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[unix-history] / usr / src / sys / netinet / tcp_input.c
/*
* Copyright (c) 1982, 1986 Regents of the University of California.
* All rights reserved. The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*
* @(#)tcp_input.c 7.2 (Berkeley) %G%
*/
#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 "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;
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, needoutput = 0;
short ostate;
struct in_addr laddr;
int dropsocket = 0;
int 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_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 (inp == 0)
goto dropwithreset;
tp = intotcpcb(inp);
if (tp == 0)
goto dropwithreset;
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;
inp->inp_options = ip_srcroute();
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] = TCPTV_KEEP;
/*
* 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:
* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
* 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;
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;
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 (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);
} 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;
m_adj(m, -todrop);
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;
goto dropafterack;
}
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 (tp->rcv_wnd == 0) {
/*
* If window is closed can only take segments at
* window edge, and have to drop data and PUSH from
* incoming segments.
*
* If new data is 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 (tp->rcv_nxt != ti->ti_seq) {
tcpstat.tcps_rcvpackafterwin++;
tcpstat.tcps_rcvbyteafterwin += ti->ti_len;
goto dropafterack;
}
if (ti->ti_len > 0) {
if (ti->ti_len == 1)
tcpstat.tcps_rcvwinprobe++;
else {
tcpstat.tcps_rcvpackafterwin++;
tcpstat.tcps_rcvbyteafterwin += ti->ti_len;
}
m_adj(m, ti->ti_len);
ti->ti_len = 0;
tiflags &= ~(TH_PUSH|TH_FIN);
}
} else {
/*
* 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) {
if (todrop >= 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 (todrop == 1)
tcpstat.tcps_rcvwinprobe++;
else {
tcpstat.tcps_rcvpackafterwin++;
tcpstat.tcps_rcvbyteafterwin += todrop;
}
goto dropafterack;
}
tcpstat.tcps_rcvpackafterwin++;
tcpstat.tcps_rcvbyteafterwin += todrop;
m_adj(m, -todrop);
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:
tp = tcp_drop(tp, ECONNREFUSED);
goto drop;
case TCPS_ESTABLISHED:
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
tp = tcp_drop(tp, ECONNRESET);
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, othewise
* 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;
tp->snd_una++; /* SYN acked */
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
tp->t_timer[TCPT_REXMT] = 0;
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)
tcpstat.tcps_rcvdupack++;
break;
}
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.
*/
if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) {
tcpstat.tcps_rttupdated++;
if (tp->t_srtt == 0)
tp->t_srtt = tp->t_rtt;
else
tp->t_srtt =
tcp_alpha * tp->t_srtt +
(1 - tcp_alpha) * tp->t_rtt;
tp->t_rtt = 0;
}
/*
* 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.
*/
if (ti->ti_ack == tp->snd_max) {
tp->t_timer[TCPT_REXMT] = 0;
needoutput = 1;
} else if (tp->t_timer[TCPT_PERSIST] == 0) {
TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
tp->t_rxtshift = 0;
}
/*
* When new data is acked, open the congestion window a bit.
*/
tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535);
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);
#define ourfinisacked (acked > 0)
} else {
sbdrop(&so->so_snd, acked);
tp->snd_wnd -= acked;
acked = 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] = TCPTV_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;
/*
* The only thing that can arrive in LAST_ACK state
* is an acknowledgment 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;
/*
* 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;
}
#undef ourfinisacked
}
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++;
tcpstat.tcps_rcvdupack--;
}
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 &&
(so->so_options & SO_OOBINLINE) == 0)
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_nxt - tp->rcv_adv);
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;
if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0);
tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK);
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 = cp[0];
if (opt == TCPOPT_EOL)
break;
if (opt == TCPOPT_NOP)
optlen = 1;
else {
optlen = 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 a page (CLBYTES), round down to nearest pagesize
* to utilize pagesize 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.
*
* 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 (CLBYTES & (CLBYTES - 1)) == 0
if (mss > CLBYTES)
mss &= ~(CLBYTES-1);
#else
if (mss > CLBYTES)
mss = mss / CLBYTES * CLBYTES;
#endif
if (in_localaddr(inp->inp_faddr))
return (mss);
return (MIN(mss, TCP_MSS));
}
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.