diff options
Diffstat (limited to 'slirp/src/tcp_input.c')
| m--------- | slirp | 0 | ||||
| -rw-r--r-- | slirp/src/tcp_input.c | 1554 |
2 files changed, 0 insertions, 1554 deletions
diff --git a/slirp b/slirp new file mode 160000 +Subproject 59a1b1f165458c2acb7ff0525b543945f741622 diff --git a/slirp/src/tcp_input.c b/slirp/src/tcp_input.c deleted file mode 100644 index 50a1145ec9..0000000000 --- a/slirp/src/tcp_input.c +++ /dev/null @@ -1,1554 +0,0 @@ -/* 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; -} |