| /* 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) |
| { |
| if (m) |
| M_DUP_DEBUG(m->slirp, m, 0, 0); |
| |
| 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); |
| |
| memset(&lhost, 0, sizeof(struct sockaddr_storage)); |
| memset(&fhost, 0, sizeof(struct sockaddr_storage)); |
| |
| /* |
| * 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; |
| switch (af) { |
| case AF_INET: |
| M_DUP_DEBUG(slirp, m, 0, |
| sizeof(struct tcpiphdr) - sizeof(struct ip) - sizeof(struct tcphdr)); |
| break; |
| case AF_INET6: |
| M_DUP_DEBUG(slirp, m, 0, |
| sizeof(struct tcpiphdr) - sizeof(struct ip6) - sizeof(struct tcphdr)); |
| break; |
| } |
| |
| 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); |
| tcp_attach(so); |
| |
| 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) |
| 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; |
| |
| 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); |
| } |
| |
| 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; |
| 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; |
| 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)) { |
| 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; |
| 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); |
| 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(so->slirp->if_mtu, so->slirp->if_mru) - |
| sizeof(struct tcphdr) - sizeof(struct ip); |
| break; |
| case AF_INET6: |
| mss = MIN(so->slirp->if_mtu, so->slirp->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 = MIN(mss, TCP_MAXSEG_MAX); |
| |
| 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; |
| } |
