--- /dev/null
+/*
+ * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
+ * The Regents of the University of California. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * @(#)tcp_input.c 8.5 (Berkeley) 4/10/94
+ * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
+ */
+
+/*
+ * Changes and additions relating to SLiRP
+ * Copyright (c) 1995 Danny Gasparovski.
+ *
+ * Please read the file COPYRIGHT for the
+ * terms and conditions of the copyright.
+ */
+
+#include <slirp.h>
+#include "ip_icmp.h"
+
+#define TCPREXMTTHRESH 3
+
+#define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
+
+/* for modulo comparisons of timestamps */
+#define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
+#define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
+
+/*
+ * 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.
+ * Set DELACK for segments received in order, but ack immediately
+ * when segments are out of order (so fast retransmit can work).
+ */
+#ifdef TCP_ACK_HACK
+#define TCP_REASS(tp, ti, m, so, flags) {\
+ if ((ti)->ti_seq == (tp)->rcv_nxt && \
+ tcpfrag_list_empty(tp) && \
+ (tp)->t_state == TCPS_ESTABLISHED) {\
+ if (ti->ti_flags & TH_PUSH) \
+ tp->t_flags |= TF_ACKNOW; \
+ else \
+ tp->t_flags |= TF_DELACK; \
+ (tp)->rcv_nxt += (ti)->ti_len; \
+ flags = (ti)->ti_flags & TH_FIN; \
+ if (so->so_emu) { \
+ if (tcp_emu((so),(m))) sbappend((so), (m)); \
+ } else \
+ sbappend((so), (m)); \
+ } else {\
+ (flags) = tcp_reass((tp), (ti), (m)); \
+ tp->t_flags |= TF_ACKNOW; \
+ } \
+}
+#else
+#define TCP_REASS(tp, ti, m, so, flags) { \
+ if ((ti)->ti_seq == (tp)->rcv_nxt && \
+ tcpfrag_list_empty(tp) && \
+ (tp)->t_state == TCPS_ESTABLISHED) { \
+ tp->t_flags |= TF_DELACK; \
+ (tp)->rcv_nxt += (ti)->ti_len; \
+ flags = (ti)->ti_flags & TH_FIN; \
+ if (so->so_emu) { \
+ if (tcp_emu((so),(m))) sbappend(so, (m)); \
+ } else \
+ sbappend((so), (m)); \
+ } else { \
+ (flags) = tcp_reass((tp), (ti), (m)); \
+ tp->t_flags |= TF_ACKNOW; \
+ } \
+}
+#endif
+static void tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt,
+ struct tcpiphdr *ti);
+static void tcp_xmit_timer(register struct tcpcb *tp, int rtt);
+
+static int
+tcp_reass(register struct tcpcb *tp, register struct tcpiphdr *ti,
+ struct mbuf *m)
+{
+ register struct tcpiphdr *q;
+ struct socket *so = tp->t_socket;
+ int flags;
+
+ /*
+ * Call with ti==NULL after become established to
+ * force pre-ESTABLISHED data up to user socket.
+ */
+ if (ti == NULL)
+ goto present;
+
+ /*
+ * Find a segment which begins after this one does.
+ */
+ for (q = tcpfrag_list_first(tp); !tcpfrag_list_end(q, tp);
+ q = tcpiphdr_next(q))
+ 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 (!tcpfrag_list_end(tcpiphdr_prev(q), tp)) {
+ register int i;
+ q = tcpiphdr_prev(q);
+ /* 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) {
+ m_free(m);
+ /*
+ * Try to present any queued data
+ * at the left window edge to the user.
+ * This is needed after the 3-WHS
+ * completes.
+ */
+ goto present; /* ??? */
+ }
+ m_adj(m, i);
+ ti->ti_len -= i;
+ ti->ti_seq += i;
+ }
+ q = tcpiphdr_next(q);
+ }
+ ti->ti_mbuf = m;
+
+ /*
+ * While we overlap succeeding segments trim them or,
+ * if they are completely covered, dequeue them.
+ */
+ while (!tcpfrag_list_end(q, 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(q->ti_mbuf, i);
+ break;
+ }
+ q = tcpiphdr_next(q);
+ m = tcpiphdr_prev(q)->ti_mbuf;
+ remque(tcpiphdr2qlink(tcpiphdr_prev(q)));
+ m_free(m);
+ }
+
+ /*
+ * Stick new segment in its place.
+ */
+ insque(tcpiphdr2qlink(ti), tcpiphdr2qlink(tcpiphdr_prev(q)));
+
+present:
+ /*
+ * Present data to user, advancing rcv_nxt through
+ * completed sequence space.
+ */
+ if (!TCPS_HAVEESTABLISHED(tp->t_state))
+ return (0);
+ ti = tcpfrag_list_first(tp);
+ if (tcpfrag_list_end(ti, 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(tcpiphdr2qlink(ti));
+ m = ti->ti_mbuf;
+ ti = tcpiphdr_next(ti);
+ if (so->so_state & SS_FCANTSENDMORE)
+ m_free(m);
+ else {
+ if (so->so_emu) {
+ if (tcp_emu(so,m)) sbappend(so, m);
+ } else
+ sbappend(so, m);
+ }
+ } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
+ return (flags);
+}
+
+/*
+ * TCP input routine, follows pages 65-76 of the
+ * protocol specification dated September, 1981 very closely.
+ */
+void
+tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
+{
+ struct ip save_ip, *ip;
+ register struct tcpiphdr *ti;
+ caddr_t optp = NULL;
+ int optlen = 0;
+ int len, tlen, off;
+ register struct tcpcb *tp = NULL;
+ register int tiflags;
+ struct socket *so = NULL;
+ int todrop, acked, ourfinisacked, needoutput = 0;
+ int iss = 0;
+ u_long tiwin;
+ int ret;
+ struct ex_list *ex_ptr;
+ Slirp *slirp;
+
+ DEBUG_CALL("tcp_input");
+ DEBUG_ARGS((dfd, " m = %8lx iphlen = %2d inso = %lx\n",
+ (long )m, iphlen, (long )inso ));
+
+ /*
+ * If called with m == 0, then we're continuing the connect
+ */
+ if (m == NULL) {
+ so = inso;
+ slirp = so->slirp;
+
+ /* Re-set a few variables */
+ tp = sototcpcb(so);
+ m = so->so_m;
+ so->so_m = NULL;
+ ti = so->so_ti;
+ tiwin = ti->ti_win;
+ tiflags = ti->ti_flags;
+
+ goto cont_conn;
+ }
+ slirp = m->slirp;
+
+ /*
+ * Get IP and TCP header together in first mbuf.
+ * Note: IP leaves IP header in first mbuf.
+ */
+ ti = mtod(m, struct tcpiphdr *);
+ if (iphlen > sizeof(struct ip )) {
+ ip_stripoptions(m, (struct mbuf *)0);
+ iphlen=sizeof(struct ip );
+ }
+ /* XXX Check if too short */
+
+
+ /*
+ * Save a copy of the IP header in case we want restore it
+ * for sending an ICMP error message in response.
+ */
+ ip=mtod(m, struct ip *);
+ save_ip = *ip;
+ save_ip.ip_len+= iphlen;
+
+ /*
+ * Checksum extended TCP header and data.
+ */
+ tlen = ((struct ip *)ti)->ip_len;
+ tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
+ memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr));
+ ti->ti_x1 = 0;
+ ti->ti_len = htons((uint16_t)tlen);
+ len = sizeof(struct ip ) + tlen;
+ if(cksum(m, len)) {
+ goto drop;
+ }
+
+ /*
+ * Check that TCP offset makes sense,
+ * pull out TCP options and adjust length. XXX
+ */
+ off = ti->ti_off << 2;
+ if (off < sizeof (struct tcphdr) || off > tlen) {
+ goto drop;
+ }
+ tlen -= off;
+ ti->ti_len = tlen;
+ if (off > sizeof (struct tcphdr)) {
+ optlen = off - sizeof (struct tcphdr);
+ optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
+ }
+ tiflags = ti->ti_flags;
+
+ /*
+ * Convert TCP protocol specific fields to host format.
+ */
+ NTOHL(ti->ti_seq);
+ NTOHL(ti->ti_ack);
+ NTOHS(ti->ti_win);
+ NTOHS(ti->ti_urp);
+
+ /*
+ * Drop TCP, IP headers and TCP options.
+ */
+ m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
+ m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
+
+ /*
+ * Locate pcb for segment.
+ */
+findso:
+ so = slirp->tcp_last_so;
+ if (so->so_fport != ti->ti_dport ||
+ so->so_lport != ti->ti_sport ||
+ so->so_laddr.s_addr != ti->ti_src.s_addr ||
+ so->so_faddr.s_addr != ti->ti_dst.s_addr) {
+ so = solookup(&slirp->tcb, ti->ti_src, ti->ti_sport,
+ ti->ti_dst, ti->ti_dport);
+ if (so)
+ slirp->tcp_last_so = so;
+ }
+
+ /*
+ * 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.
+ *
+ * state == CLOSED means we've done socreate() but haven't
+ * attached it to a protocol yet...
+ *
+ * XXX If a TCB does not exist, and the TH_SYN flag is
+ * the only flag set, then create a session, mark it
+ * as if it was LISTENING, and continue...
+ */
+ if (so == NULL) {
+ if (slirp->restricted) {
+ /* Any hostfwds will have an existing socket, so we only get here
+ * for non-hostfwd connections. These should be dropped, unless it
+ * happens to be a guestfwd.
+ */
+ for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
+ if (ex_ptr->ex_fport == ti->ti_dport &&
+ ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
+ break;
+ }
+ }
+ if (!ex_ptr) {
+ goto dropwithreset;
+ }
+ }
+
+ if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
+ goto dropwithreset;
+
+ if ((so = socreate(slirp)) == NULL)
+ goto dropwithreset;
+ if (tcp_attach(so) < 0) {
+ free(so); /* Not sofree (if it failed, it's not insqued) */
+ goto dropwithreset;
+ }
+
+ sbreserve(&so->so_snd, TCP_SNDSPACE);
+ sbreserve(&so->so_rcv, TCP_RCVSPACE);
+
+ so->so_laddr = ti->ti_src;
+ so->so_lport = ti->ti_sport;
+ so->so_faddr = ti->ti_dst;
+ so->so_fport = ti->ti_dport;
+
+ if ((so->so_iptos = tcp_tos(so)) == 0)
+ so->so_iptos = ((struct ip *)ti)->ip_tos;
+
+ tp = sototcpcb(so);
+ tp->t_state = TCPS_LISTEN;
+ }
+
+ /*
+ * If this is a still-connecting socket, this probably
+ * a retransmit of the SYN. Whether it's a retransmit SYN
+ * or something else, we nuke it.
+ */
+ if (so->so_state & SS_ISFCONNECTING)
+ goto drop;
+
+ tp = sototcpcb(so);
+
+ /* XXX Should never fail */
+ if (tp == NULL)
+ goto dropwithreset;
+ if (tp->t_state == TCPS_CLOSED)
+ goto drop;
+
+ tiwin = ti->ti_win;
+
+ /*
+ * Segment received on connection.
+ * Reset idle time and keep-alive timer.
+ */
+ tp->t_idle = 0;
+ if (SO_OPTIONS)
+ tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
+ else
+ tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
+
+ /*
+ * Process options if not in LISTEN state,
+ * else do it below (after getting remote address).
+ */
+ if (optp && tp->t_state != TCPS_LISTEN)
+ tcp_dooptions(tp, (u_char *)optp, optlen, ti);
+
+ /*
+ * Header prediction: check for the two common cases
+ * of a uni-directional data xfer. If the packet has
+ * no control flags, is in-sequence, the window didn't
+ * change and we're not retransmitting, it's a
+ * candidate. If the length is zero and the ack moved
+ * forward, we're the sender side of the xfer. Just
+ * free the data acked & wake any higher level process
+ * that was blocked waiting for space. If the length
+ * is non-zero and the ack didn't move, we're the
+ * receiver side. If we're getting packets in-order
+ * (the reassembly queue is empty), add the data to
+ * the socket buffer and note that we need a delayed ack.
+ *
+ * XXX Some of these tests are not needed
+ * eg: the tiwin == tp->snd_wnd prevents many more
+ * predictions.. with no *real* advantage..
+ */
+ if (tp->t_state == TCPS_ESTABLISHED &&
+ (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
+ ti->ti_seq == tp->rcv_nxt &&
+ tiwin && tiwin == tp->snd_wnd &&
+ tp->snd_nxt == tp->snd_max) {
+ if (ti->ti_len == 0) {
+ if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
+ SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
+ tp->snd_cwnd >= tp->snd_wnd) {
+ /*
+ * this is a pure ack for outstanding data.
+ */
+ if (tp->t_rtt &&
+ SEQ_GT(ti->ti_ack, tp->t_rtseq))
+ tcp_xmit_timer(tp, tp->t_rtt);
+ acked = ti->ti_ack - tp->snd_una;
+ sbdrop(&so->so_snd, acked);
+ tp->snd_una = ti->ti_ack;
+ m_free(m);
+
+ /*
+ * If all outstanding data are acked, stop
+ * retransmit timer, otherwise restart timer
+ * using current (possibly backed-off) value.
+ * If process is waiting for space,
+ * wakeup/selwakeup/signal. If data
+ * are ready to send, let tcp_output
+ * decide between more output or persist.
+ */
+ if (tp->snd_una == tp->snd_max)
+ tp->t_timer[TCPT_REXMT] = 0;
+ else if (tp->t_timer[TCPT_PERSIST] == 0)
+ tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+
+ /*
+ * This is called because sowwakeup might have
+ * put data into so_snd. Since we don't so sowwakeup,
+ * we don't need this.. XXX???
+ */
+ if (so->so_snd.sb_cc)
+ (void) tcp_output(tp);
+
+ return;
+ }
+ } else if (ti->ti_ack == tp->snd_una &&
+ tcpfrag_list_empty(tp) &&
+ ti->ti_len <= sbspace(&so->so_rcv)) {
+ /*
+ * this is a pure, in-sequence data packet
+ * with nothing on the reassembly queue and
+ * we have enough buffer space to take it.
+ */
+ tp->rcv_nxt += ti->ti_len;
+ /*
+ * Add data to socket buffer.
+ */
+ if (so->so_emu) {
+ if (tcp_emu(so,m)) sbappend(so, m);
+ } else
+ sbappend(so, m);
+
+ /*
+ * If this is a short packet, then ACK now - with Nagel
+ * congestion avoidance sender won't send more until
+ * he gets an ACK.
+ *
+ * It is better to not delay acks at all to maximize
+ * TCP throughput. See RFC 2581.
+ */
+ tp->t_flags |= TF_ACKNOW;
+ tcp_output(tp);
+ return;
+ }
+ } /* header prediction */
+ /*
+ * 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: {
+
+ if (tiflags & TH_RST)
+ goto drop;
+ if (tiflags & TH_ACK)
+ goto dropwithreset;
+ if ((tiflags & TH_SYN) == 0)
+ goto drop;
+
+ /*
+ * This has way too many gotos...
+ * But a bit of spaghetti code never hurt anybody :)
+ */
+
+ /*
+ * If this is destined for the control address, then flag to
+ * tcp_ctl once connected, otherwise connect
+ */
+ if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
+ slirp->vnetwork_addr.s_addr) {
+ if (so->so_faddr.s_addr != slirp->vhost_addr.s_addr &&
+ so->so_faddr.s_addr != slirp->vnameserver_addr.s_addr) {
+ /* May be an add exec */
+ for (ex_ptr = slirp->exec_list; ex_ptr;
+ ex_ptr = ex_ptr->ex_next) {
+ if(ex_ptr->ex_fport == so->so_fport &&
+ so->so_faddr.s_addr == ex_ptr->ex_addr.s_addr) {
+ so->so_state |= SS_CTL;
+ break;
+ }
+ }
+ if (so->so_state & SS_CTL) {
+ goto cont_input;
+ }
+ }
+ /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
+ }
+
+ if (so->so_emu & EMU_NOCONNECT) {
+ so->so_emu &= ~EMU_NOCONNECT;
+ goto cont_input;
+ }
+
+ if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) {
+ u_char code=ICMP_UNREACH_NET;
+ DEBUG_MISC((dfd, " tcp fconnect errno = %d-%s\n",
+ errno,strerror(errno)));
+ if(errno == ECONNREFUSED) {
+ /* ACK the SYN, send RST to refuse the connection */
+ tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0,
+ TH_RST|TH_ACK);
+ } else {
+ if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
+ HTONL(ti->ti_seq); /* restore tcp header */
+ HTONL(ti->ti_ack);
+ HTONS(ti->ti_win);
+ HTONS(ti->ti_urp);
+ m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
+ m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
+ *ip=save_ip;
+ icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
+ }
+ tcp_close(tp);
+ m_free(m);
+ } else {
+ /*
+ * Haven't connected yet, save the current mbuf
+ * and ti, and return
+ * XXX Some OS's don't tell us whether the connect()
+ * succeeded or not. So we must time it out.
+ */
+ so->so_m = m;
+ so->so_ti = ti;
+ tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
+ tp->t_state = TCPS_SYN_RECEIVED;
+ tcp_template(tp);
+ }
+ return;
+
+ cont_conn:
+ /* m==NULL
+ * Check if the connect succeeded
+ */
+ if (so->so_state & SS_NOFDREF) {
+ tp = tcp_close(tp);
+ goto dropwithreset;
+ }
+ cont_input:
+ tcp_template(tp);
+
+ if (optp)
+ tcp_dooptions(tp, (u_char *)optp, optlen, ti);
+
+ if (iss)
+ tp->iss = iss;
+ else
+ tp->iss = slirp->tcp_iss;
+ slirp->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;
+ goto trimthenstep6;
+ } /* case TCPS_LISTEN */
+
+ /*
+ * 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) {
+ tcp_drop(tp, 0); /* XXX Check t_softerror! */
+ }
+ 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)) {
+ soisfconnected(so);
+ tp->t_state = TCPS_ESTABLISHED;
+
+ (void) tcp_reass(tp, (struct tcpiphdr *)0,
+ (struct mbuf *)0);
+ /*
+ * if we didn't have to retransmit the SYN,
+ * use its rtt as our initial srtt & rtt var.
+ */
+ if (tp->t_rtt)
+ tcp_xmit_timer(tp, tp->t_rtt);
+ } 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;
+ }
+ tp->snd_wl1 = ti->ti_seq - 1;
+ tp->rcv_up = ti->ti_seq;
+ goto step6;
+ } /* switch tp->t_state */
+ /*
+ * States other than LISTEN or SYN_SENT.
+ * 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--;
+ }
+ /*
+ * Following if statement from Stevens, vol. 2, p. 960.
+ */
+ if (todrop > ti->ti_len
+ || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
+ /*
+ * Any valid FIN must be to the left of the window.
+ * At this point the FIN must be a duplicate or out
+ * of sequence; drop it.
+ */
+ tiflags &= ~TH_FIN;
+
+ /*
+ * Send an ACK to resynchronize and drop any data.
+ * But keep on processing for RST or ACK.
+ */
+ tp->t_flags |= TF_ACKNOW;
+ todrop = ti->ti_len;
+ }
+ 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);
+ 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) {
+ 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;
+ tp = tcp_close(tp);
+ goto findso;
+ }
+ /*
+ * 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;
+ } else {
+ goto dropafterack;
+ }
+ }
+ 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:
+ case TCPS_ESTABLISHED:
+ case TCPS_FIN_WAIT_1:
+ case TCPS_FIN_WAIT_2:
+ case TCPS_CLOSE_WAIT:
+ tp->t_state = TCPS_CLOSED;
+ tcp_close(tp);
+ goto drop;
+
+ case TCPS_CLOSING:
+ case TCPS_LAST_ACK:
+ case TCPS_TIME_WAIT:
+ 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,0);
+ 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. una<=ack<=max
+ */
+ case TCPS_SYN_RECEIVED:
+
+ if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
+ SEQ_GT(ti->ti_ack, tp->snd_max))
+ goto dropwithreset;
+ tp->t_state = TCPS_ESTABLISHED;
+ /*
+ * The sent SYN is ack'ed with our sequence number +1
+ * The first data byte already in the buffer will get
+ * lost if no correction is made. This is only needed for
+ * SS_CTL since the buffer is empty otherwise.
+ * tp->snd_una++; or:
+ */
+ tp->snd_una=ti->ti_ack;
+ if (so->so_state & SS_CTL) {
+ /* So tcp_ctl reports the right state */
+ ret = tcp_ctl(so);
+ if (ret == 1) {
+ soisfconnected(so);
+ so->so_state &= ~SS_CTL; /* success XXX */
+ } else if (ret == 2) {
+ so->so_state &= SS_PERSISTENT_MASK;
+ so->so_state |= SS_NOFDREF; /* CTL_CMD */
+ } else {
+ needoutput = 1;
+ tp->t_state = TCPS_FIN_WAIT_1;
+ }
+ } else {
+ soisfconnected(so);
+ }
+
+ (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
+ tp->snd_wl1 = ti->ti_seq - 1;
+ /* Avoid ack processing; snd_una==ti_ack => dup ack */
+ goto synrx_to_est;
+ /* 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 && tiwin == tp->snd_wnd) {
+ DEBUG_MISC((dfd, " dup ack m = %lx so = %lx\n",
+ (long )m, (long )so));
+ /*
+ * If we have outstanding data (other than
+ * 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
+ * threshold of them, assume a packet
+ * has been dropped and retransmit it.
+ * Kludge snd_nxt & the congestion
+ * window so we send only this one
+ * packet.
+ *
+ * We know we're losing at the current
+ * window size so do congestion avoidance
+ * (set ssthresh to half the current window
+ * and pull our congestion window back to
+ * the new ssthresh).
+ *
+ * Dup acks mean that packets have left the
+ * network (they're now cached at the receiver)
+ * so bump cwnd by the amount in the receiver
+ * to keep a constant cwnd packets in the
+ * network.
+ */
+ 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);
+ tp->snd_cwnd = tp->snd_ssthresh +
+ tp->t_maxseg * tp->t_dupacks;
+ if (SEQ_GT(onxt, tp->snd_nxt))
+ tp->snd_nxt = onxt;
+ goto drop;
+ } else if (tp->t_dupacks > TCPREXMTTHRESH) {
+ tp->snd_cwnd += tp->t_maxseg;
+ (void) tcp_output(tp);
+ goto drop;
+ }
+ } else
+ tp->t_dupacks = 0;
+ break;
+ }
+ synrx_to_est:
+ /*
+ * If the congestion window was inflated to account
+ * for the other side's cached packets, retract it.
+ */
+ if (tp->t_dupacks > TCPREXMTTHRESH &&
+ tp->snd_cwnd > tp->snd_ssthresh)
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->t_dupacks = 0;
+ if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
+ goto dropafterack;
+ }
+ acked = ti->ti_ack - tp->snd_una;
+
+ /*
+ * 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))
+ tcp_xmit_timer(tp,tp->t_rtt);
+
+ /*
+ * 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
+ * (maxseg^2 / cwnd per packet).
+ */
+ {
+ register u_int cw = tp->snd_cwnd;
+ register u_int incr = tp->t_maxseg;
+
+ if (cw > tp->snd_ssthresh)
+ incr = incr * incr / cw;
+ tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
+ }
+ 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;
+ }
+ 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_FCANTRCVMORE) {
+ 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;
+ }
+ 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) {
+ 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;
+ }
+ } /* switch(tp->t_state) */
+
+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 && tiwin > tp->snd_wnd))))) {
+ tp->snd_wnd = tiwin;
+ 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 > so->so_rcv.sb_datalen) {
+ ti->ti_urp = 0;
+ tiflags &= ~TH_URG;
+ goto dodata;
+ }
+ /*
+ * 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 (in one of two places).
+ */
+ if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
+ tp->rcv_up = ti->ti_seq + ti->ti_urp;
+ so->so_urgc = so->so_rcv.sb_cc +
+ (tp->rcv_up - tp->rcv_nxt); /* -1; */
+ tp->rcv_up = ti->ti_seq + ti->ti_urp;
+
+ }
+ } 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:
+
+ /*
+ * If this is a small packet, then ACK now - with Nagel
+ * congestion avoidance sender won't send more until
+ * he gets an ACK.
+ */
+ if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
+ ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
+ tp->t_flags |= TF_ACKNOW;
+ }
+
+ /*
+ * 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);
+ } else {
+ m_free(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) {
+ /*
+ * If we receive a FIN we can't send more data,
+ * set it SS_FDRAIN
+ * Shutdown the socket if there is no rx data in the
+ * buffer.
+ * soread() is called on completion of shutdown() and
+ * will got to TCPS_LAST_ACK, and use tcp_output()
+ * to send the FIN.
+ */
+ sofwdrain(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:
+ if(so->so_emu == EMU_CTL) /* no shutdown on socket */
+ tp->t_state = TCPS_LAST_ACK;
+ else
+ 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;
+ 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;
+ }
+ }
+
+ /*
+ * 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_free(m);
+ tp->t_flags |= TF_ACKNOW;
+ (void) tcp_output(tp);
+ return;
+
+dropwithreset:
+ /* reuses m if m!=NULL, m_free() unnecessary */
+ if (tiflags & TH_ACK)
+ tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
+ else {
+ if (tiflags & TH_SYN) ti->ti_len++;
+ tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
+ TH_RST|TH_ACK);
+ }
+
+ return;
+
+drop:
+ /*
+ * Drop space held by incoming segment and return.
+ */
+ m_free(m);
+}
+
+static void
+tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti)
+{
+ uint16_t mss;
+ int opt, optlen;
+
+ DEBUG_CALL("tcp_dooptions");
+ DEBUG_ARGS((dfd, " tp = %lx cnt=%i\n", (long)tp, cnt));
+
+ 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:
+ continue;
+
+ case TCPOPT_MAXSEG:
+ if (optlen != TCPOLEN_MAXSEG)
+ continue;
+ if (!(ti->ti_flags & TH_SYN))
+ continue;
+ memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
+ NTOHS(mss);
+ (void) tcp_mss(tp, mss); /* sets t_maxseg */
+ break;
+ }
+ }
+}
+
+
+/*
+ * 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.
+ */
+
+#ifdef notdef
+
+void
+tcp_pulloutofband(so, ti, m)
+ struct socket *so;
+ struct tcpiphdr *ti;
+ register struct mbuf *m;
+{
+ int cnt = ti->ti_urp - 1;
+
+ 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;
+ memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
+ m->m_len--;
+ return;
+ }
+ cnt -= m->m_len;
+ m = m->m_next; /* XXX WRONG! Fix it! */
+ if (m == 0)
+ break;
+ }
+ panic("tcp_pulloutofband");
+}
+
+#endif /* notdef */
+
+/*
+ * Collect new round-trip time estimate
+ * and update averages and current timeout.
+ */
+
+static void
+tcp_xmit_timer(register struct tcpcb *tp, int rtt)
+{
+ register short delta;
+
+ DEBUG_CALL("tcp_xmit_timer");
+ DEBUG_ARG("tp = %lx", (long)tp);
+ DEBUG_ARG("rtt = %d", rtt);
+
+ if (tp->t_srtt != 0) {
+ /*
+ * 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 rtt to origin 0.
+ */
+ delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
+ 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 + 4 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 >> TCP_RTTVAR_SHIFT);
+ 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 3*rtt).
+ */
+ tp->t_srtt = rtt << TCP_RTT_SHIFT;
+ tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
+ }
+ tp->t_rtt = 0;
+ tp->t_rxtshift = 0;
+
+ /*
+ * the retransmit should happen at rtt + 4 * rttvar.
+ * Because of the way we do the smoothing, srtt and rttvar
+ * will each average +1/2 tick of bias. When we compute
+ * the retransmit timer, we want 1/2 tick of rounding and
+ * 1 extra tick because of +-1/2 tick uncertainty in the
+ * firing of the timer. The bias will give us exactly the
+ * 1.5 tick we need. But, because the bias is
+ * statistical, we have to test that we don't drop below
+ * the minimum feasible timer (which is 2 ticks).
+ */
+ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
+ (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
+
+ /*
+ * We received an ack for a packet that wasn't retransmitted;
+ * it is probably safe to discard any error indications we've
+ * received recently. This isn't quite right, but close enough
+ * for now (a route might have failed after we sent a segment,
+ * and the return path might not be symmetrical).
+ */
+ tp->t_softerror = 0;
+}
+
+/*
+ * Determine a reasonable value for maxseg size.
+ * If the route is known, check route for mtu.
+ * If none, use an mss that can be handled on the outgoing
+ * interface without forcing IP to fragment; if bigger than
+ * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
+ * to utilize large mbufs. If no route is found, route has no mtu,
+ * or the destination isn't local, use a default, hopefully conservative
+ * size (usually 512 or the default IP max size, but no more than the mtu
+ * of the interface), 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.
+ * While looking at the routing entry, we also initialize other path-dependent
+ * parameters from pre-set or cached values in the routing entry.
+ */
+
+int
+tcp_mss(struct tcpcb *tp, u_int offer)
+{
+ struct socket *so = tp->t_socket;
+ int mss;
+
+ DEBUG_CALL("tcp_mss");
+ DEBUG_ARG("tp = %lx", (long)tp);
+ DEBUG_ARG("offer = %d", offer);
+
+ mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
+ if (offer)
+ mss = min(mss, offer);
+ mss = max(mss, 32);
+ if (mss < tp->t_maxseg || offer != 0)
+ tp->t_maxseg = mss;
+
+ tp->snd_cwnd = mss;
+
+ sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ?
+ (mss - (TCP_SNDSPACE % mss)) :
+ 0));
+ sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ?
+ (mss - (TCP_RCVSPACE % mss)) :
+ 0));
+
+ DEBUG_MISC((dfd, " returning mss = %d\n", mss));
+
+ return mss;
+}
Code Review / kvmfornfv.git / blobdiff