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 #include "qemu-timer.h"
  10
  11 #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
  12
  13 static void
  14 ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)
  15 {
  16         ifm->ifs_next = ifmhead->ifs_next;
  17         ifmhead->ifs_next = ifm;
  18         ifm->ifs_prev = ifmhead;
  19         ifm->ifs_next->ifs_prev = ifm;
  20 }
  21
  22 static void
  23 ifs_remque(struct mbuf *ifm)
  24 {
  25         ifm->ifs_prev->ifs_next = ifm->ifs_next;
  26         ifm->ifs_next->ifs_prev = ifm->ifs_prev;
  27 }
  28
  29 void
  30 if_init(Slirp *slirp)
  31 {
  32     slirp->if_fastq.ifq_next = slirp->if_fastq.ifq_prev = &slirp->if_fastq;
  33     slirp->if_batchq.ifq_next = slirp->if_batchq.ifq_prev = &slirp->if_batchq;
  34     slirp->next_m = &slirp->if_batchq;
  35 }
  36
  37 /*
  38  * if_output: Queue packet into an output queue.
  39  * There are 2 output queue's, if_fastq and if_batchq.
  40  * Each output queue is a doubly linked list of double linked lists
  41  * of mbufs, each list belonging to one "session" (socket).  This
  42  * way, we can output packets fairly by sending one packet from each
  43  * session, instead of all the packets from one session, then all packets
  44  * from the next session, etc.  Packets on the if_fastq get absolute
  45  * priority, but if one session hogs the link, it gets "downgraded"
  46  * to the batchq until it runs out of packets, then it'll return
  47  * to the fastq (eg. if the user does an ls -alR in a telnet session,
  48  * it'll temporarily get downgraded to the batchq)
  49  */
  50 void
  51 if_output(struct socket *so, struct mbuf *ifm)
  52 {
  53         Slirp *slirp = ifm->slirp;
  54         struct mbuf *ifq;
  55         int on_fastq = 1;
  56
  57         DEBUG_CALL("if_output");
  58         DEBUG_ARG("so = %lx", (long)so);
  59         DEBUG_ARG("ifm = %lx", (long)ifm);
  60
  61         /*
  62          * First remove the mbuf from m_usedlist,
  63          * since we're gonna use m_next and m_prev ourselves
  64          * XXX Shouldn't need this, gotta change dtom() etc.
  65          */
  66         if (ifm->m_flags & M_USEDLIST) {
  67                 remque(ifm);
  68                 ifm->m_flags &= ~M_USEDLIST;
  69         }
  70
  71         /*
  72          * See if there's already a batchq list for this session.
  73          * This can include an interactive session, which should go on fastq,
  74          * but gets too greedy... hence it'll be downgraded from fastq to batchq.
  75          * We mustn't put this packet back on the fastq (or we'll send it out of order)
  76          * XXX add cache here?
  77          */
  78         for (ifq = slirp->if_batchq.ifq_prev; ifq != &slirp->if_batchq;
  79              ifq = ifq->ifq_prev) {
  80                 if (so == ifq->ifq_so) {
  81                         /* A match! */
  82                         ifm->ifq_so = so;
  83                         ifs_insque(ifm, ifq->ifs_prev);
  84                         goto diddit;
  85                 }
  86         }
  87
  88         /* No match, check which queue to put it on */
  89         if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
  90                 ifq = slirp->if_fastq.ifq_prev;
  91                 on_fastq = 1;
  92                 /*
  93                  * Check if this packet is a part of the last
  94                  * packet's session
  95                  */
  96                 if (ifq->ifq_so == so) {
  97                         ifm->ifq_so = so;
  98                         ifs_insque(ifm, ifq->ifs_prev);
  99                         goto diddit;
 100                 }
 101         } else
 102                 ifq = slirp->if_batchq.ifq_prev;
 103
 104         /* Create a new doubly linked list for this session */
 105         ifm->ifq_so = so;
 106         ifs_init(ifm);
 107         insque(ifm, ifq);
 108
 109         /* Expiration date = Now + 1 second */
 110         ifm->expiration_date = qemu_get_clock_ns(rt_clock) + 1000000000ULL;
 111
 112 diddit:
 113         slirp->if_queued++;
 114
 115         if (so) {
 116                 /* Update *_queued */
 117                 so->so_queued++;
 118                 so->so_nqueued++;
 119                 /*
 120                  * Check if the interactive session should be downgraded to
 121                  * the batchq.  A session is downgraded if it has queued 6
 122                  * packets without pausing, and at least 3 of those packets
 123                  * have been sent over the link
 124                  * (XXX These are arbitrary numbers, probably not optimal..)
 125                  */
 126                 if (on_fastq && ((so->so_nqueued >= 6) &&
 127                                  (so->so_nqueued - so->so_queued) >= 3)) {
 128
 129                         /* Remove from current queue... */
 130                         remque(ifm->ifs_next);
 131
 132                         /* ...And insert in the new.  That'll teach ya! */
 133                         insque(ifm->ifs_next, &slirp->if_batchq);
 134                 }
 135         }
 136
 137 #ifndef FULL_BOLT
 138         /*
 139          * This prevents us from malloc()ing too many mbufs
 140          */
 141         if_start(ifm->slirp);
 142 #endif
 143 }
 144
 145 /*
 146  * Send a packet
 147  * We choose a packet based on it's position in the output queues;
 148  * If there are packets on the fastq, they are sent FIFO, before
 149  * everything else.  Otherwise we choose the first packet from the
 150  * batchq and send it.  the next packet chosen will be from the session
 151  * after this one, then the session after that one, and so on..  So,
 152  * for example, if there are 3 ftp session's fighting for bandwidth,
 153  * one packet will be sent from the first session, then one packet
 154  * from the second session, then one packet from the third, then back
 155  * to the first, etc. etc.
 156  */
 157 void
 158 if_start(Slirp *slirp)
 159 {
 160     int requeued = 0;
 161     uint64_t now;
 162
 163         struct mbuf *ifm, *ifqt;
 164
 165         DEBUG_CALL("if_start");
 166
 167         if (slirp->if_queued == 0)
 168            return; /* Nothing to do */
 169
 170  again:
 171         /* check if we can really output */
 172         if (!slirp_can_output(slirp->opaque))
 173             return;
 174
 175         now = qemu_get_clock_ns(rt_clock);
 176
 177         /*
 178          * See which queue to get next packet from
 179          * If there's something in the fastq, select it immediately
 180          */
 181         if (slirp->if_fastq.ifq_next != &slirp->if_fastq) {
 182                 ifm = slirp->if_fastq.ifq_next;
 183         } else {
 184                 /* Nothing on fastq, see if next_m is valid */
 185                 if (slirp->next_m != &slirp->if_batchq)
 186                    ifm = slirp->next_m;
 187                 else
 188                    ifm = slirp->if_batchq.ifq_next;
 189
 190                 /* Set which packet to send on next iteration */
 191                 slirp->next_m = ifm->ifq_next;
 192         }
 193         /* Remove it from the queue */
 194         ifqt = ifm->ifq_prev;
 195         remque(ifm);
 196         slirp->if_queued--;
 197
 198         /* If there are more packets for this session, re-queue them */
 199         if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
 200                 insque(ifm->ifs_next, ifqt);
 201                 ifs_remque(ifm);
 202         }
 203
 204         /* Update so_queued */
 205         if (ifm->ifq_so) {
 206                 if (--ifm->ifq_so->so_queued == 0)
 207                    /* If there's no more queued, reset nqueued */
 208                    ifm->ifq_so->so_nqueued = 0;
 209         }
 210
 211         if (ifm->expiration_date < now) {
 212             /* Expired */
 213             m_free(ifm);
 214         } else {
 215             /* Encapsulate the packet for sending */
 216             if (if_encap(slirp, ifm)) {
 217                 m_free(ifm);
 218             } else {
 219                 /* re-queue */
 220                 insque(ifm, ifqt);
 221                 requeued++;
 222             }
 223         }
 224
 225         if (slirp->if_queued)
 226            goto again;
 227
 228         slirp->if_queued = requeued;
 229 }