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 "qemu/osdep.h"
   9 #include <slirp.h>
  10 #include "qemu/timer.h"
  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.qh_link = slirp->if_fastq.qh_rlink = &slirp->if_fastq;
  32     slirp->if_batchq.qh_link = slirp->if_batchq.qh_rlink = &slirp->if_batchq;
  33     slirp->next_m = (struct mbuf *) &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 = %p", so);
  58         DEBUG_ARG("ifm = %p", 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 = (struct mbuf *) slirp->if_batchq.qh_rlink;
  78              (struct quehead *) 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 = (struct mbuf *) slirp->if_fastq.qh_rlink;
  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 = (struct mbuf *) slirp->if_batchq.qh_rlink;
 103                 /* Set next_m if the queue was empty so far */
 104                 if ((struct quehead *) slirp->next_m == &slirp->if_batchq) {
 105                     slirp->next_m = ifm;
 106                 }
 107         }
 108
 109         /* Create a new doubly linked list for this session */
 110         ifm->ifq_so = so;
 111         ifs_init(ifm);
 112         insque(ifm, ifq);
 113
 114 diddit:
 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 its 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 if_start(Slirp *slirp)
 158 {
 159     uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 160     bool from_batchq, next_from_batchq;
 161     struct mbuf *ifm, *ifm_next, *ifqt;
 162
 163     DEBUG_CALL("if_start");
 164
 165     if (slirp->if_start_busy) {
 166         return;
 167     }
 168     slirp->if_start_busy = true;
 169
 170     if (slirp->if_fastq.qh_link != &slirp->if_fastq) {
 171         ifm_next = (struct mbuf *) slirp->if_fastq.qh_link;
 172         next_from_batchq = false;
 173     } else if ((struct quehead *) slirp->next_m != &slirp->if_batchq) {
 174         /* Nothing on fastq, pick up from batchq via next_m */
 175         ifm_next = slirp->next_m;
 176         next_from_batchq = true;
 177     } else {
 178         ifm_next = NULL;
 179     }
 180
 181     while (ifm_next) {
 182         ifm = ifm_next;
 183         from_batchq = next_from_batchq;
 184
 185         ifm_next = ifm->ifq_next;
 186         if ((struct quehead *) ifm_next == &slirp->if_fastq) {
 187             /* No more packets in fastq, switch to batchq */
 188             ifm_next = slirp->next_m;
 189             next_from_batchq = true;
 190         }
 191         if ((struct quehead *) ifm_next == &slirp->if_batchq) {
 192             /* end of batchq */
 193             ifm_next = NULL;
 194         }
 195
 196         /* Try to send packet unless it already expired */
 197         if (ifm->expiration_date >= now && !if_encap(slirp, ifm)) {
 198             /* Packet is delayed due to pending ARP or NDP resolution */
 199             continue;
 200         }
 201
 202         if (ifm == slirp->next_m) {
 203             /* Set which packet to send on next iteration */
 204             slirp->next_m = ifm->ifq_next;
 205         }
 206
 207         /* Remove it from the queue */
 208         ifqt = ifm->ifq_prev;
 209         remque(ifm);
 210
 211         /* If there are more packets for this session, re-queue them */
 212         if (ifm->ifs_next != ifm) {
 213             struct mbuf *next = ifm->ifs_next;
 214
 215             insque(next, ifqt);
 216             ifs_remque(ifm);
 217
 218             if (!from_batchq) {
 219                 /* Next packet in fastq is from the same session */
 220                 ifm_next = next;
 221                 next_from_batchq = false;
 222             } else if ((struct quehead *) slirp->next_m == &slirp->if_batchq) {
 223                 /* Set next_m and ifm_next if the session packet is now the
 224                  * only one on batchq */
 225                 slirp->next_m = ifm_next = next;
 226             }
 227         }
 228
 229         /* Update so_queued */
 230         if (ifm->ifq_so && --ifm->ifq_so->so_queued == 0) {
 231             /* If there's no more queued, reset nqueued */
 232             ifm->ifq_so->so_nqueued = 0;
 233         }
 234
 235         m_free(ifm);
 236     }
 237
 238     slirp->if_start_busy = false;
 239 }