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Sourcecode: qemu version File versions

if.c

/*
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include <slirp.h>

int     if_queued = 0;                  /* Number of packets queued so far */

struct  mbuf if_fastq;                  /* fast queue (for interactive data) */
struct  mbuf if_batchq;                 /* queue for non-interactive data */
struct      mbuf *next_m;                 /* Pointer to next mbuf to output */

#define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))

static void
ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)
{
      ifm->ifs_next = ifmhead->ifs_next;
      ifmhead->ifs_next = ifm;
      ifm->ifs_prev = ifmhead;
      ifm->ifs_next->ifs_prev = ifm;
}

static void
ifs_remque(struct mbuf *ifm)
{
      ifm->ifs_prev->ifs_next = ifm->ifs_next;
      ifm->ifs_next->ifs_prev = ifm->ifs_prev;
}

void
if_init()
{
      if_fastq.ifq_next = if_fastq.ifq_prev = &if_fastq;
      if_batchq.ifq_next = if_batchq.ifq_prev = &if_batchq;
        //  sl_compress_init(&comp_s);
      next_m = &if_batchq;
}

#if 0
/*
 * This shouldn't be needed since the modem is blocking and
 * we don't expect any signals, but what the hell..
 */
inline int
writen(fd, bptr, n)
      int fd;
      char *bptr;
      int n;
{
      int ret;
      int total;

      /* This should succeed most of the time */
      ret = send(fd, bptr, n,0);
      if (ret == n || ret <= 0)
         return ret;

      /* Didn't write everything, go into the loop */
      total = ret;
      while (n > total) {
            ret = send(fd, bptr+total, n-total,0);
            if (ret <= 0)
               return ret;
            total += ret;
      }
      return total;
}

/*
 * if_input - read() the tty, do "top level" processing (ie: check for any escapes),
 * and pass onto (*ttyp->if_input)
 *
 * XXXXX Any zeros arriving by themselves are NOT placed into the arriving packet.
 */
#define INBUFF_SIZE 2048 /* XXX */
void
if_input(ttyp)
      struct ttys *ttyp;
{
      u_char if_inbuff[INBUFF_SIZE];
      int if_n;

      DEBUG_CALL("if_input");
      DEBUG_ARG("ttyp = %lx", (long)ttyp);

      if_n = recv(ttyp->fd, (char *)if_inbuff, INBUFF_SIZE,0);

      DEBUG_MISC((dfd, " read %d bytes\n", if_n));

      if (if_n <= 0) {
            if (if_n == 0 || (errno != EINTR && errno != EAGAIN)) {
                  if (ttyp->up)
                     link_up--;
                  tty_detached(ttyp, 0);
            }
            return;
      }
      if (if_n == 1) {
            if (*if_inbuff == '0') {
                  ttyp->ones = 0;
                  if (++ttyp->zeros >= 5)
                     slirp_exit(0);
                  return;
            }
            if (*if_inbuff == '1') {
                  ttyp->zeros = 0;
                  if (++ttyp->ones >= 5)
                     tty_detached(ttyp, 0);
                  return;
            }
      }
      ttyp->ones = ttyp->zeros = 0;

      (*ttyp->if_input)(ttyp, if_inbuff, if_n);
}
#endif

/*
 * if_output: Queue packet into an output queue.
 * There are 2 output queue's, if_fastq and if_batchq.
 * Each output queue is a doubly linked list of double linked lists
 * of mbufs, each list belonging to one "session" (socket).  This
 * way, we can output packets fairly by sending one packet from each
 * session, instead of all the packets from one session, then all packets
 * from the next session, etc.  Packets on the if_fastq get absolute
 * priority, but if one session hogs the link, it gets "downgraded"
 * to the batchq until it runs out of packets, then it'll return
 * to the fastq (eg. if the user does an ls -alR in a telnet session,
 * it'll temporarily get downgraded to the batchq)
 */
void
if_output(so, ifm)
      struct socket *so;
      struct mbuf *ifm;
{
      struct mbuf *ifq;
      int on_fastq = 1;

      DEBUG_CALL("if_output");
      DEBUG_ARG("so = %lx", (long)so);
      DEBUG_ARG("ifm = %lx", (long)ifm);

      /*
       * First remove the mbuf from m_usedlist,
       * since we're gonna use m_next and m_prev ourselves
       * XXX Shouldn't need this, gotta change dtom() etc.
       */
      if (ifm->m_flags & M_USEDLIST) {
            remque(ifm);
            ifm->m_flags &= ~M_USEDLIST;
      }

      /*
       * See if there's already a batchq list for this session.
       * This can include an interactive session, which should go on fastq,
       * but gets too greedy... hence it'll be downgraded from fastq to batchq.
       * We mustn't put this packet back on the fastq (or we'll send it out of order)
       * XXX add cache here?
       */
      for (ifq = if_batchq.ifq_prev; ifq != &if_batchq; ifq = ifq->ifq_prev) {
            if (so == ifq->ifq_so) {
                  /* A match! */
                  ifm->ifq_so = so;
                  ifs_insque(ifm, ifq->ifs_prev);
                  goto diddit;
            }
      }

      /* No match, check which queue to put it on */
      if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
            ifq = if_fastq.ifq_prev;
            on_fastq = 1;
            /*
             * Check if this packet is a part of the last
             * packet's session
             */
            if (ifq->ifq_so == so) {
                  ifm->ifq_so = so;
                  ifs_insque(ifm, ifq->ifs_prev);
                  goto diddit;
            }
      } else
            ifq = if_batchq.ifq_prev;

      /* Create a new doubly linked list for this session */
      ifm->ifq_so = so;
      ifs_init(ifm);
      insque(ifm, ifq);

diddit:
      ++if_queued;

      if (so) {
            /* Update *_queued */
            so->so_queued++;
            so->so_nqueued++;
            /*
             * Check if the interactive session should be downgraded to
             * the batchq.  A session is downgraded if it has queued 6
             * packets without pausing, and at least 3 of those packets
             * have been sent over the link
             * (XXX These are arbitrary numbers, probably not optimal..)
             */
            if (on_fastq && ((so->so_nqueued >= 6) &&
                         (so->so_nqueued - so->so_queued) >= 3)) {

                  /* Remove from current queue... */
                  remque(ifm->ifs_next);

                  /* ...And insert in the new.  That'll teach ya! */
                  insque(ifm->ifs_next, &if_batchq);
            }
      }

#ifndef FULL_BOLT
      /*
       * This prevents us from malloc()ing too many mbufs
       */
      if (link_up) {
            /* if_start will check towrite */
            if_start();
      }
#endif
}

/*
 * Send a packet
 * We choose a packet based on it's position in the output queues;
 * If there are packets on the fastq, they are sent FIFO, before
 * everything else.  Otherwise we choose the first packet from the
 * batchq and send it.  the next packet chosen will be from the session
 * after this one, then the session after that one, and so on..  So,
 * for example, if there are 3 ftp session's fighting for bandwidth,
 * one packet will be sent from the first session, then one packet
 * from the second session, then one packet from the third, then back
 * to the first, etc. etc.
 */
void
if_start(void)
{
      struct mbuf *ifm, *ifqt;

      DEBUG_CALL("if_start");

      if (if_queued == 0)
         return; /* Nothing to do */

 again:
        /* check if we can really output */
        if (!slirp_can_output())
            return;

      /*
       * See which queue to get next packet from
       * If there's something in the fastq, select it immediately
       */
      if (if_fastq.ifq_next != &if_fastq) {
            ifm = if_fastq.ifq_next;
      } else {
            /* Nothing on fastq, see if next_m is valid */
            if (next_m != &if_batchq)
               ifm = next_m;
            else
               ifm = if_batchq.ifq_next;

            /* Set which packet to send on next iteration */
            next_m = ifm->ifq_next;
      }
      /* Remove it from the queue */
      ifqt = ifm->ifq_prev;
      remque(ifm);
      --if_queued;

      /* If there are more packets for this session, re-queue them */
      if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
            insque(ifm->ifs_next, ifqt);
            ifs_remque(ifm);
      }

      /* Update so_queued */
      if (ifm->ifq_so) {
            if (--ifm->ifq_so->so_queued == 0)
               /* If there's no more queued, reset nqueued */
               ifm->ifq_so->so_nqueued = 0;
      }

      /* Encapsulate the packet for sending */
        if_encap((uint8_t *)ifm->m_data, ifm->m_len);

        m_free(ifm);

      if (if_queued)
         goto again;
}

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