slirp/if.c

   1 /*
   2  * Copyright (c) 1995 Danny Gasparovski.
   3  *
   4  * Please read the file COPYRIGHT for the
   5  * terms and conditions of the copyright.
   6  */
   7
   8 #include <slirp.h>
   9
  10 #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
  11
  12 static void
  13 ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)
  14 {
  15         ifm->ifs_next = ifmhead->ifs_next;
  16         ifmhead->ifs_next = ifm;
  17         ifm->ifs_prev = ifmhead;
  18         ifm->ifs_next->ifs_prev = ifm;
  19 }
  20
  21 static void
  22 ifs_remque(struct mbuf *ifm)
  23 {
  24         ifm->ifs_prev->ifs_next = ifm->ifs_next;
  25         ifm->ifs_next->ifs_prev = ifm->ifs_prev;
  26 }
  27
  28 void
  29 if_init(Slirp *slirp)
  30 {
  31     slirp->if_fastq.ifq_next = slirp->if_fastq.ifq_prev = &slirp->if_fastq;
  32     slirp->if_batchq.ifq_next = slirp->if_batchq.ifq_prev = &slirp->if_batchq;
  33     slirp->next_m = &slirp->if_batchq;
  34 }
  35
  36 /*
  37  * if_output: Queue packet into an output queue.
  38  * There are 2 output queue's, if_fastq and if_batchq.
  39  * Each output queue is a doubly linked list of double linked lists
  40  * of mbufs, each list belonging to one "session" (socket).  This
  41  * way, we can output packets fairly by sending one packet from each
  42  * session, instead of all the packets from one session, then all packets
  43  * from the next session, etc.  Packets on the if_fastq get absolute
  44  * priority, but if one session hogs the link, it gets "downgraded"
  45  * to the batchq until it runs out of packets, then it'll return
  46  * to the fastq (eg. if the user does an ls -alR in a telnet session,
  47  * it'll temporarily get downgraded to the batchq)
  48  */
  49 void
  50 if_output(struct socket *so, struct mbuf *ifm)
  51 {
  52         Slirp *slirp = ifm->slirp;
  53         struct mbuf *ifq;
  54         int on_fastq = 1;
  55
  56         DEBUG_CALL("if_output");
  57         DEBUG_ARG("so = %lx", (long)so);
  58         DEBUG_ARG("ifm = %lx", (long)ifm);
  59
  60         /*
  61          * First remove the mbuf from m_usedlist,
  62          * since we're gonna use m_next and m_prev ourselves
  63          * XXX Shouldn't need this, gotta change dtom() etc.
  64          */
  65         if (ifm->m_flags & M_USEDLIST) {
  66                 remque(ifm);
  67                 ifm->m_flags &= ~M_USEDLIST;
  68         }
  69
  70         /*
  71          * See if there's already a batchq list for this session.
  72          * This can include an interactive session, which should go on fastq,
  73          * but gets too greedy... hence it'll be downgraded from fastq to batchq.
  74          * We mustn't put this packet back on the fastq (or we'll send it out of order)
  75          * XXX add cache here?
  76          */
  77         for (ifq = slirp->if_batchq.ifq_prev; ifq != &slirp->if_batchq;
  78              ifq = ifq->ifq_prev) {
  79                 if (so == ifq->ifq_so) {
  80                         /* A match! */
  81                         ifm->ifq_so = so;
  82                         ifs_insque(ifm, ifq->ifs_prev);
  83                         goto diddit;
  84                 }
  85         }
  86
  87         /* No match, check which queue to put it on */
  88         if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
  89                 ifq = slirp->if_fastq.ifq_prev;
  90                 on_fastq = 1;
  91                 /*
  92                  * Check if this packet is a part of the last
  93                  * packet's session
  94                  */
  95                 if (ifq->ifq_so == so) {
  96                         ifm->ifq_so = so;
  97                         ifs_insque(ifm, ifq->ifs_prev);
  98                         goto diddit;
  99                 }
 100         } else
 101                 ifq = slirp->if_batchq.ifq_prev;
 102
 103         /* Create a new doubly linked list for this session */
 104         ifm->ifq_so = so;
 105         ifs_init(ifm);
 106         insque(ifm, ifq);
 107
 108 diddit:
 109         slirp->if_queued++;
 110
 111         if (so) {
 112                 /* Update *_queued */
 113                 so->so_queued++;
 114                 so->so_nqueued++;
 115                 /*
 116                  * Check if the interactive session should be downgraded to
 117                  * the batchq.  A session is downgraded if it has queued 6
 118                  * packets without pausing, and at least 3 of those packets
 119                  * have been sent over the link
 120                  * (XXX These are arbitrary numbers, probably not optimal..)
 121                  */
 122                 if (on_fastq && ((so->so_nqueued >= 6) &&
 123                                  (so->so_nqueued - so->so_queued) >= 3)) {
 124
 125                         /* Remove from current queue... */
 126                         remque(ifm->ifs_next);
 127
 128                         /* ...And insert in the new.  That'll teach ya! */
 129                         insque(ifm->ifs_next, &slirp->if_batchq);
 130                 }
 131         }
 132
 133 #ifndef FULL_BOLT
 134         /*
 135          * This prevents us from malloc()ing too many mbufs
 136          */
 137         if_start(ifm->slirp);
 138 #endif
 139 }
 140
 141 /*
 142  * Send a packet
 143  * We choose a packet based on it's position in the output queues;
 144  * If there are packets on the fastq, they are sent FIFO, before
 145  * everything else.  Otherwise we choose the first packet from the
 146  * batchq and send it.  the next packet chosen will be from the session
 147  * after this one, then the session after that one, and so on..  So,
 148  * for example, if there are 3 ftp session's fighting for bandwidth,
 149  * one packet will be sent from the first session, then one packet
 150  * from the second session, then one packet from the third, then back
 151  * to the first, etc. etc.
 152  */
 153 void
 154 if_start(Slirp *slirp)
 155 {
 156         struct mbuf *ifm, *ifqt;
 157
 158         DEBUG_CALL("if_start");
 159
 160         if (slirp->if_queued == 0)
 161            return; /* Nothing to do */
 162
 163  again:
 164         /* check if we can really output */
 165         if (!slirp_can_output(slirp->opaque))
 166             return;
 167
 168         /*
 169          * See which queue to get next packet from
 170          * If there's something in the fastq, select it immediately
 171          */
 172         if (slirp->if_fastq.ifq_next != &slirp->if_fastq) {
 173                 ifm = slirp->if_fastq.ifq_next;
 174         } else {
 175                 /* Nothing on fastq, see if next_m is valid */
 176                 if (slirp->next_m != &slirp->if_batchq)
 177                    ifm = slirp->next_m;
 178                 else
 179                    ifm = slirp->if_batchq.ifq_next;
 180
 181                 /* Set which packet to send on next iteration */
 182                 slirp->next_m = ifm->ifq_next;
 183         }
 184         /* Remove it from the queue */
 185         ifqt = ifm->ifq_prev;
 186         remque(ifm);
 187         slirp->if_queued--;
 188
 189         /* If there are more packets for this session, re-queue them */
 190         if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
 191                 insque(ifm->ifs_next, ifqt);
 192                 ifs_remque(ifm);
 193         }
 194
 195         /* Update so_queued */
 196         if (ifm->ifq_so) {
 197                 if (--ifm->ifq_so->so_queued == 0)
 198                    /* If there's no more queued, reset nqueued */
 199                    ifm->ifq_so->so_nqueued = 0;
 200         }
 201
 202         /* Encapsulate the packet for sending */
 203         if_encap(slirp, (uint8_t *)ifm->m_data, ifm->m_len);
 204
 205         m_free(ifm);
 206
 207         if (slirp->if_queued)
 208            goto again;
 209 }