usr/src/sys/netinet/tcp_subr.c

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that this notice is preserved and that due credit is given
 * to the University of California at Berkeley. The name of the University
 * may not be used to endorse or promote products derived from this
 * software without specific prior written permission. This software
 * is provided ``as is'' without express or implied warranty.
 *
 *      @(#)tcp_subr.c  7.13 (Berkeley) %G%
 */

#include "param.h"
#include "systm.h"
#include "mbuf.h"
#include "socket.h"
#include "socketvar.h"
#include "protosw.h"
#include "errno.h"

#include "../net/route.h"
#include "../net/if.h"

#include "in.h"
#include "in_pcb.h"
#include "in_systm.h"
#include "ip.h"
#include "ip_var.h"
#include "ip_icmp.h"
#include "tcp.h"
#include "tcp_fsm.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"
#include "tcpip.h"

int     tcp_ttl = TCP_TTL;

/*
 * Tcp initialization
 */
tcp_init()
{

        tcp_iss = 1;            /* wrong */
        tcb.inp_next = tcb.inp_prev = &tcb;
}

/*
 * 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_off = MMAXOFF - sizeof (struct tcpiphdr);
                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 flags==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.
 */
tcp_respond(tp, ti, ack, seq, flags)
        struct tcpcb *tp;
        register struct tcpiphdr *ti;
        tcp_seq ack, seq;
        int flags;
{
        register struct mbuf *m;
        int win = 0, tlen;
        struct route *ro = 0;

        if (tp) {
                win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);
                ro = &tp->t_inpcb->inp_route;
        }
        if (flags == 0) {
                m = m_get(M_DONTWAIT, MT_HEADER);
                if (m == NULL)
                        return;
#ifdef TCP_COMPAT_42
                tlen = 1;
#else
                tlen = 0;
#endif
                m->m_len = sizeof (struct tcpiphdr) + tlen;
                *mtod(m, struct tcpiphdr *) = *ti;
                ti = mtod(m, struct tcpiphdr *);
                flags = TH_ACK;
        } else {
                m = dtom(ti);
                m_freem(m->m_next);
                m->m_next = 0;
                m->m_off = (int)ti - (int)m;
                tlen = 0;
                m->m_len = sizeof (struct tcpiphdr);
#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_next = ti->ti_prev = 0;
        ti->ti_x1 = 0;
        ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen));
        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;
        ti->ti_win = htons((u_short)win);
        ti->ti_urp = 0;
        ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + tlen);
        ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + tlen;
        ((struct ip *)ti)->ip_ttl = tcp_ttl;
        (void) ip_output(m, (struct mbuf *)0, ro, 0);
}

/*
 * 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;
{
        struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB);
        register struct tcpcb *tp;

        if (m == NULL)
                return ((struct tcpcb *)0);
        tp = mtod(m, struct tcpcb *);
        tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp;
        tp->t_maxseg = TCP_MSS;
        tp->t_flags = 0;                /* sends options! */
        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 + 2 * rttvar gives
         * reasonable initial retransmit time.
         */
        tp->t_srtt = TCPTV_SRTTBASE;
        tp->t_rttvar = TCPTV_SRTTDFLT << 2;
        TCPT_RANGESET(tp->t_rxtcur,
            ((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1,
            TCPTV_MIN, TCPTV_REXMTMAX);
        tp->snd_cwnd = sbspace(&inp->inp_socket->so_snd);
        tp->snd_ssthresh = 65535;               /* XXX */
        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, errno)
        register struct tcpcb *tp;
        int errno;
{
        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++;
        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 tcpiphdr *t;
        struct inpcb *inp = tp->t_inpcb;
        struct socket *so = inp->inp_socket;
        register struct mbuf *m;

        t = tp->seg_next;
        while (t != (struct tcpiphdr *)tp) {
                t = (struct tcpiphdr *)t->ti_next;
                m = dtom(t->ti_prev);
                remque(t->ti_prev);
                m_freem(m);
        }
        if (tp->t_template)
                (void) m_free(dtom(tp->t_template));
        (void) m_free(dtom(tp));
        inp->inp_ppcb = 0;
        soisdisconnected(so);
        in_pcbdetach(inp);
        tcpstat.tcps_closed++;
        return ((struct tcpcb *)0);
}

tcp_drain()
{

}

/*
 * Notify a tcp user of an asynchronous error;
 * just wake up so that he can collect error status.
 */
tcp_notify(inp)
        register struct inpcb *inp;
{

        wakeup((caddr_t) &inp->inp_socket->so_timeo);
        sorwakeup(inp->inp_socket);
        sowwakeup(inp->inp_socket);
}
tcp_ctlinput(cmd, sa)
        int cmd;
        struct sockaddr *sa;
{
        extern u_char inetctlerrmap[];
        struct sockaddr_in *sin;
        int tcp_quench(), in_rtchange();

        if ((unsigned)cmd > PRC_NCMDS)
                return;
        if (sa->sa_family != AF_INET && sa->sa_family != AF_IMPLINK)
                return;
        sin = (struct sockaddr_in *)sa;
        if (sin->sin_addr.s_addr == INADDR_ANY)
                return;

        switch (cmd) {

        case PRC_QUENCH:
                in_pcbnotify(&tcb, &sin->sin_addr, 0, tcp_quench);
                break;

        case PRC_ROUTEDEAD:
        case PRC_REDIRECT_NET:
        case PRC_REDIRECT_HOST:
        case PRC_REDIRECT_TOSNET:
        case PRC_REDIRECT_TOSHOST:
                in_pcbnotify(&tcb, &sin->sin_addr, 0, in_rtchange);
                break;

        default:
                if (inetctlerrmap[cmd] == 0)
                        return;         /* XXX */
                in_pcbnotify(&tcb, &sin->sin_addr, (int)inetctlerrmap[cmd],
                        tcp_notify);
        }
}

/*
 * When a source quench is received, close congestion window
 * to one segment.  We will gradually open it again as we proceed.
 */
tcp_quench(inp)
        struct inpcb *inp;
{
        struct tcpcb *tp = intotcpcb(inp);

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