+++ /dev/null
-/* SPDX-License-Identifier: BSD-3-Clause */
-/*
- * 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.
- */
-
-#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).
- */
-#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; \
- } \
-}
-
-static void tcp_dooptions(struct tcpcb *tp, uint8_t *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, unsigned short af)
-{
- struct ip save_ip, *ip;
- struct ip6 save_ip6, *ip6;
- register struct tcpiphdr *ti;
- char *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;
- uint32_t tiwin;
- int ret;
- struct sockaddr_storage lhost, fhost;
- struct sockaddr_in *lhost4, *fhost4;
- struct sockaddr_in6 *lhost6, *fhost6;
- struct gfwd_list *ex_ptr;
- Slirp *slirp;
-
- DEBUG_CALL("tcp_input");
- DEBUG_ARG("m = %p iphlen = %2d inso = %p",
- m, iphlen, 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;
-
- ip = mtod(m, struct ip *);
- ip6 = mtod(m, struct ip6 *);
-
- switch (af) {
- case AF_INET:
- 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.
- */
- save_ip = *ip;
- save_ip.ip_len += iphlen;
-
- /*
- * Get IP and TCP header together in first mbuf.
- * Note: IP leaves IP header in first mbuf.
- */
- m->m_data -= sizeof(struct tcpiphdr) - sizeof(struct ip)
- - sizeof(struct tcphdr);
- m->m_len += sizeof(struct tcpiphdr) - sizeof(struct ip)
- - sizeof(struct tcphdr);
- ti = mtod(m, struct tcpiphdr *);
-
- /*
- * Checksum extended TCP header and data.
- */
- tlen = ip->ip_len;
- tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
- memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
- memset(&ti->ti, 0, sizeof(ti->ti));
- ti->ti_x0 = 0;
- ti->ti_src = save_ip.ip_src;
- ti->ti_dst = save_ip.ip_dst;
- ti->ti_pr = save_ip.ip_p;
- ti->ti_len = htons((uint16_t)tlen);
- break;
-
- case AF_INET6:
- /*
- * Save a copy of the IP header in case we want restore it
- * for sending an ICMP error message in response.
- */
- save_ip6 = *ip6;
- /*
- * Get IP and TCP header together in first mbuf.
- * Note: IP leaves IP header in first mbuf.
- */
- m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip6)
- + sizeof(struct tcphdr));
- m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip6)
- + sizeof(struct tcphdr));
- ti = mtod(m, struct tcpiphdr *);
-
- tlen = ip6->ip_pl;
- tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
- memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
- memset(&ti->ti, 0, sizeof(ti->ti));
- ti->ti_x0 = 0;
- ti->ti_src6 = save_ip6.ip_src;
- ti->ti_dst6 = save_ip6.ip_dst;
- ti->ti_nh6 = save_ip6.ip_nh;
- ti->ti_len = htons((uint16_t)tlen);
- break;
-
- default:
- g_assert_not_reached();
- }
-
- len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + 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, char *) + 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:
- lhost.ss_family = af;
- fhost.ss_family = af;
- switch (af) {
- case AF_INET:
- lhost4 = (struct sockaddr_in *) &lhost;
- lhost4->sin_addr = ti->ti_src;
- lhost4->sin_port = ti->ti_sport;
- fhost4 = (struct sockaddr_in *) &fhost;
- fhost4->sin_addr = ti->ti_dst;
- fhost4->sin_port = ti->ti_dport;
- break;
- case AF_INET6:
- lhost6 = (struct sockaddr_in6 *) &lhost;
- lhost6->sin6_addr = ti->ti_src6;
- lhost6->sin6_port = ti->ti_sport;
- fhost6 = (struct sockaddr_in6 *) &fhost;
- fhost6->sin6_addr = ti->ti_dst6;
- fhost6->sin6_port = ti->ti_dport;
- break;
- default:
- g_assert_not_reached();
- }
-
- so = solookup(&slirp->tcp_last_so, &slirp->tcb, &lhost, &fhost);
-
- /*
- * 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) {
- /* TODO: IPv6 */
- 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->guestfwd_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;
-
- so = socreate(slirp);
- if (tcp_attach(so) < 0) {
- g_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->lhost.ss = lhost;
- so->fhost.ss = fhost;
-
- so->so_iptos = tcp_tos(so);
- if (so->so_iptos == 0) {
- switch (af) {
- case AF_INET:
- so->so_iptos = ((struct ip *)ti)->ip_tos;
- break;
- case AF_INET6:
- break;
- default:
- g_assert_not_reached();
- }
- }
-
- 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 (slirp_do_keepalive)
- 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, (uint8_t *)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;
- sodrop(so, 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
- */
- /* TODO: IPv6 */
- if (af == AF_INET &&
- (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->guestfwd_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, so->so_ffamily) == -1) &&
- (errno != EAGAIN) &&
- (errno != EINPROGRESS) && (errno != EWOULDBLOCK)
- ) {
- uint8_t code;
- DEBUG_MISC(" tcp fconnect errno = %d-%s", 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, af);
- } else {
- switch (af) {
- case AF_INET:
- code = ICMP_UNREACH_NET;
- if (errno == EHOSTUNREACH) {
- code = ICMP_UNREACH_HOST;
- }
- break;
- case AF_INET6:
- code = ICMP6_UNREACH_NO_ROUTE;
- if (errno == EHOSTUNREACH) {
- code = ICMP6_UNREACH_ADDRESS;
- }
- break;
- default:
- g_assert_not_reached();
- }
- 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);
- switch (af) {
- case AF_INET:
- m->m_data += sizeof(struct tcpiphdr) - sizeof(struct ip)
- - sizeof(struct tcphdr);
- m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct ip)
- - sizeof(struct tcphdr);
- *ip = save_ip;
- icmp_send_error(m, ICMP_UNREACH, code, 0, strerror(errno));
- break;
- case AF_INET6:
- m->m_data += sizeof(struct tcpiphdr) - (sizeof(struct ip6)
- + sizeof(struct tcphdr));
- m->m_len -= sizeof(struct tcpiphdr) - (sizeof(struct ip6)
- + sizeof(struct tcphdr));
- *ip6 = save_ip6;
- icmp6_send_error(m, ICMP6_UNREACH, code);
- break;
- default:
- g_assert_not_reached();
- }
- }
- 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;
- /*
- * Initialize receive sequence numbers now so that we can send a
- * valid RST if the remote end rejects our connection.
- */
- tp->irs = ti->ti_seq;
- tcp_rcvseqinit(tp);
- 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, (uint8_t *)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(" dup ack m = %p so = %p", m, 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;
- unsigned 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 unsigned cw = tp->snd_cwnd;
- register unsigned 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;
- sodrop(so, (int)so->so_snd.sb_cc);
- ourfinisacked = 1;
- } else {
- sodrop(so, 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, af);
- 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, af);
- }
-
- return;
-
-drop:
- /*
- * Drop space held by incoming segment and return.
- */
- m_free(m);
-}
-
-static void
-tcp_dooptions(struct tcpcb *tp, uint8_t *cp, int cnt, struct tcpiphdr *ti)
-{
- uint16_t mss;
- int opt, optlen;
-
- DEBUG_CALL("tcp_dooptions");
- DEBUG_ARG("tp = %p cnt=%i", 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;
- }
- }
-}
-
-/*
- * 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 = %p", 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, unsigned offer)
-{
- struct socket *so = tp->t_socket;
- int mss;
-
- DEBUG_CALL("tcp_mss");
- DEBUG_ARG("tp = %p", tp);
- DEBUG_ARG("offer = %d", offer);
-
- switch (so->so_ffamily) {
- case AF_INET:
- mss = MIN(IF_MTU, IF_MRU) - sizeof(struct tcphdr)
- - sizeof(struct ip);
- break;
- case AF_INET6:
- mss = MIN(IF_MTU, IF_MRU) - sizeof(struct tcphdr)
- - sizeof(struct ip6);
- break;
- default:
- g_assert_not_reached();
- }
-
- 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(" returning mss = %d", mss);
-
- return mss;
-}
projects / mirror_qemu.git / blobdiff