localize header files

[unix-history] / usr / src / sys / netinet / tcp_output.c

/*      tcp_output.c    4.46    82/10/09        */

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/mbuf.h"
#include "../h/protosw.h"
#include "../h/socket.h"
#include "../h/socketvar.h"
#include "../netinet/in.h"
#include "../net/route.h"
#include "../netinet/in_pcb.h"
#include "../netinet/in_systm.h"
#include "../netinet/ip.h"
#include "../netinet/ip_var.h"
#include "../netinet/tcp.h"
#define TCPOUTFLAGS
#include "../netinet/tcp_fsm.h"
#include "../netinet/tcp_seq.h"
#include "../netinet/tcp_timer.h"
#include "../netinet/tcp_var.h"
#include "../netinet/tcpip.h"
#include "../netinet/tcp_debug.h"
#include <errno.h>

char *tcpstates[]; /* XXX */

/*
* Initial options.
*/
u_char  tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, };

/*
* Tcp output routine: figure out what should be sent and send it.
*/
tcp_output(tp)
       register struct tcpcb *tp;
{
       register struct socket *so = tp->t_inpcb->inp_socket;
       register int len;
       struct mbuf *m0;
       int off, flags, win, error;
       register struct mbuf *m;
       register struct tcpiphdr *ti;
       u_char *opt;
       unsigned optlen = 0;
       int sendalot;


       /*
        * Determine length of data that should be transmitted,
        * and flags that will be used.
        * If there is some data or critical controls (SYN, RST)
        * to send, then transmit; otherwise, investigate further.
        */
again:
       sendalot = 0;
       off = tp->snd_nxt - tp->snd_una;
       len = MIN(so->so_snd.sb_cc, tp->snd_wnd+tp->t_force) - off;
       if (len < 0)
               return (0);     /* ??? */       /* past FIN */
       if (len > tp->t_maxseg) {
               len = tp->t_maxseg;
               sendalot = 1;
       }

       flags = tcp_outflags[tp->t_state];
       if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc)
               flags &= ~TH_FIN;
       if (flags & (TH_SYN|TH_RST|TH_FIN))
               goto send;
       if (SEQ_GT(tp->snd_up, tp->snd_una))
               goto send;

       /*
        * Sender silly window avoidance.  If can send all data,
        * a maximum segment, at least 1/4 of window do it,
        * or are forced, do it; otherwise don't bother.
        */
       if (len) {
               if (len == tp->t_maxseg || off+len >= so->so_snd.sb_cc)
                       goto send;
               if (len * 4 >= tp->snd_wnd)             /* a lot */
                       goto send;
               if (tp->t_force)
                       goto send;
       }

       /*
        * Send if we owe peer an ACK.
        */
       if (tp->t_flags&TF_ACKNOW)
               goto send;


       /*
        * Calculate available window in i, and also amount
        * of window known to peer (as advertised window less
        * next expected input.)  If this is 35% or more of the
        * maximum possible window, then want to send a segment to peer.
        */
       win = sbspace(&so->so_rcv);
       if (win > 0 &&
           ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35))
               goto send;

       /*
        * TCP window updates are not reliable, rather a polling protocol
        * using ``persist'' packets is used to insure receipt of window
        * updates.  The three ``states'' for the output side are:
        *      idle                    not doing retransmits or persists
        *      persisting              to move a zero window
        *      (re)transmitting        and thereby not persisting
        *
        * tp->t_timer[TCPT_PERSIST]
        *      is set when we are in persist state.
        * tp->t_force
        *      is set when we are called to send a persist packet.
        * tp->t_timer[TCPT_REXMT]
        *      is set when we are retransmitting
        * The output side is idle when both timers are zero.
        *
        * If send window is closed, there is data to transmit, and no
        * retransmit or persist is pending, then go to persist state,
        * arranging to force out a byte to get more current window information
        * if nothing happens soon.
        */
       if (tp->snd_wnd == 0 && so->so_snd.sb_cc &&
           tp->t_timer[TCPT_REXMT] == 0 && tp->t_timer[TCPT_PERSIST] == 0) {
               tp->t_rxtshift = 0;
               tcp_setpersist(tp);
       }

       /*
        * No reason to send a segment, just return.
        */
       return (0);

send:
       /*
        * Grab a header mbuf, attaching a copy of data to
        * be transmitted, and initialize the header from
        * the template for sends on this connection.
        */
       MGET(m, 0);
       if (m == 0)
               return (ENOBUFS);
       m->m_off = MMAXOFF - sizeof (struct tcpiphdr);
       m->m_len = sizeof (struct tcpiphdr);
       if (len) {
               m->m_next = m_copy(so->so_snd.sb_mb, off, len);
               if (m->m_next == 0)
                       len = 0;
       }
       ti = mtod(m, struct tcpiphdr *);
       if (tp->t_template == 0)
               panic("tcp_output");
       bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr));

       /*
        * Fill in fields, remembering maximum advertised
        * window for use in delaying messages about window sizes.
        */
       ti->ti_seq = tp->snd_nxt;
       ti->ti_ack = tp->rcv_nxt;
#if vax
       ti->ti_seq = htonl(ti->ti_seq);
       ti->ti_ack = htonl(ti->ti_ack);
#endif
       /*
        * Before ESTABLISHED, force sending of initial options
        * unless TCP set to not do any options.
        */
       if (tp->t_state < TCPS_ESTABLISHED) {
               if (tp->t_flags&TF_NOOPT)
                       goto noopt;
               opt = tcp_initopt;
               optlen = sizeof (tcp_initopt);
               *(u_short *)(opt + 2) = MIN(so->so_rcv.sb_hiwat / 2, 1024);
#if vax
               *(u_short *)(opt + 2) = htons(*(u_short *)(opt + 2));
#endif
       } else {
               if (tp->t_tcpopt == 0)
                       goto noopt;
               opt = mtod(tp->t_tcpopt, u_char *);
               optlen = tp->t_tcpopt->m_len;
       }
       if (opt) {
               m0 = m->m_next;
               m->m_next = m_get(M_DONTWAIT);
               if (m->m_next == 0) {
                       (void) m_free(m);
                       m_freem(m0);
                       return (ENOBUFS);
               }
               m->m_next->m_next = m0;
               m0 = m->m_next;
               m0->m_len = optlen;
               bcopy((caddr_t)opt, mtod(m0, caddr_t), optlen);
               opt = (u_char *)(mtod(m0, caddr_t) + optlen);
               while (m0->m_len & 0x3) {
                       *opt++ = TCPOPT_EOL;
                       m0->m_len++;
               }
               optlen = m0->m_len;
               ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
       }
noopt:
       ti->ti_flags = flags;
       win = sbspace(&so->so_rcv);
       if (win < so->so_rcv.sb_hiwat / 4)      /* avoid silly window */
               win = 0;
       if (win > 0)
#if vax
               ti->ti_win = htons((u_short)win);
#else
               ti->ti_win = win;
#endif
       if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
               ti->ti_urp = tp->snd_up - tp->snd_nxt;
#if vax
               ti->ti_urp = htons(ti->ti_urp);
#endif
               ti->ti_flags |= TH_URG;
       } else
               /*
                * If no urgent pointer to send, then we pull
                * the urgent pointer to the left edge of the send window
                * so that it doesn't drift into the send window on sequence
                * number wraparound.
                */
               tp->snd_up = tp->snd_una;               /* drag it along */
       /*
        * If anything to send and we can send it all, set PUSH.
        * (This will keep happy those implementations which only
        * give data to the user when a buffer fills or a PUSH comes in.
        */
       if (len && off+len == so->so_snd.sb_cc)
               ti->ti_flags |= TH_PUSH;

       /*
        * Put TCP length in extended header, and then
        * checksum extended header and data.
        */
       if (len + optlen) {
               ti->ti_len = sizeof (struct tcphdr) + optlen + len;
#if vax
               ti->ti_len = htons((u_short)ti->ti_len);
#endif
       }
       ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len);

       /*
        * In transmit state, time the transmission and arrange for
        * the retransmit.  In persist state, reset persist time for
        * next persist.
        */
       if (tp->t_force == 0) {
               /*
                * Advance snd_nxt over sequence space of this segment.
                */
               if (flags & (TH_SYN|TH_FIN))
                       tp->snd_nxt++;
               tp->snd_nxt += len;
               if (SEQ_GT(tp->snd_nxt, tp->snd_max))
                       tp->snd_max = tp->snd_nxt;

               /*
                * Time this transmission if not a retransmission and
                * not currently timing anything.
                */
               if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) {
                       tp->t_rtt = 1;
                       tp->t_rtseq = tp->snd_nxt - len;
               }

               /*
                * Set retransmit timer if not currently set.
                * Initial value for retransmit timer to tcp_beta*tp->t_srtt.
                * Initialize shift counter which is used for exponential
                * backoff of retransmit time.
                */
               if (tp->t_timer[TCPT_REXMT] == 0 &&
                   tp->snd_nxt != tp->snd_una) {
                       TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
                           tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
                       tp->t_rtt = 0;
                       tp->t_rxtshift = 0;
               }
               tp->t_timer[TCPT_PERSIST] = 0;
       } else {
               if (SEQ_GT(tp->snd_una+1, tp->snd_max))
                       tp->snd_max = tp->snd_una+1;
       }

       /*
        * Trace.
        */
       if (so->so_options & SO_DEBUG)
               tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0);

       /*
        * Fill in IP length and desired time to live and
        * send to IP level.
        */
       ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len;
       ((struct ip *)ti)->ip_ttl = TCP_TTL;
       if (error = ip_output(m, tp->t_ipopt, (so->so_options & SO_DONTROUTE) ?
           &routetoif : &tp->t_inpcb->inp_route, 0))
               return (error);

       /*
        * Data sent (as far as we can tell).
        * If this advertises a larger window than any other segment,
        * then remember the size of the advertised window.
        * Drop send for purpose of ACK requirements.
        */
       if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
               tp->rcv_adv = tp->rcv_nxt + win;
       tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
       if (sendalot && tp->t_force == 0)
               goto again;
       return (0);
}

tcp_setpersist(tp)
       register struct tcpcb *tp;
{

       if (tp->t_timer[TCPT_REXMT])
               panic("tcp_output REXMT");
       /*
        * Start/restart persistance timer.
        */
       TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
           ((int)(tcp_beta * tp->t_srtt)) << tp->t_rxtshift,
           TCPTV_PERSMIN, TCPTV_MAX);
       tp->t_rxtshift++;
       if (tp->t_rxtshift >= TCP_MAXRXTSHIFT)
               tp->t_rxtshift = 0;
}