[apple/xnu.git] / bsd / netinet / tcp_subr.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * 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
 */

#if ISFB31
#include "opt_compat.h"
#include "opt_tcpdebug.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/syslog.h>


#if ISFB31
#include <vm/vm_zone.h>
#endif

#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>
#if INET6
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/in6_pcb.h>
#endif
#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>
#if TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
#include <netinet6/ip6protosw.h>

#if IPSEC
#include <netinet6/ipsec.h>
#endif /*IPSEC*/

#include <sys/kdebug.h>

#define DBG_FNC_TCP_CLOSE       NETDBG_CODE(DBG_NETTCP, ((5 << 8) | 2))


int     tcp_mssdflt = TCP_MSS;
SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt,
        CTLFLAG_RW, &tcp_mssdflt , 0, "");

int     tcp_v6mssdflt = TCP6_MSS;
SYSCTL_INT(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
        CTLFLAG_RW, &tcp_v6mssdflt , 0, "");

static int      tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
SYSCTL_INT(_net_inet_tcp, TCPCTL_RTTDFLT, rttdflt,
        CTLFLAG_RW, &tcp_rttdflt , 0, "");

static int      tcp_do_rfc1323 = 1;
SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323,
        CTLFLAG_RW, &tcp_do_rfc1323 , 0, "");

static int      tcp_do_rfc1644 = 0;
SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644,
        CTLFLAG_RW, &tcp_do_rfc1644 , 0, "");

SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD, &tcbinfo.ipi_count,
           0, "Number of active PCBs");

static void     tcp_cleartaocache __P((void));
static void     tcp_notify __P((struct inpcb *, int));
extern u_long   current_active_connections;




/*
 * Target size of TCP PCB hash tables. Must be a power of two.
 *
 * Note that this can be overridden by the kernel environment
 * variable net.inet.tcp.tcbhashsize
 */
#ifndef TCBHASHSIZE
#define TCBHASHSIZE     4096
#endif

/*
 * This is the actual shape of what we allocate using the zone
 * allocator.  Doing it this way allows us to protect both structures
 * using the same generation count, and also eliminates the overhead
 * of allocating tcpcbs separately.  By hiding the structure here,
 * we avoid changing most of the rest of the code (although it needs
 * to be changed, eventually, for greater efficiency).
 */
#define ALIGNMENT       32
#define ALIGNM1         (ALIGNMENT - 1)
struct  inp_tp {
        union {
                struct  inpcb inp;
                char    align[(sizeof(struct inpcb) + ALIGNM1) & ~ALIGNM1];
        } inp_tp_u;
        struct  tcpcb tcb;
};
#undef ALIGNMENT
#undef ALIGNM1

static struct tcpcb dummy_tcb;


extern struct   inpcbhead       time_wait_slots[];
extern int              cur_tw_slot;
extern u_long           *delack_bitmask;


int  get_inpcb_str_size()
{
        return sizeof(struct inpcb);
}


int  get_tcp_str_size()
{
        return sizeof(struct tcpcb);
}

int     tcp_freeq __P((struct tcpcb *tp));


/*
 * Tcp initialization
 */
void
tcp_init()
{
        int hashsize;
        vm_size_t       str_size;
        int  i;

        tcp_iss = random();     /* wrong, but better than a constant */
        tcp_ccgen = 1;
        tcp_cleartaocache();
        LIST_INIT(&tcb);
        tcbinfo.listhead = &tcb;
        if (!(getenv_int("net.inet.tcp.tcbhashsize", &hashsize)))
                hashsize = TCBHASHSIZE;
        if (!powerof2(hashsize)) {
                printf("WARNING: TCB hash size not a power of 2\n");
                hashsize = 512; /* safe default */
        }
        tcbinfo.hashsize = hashsize;
        tcbinfo.hashbase = hashinit(hashsize, M_PCB, &tcbinfo.hashmask);
        tcbinfo.porthashbase = hashinit(hashsize, M_PCB,
                                        &tcbinfo.porthashmask);
#if ISFB31
        tcbinfo.ipi_zone = (void *) zinit("tcpcb", sizeof(struct inp_tp), maxsockets,
                                 ZONE_INTERRUPT, 0);
#else
        str_size = (vm_size_t) sizeof(struct inp_tp);
        tcbinfo.ipi_zone = (void *) zinit(str_size, 120000*str_size, 8192, "inpcb_zone");
#endif
#if INET6
#define TCP_LGHDR (sizeof(struct tcpip6hdr))
#else /* INET6 */
#define TCP_LGHDR (sizeof(struct tcpiphdr))
#endif /* INET6 */
        if (max_protohdr < TCP_LGHDR)
                max_protohdr = TCP_LGHDR;
        if ((max_linkhdr + TCP_LGHDR) > MHLEN)
                panic("tcp_init");

        tcbinfo.last_pcb = 0;
        dummy_tcb.t_state = TCP_NSTATES;
        dummy_tcb.t_flags = 0;
        tcbinfo.dummy_cb = (caddr_t) &dummy_tcb;
        in_pcb_nat_init(&tcbinfo, AF_INET, IPPROTO_TCP, SOCK_STREAM);

        delack_bitmask = _MALLOC((4 * hashsize)/32, M_PCB, M_NOWAIT);
        if (delack_bitmask == 0) 
             panic("Delack Memory");

        for (i=0; i < (tcbinfo.hashsize / 32); i++)
                 delack_bitmask[i] = 0;

        for (i=0; i < N_TIME_WAIT_SLOTS; i++) {
             LIST_INIT(&time_wait_slots[i]);
        }
#undef TCP_LGHDR
}

/*
 * 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 tcptemp *
tcp_template(tp)
        struct tcpcb *tp;
{
        register struct inpcb *inp = tp->t_inpcb;
        register struct mbuf *m;
        register struct tcptemp *n;

        if ((n = tp->t_template) == 0) {
                m = m_get(M_DONTWAIT, MT_HEADER);
                if (m == NULL)
                        return (0);
                m->m_len = sizeof (struct tcptemp);
                n = mtod(m, struct tcptemp *);
        }
        bzero(n->tt_x1, sizeof(n->tt_x1));
        n->tt_pr = IPPROTO_TCP;
        n->tt_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));
        n->tt_src = inp->inp_laddr;
        n->tt_dst = inp->inp_faddr;
        n->tt_sport = inp->inp_lport;
        n->tt_dport = inp->inp_fport;
        n->tt_seq = 0;
        n->tt_ack = 0;
        n->tt_x2 = 0;
        n->tt_off = 5;
        n->tt_flags = 0;
        n->tt_win = 0;
        n->tt_sum = 0;
        n->tt_urp = 0;
#if INET6
        n->tt_flow = inp->inp_flow & IPV6_FLOWINFO_MASK;
        if (ip6_auto_flowlabel) {
                n->tt_flow &= ~IPV6_FLOWLABEL_MASK;
                n->tt_flow |= (htonl(ip6_flow_seq++) & IPV6_FLOWLABEL_MASK);
        }
        n->tt_vfc |= IPV6_VERSION;
        n->tt_pr6 = IPPROTO_TCP;
        n->tt_len6 = n->tt_len;
        n->tt_src6 = inp->in6p_laddr;
        n->tt_dst6 = inp->in6p_faddr;
#endif /* INET6 */
        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, iph, th, m, ack, seq, flags, isipv6)
        struct tcpcb *tp;
        void *iph;
        register struct tcphdr *th;
        register struct mbuf *m;
        tcp_seq ack, seq;
        int flags;
#if INET6
        int isipv6;
#endif
{
        register int tlen;
        int win = 0;
        struct route *ro = 0;
        struct route sro;
        struct ip *ip = iph;
        struct tcpiphdr *ti = iph;
        struct tcphdr *nth;
#if INET6
        struct route_in6 *ro6 = 0;
        struct route_in6 sro6;
        struct ip6_hdr *ip6 = iph;
        struct tcpip6hdr *ti6 = iph;
#endif /* INET6 */

        if (tp) {
                if (!(flags & TH_RST))
                        win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);
#if INET6
                if (isipv6)
                        ro6 = &tp->t_inpcb->in6p_route;
                else
#endif /* INET6 */
                ro = &tp->t_inpcb->inp_route;
        } else {
#if INET6
                if (isipv6) {
                        ro6 = &sro6;
                        bzero(ro6, sizeof *ro6);
                } else {
#endif /* INET6 */
                ro = &sro;
                bzero(ro, sizeof *ro);
#if INET6
                }
#endif /* INET6 */
        }
        if (m == 0) {
                m = m_gethdr(M_DONTWAIT, MT_HEADER);
                if (m == NULL)
                        return;
#if TCP_COMPAT_42
                tlen = 1;
#else
                tlen = 0;
#endif
                m->m_data += max_linkhdr;
#if INET6
                if (isipv6) {
                        ti6 = mtod(m, struct tcpip6hdr *);
                        bcopy((caddr_t)ip6, (caddr_t)&ti6->ti6_i,
                              sizeof(struct ip6_hdr));
                        ip6 = &ti6->ti6_i;
                        nth = &ti6->ti6_t;
                } else {
#endif /* INET6 */
                ti = mtod(m, struct tcpiphdr *);
                bcopy((caddr_t)ip, (caddr_t)&ti->ti_i, sizeof(struct ip));
                ip = (struct ip *)&ti->ti_i;
                nth = &ti->ti_t;
#if INET6
                }
#endif /* INET6 */
                bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
                flags = TH_ACK;
        } else {
                m_freem(m->m_next);
                m->m_next = 0;
                m->m_data = (caddr_t)ti;
                /* m_len is set later */
                tlen = 0;
#define xchg(a,b,type) { type t; t=a; a=b; b=t; }
#if INET6
                if (isipv6) {
                        struct in6_addr t;

                        t = ip6->ip6_dst;
                        ip6->ip6_dst = ip6->ip6_src;
                        ip6->ip6_src = t;
                        nth = (struct tcphdr *)(ip6 + 1);
                        if (th != nth) {
                                /*
                                 * this is the case if an extension header
                                 * exists between the IPv6 header and the
                                 * TCP header.
                                 */
                                nth->th_sport = th->th_sport;
                                nth->th_dport = th->th_dport;
                        }
                } else {
#endif /* INET6 */
                        xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, n_long);
                        nth = th;
#if INET6
                }
#endif /* INET6 */
                xchg(nth->th_dport, nth->th_sport, n_short);
#undef xchg
        }
        nth->th_seq = htonl(seq);
        nth->th_ack = htonl(ack);
        nth->th_x2 = 0;
        nth->th_off = sizeof (struct tcphdr) >> 2;
        nth->th_flags = flags;
        if (tp)
                nth->th_win = htons((u_short) (win >> tp->rcv_scale));
        else
                nth->th_win = htons((u_short)win);
        nth->th_urp = 0;
        nth->th_sum = 0;
        tlen += sizeof (struct tcphdr);
#if INET6
        if (isipv6) {
                m->m_len = tlen + sizeof(struct ip6_hdr);
                m->m_pkthdr.len = tlen + sizeof(struct ip6_hdr);
                m->m_pkthdr.rcvif = (struct ifnet *) 0;
                ip6->ip6_plen = htons((u_short)tlen);
                ip6->ip6_nxt = IPPROTO_TCP;
                ip6->ip6_hlim = in6_selecthlim(tp ? tp->t_inpcb : NULL,
                                               ro6 && ro6->ro_rt ?
                                               ro6->ro_rt->rt_ifp :
                                               NULL);
                nth->th_sum = in6_cksum(m, IPPROTO_TCP,
                                         sizeof(struct ip6_hdr), tlen);
                ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
                if (ip6_auto_flowlabel) {
                        ip6->ip6_flow |=
                                (htonl(ip6_flow_seq++) & IPV6_FLOWLABEL_MASK);
                }
        } else {
#endif /* INET6 */
        ti->ti_len = htons((u_short)(tlen));
        m->m_len = tlen + sizeof(struct ip);
        m->m_pkthdr.len = tlen + sizeof(struct ip);
        m->m_pkthdr.rcvif = (struct ifnet *) 0;
        bzero(ti->ti_x1, sizeof(ti->ti_x1));
        nth->th_sum = in_cksum(m, tlen + sizeof(struct ip));
        ip->ip_len = tlen + sizeof (struct ip);
        ip->ip_ttl = ip_defttl;
#if INET6
        }
#endif /* INET6 */
#if TCPDEBUG
        if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
                tcp_trace(TA_OUTPUT, 0, tp,
#if INET6
                          isipv6 ? (void *)ip6 :
#endif /* INET6 */
                          ip,
                          nth, 0);
#endif
#if IPSEC
        ipsec_setsocket(m, tp ? tp->t_inpcb->inp_socket : NULL);
#endif /*IPSEC*/
#if INET6
        if (isipv6) {
                (void)ip6_output(m, NULL, ro6, 0, NULL, NULL);
                if (ro6 == &sro6 && ro6->ro_rt)
                        RTFREE(ro6->ro_rt);
        } else {
#endif /* INET6 */
        (void)ip_output(m, NULL, ro, 0, NULL);
        if (ro == &sro && ro->ro_rt) {
                RTFREE(ro->ro_rt);
        }
#if INET6
        }
#endif /* INET6 */
}

/*
 * Create a new TCP control block, making an
 * empty reassembly queue and hooking it to the argument
 * protocol control block.  The `inp' parameter must have
 * come from the zone allocator set up in tcp_init().
 */
struct tcpcb *
tcp_newtcpcb(inp)
        struct inpcb *inp;
{
        struct inp_tp *it;
        register struct tcpcb *tp;
        register struct socket *so = inp->inp_socket;   
#if INET6
        int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
#endif /* INET6 */


        if (so->cached_in_sock_layer == 0) {
             it = (struct inp_tp *)inp;
             tp = &it->tcb;
        }
        else
             tp = (struct tcpcb *) inp->inp_saved_ppcb;

        bzero((char *) tp, sizeof(struct tcpcb));
        tp->segq.lh_first = NULL;
        tp->t_maxseg = tp->t_maxopd =
#if INET6
                isipv6 ? tcp_v6mssdflt :
#endif /* INET6 */
                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;      /* XXX */
        /*
         * 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;
        /*
         * IPv4 TTL initialization is necessary for an IPv6 socket as well,
         * because the socket may be bound to an IPv6 wildcard address,
         * which may match an IPv4-mapped IPv6 address.
         * XXX: is there a better approach?
         */
        inp->inp_ip_ttl = ip_defttl;
        inp->inp_ppcb = (caddr_t)tp;
        return (tp);            /* XXX */
}

/*
 * Drop a TCP connection, reporting
 * the specified error.  If connection is synchronized,
 * then send a RST to peer.
 */
struct tcpcb *
tcp_drop(tp, errno)
        register struct tcpcb *tp;
        int errno;
{
        struct socket *so = tp->t_inpcb->inp_socket;

        switch (tp->t_state) 
        {
        case TCPS_ESTABLISHED:
        case TCPS_FIN_WAIT_1:
        case TCPS_CLOSING:
        case TCPS_CLOSE_WAIT:
        case TCPS_LAST_ACK:
             current_active_connections--;
             break;
        }
             
        if (TCPS_HAVERCVDSYN(tp->t_state)) {
                tp->t_state = TCPS_CLOSED;
                (void) tcp_output(tp);
                tcpstat.tcps_drops++;
        } else
                tcpstat.tcps_conndrops++;
        if (errno == ETIMEDOUT && tp->t_softerror)
                errno = tp->t_softerror;
        so->so_error = errno;
        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 mbuf *q;
        register struct mbuf *nq;
        struct inpcb *inp = tp->t_inpcb;
        struct socket *so = inp->inp_socket;
#if INET6
        int isipv6 = INP_CHECK_SOCKAF(so, AF_INET6);
#endif /* INET6 */
        register struct rtentry *rt;
        int dosavessthresh;


        KERNEL_DEBUG(DBG_FNC_TCP_CLOSE | DBG_FUNC_START, tp,0,0,0,0);
        switch (tp->t_state) 
        {
        case TCPS_ESTABLISHED:
        case TCPS_FIN_WAIT_1:
        case TCPS_CLOSING:
        case TCPS_CLOSE_WAIT:
        case TCPS_LAST_ACK:
             current_active_connections--;
             break;
        }


        /*
         * 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) {
                register u_long i = 0;
#if INET6
                if (isipv6) {
                        struct sockaddr_in6 *sin6;

                        if ((rt = inp->in6p_route.ro_rt) == NULL)
                                goto no_valid_rt;
                        sin6 = (struct sockaddr_in6 *)rt_key(rt);
                        if (IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr))
                                goto no_valid_rt;
                }
                else
#endif /* INET6 */              
                if ((rt = inp->inp_route.ro_rt) == NULL ||
                    ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr
                    == INADDR_ANY)
                        goto no_valid_rt;

                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++;
                }
                /*
                 * The old comment here said:
                 * 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.
                 *
                 * But we want to save the ssthresh even if no pipesize is
                 * specified explicitly in the route, because such
                 * connections still have an implicit pipesize specified
                 * by the global tcp_sendspace.  In the absence of a reliable
                 * way to calculate the pipesize, it will have to do.
                 */
                i = tp->snd_ssthresh;
                if (rt->rt_rmx.rmx_sendpipe != 0)
                        dosavessthresh = (i < rt->rt_rmx.rmx_sendpipe / 2);
                else
                        dosavessthresh = (i < so->so_snd.sb_hiwat / 2);
                if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
                     i != 0 && rt->rt_rmx.rmx_ssthresh != 0)
                    || dosavessthresh) {
                        /*
                         * 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 +
#if INET6
                                      isipv6 ? sizeof (struct tcpip6hdr) :
#endif /* INET6 */
                                      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++;
                }
        }
    no_valid_rt:
        /* free the reassembly queue, if any */
        (void) tcp_freeq(tp);

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

        if (so->cached_in_sock_layer)
            inp->inp_saved_ppcb = (caddr_t) tp;

        inp->inp_ppcb = NULL;
        soisdisconnected(so);
#if INET6
        if (isipv6)
                in6_pcbdetach(inp);
        else
#endif /* INET6 */
        in_pcbdetach(inp);
        tcpstat.tcps_closed++;
        KERNEL_DEBUG(DBG_FNC_TCP_CLOSE | DBG_FUNC_END, tcpstat.tcps_closed,0,0,0,0);
        return ((struct tcpcb *)0);
}

int
tcp_freeq(tp)
        struct tcpcb *tp;
{
        register struct ipqent *qe;
        int rv = 0;

        while ((qe = tp->segq.lh_first) != NULL) {
                LIST_REMOVE(qe, ipqe_q);
                m_freem(qe->ipqe_m);
                FREE(qe, M_SONAME);
                rv = 1;
        }
        return (rv);
}

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;
        wakeup((caddr_t) &so->so_timeo);
        sorwakeup(so);
        sowwakeup(so);
}


static int
tcp_pcblist SYSCTL_HANDLER_ARGS
{
        int error, i, n, s;
        struct inpcb *inp, **inp_list;
        inp_gen_t gencnt;
        struct xinpgen xig;

        /*
         * The process of preparing the TCB list is too time-consuming and
         * resource-intensive to repeat twice on every request.
         */
        if (req->oldptr == 0) {
                n = tcbinfo.ipi_count;
                req->oldidx = 2 * (sizeof xig)
                        + (n + n/8) * sizeof(struct xtcpcb);
                return 0;
        }

        if (req->newptr != 0)
                return EPERM;

        /*
         * OK, now we're committed to doing something.
         */
        s = splnet();
        gencnt = tcbinfo.ipi_gencnt;
        n = tcbinfo.ipi_count;
        splx(s);

        xig.xig_len = sizeof xig;
        xig.xig_count = n;
        xig.xig_gen = gencnt;
        xig.xig_sogen = so_gencnt;
        error = SYSCTL_OUT(req, &xig, sizeof xig);
        if (error)
                return error;

        inp_list = _MALLOC(n * sizeof *inp_list, M_TEMP, M_WAITOK);
        if (inp_list == 0)
                return ENOMEM;
        
        s = splnet();
        for (inp = tcbinfo.listhead->lh_first, i = 0; inp && i < n;
             inp = inp->inp_list.le_next) {
                if (inp->inp_gencnt <= gencnt)
                        inp_list[i++] = inp;
        }
        splx(s);
        n = i;

        error = 0;
        for (i = 0; i < n; i++) {
                inp = inp_list[i];
                if (inp->inp_gencnt <= gencnt) {
                        struct xtcpcb xt;
                        xt.xt_len = sizeof xt;
                        /* XXX should avoid extra copy */
                        bcopy(inp, &xt.xt_inp, sizeof *inp);
                        bcopy(inp->inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
                        if (inp->inp_socket)
                                sotoxsocket(inp->inp_socket, &xt.xt_socket);
                        error = SYSCTL_OUT(req, &xt, sizeof xt);
                }
        }
        if (!error) {
                /*
                 * Give the user an updated idea of our state.
                 * If the generation differs from what we told
                 * her before, she knows that something happened
                 * while we were processing this request, and it
                 * might be necessary to retry.
                 */
                s = splnet();
                xig.xig_gen = tcbinfo.ipi_gencnt;
                xig.xig_sogen = so_gencnt;
                xig.xig_count = tcbinfo.ipi_count;
                splx(s);
                error = SYSCTL_OUT(req, &xig, sizeof xig);
        }
        FREE(inp_list, M_TEMP);
        return error;
}


SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0,
            tcp_pcblist, "S,xtcpcb", "List of active TCP connections");

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;
        else if (cmd == PRC_MSGSIZE)
                notify = tcp_mtudisc;
        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);
}

#if INET6
void
tcp6_ctlinput(cmd, sa, d)
        int cmd;
        struct sockaddr *sa;
        void *d;
{
        register struct tcphdr *thp;
        struct tcphdr th;
        void (*notify) __P((struct inpcb *, int)) = tcp_notify;
        struct sockaddr_in6 sa6;
        struct ip6_hdr *ip6;
        struct mbuf *m;
        int off = 0 ;

        if (sa->sa_family != AF_INET6 ||
            sa->sa_len != sizeof(struct sockaddr_in6))
                return;

        if (cmd == PRC_QUENCH)
                notify = tcp_quench;
        else if (cmd == PRC_MSGSIZE)
                notify = tcp_mtudisc;
        else if (!PRC_IS_REDIRECT(cmd) &&
                 ((unsigned)cmd > PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
                return;

        /* if the parameter is from icmp6, decode it. */
        if (d != NULL) {
                struct ip6ctlparam *ip6cp = (struct ip6ctlparam *)d;
                m = ip6cp->ip6c_m;
                ip6 = ip6cp->ip6c_ip6;
                off = ip6cp->ip6c_off;
        } else {
                m = NULL;
                ip6 = NULL;
        }

        /* translate addresses into internal form */
        sa6 = *(struct sockaddr_in6 *)sa;
        if (IN6_IS_ADDR_LINKLOCAL(&sa6.sin6_addr) && m && m->m_pkthdr.rcvif)
                sa6.sin6_addr.s6_addr16[1] = htons(m->m_pkthdr.rcvif->if_index);

        if (ip6) {
                /*
                 * XXX: We assume that when IPV6 is non NULL,
                 * M and OFF are valid.
                 */
                struct in6_addr s;

                /* translate addresses into internal form */
                memcpy(&s, &ip6->ip6_src, sizeof(s));
                if (IN6_IS_ADDR_LINKLOCAL(&s))
                        s.s6_addr16[1] = htons(m->m_pkthdr.rcvif->if_index);


                if (m->m_len < off + sizeof(*thp)) {
                        /*
                         * this should be rare case,
                         * so we compromise on this copy...
                         */
                        m_copydata(m, off, sizeof(th), (caddr_t)&th);
                        thp = &th;
                } else
                        thp = (struct tcphdr *)(mtod(m, caddr_t) + off);
                in6_pcbnotify(&tcb, (struct sockaddr *)&sa6, thp->th_dport,
                              &s, thp->th_sport, cmd, notify);
        } else
                in6_pcbnotify(&tcb, (struct sockaddr *)&sa6, 0, &zeroin6_addr,
                              0, cmd, notify);
}
#endif /* INET6 */

/*
 * 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, errno)
        struct inpcb *inp;
        int errno;
{
        struct tcpcb *tp = intotcpcb(inp);

        if (tp)
                tp->snd_cwnd = tp->t_maxseg;
}

/*
 * 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, errno)
        struct inpcb *inp;
        int errno;
{
        struct tcpcb *tp = intotcpcb(inp);
        struct rtentry *rt;
        struct rmxp_tao *taop;
        struct socket *so = inp->inp_socket;
        int offered;
        int mss;
#if INET6
        int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV4) == 0;
#endif /* INET6 */

        if (tp) {
#if INET6
                if (isipv6)
                        rt = tcp_rtlookup6(inp);
                else
#endif /* INET6 */
                rt = tcp_rtlookup(inp);
                if (!rt || !rt->rt_rmx.rmx_mtu) {
                        tp->t_maxopd = tp->t_maxseg =
#if INET6
                                isipv6 ? tcp_v6mssdflt :
#endif /* INET6 */
                                tcp_mssdflt;
                        return;
                }
                taop = rmx_taop(rt->rt_rmx);
                offered = taop->tao_mssopt;
                mss = rt->rt_rmx.rmx_mtu -
#if INET6
                        (isipv6 ?
                         sizeof(struct tcpip6hdr) :
#endif /* INET6 */
                         sizeof(struct tcpiphdr)
#if INET6
                         )
#endif /* INET6 */
                        ;

                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);
        }
}

/*
 * 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;
}

#if INET6
struct rtentry *
tcp_rtlookup6(inp)
        struct inpcb *inp;
{
        struct route_in6 *ro6;
        struct rtentry *rt;

        ro6 = &inp->in6p_route;
        rt = ro6->ro_rt;
        if (rt == NULL || !(rt->rt_flags & RTF_UP)) {
                /* No route yet, so try to acquire one */
                if (!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr)) {
                        ro6->ro_dst.sin6_family = AF_INET6;
                        ro6->ro_dst.sin6_len = sizeof(ro6->ro_dst);
                        ro6->ro_dst.sin6_addr = inp->in6p_faddr;
                        rtalloc((struct route *)ro6);
                        rt = ro6->ro_rt;
                }
        }
        return rt;
}
#endif /* INET6 */

#if IPSEC
/* compute ESP/AH header size for TCP, including outer IP header. */
size_t
ipsec_hdrsiz_tcp(tp, isipv6)
        struct tcpcb *tp;
#if INET6
        int isipv6;
#endif /* INET6 */
{
        struct inpcb *inp;
        struct mbuf *m;
        size_t hdrsiz;
        struct ip *ip;
#if INET6
        struct ip6_hdr *ip6 = NULL;
#endif /* INET6 */
        struct tcphdr *th;

        if (!tp || !tp->t_template || !(inp = tp->t_inpcb))
                return 0;
        MGETHDR(m, M_DONTWAIT, MT_DATA);
        if (!m)
                return 0;
        
#if INET6
        if (isipv6) {
                ip6 = mtod(m, struct ip6_hdr *);
                th = (struct tcphdr *)(ip6 + 1);
                m->m_pkthdr.len = m->m_len = sizeof(struct tcpip6hdr);
                bcopy((caddr_t)&tp->t_template->tt_i6, (caddr_t)ip6,
                      sizeof(struct ip6_hdr));
                bcopy((caddr_t)&tp->t_template->tt_t, (caddr_t)th,
                      sizeof(struct tcphdr));
        } else {
#endif /* INET6 */
        ip = mtod(m, struct ip *);
        th = (struct tcphdr *)(ip + 1);
        m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
        bcopy((caddr_t)&tp->t_template->tt_i, (caddr_t)ip, sizeof(struct ip));
        bcopy((caddr_t)&tp->t_template->tt_t, (caddr_t)th,
              sizeof(struct tcphdr));
#if INET6
        }
#endif /* INET6 */

#if INET6
        if (isipv6)
                hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
        else
#endif /* INET6 */
        hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);

        m_free(m);
        return hdrsiz;
}
#endif /*IPSEC*/

/*
 * 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;
{
#if INET6
        int isipv6 = (inp->inp_vflag & INP_IPV4) == 0;
#endif /* INET6 */
        struct rtentry *rt;

#if INET6
        if (isipv6)
                rt = tcp_rtlookup6(inp);
        else
#endif /* INET6 */
        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()
{
}