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/*

 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995

 *      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. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *      This product includes software developed by the University of

 *      California, Berkeley and its contributors.

 * 4. 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_subr.c  8.2 (Berkeley) 5/24/95

 *      tcp_subr.c,v 1.2 1998/08/20 21:47:37 joel Exp

 */

#include "opt_tcpdebug.h"

#include <sys/param.h>

#include <sys/queue.h>

#include <sys/proc.h>

#include <sys/systm.h>

#include <sys/kernel.h>

#include <sys/sysctl.h>

#include <sys/malloc.h>

#include <sys/mbuf.h>

#include <sys/socket.h>

#include <sys/socketvar.h>

#include <sys/protosw.h>

#include <sys/errno.h>

#include <net/route.h>

#include <net/if.h>

#define _IP_VHL

#include <netinet/in.h>

#include <netinet/in_systm.h>

#include <netinet/ip.h>

#include <netinet/in_pcb.h>

#include <netinet/in_var.h>

#include <netinet/ip_var.h>

#include <netinet/ip_icmp.h>

#include <netinet/tcp.h>

#include <netinet/tcp_fsm.h>

#include <netinet/tcp_seq.h>

#include <netinet/tcp_timer.h>

#include <netinet/tcp_var.h>

#include <netinet/tcpip.h>

#ifdef TCPDEBUG

#include <netinet/tcp_debug.h>

#endif

int     tcp_mssdflt = TCP_MSS;

SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt,

        CTLFLAG_RW, &tcp_mssdflt , 0, "");

static int      tcp_do_rfc1323 = 1;

static int      tcp_do_rfc1644 = 1;

#if !defined(__rtems__)

static int      tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;

SYSCTL_INT(_net_inet_tcp, TCPCTL_RTTDFLT, rttdflt,

        CTLFLAG_RW, &tcp_rttdflt , 0, "");

SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323,

        CTLFLAG_RW, &tcp_do_rfc1323 , 0, "");

SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644,

        CTLFLAG_RW, &tcp_do_rfc1644 , 0, "");

#endif

static void     tcp_cleartaocache(void);

static void     tcp_notify __P((struct inpcb *, int));

/*

 * Target size of TCP PCB hash table. Will be rounded down to a prime

 * number.

 */

#ifndef TCBHASHSIZE

#define TCBHASHSIZE     128

#endif

/*

 * Tcp initialization

 */

void

tcp_init()

{

        tcp_iss = random();     /* wrong, but better than a constant */

        tcp_ccgen = 1;

        tcp_cleartaocache();

        LIST_INIT(&tcb);

        tcbinfo.listhead = &tcb;

        tcbinfo.hashbase = hashinit(TCBHASHSIZE, M_PCB, &tcbinfo.hashmask);

        if (max_protohdr < sizeof(struct tcpiphdr))

                max_protohdr = sizeof(struct tcpiphdr);

        if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN)

                panic("tcp_init");

}

/*

 * Create template to be used to send tcp packets on a connection.

 * Call after host entry created, allocates an mbuf and fills

 * in a skeletal tcp/ip header, minimizing the amount of work

 * necessary when the connection is used.

 */

struct tcpiphdr *

tcp_template(tp)

        struct tcpcb *tp;

{

        register struct inpcb *inp = tp->t_inpcb;

        register struct mbuf *m;

        register struct tcpiphdr *n;

        if ((n = tp->t_template) == 0) {

                m = m_get(M_DONTWAIT, MT_HEADER);

                if (m == NULL)

                        return (0);

                m->m_len = sizeof (struct tcpiphdr);

                n = mtod(m, struct tcpiphdr *);

        }

        n->ti_next = n->ti_prev = 0;

        n->ti_x1 = 0;

        n->ti_pr = IPPROTO_TCP;

        n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));

        n->ti_src = inp->inp_laddr;

        n->ti_dst = inp->inp_faddr;

        n->ti_sport = inp->inp_lport;

        n->ti_dport = inp->inp_fport;

        n->ti_seq = 0;

        n->ti_ack = 0;

        n->ti_x2 = 0;

        n->ti_off = 5;

        n->ti_flags = 0;

        n->ti_win = 0;

        n->ti_sum = 0;

        n->ti_urp = 0;

        return (n);

}

/*

 * Send a single message to the TCP at address specified by

 * the given TCP/IP header.  If m == 0, then we make a copy

 * of the tcpiphdr at ti and send directly to the addressed host.

 * This is used to force keep alive messages out using the TCP

 * template for a connection tp->t_template.  If flags are given

 * then we send a message back to the TCP which originated the

 * segment ti, and discard the mbuf containing it and any other

 * attached mbufs.

 *

 * In any case the ack and sequence number of the transmitted

 * segment are as specified by the parameters.

 *

 * NOTE: If m != NULL, then ti must point to *inside* the mbuf.

 */

void

tcp_respond(tp, ti, m, ack, seq, flags)

        struct tcpcb *tp;

        register struct tcpiphdr *ti;

        register struct mbuf *m;

        tcp_seq ack, seq;

        int flags;

{

        register int tlen;

        int win = 0;

        struct route *ro = 0;

        struct route sro;

        if (tp) {

                win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);

                ro = &tp->t_inpcb->inp_route;

        } else {

                ro = &sro;

                bzero(ro, sizeof *ro);

        }

        if (m == 0) {

                m = m_gethdr(M_DONTWAIT, MT_HEADER);

                if (m == NULL)

                        return;

#ifdef TCP_COMPAT_42

                tlen = 1;

#else

                tlen = 0;

#endif

                m->m_data += max_linkhdr;

                *mtod(m, struct tcpiphdr *) = *ti;

                ti = mtod(m, struct tcpiphdr *);

                flags = TH_ACK;

        } else {

                m_freem(m->m_next);

                m->m_next = 0;

                m->m_data = (caddr_t)ti;

                m->m_len = sizeof (struct tcpiphdr);

                tlen = 0;

#define xchg(a,b,type) { type t; t=a; a=b; b=t; }

                xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long);

                xchg(ti->ti_dport, ti->ti_sport, u_short);

#undef xchg

        }

        ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen));

        tlen += sizeof (struct tcpiphdr);

        m->m_len = tlen;

        m->m_pkthdr.len = tlen;

        m->m_pkthdr.rcvif = (struct ifnet *) 0;

        ti->ti_next = ti->ti_prev = 0;

        ti->ti_x1 = 0;

        ti->ti_seq = htonl(seq);

        ti->ti_ack = htonl(ack);

        ti->ti_x2 = 0;

        ti->ti_off = sizeof (struct tcphdr) >> 2;

        ti->ti_flags = flags;

        if (tp)

                ti->ti_win = htons((u_short) (win >> tp->rcv_scale));

        else

                ti->ti_win = htons((u_short)win);

        ti->ti_urp = 0;

        ti->ti_sum = 0;

        ti->ti_sum = in_cksum(m, tlen);

        ((struct ip *)ti)->ip_len = tlen;

        ((struct ip *)ti)->ip_ttl = ip_defttl;

#ifdef TCPDEBUG

        if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))

                tcp_trace(TA_OUTPUT, 0, tp, ti, 0);

#endif

        (void) ip_output(m, NULL, ro, 0, NULL);

        if (ro == &sro && ro->ro_rt) {

                RTFREE(ro->ro_rt);

        }

}

/*

 * Create a new TCP control block, making an

 * empty reassembly queue and hooking it to the argument

 * protocol control block.

 */

struct tcpcb *

tcp_newtcpcb(inp)

        struct inpcb *inp;

{

        register struct tcpcb *tp;

        tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT);

        if (tp == NULL)

                return ((struct tcpcb *)0);

        bzero((char *) tp, sizeof(struct tcpcb));

        tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp;

        tp->t_maxseg = tp->t_maxopd = tcp_mssdflt;

        if (tcp_do_rfc1323)

                tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);

        if (tcp_do_rfc1644)

                tp->t_flags |= TF_REQ_CC;

        tp->t_inpcb = inp;

        /*

         * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no

         * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives

         * reasonable initial retransmit time.

         */

        tp->t_srtt = TCPTV_SRTTBASE;

        tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;

        tp->t_rttmin = TCPTV_MIN;

        tp->t_rxtcur = TCPTV_RTOBASE;

        tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;

        tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;

        inp->inp_ip_ttl = ip_defttl;

        inp->inp_ppcb = (caddr_t)tp;

        return (tp);

}

/*

 * Drop a TCP connection, reporting

 * the specified error.  If connection is synchronized,

 * then send a RST to peer.

 */

struct tcpcb *

tcp_drop(tp, errnum)

        register struct tcpcb *tp;

        int errnum;

{

        struct socket *so = tp->t_inpcb->inp_socket;

        if (TCPS_HAVERCVDSYN(tp->t_state)) {

                tp->t_state = TCPS_CLOSED;

                (void) tcp_output(tp);

                tcpstat.tcps_drops++;

        } else

                tcpstat.tcps_conndrops++;

        if (errnum == ETIMEDOUT && tp->t_softerror)

                errnum = tp->t_softerror;

        so->so_error = errnum;

        return (tcp_close(tp));

}

/*

 * Close a TCP control block:

 *      discard all space held by the tcp

 *      discard internet protocol block

 *      wake up any sleepers

 */

struct tcpcb *

tcp_close(tp)

        register struct tcpcb *tp;

{

        register struct tcpiphdr *t;

        struct inpcb *inp = tp->t_inpcb;

        struct socket *so = inp->inp_socket;

        register struct mbuf *m;

        register struct rtentry *rt;

        /*

         * If we got enough samples through the srtt filter,

         * save the rtt and rttvar in the routing entry.

         * 'Enough' is arbitrarily defined as the 16 samples.

         * 16 samples is enough for the srtt filter to converge

         * to within 5% of the correct value; fewer samples and

         * we could save a very bogus rtt.

         *

         * Don't update the default route's characteristics and don't

         * update anything that the user "locked".

         */

        if (tp->t_rttupdated >= 16 &&

            (rt = inp->inp_route.ro_rt) &&

            ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) {

                register u_long i = 0;

                if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {

                        i = tp->t_srtt *

                            (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));

                        if (rt->rt_rmx.rmx_rtt && i)

                                /*

                                 * filter this update to half the old & half

                                 * the new values, converting scale.

                                 * See route.h and tcp_var.h for a

                                 * description of the scaling constants.

                                 */

                                rt->rt_rmx.rmx_rtt =

                                    (rt->rt_rmx.rmx_rtt + i) / 2;

                        else

                                rt->rt_rmx.rmx_rtt = i;

                        tcpstat.tcps_cachedrtt++;

                }

                if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {

                        i = tp->t_rttvar *

                            (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE));

                        if (rt->rt_rmx.rmx_rttvar && i)

                                rt->rt_rmx.rmx_rttvar =

                                    (rt->rt_rmx.rmx_rttvar + i) / 2;

                        else

                                rt->rt_rmx.rmx_rttvar = i;

                        tcpstat.tcps_cachedrttvar++;

                }

                /*

                 * update the pipelimit (ssthresh) if it has been updated

                 * already or if a pipesize was specified & the threshhold

                 * got below half the pipesize.  I.e., wait for bad news

                 * before we start updating, then update on both good

                 * and bad news.

                 */

                if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&

                    ((i = tp->snd_ssthresh) != 0) && rt->rt_rmx.rmx_ssthresh) ||

                    i < (rt->rt_rmx.rmx_sendpipe / 2)) {

                        /*

                         * convert the limit from user data bytes to

                         * packets then to packet data bytes.

                         */

                        i = (i + tp->t_maxseg / 2) / tp->t_maxseg;

                        if (i < 2)

                                i = 2;

                        i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr));

                        if (rt->rt_rmx.rmx_ssthresh)

                                rt->rt_rmx.rmx_ssthresh =

                                    (rt->rt_rmx.rmx_ssthresh + i) / 2;

                        else

                                rt->rt_rmx.rmx_ssthresh = i;

                        tcpstat.tcps_cachedssthresh++;

                }

        }

        /* free the reassembly queue, if any */

        t = tp->seg_next;

        while (t != (struct tcpiphdr *)tp) {

                t = (struct tcpiphdr *)t->ti_next;

                m = REASS_MBUF((struct tcpiphdr *)t->ti_prev);

                remque(t->ti_prev);

                m_freem(m);

        }

        if (tp->t_template)

                (void) m_free(dtom(tp->t_template));

        free(tp, M_PCB);

        inp->inp_ppcb = 0;

        soisdisconnected(so);

        in_pcbdetach(inp);

        tcpstat.tcps_closed++;

        return ((struct tcpcb *)0);

}

void

tcp_drain()

{

}

/*

 * Notify a tcp user of an asynchronous error;

 * store error as soft error, but wake up user

 * (for now, won't do anything until can select for soft error).

 */

static void

tcp_notify(inp, error)

        struct inpcb *inp;

        int error;

{

        register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb;

        register struct socket *so = inp->inp_socket;

        /*

         * Ignore some errors if we are hooked up.

         * If connection hasn't completed, has retransmitted several times,

         * and receives a second error, give up now.  This is better

         * than waiting a long time to establish a connection that

         * can never complete.

         */

        if (tp->t_state == TCPS_ESTABLISHED &&

             (error == EHOSTUNREACH || error == ENETUNREACH ||

              error == EHOSTDOWN)) {

                return;

        } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&

            tp->t_softerror)

                so->so_error = error;

        else

                tp->t_softerror = error;

        soconnwakeup (so);

        sorwakeup(so);

        sowwakeup(so);

}

void

tcp_ctlinput(cmd, sa, vip)

        int cmd;

        struct sockaddr *sa;

        void *vip;

{

        register struct ip *ip = vip;

        register struct tcphdr *th;

        void (*notify) __P((struct inpcb *, int)) = tcp_notify;

        if (cmd == PRC_QUENCH)

                notify = tcp_quench;

#if 1

        else if (cmd == PRC_MSGSIZE)

                notify = tcp_mtudisc;

#endif

        else if (!PRC_IS_REDIRECT(cmd) &&

                 ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0))

                return;

        if (ip) {

                th = (struct tcphdr *)((caddr_t)ip

                                       + (IP_VHL_HL(ip->ip_vhl) << 2));

                in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport,

                        cmd, notify);

        } else

                in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify);

}

/*

 * When a source quench is received, close congestion window

 * to one segment.  We will gradually open it again as we proceed.

 */

void

tcp_quench(inp, errnum)

        struct inpcb *inp;

        int errnum;

{

        struct tcpcb *tp = intotcpcb(inp);

        if (tp)

                tp->snd_cwnd = tp->t_maxseg;

}

#if 1

/*

 * When `need fragmentation' ICMP is received, update our idea of the MSS

 * based on the new value in the route.  Also nudge TCP to send something,

 * since we know the packet we just sent was dropped.

 * This duplicates some code in the tcp_mss() function in tcp_input.c.

 */

void

tcp_mtudisc(inp, errnum)

        struct inpcb *inp;

        int errnum;

{

        struct tcpcb *tp = intotcpcb(inp);

        struct rtentry *rt;

        struct rmxp_tao *taop;

        struct socket *so = inp->inp_socket;

        int offered;

        int mss;

        if (tp) {

                rt = tcp_rtlookup(inp);

                if (!rt || !rt->rt_rmx.rmx_mtu) {

                        tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;

                        return;

                }

                taop = rmx_taop(rt->rt_rmx);

                offered = taop->tao_mssopt;

                mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr);

                if (offered)

                        mss = min(mss, offered);

                /*

                 * XXX - The above conditional probably violates the TCP

                 * spec.  The problem is that, since we don't know the

                 * other end's MSS, we are supposed to use a conservative

                 * default.  But, if we do that, then MTU discovery will

                 * never actually take place, because the conservative

                 * default is much less than the MTUs typically seen

                 * on the Internet today.  For the moment, we'll sweep

                 * this under the carpet.

                 *

                 * The conservative default might not actually be a problem

                 * if the only case this occurs is when sending an initial

                 * SYN with options and data to a host we've never talked

                 * to before.  Then, they will reply with an MSS value which

                 * will get recorded and the new parameters should get

                 * recomputed.  For Further Study.

                 */

                if (tp->t_maxopd <= mss)

                        return;

                tp->t_maxopd = mss;

                if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&

                    (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)

                        mss -= TCPOLEN_TSTAMP_APPA;

                if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&

                    (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)

                        mss -= TCPOLEN_CC_APPA;

#if     (MCLBYTES & (MCLBYTES - 1)) == 0

                if (mss > MCLBYTES)

                        mss &= ~(MCLBYTES-1);

#else

                if (mss > MCLBYTES)

                        mss = mss / MCLBYTES * MCLBYTES;

#endif

                if (so->so_snd.sb_hiwat < mss)

                        mss = so->so_snd.sb_hiwat;

                tp->t_maxseg = mss;

                tcpstat.tcps_mturesent++;

                tp->t_rtt = 0;

                tp->snd_nxt = tp->snd_una;

                tcp_output(tp);

        }

}

#endif

/*

 * Look-up the routing entry to the peer of this inpcb.  If no route

 * is found and it cannot be allocated the return NULL.  This routine

 * is called by TCP routines that access the rmx structure and by tcp_mss

 * to get the interface MTU.

 */

struct rtentry *

tcp_rtlookup(inp)

        struct inpcb *inp;

{

        struct route *ro;

        struct rtentry *rt;

        ro = &inp->inp_route;

        rt = ro->ro_rt;

        if (rt == NULL || !(rt->rt_flags & RTF_UP)) {

                /* No route yet, so try to acquire one */

                if (inp->inp_faddr.s_addr != INADDR_ANY) {

                        ro->ro_dst.sa_family = AF_INET;

                        ro->ro_dst.sa_len = sizeof(ro->ro_dst);

                        ((struct sockaddr_in *) &ro->ro_dst)->sin_addr =

                                inp->inp_faddr;

                        rtalloc(ro);

                        rt = ro->ro_rt;

                }

        }

        return rt;

}

/*

 * Return a pointer to the cached information about the remote host.

 * The cached information is stored in the protocol specific part of

 * the route metrics.

 */

struct rmxp_tao *

tcp_gettaocache(inp)

        struct inpcb *inp;

{

        struct rtentry *rt = tcp_rtlookup(inp);

        /* Make sure this is a host route and is up. */

        if (rt == NULL ||

            (rt->rt_flags & (RTF_UP|RTF_HOST)) != (RTF_UP|RTF_HOST))

                return NULL;

        return rmx_taop(rt->rt_rmx);

}

/*

 * Clear all the TAO cache entries, called from tcp_init.

 *

 * XXX

 * This routine is just an empty one, because we assume that the routing

 * routing tables are initialized at the same time when TCP, so there is

 * nothing in the cache left over.

 */

static void

tcp_cleartaocache(void)

{ }