/* * Copyright (c) 1982, 1986, 1988 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms are permitted * provided that this notice is preserved and that due credit is given * to the University of California at Berkeley. The name of the University * may not be used to endorse or promote products derived from this * software without specific prior written permission. This software * is provided ``as is'' without express or implied warranty. * * @(#)tcp_input.c 7.15.1.2 (Berkeley) 3/16/88 */ #include "param.h" #include "systm.h" #include "mbuf.h" #include "protosw.h" #include "socket.h" #include "socketvar.h" #include "errno.h" #include "../net/if.h" #include "../net/route.h" #include "domain.h" #include "in.h" #include "in_pcb.h" #include "in_systm.h" #include "ip.h" #include "ip_var.h" #include "tcp.h" #include "tcp_fsm.h" #include "tcp_seq.h" #include "tcp_timer.h" #include "tcp_var.h" #include "tcpip.h" #include "tcp_debug.h" int tcpprintfs = 0; int tcpcksum = 1; int tcprexmtthresh = 3; struct tcpiphdr tcp_saveti; extern tcpnodelack; struct tcpcb *tcp_newtcpcb(); /* * Insert segment ti into reassembly queue of tcp with * control block tp. Return TH_FIN if reassembly now includes * a segment with FIN. The macro form does the common case inline * (segment is the next to be received on an established connection, * and the queue is empty), avoiding linkage into and removal * from the queue and repetition of various conversions. */ #define TCP_REASS(tp, ti, m, so, flags) { \ if ((ti)->ti_seq == (tp)->rcv_nxt && \ (tp)->seg_next == (struct tcpiphdr *)(tp) && \ (tp)->t_state == TCPS_ESTABLISHED) { \ (tp)->rcv_nxt += (ti)->ti_len; \ flags = (ti)->ti_flags & TH_FIN; \ tcpstat.tcps_rcvpack++;\ tcpstat.tcps_rcvbyte += (ti)->ti_len;\ sbappend(&(so)->so_rcv, (m)); \ sorwakeup(so); \ } else \ (flags) = tcp_reass((tp), (ti)); \ } tcp_reass(tp, ti) register struct tcpcb *tp; register struct tcpiphdr *ti; { register struct tcpiphdr *q; struct socket *so = tp->t_inpcb->inp_socket; struct mbuf *m; int flags; /* * Call with ti==0 after become established to * force pre-ESTABLISHED data up to user socket. */ if (ti == 0) goto present; /* * Find a segment which begins after this one does. */ for (q = tp->seg_next; q != (struct tcpiphdr *)tp; q = (struct tcpiphdr *)q->ti_next) if (SEQ_GT(q->ti_seq, ti->ti_seq)) break; /* * If there is a preceding segment, it may provide some of * our data already. If so, drop the data from the incoming * segment. If it provides all of our data, drop us. */ if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { register int i; q = (struct tcpiphdr *)q->ti_prev; /* conversion to int (in i) handles seq wraparound */ i = q->ti_seq + q->ti_len - ti->ti_seq; if (i > 0) { if (i >= ti->ti_len) { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += ti->ti_len; goto drop; } m_adj(dtom(ti), i); ti->ti_len -= i; ti->ti_seq += i; } q = (struct tcpiphdr *)(q->ti_next); } tcpstat.tcps_rcvoopack++; tcpstat.tcps_rcvoobyte += ti->ti_len; /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ while (q != (struct tcpiphdr *)tp) { register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; if (i <= 0) break; if (i < q->ti_len) { q->ti_seq += i; q->ti_len -= i; m_adj(dtom(q), i); break; } q = (struct tcpiphdr *)q->ti_next; m = dtom(q->ti_prev); remque(q->ti_prev); m_freem(m); } /* * Stick new segment in its place. */ insque(ti, q->ti_prev); present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (TCPS_HAVERCVDSYN(tp->t_state) == 0) return (0); ti = tp->seg_next; if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) return (0); if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) return (0); do { tp->rcv_nxt += ti->ti_len; flags = ti->ti_flags & TH_FIN; remque(ti); m = dtom(ti); ti = (struct tcpiphdr *)ti->ti_next; if (so->so_state & SS_CANTRCVMORE) m_freem(m); else sbappend(&so->so_rcv, m); } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); sorwakeup(so); return (flags); drop: m_freem(dtom(ti)); return (0); } /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ tcp_input(m0) struct mbuf *m0; { register struct tcpiphdr *ti; struct inpcb *inp; register struct mbuf *m; struct mbuf *om = 0; int len, tlen, off; register struct tcpcb *tp = 0; register int tiflags; struct socket *so; int todrop, acked, ourfinisacked, needoutput = 0; short ostate; struct in_addr laddr; int dropsocket = 0; long iss = 0; tcpstat.tcps_rcvtotal++; /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ m = m0; ti = mtod(m, struct tcpiphdr *); if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) ip_stripoptions((struct ip *)ti, (struct mbuf *)0); if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { tcpstat.tcps_rcvshort++; return; } ti = mtod(m, struct tcpiphdr *); } /* * Checksum extended TCP header and data. */ tlen = ((struct ip *)ti)->ip_len; len = sizeof (struct ip) + tlen; if (tcpcksum) { ti->ti_next = ti->ti_prev = 0; ti->ti_x1 = 0; ti->ti_pad = 0; ti->ti_len = (u_short)tlen; ti->ti_len = htons((u_short)ti->ti_len); if (ti->ti_sum = in_cksum(m, len)) { if (tcpprintfs) printf("tcp sum: src %x\n", ti->ti_src); tcpstat.tcps_rcvbadsum++; goto drop; } } /* * Check that TCP offset makes sense, * pull out TCP options and adjust length. */ off = ti->ti_off << 2; if (off < sizeof (struct tcphdr) || off > tlen) { if (tcpprintfs) printf("tcp off: src %x off %d\n", ti->ti_src, off); tcpstat.tcps_rcvbadoff++; goto drop; } tlen -= off; ti->ti_len = tlen; if (off > sizeof (struct tcphdr)) { if (m->m_len < sizeof(struct ip) + off) { if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { tcpstat.tcps_rcvshort++; return; } ti = mtod(m, struct tcpiphdr *); } om = m_get(M_DONTWAIT, MT_DATA); if (om == 0) goto drop; om->m_len = off - sizeof (struct tcphdr); { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); m->m_len -= om->m_len; bcopy(op+om->m_len, op, (unsigned)(m->m_len-sizeof (struct tcpiphdr))); } } tiflags = ti->ti_flags; /* * Drop TCP and IP headers; TCP options were dropped above. */ m->m_off += sizeof(struct tcpiphdr); m->m_len -= sizeof(struct tcpiphdr); /* * Convert TCP protocol specific fields to host format. */ ti->ti_seq = ntohl(ti->ti_seq); ti->ti_ack = ntohl(ti->ti_ack); ti->ti_win = ntohs(ti->ti_win); ti->ti_urp = ntohs(ti->ti_urp); /* * Locate pcb for segment. */ findpcb: inp = in_pcblookup (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, INPLOOKUP_WILDCARD); /* * If the state is CLOSED (i.e., TCB does not exist) then * all data in the incoming segment is discarded. * If the TCB exists but is in CLOSED state, it is embryonic, * but should either do a listen or a connect soon. */ if (inp == 0) goto dropwithreset; tp = intotcpcb(inp); if (tp == 0) goto dropwithreset; if (tp->t_state == TCPS_CLOSED) goto drop; so = inp->inp_socket; if (so->so_options & SO_DEBUG) { ostate = tp->t_state; tcp_saveti = *ti; } if (so->so_options & SO_ACCEPTCONN) { so = sonewconn(so); if (so == 0) goto drop; /* * This is ugly, but .... * * Mark socket as temporary until we're * committed to keeping it. The code at * ``drop'' and ``dropwithreset'' check the * flag dropsocket to see if the temporary * socket created here should be discarded. * We mark the socket as discardable until * we're committed to it below in TCPS_LISTEN. */ dropsocket++; inp = (struct inpcb *)so->so_pcb; inp->inp_laddr = ti->ti_dst; inp->inp_lport = ti->ti_dport; #if BSD>=43 inp->inp_options = ip_srcroute(); #endif tp = intotcpcb(inp); tp->t_state = TCPS_LISTEN; } /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_idle = 0; tp->t_timer[TCPT_KEEP] = tcp_keepidle; /* * Process options if not in LISTEN state, * else do it below (after getting remote address). */ if (om && tp->t_state != TCPS_LISTEN) { tcp_dooptions(tp, om, ti); om = 0; } /* * Calculate amount of space in receive window, * and then do TCP input processing. * Receive window is amount of space in rcv queue, * but not less than advertised window. */ { int win; win = sbspace(&so->so_rcv); if (win < 0) win = 0; tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } switch (tp->t_state) { /* * If the state is LISTEN then ignore segment if it contains an RST. * If the segment contains an ACK then it is bad and send a RST. * If it does not contain a SYN then it is not interesting; drop it. * Don't bother responding if the destination was a broadcast. * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial * tp->iss, and send a segment: * * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. * Fill in remote peer address fields if not previously specified. * Enter SYN_RECEIVED state, and process any other fields of this * segment in this state. */ case TCPS_LISTEN: { struct mbuf *am; register struct sockaddr_in *sin; if (tiflags & TH_RST) goto drop; if (tiflags & TH_ACK) goto dropwithreset; if ((tiflags & TH_SYN) == 0) goto drop; if (in_broadcast(ti->ti_dst)) goto drop; am = m_get(M_DONTWAIT, MT_SONAME); if (am == NULL) goto drop; am->m_len = sizeof (struct sockaddr_in); sin = mtod(am, struct sockaddr_in *); sin->sin_family = AF_INET; sin->sin_addr = ti->ti_src; sin->sin_port = ti->ti_sport; laddr = inp->inp_laddr; if (inp->inp_laddr.s_addr == INADDR_ANY) inp->inp_laddr = ti->ti_dst; if (in_pcbconnect(inp, am)) { inp->inp_laddr = laddr; (void) m_free(am); goto drop; } (void) m_free(am); tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); dropsocket = 0; /* socket is already gone */ goto drop; } if (om) { tcp_dooptions(tp, om, ti); om = 0; } if (iss) tp->iss = iss; else tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; tp->irs = ti->ti_seq; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; tp->t_state = TCPS_SYN_RECEIVED; tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; dropsocket = 0; /* committed to socket */ tcpstat.tcps_accepts++; goto trimthenstep6; } /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((tiflags & TH_ACK) && (SEQ_LEQ(ti->ti_ack, tp->iss) || SEQ_GT(ti->ti_ack, tp->snd_max))) goto dropwithreset; if (tiflags & TH_RST) { if (tiflags & TH_ACK) tp = tcp_drop(tp, ECONNREFUSED); goto drop; } if ((tiflags & TH_SYN) == 0) goto drop; if (tiflags & TH_ACK) { tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; } tp->t_timer[TCPT_REXMT] = 0; tp->irs = ti->ti_seq; tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { tcpstat.tcps_connects++; soisconnected(so); tp->t_state = TCPS_ESTABLISHED; tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); (void) tcp_reass(tp, (struct tcpiphdr *)0); /* * if we didn't have to retransmit the SYN, * use its rtt as our initial srtt & rtt var. */ if (tp->t_rtt) { tp->t_srtt = tp->t_rtt << 3; tp->t_rttvar = tp->t_rtt << 1; TCPT_RANGESET(tp->t_rxtcur, ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, TCPTV_MIN, TCPTV_REXMTMAX); tp->t_rtt = 0; } } else tp->t_state = TCPS_SYN_RECEIVED; trimthenstep6: /* * Advance ti->ti_seq to correspond to first data byte. * If data, trim to stay within window, * dropping FIN if necessary. */ ti->ti_seq++; if (ti->ti_len > tp->rcv_wnd) { todrop = ti->ti_len - tp->rcv_wnd; #if BSD>=43 m_adj(m, -todrop); #else /* XXX work around 4.2 m_adj bug */ if (m->m_len) { m_adj(m, -todrop); } else { /* skip tcp/ip header in first mbuf */ m_adj(m->m_next, -todrop); } #endif ti->ti_len = tp->rcv_wnd; tiflags &= ~TH_FIN; tcpstat.tcps_rcvpackafterwin++; tcpstat.tcps_rcvbyteafterwin += todrop; } tp->snd_wl1 = ti->ti_seq - 1; tp->rcv_up = ti->ti_seq; goto step6; } /* * States other than LISTEN or SYN_SENT. * First check that at least some bytes of segment are within * receive window. If segment begins before rcv_nxt, * drop leading data (and SYN); if nothing left, just ack. */ todrop = tp->rcv_nxt - ti->ti_seq; if (todrop > 0) { if (tiflags & TH_SYN) { tiflags &= ~TH_SYN; ti->ti_seq++; if (ti->ti_urp > 1) ti->ti_urp--; else tiflags &= ~TH_URG; todrop--; } if (todrop > ti->ti_len || todrop == ti->ti_len && (tiflags&TH_FIN) == 0) { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += ti->ti_len; /* * If segment is just one to the left of the window, * check two special cases: * 1. Don't toss RST in response to 4.2-style keepalive. * 2. If the only thing to drop is a FIN, we can drop * it, but check the ACK or we will get into FIN * wars if our FINs crossed (both CLOSING). * In either case, send ACK to resynchronize, * but keep on processing for RST or ACK. */ if ((tiflags & TH_FIN && todrop == ti->ti_len + 1) #ifdef TCP_COMPAT_42 || (tiflags & TH_RST && ti->ti_seq == tp->rcv_nxt - 1) #endif ) { todrop = ti->ti_len; tiflags &= ~TH_FIN; tp->t_flags |= TF_ACKNOW; } else goto dropafterack; } else { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += todrop; } m_adj(m, todrop); ti->ti_seq += todrop; ti->ti_len -= todrop; if (ti->ti_urp > todrop) ti->ti_urp -= todrop; else { tiflags &= ~TH_URG; ti->ti_urp = 0; } } /* * If new data are received on a connection after the * user processes are gone, then RST the other end. */ if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { tp = tcp_close(tp); tcpstat.tcps_rcvafterclose++; goto dropwithreset; } /* * If segment ends after window, drop trailing data * (and PUSH and FIN); if nothing left, just ACK. */ todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); if (todrop > 0) { tcpstat.tcps_rcvpackafterwin++; if (todrop >= ti->ti_len) { tcpstat.tcps_rcvbyteafterwin += ti->ti_len; /* * If a new connection request is received * while in TIME_WAIT, drop the old connection * and start over if the sequence numbers * are above the previous ones. */ if (tiflags & TH_SYN && tp->t_state == TCPS_TIME_WAIT && SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { iss = tp->rcv_nxt + TCP_ISSINCR; (void) tcp_close(tp); goto findpcb; } /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. Continue processing, but * remember to ack. Otherwise, drop segment * and ack. */ if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { tp->t_flags |= TF_ACKNOW; tcpstat.tcps_rcvwinprobe++; } else goto dropafterack; } else tcpstat.tcps_rcvbyteafterwin += todrop; #if BSD>=43 m_adj(m, -todrop); #else /* XXX work around m_adj bug */ if (m->m_len) { m_adj(m, -todrop); } else { /* skip tcp/ip header in first mbuf */ m_adj(m->m_next, -todrop); } #endif ti->ti_len -= todrop; tiflags &= ~(TH_PUSH|TH_FIN); } /* * If the RST bit is set examine the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK, TIME_WAIT STATES * Close the tcb. */ if (tiflags&TH_RST) switch (tp->t_state) { case TCPS_SYN_RECEIVED: so->so_error = ECONNREFUSED; goto close; case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: so->so_error = ECONNRESET; close: tp->t_state = TCPS_CLOSED; tcpstat.tcps_drops++; tp = tcp_close(tp); goto drop; case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: tp = tcp_close(tp); goto drop; } /* * If a SYN is in the window, then this is an * error and we send an RST and drop the connection. */ if (tiflags & TH_SYN) { tp = tcp_drop(tp, ECONNRESET); goto dropwithreset; } /* * If the ACK bit is off we drop the segment and return. */ if ((tiflags & TH_ACK) == 0) goto drop; /* * Ack processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state if the ack ACKs our SYN then enter * ESTABLISHED state and continue processing, otherwise * send an RST. */ case TCPS_SYN_RECEIVED: if (SEQ_GT(tp->snd_una, ti->ti_ack) || SEQ_GT(ti->ti_ack, tp->snd_max)) goto dropwithreset; tcpstat.tcps_connects++; soisconnected(so); tp->t_state = TCPS_ESTABLISHED; tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); (void) tcp_reass(tp, (struct tcpiphdr *)0); tp->snd_wl1 = ti->ti_seq - 1; /* fall into ... */ /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < ti->ti_ack <= tp->snd_max * then advance tp->snd_una to ti->ti_ack and drop * data from the retransmission queue. If this ACK reflects * more up to date window information we update our window information. */ case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { if (ti->ti_len == 0 && ti->ti_win == tp->snd_wnd) { tcpstat.tcps_rcvdupack++; /* * If we have outstanding data (not a * window probe), this is a completely * duplicate ack (ie, window info didn't * change), the ack is the biggest we've * seen and we've seen exactly our rexmt * threshhold of them, assume a packet * has been dropped and retransmit it. * Kludge snd_nxt & the congestion * window so we send only this one * packet. If this packet fills the * only hole in the receiver's seq. * space, the next real ack will fully * open our window. This means we * have to do the usual slow-start to * not overwhelm an intermediate gateway * with a burst of packets. Leave * here with the congestion window set * to allow 2 packets on the next real * ack and the exp-to-linear thresh * set for half the current window * size (since we know we're losing at * the current window size). */ if (tp->t_timer[TCPT_REXMT] == 0 || ti->ti_ack != tp->snd_una) tp->t_dupacks = 0; else if (++tp->t_dupacks == tcprexmtthresh) { tcp_seq onxt = tp->snd_nxt; u_int win = MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; tp->t_timer[TCPT_REXMT] = 0; tp->t_rtt = 0; tp->snd_nxt = ti->ti_ack; tp->snd_cwnd = tp->t_maxseg; (void) tcp_output(tp); if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; goto drop; } } else tp->t_dupacks = 0; break; } tp->t_dupacks = 0; if (SEQ_GT(ti->ti_ack, tp->snd_max)) { tcpstat.tcps_rcvacktoomuch++; goto dropafterack; } acked = ti->ti_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; /* * If transmit timer is running and timed sequence * number was acked, update smoothed round trip time. * Since we now have an rtt measurement, cancel the * timer backoff (cf., Phil Karn's retransmit alg.). * Recompute the initial retransmit timer. */ if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { tcpstat.tcps_rttupdated++; if (tp->t_srtt != 0) { register short delta; /* * srtt is stored as fixed point with 3 bits * after the binary point (i.e., scaled by 8). * The following magic is equivalent * to the smoothing algorithm in rfc793 * with an alpha of .875 * (srtt = rtt/8 + srtt*7/8 in fixed point). * Adjust t_rtt to origin 0. */ delta = tp->t_rtt - 1 - (tp->t_srtt >> 3); if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1; /* * We accumulate a smoothed rtt variance * (actually, a smoothed mean difference), * then set the retransmit timer to smoothed * rtt + 2 times the smoothed variance. * rttvar is stored as fixed point * with 2 bits after the binary point * (scaled by 4). The following is equivalent * to rfc793 smoothing with an alpha of .75 * (rttvar = rttvar*3/4 + |delta| / 4). * This replaces rfc793's wired-in beta. */ if (delta < 0) delta = -delta; delta -= (tp->t_rttvar >> 2); if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1; } else { /* * No rtt measurement yet - use the * unsmoothed rtt. Set the variance * to half the rtt (so our first * retransmit happens at 2*rtt) */ tp->t_srtt = tp->t_rtt << 3; tp->t_rttvar = tp->t_rtt << 1; } tp->t_rtt = 0; tp->t_rxtshift = 0; TCPT_RANGESET(tp->t_rxtcur, ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, TCPTV_MIN, TCPTV_REXMTMAX); } /* * If all outstanding data is acked, stop retransmit * timer and remember to restart (more output or persist). * If there is more data to be acked, restart retransmit * timer, using current (possibly backed-off) value. */ if (ti->ti_ack == tp->snd_max) { tp->t_timer[TCPT_REXMT] = 0; needoutput = 1; } else if (tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; /* * When new data is acked, open the congestion window. * If the window gives us less than ssthresh packets * in flight, open exponentially (maxseg per packet). * Otherwise open linearly (maxseg per window, * or maxseg^2 / cwnd per packet). */ { u_long incr = tp->t_maxseg; if (tp->snd_cwnd > tp->snd_ssthresh) incr = MAX((long)(incr * incr / tp->snd_cwnd), 1L); tp->snd_cwnd = MIN((long)(tp->snd_cwnd + incr), IP_MAXPACKET); /* XXX */ } if (acked > so->so_snd.sb_cc) { tp->snd_wnd -= so->so_snd.sb_cc; sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { sbdrop(&so->so_snd, acked); tp->snd_wnd -= acked; ourfinisacked = 0; } if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) sowwakeup(so); tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; switch (tp->t_state) { /* * In FIN_WAIT_1 STATE in addition to the processing * for the ESTABLISHED state if our FIN is now acknowledged * then enter FIN_WAIT_2. */ case TCPS_FIN_WAIT_1: if (ourfinisacked) { /* * If we can't receive any more * data, then closing user can proceed. * Starting the timer is contrary to the * specification, but if we don't get a FIN * we'll hang forever. */ if (so->so_state & SS_CANTRCVMORE) { soisdisconnected(so); tp->t_timer[TCPT_2MSL] = tcp_maxidle; } tp->t_state = TCPS_FIN_WAIT_2; } break; /* * In CLOSING STATE in addition to the processing for * the ESTABLISHED state if the ACK acknowledges our FIN * then enter the TIME-WAIT state, otherwise ignore * the segment. */ case TCPS_CLOSING: if (ourfinisacked) { tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; soisdisconnected(so); } break; /* * In LAST_ACK, we may still be waiting for data to drain * and/or to be acked, as well as for the ack of our FIN. * If our FIN is now acknowledged, delete the TCB, * enter the closed state and return. */ case TCPS_LAST_ACK: if (ourfinisacked) { tp = tcp_close(tp); goto drop; } break; /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ case TCPS_TIME_WAIT: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; goto dropafterack; } } step6: /* * Update window information. * Don't look at window if no ACK: TAC's send garbage on first SYN. */ if ((tiflags & TH_ACK) && (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) { /* keep track of pure window updates */ if (ti->ti_len == 0 && tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = ti->ti_win; tp->snd_wl1 = ti->ti_seq; tp->snd_wl2 = ti->ti_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = 1; } /* * Process segments with URG. */ if ((tiflags & TH_URG) && ti->ti_urp && TCPS_HAVERCVDFIN(tp->t_state) == 0) { /* * This is a kludge, but if we receive and accept * random urgent pointers, we'll crash in * soreceive. It's hard to imagine someone * actually wanting to send this much urgent data. */ if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { ti->ti_urp = 0; /* XXX */ tiflags &= ~TH_URG; /* XXX */ goto dodata; /* XXX */ } /* * If this segment advances the known urgent pointer, * then mark the data stream. This should not happen * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since * a FIN has been received from the remote side. * In these states we ignore the URG. * * According to RFC961 (Assigned Protocols), * the urgent pointer points to the last octet * of urgent data. We continue, however, * to consider it to indicate the first octet * of data past the urgent section * as the original spec states. */ if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { tp->rcv_up = ti->ti_seq + ti->ti_urp; so->so_oobmark = so->so_rcv.sb_cc + (tp->rcv_up - tp->rcv_nxt) - 1; if (so->so_oobmark == 0) so->so_state |= SS_RCVATMARK; sohasoutofband(so); tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); } /* * Remove out of band data so doesn't get presented to user. * This can happen independent of advancing the URG pointer, * but if two URG's are pending at once, some out-of-band * data may creep in... ick. */ if (ti->ti_urp <= ti->ti_len #ifdef SO_OOBINLINE && (so->so_options & SO_OOBINLINE) == 0 #endif ) tcp_pulloutofband(so, ti); } else /* * If no out of band data is expected, * pull receive urgent pointer along * with the receive window. */ if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) tp->rcv_up = tp->rcv_nxt; dodata: /* XXX */ /* * Process the segment text, merging it into the TCP sequencing queue, * and arranging for acknowledgment of receipt if necessary. * This process logically involves adjusting tp->rcv_wnd as data * is presented to the user (this happens in tcp_usrreq.c, * case PRU_RCVD). If a FIN has already been received on this * connection then we just ignore the text. */ if ((ti->ti_len || (tiflags&TH_FIN)) && TCPS_HAVERCVDFIN(tp->t_state) == 0) { TCP_REASS(tp, ti, m, so, tiflags); if (tcpnodelack == 0) tp->t_flags |= TF_DELACK; else tp->t_flags |= TF_ACKNOW; /* * Note the amount of data that peer has sent into * our window, in order to estimate the sender's * buffer size. */ len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); if (len > tp->max_rcvd) tp->max_rcvd = len; } else { m_freem(m); tiflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. */ if (tiflags & TH_FIN) { if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { socantrcvmore(so); tp->t_flags |= TF_ACKNOW; tp->rcv_nxt++; } switch (tp->t_state) { /* * In SYN_RECEIVED and ESTABLISHED STATES * enter the CLOSE_WAIT state. */ case TCPS_SYN_RECEIVED: case TCPS_ESTABLISHED: tp->t_state = TCPS_CLOSE_WAIT; break; /* * If still in FIN_WAIT_1 STATE FIN has not been acked so * enter the CLOSING state. */ case TCPS_FIN_WAIT_1: tp->t_state = TCPS_CLOSING; break; /* * In FIN_WAIT_2 state enter the TIME_WAIT state, * starting the time-wait timer, turning off the other * standard timers. */ case TCPS_FIN_WAIT_2: tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; break; } } if (so->so_options & SO_DEBUG) tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) (void) tcp_output(tp); return; dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. */ if (tiflags & TH_RST) goto drop; m_freem(m); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); return; dropwithreset: if (om) { (void) m_free(om); om = 0; } /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. * Don't bother to respond if destination was broadcast. */ if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) goto drop; if (tiflags & TH_ACK) tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); else { if (tiflags & TH_SYN) ti->ti_len++; tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, TH_RST|TH_ACK); } /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; drop: if (om) (void) m_free(om); /* * Drop space held by incoming segment and return. */ if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); m_freem(m); /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; } tcp_dooptions(tp, om, ti) struct tcpcb *tp; struct mbuf *om; struct tcpiphdr *ti; { register u_char *cp; int opt, optlen, cnt; cp = mtod(om, u_char *); cnt = om->m_len; for (; cnt > 0; cnt -= optlen, cp += optlen) { opt = UCHAR(cp[0]); if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { optlen = UCHAR(cp[1]); if (optlen <= 0) break; } switch (opt) { default: break; case TCPOPT_MAXSEG: if (optlen != 4) continue; if (!(ti->ti_flags & TH_SYN)) continue; tp->t_maxseg = *(u_short *)(cp + 2); tp->t_maxseg = ntohs((u_short)tp->t_maxseg); tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); break; } } (void) m_free(om); } /* * Pull out of band byte out of a segment so * it doesn't appear in the user's data queue. * It is still reflected in the segment length for * sequencing purposes. */ tcp_pulloutofband(so, ti) struct socket *so; struct tcpiphdr *ti; { register struct mbuf *m; int cnt = ti->ti_urp - 1; m = dtom(ti); while (cnt >= 0) { if (m->m_len > cnt) { char *cp = mtod(m, caddr_t) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); m->m_len--; return; } cnt -= m->m_len; m = m->m_next; if (m == 0) break; } panic("tcp_pulloutofband"); } /* * Determine a reasonable value for maxseg size. * If the route is known, use one that can be handled * on the given interface without forcing IP to fragment. * If bigger than an mbuf cluster (MCLBYTES), round down to nearest size * to utilize large mbufs. * If interface pointer is unavailable, or the destination isn't local, * use a conservative size (512 or the default IP max size, but no more * than the mtu of the interface through which we route), * as we can't discover anything about intervening gateways or networks. * We also initialize the congestion/slow start window to be a single * segment if the destination isn't local; this information should * probably all be saved with the routing entry at the transport level. * * This is ugly, and doesn't belong at this level, but has to happen somehow. */ tcp_mss(tp) register struct tcpcb *tp; { struct route *ro; struct ifnet *ifp; int mss; struct inpcb *inp; inp = tp->t_inpcb; ro = &inp->inp_route; if ((ro->ro_rt == (struct rtentry *)0) || (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { /* No route yet, so try to acquire one */ if (inp->inp_faddr.s_addr != INADDR_ANY) { ro->ro_dst.sa_family = AF_INET; ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = inp->inp_faddr; rtalloc(ro); } if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) return (TCP_MSS); } mss = ifp->if_mtu - sizeof(struct tcpiphdr); #if (MCLBYTES & (MCLBYTES - 1)) == 0 if (mss > MCLBYTES) mss &= ~(MCLBYTES-1); #else if (mss > MCLBYTES) mss = mss / MCLBYTES * MCLBYTES; #endif if (in_localaddr(inp->inp_faddr)) return (mss); mss = MIN(mss, TCP_MSS); tp->snd_cwnd = mss; return (mss); } #if BSD<43 /* XXX this belongs in netinet/in.c */ in_localaddr(in) struct in_addr in; { register u_long i = ntohl(in.s_addr); register struct ifnet *ifp; register struct sockaddr_in *sin; register u_long mask; if (IN_CLASSA(i)) mask = IN_CLASSA_NET; else if (IN_CLASSB(i)) mask = IN_CLASSB_NET; else if (IN_CLASSC(i)) mask = IN_CLASSC_NET; else return (0); i &= mask; for (ifp = ifnet; ifp; ifp = ifp->if_next) { if (ifp->if_addr.sa_family != AF_INET) continue; sin = (struct sockaddr_in *)&ifp->if_addr; if ((sin->sin_addr.s_addr & mask) == i) return (1); } return (0); } #endif