
        !           240:        return (tcp_close(tp));
        !           241: }
        !           242: 
        !           243: /*
        !           244:  * Close a TCP control block:
        !           245:  *     discard all space held by the tcp
        !           246:  *     discard internet protocol block
        !           247:  *     wake up any sleepers
        !           248:  */
        !           249: struct tcpcb *
        !           250: tcp_close(tp)
        !           251:        register struct tcpcb *tp;
        !           252: {
        !           253:        register struct tcpiphdr *t;
        !           254:        struct inpcb *inp = tp->t_inpcb;
        !           255:        struct socket *so = inp->inp_socket;
        !           256:        register struct mbuf *m;
        !           257: #ifdef RTV_RTT
        !           258:        register struct rtentry *rt;
        !           259: 
        !           260:        /*
        !           261:         * If we sent enough data to get some meaningful characteristics,
        !           262:         * save them in the routing entry.  'Enough' is arbitrarily 
        !           263:         * defined as 4K (default tcp_sendspace) * 16.  This would
        !           264:         * give us 16 rtt samples assuming we only get one sample per
        !           265:         * window (the usual case on a long haul net).  16 samples is
        !           266:         * enough for the srtt filter to converge to within 5% of the correct
        !           267:         * value; fewer samples and we could save a very bogus rtt.
        !           268:         *
        !           269:         * Don't update the default route's characteristics and don't
        !           270:         * update anything that the user "locked".
        !           271:         */
        !           272:        if (SEQ_LT(tp->iss+(4096*16), tp->snd_max) &&
        !           273:            (rt = inp->inp_route.ro_rt) &&
        !           274:            ((struct sockaddr_in *) rt_key(rt))->sin_addr.s_addr !=
        !           275:            INADDR_ANY) {
        !           276:                register u_long i;
        !           277: 
        !           278:                if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {
        !           279:                        i = tp->t_srtt *
        !           280:                            (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));
        !           281:                        if (rt->rt_rmx.rmx_rtt && i)
        !           282:                                /*
        !           283:                                 * filter this update to half the old & half
        !           284:                                 * the new values, converting scale.
        !           285:                                 * See route.h and tcp_var.h for a
        !           286:                                 * description of the scaling constants.
        !           287:                                 */
        !           288:                                rt->rt_rmx.rmx_rtt =
        !           289:                                    (rt->rt_rmx.rmx_rtt + i) / 2;
        !           290:                        else
        !           291:                                rt->rt_rmx.rmx_rtt = i;
        !           292:                }
        !           293:                if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {
        !           294:                        i = tp->t_rttvar *
        !           295:                            (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE));
        !           296:                        if (rt->rt_rmx.rmx_rttvar && i)
        !           297:                                rt->rt_rmx.rmx_rttvar =
        !           298:                                    (rt->rt_rmx.rmx_rttvar + i) / 2;
        !           299:                        else
        !           300:                                rt->rt_rmx.rmx_rttvar = i;
        !           301:                }
        !           302:                /*
        !           303:                 * update the pipelimit (ssthresh) if it has been updated
        !           304:                 * already or if a pipesize was specified & the threshhold
        !           305:                 * got below half the pipesize.  I.e., wait for bad news
        !           306:                 * before we start updating, then update on both good
        !           307:                 * and bad news.
        !           308:                 */
        !           309:                if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
        !           310:                    (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh ||
        !           311:                    i < (rt->rt_rmx.rmx_sendpipe / 2)) {
        !           312:                        /*
        !           313:                         * convert the limit from user data bytes to
        !           314:                         * packets then to packet data bytes.
        !           315:                         */
        !           316:                        i = (i + tp->t_maxseg / 2) / tp->t_maxseg;
        !           317:                        if (i < 2)
        !           318:                                i = 2;
        !           319:                        i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr));
        !           320:                        if (rt->rt_rmx.rmx_ssthresh)
        !           321:                                rt->rt_rmx.rmx_ssthresh =
        !           322:                                    (rt->rt_rmx.rmx_ssthresh + i) / 2;
        !           323:                        else
        !           324:                                rt->rt_rmx.rmx_ssthresh = i;
        !           325:                }
        !           326:        }
        !           327: #endif RTV_RTT
        !           328:        /* free the reassembly queue, if any */
        !           329:        t = tp->seg_next;
        !           330:        while (t != (struct tcpiphdr *)tp) {
        !           331:                t = (struct tcpiphdr *)t->ti_next;
        !           332:                m = REASS_MBUF((struct tcpiphdr *)t->ti_prev);
        !           333:                remque(t->ti_prev);
        !           334:                m_freem(m);
        !           335:        }
        !           336:        if (tp->t_template)
        !           337:                (void) m_free(dtom(tp->t_template));
        !           338:        (void) m_free(dtom(tp));
        !           339:        inp->inp_ppcb = 0;
        !           340:        soisdisconnected(so);
        !           341:        /* clobber input pcb cache if we're closing the cached connection */
        !           342:        if (inp == tcp_last_inpcb)
        !           343:                tcp_last_inpcb = &tcb;
        !           344:        in_pcbdetach(inp);
        !           345:        tcpstat.tcps_closed++;
        !           346:        return ((struct tcpcb *)0);
        !           347: }
        !           348: 
        !           349: tcp_drain()
        !           350: {
        !           351: 
        !           352: }
        !           353: 
        !           354: /*
        !           355:  * Notify a tcp user of an asynchronous error;
        !           356:  * store error as soft error, but wake up user
        !           357:  * (for now, won't do anything until can select for soft error).
        !           358:  */
        !           359: tcp_notify(inp, error)
        !           360:        register struct inpcb *inp;
        !           361:        int error;
        !           362: {
        !           363: 
        !           364:        ((struct tcpcb *)inp->inp_ppcb)->t_softerror = error;
        !           365:        wakeup((caddr_t) &inp->inp_socket->so_timeo);
        !           366:        sorwakeup(inp->inp_socket);
        !           367:        sowwakeup(inp->inp_socket);
        !           368: }
        !           369: 
        !           370: tcp_ctlinput(cmd, sa, ip)
        !           371:        int cmd;
        !           372:        struct sockaddr *sa;
        !           373:        register struct ip *ip;
        !           374: {
        !           375:        register struct tcphdr *th;
        !           376:        extern struct in_addr zeroin_addr;
        !           377:        extern u_char inetctlerrmap[];
        !           378:        int (*notify)() = tcp_notify, tcp_quench();
        !           379: 
        !           380:        if (cmd == PRC_QUENCH)
        !           381:                notify = tcp_quench;
        !           382:        else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0)
        !           383:                return;
        !           384:        if (ip) {
        !           385:                th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2));
        !           386:                in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport,
        !           387:                        cmd, notify);
        !           388:        } else
        !           389:                in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify);
        !           390: }
        !           391: 
        !           392: /*
        !           393:  * When a source quench is received, close congestion window
        !           394:  * to one segment.  We will gradually open it again as we proceed.
        !           395:  */
        !           396: tcp_quench(inp)
        !           397:        struct inpcb *inp;
        !           398: {
        !           399:        struct tcpcb *tp = intotcpcb(inp);
        !           400: 
        !           401:        if (tp)
        !           402:                tp->snd_cwnd = tp->t_maxseg;
        !           403: }

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