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 }
  34
  35 /*
  36  * if_output: Queue packet into an output queue.
  37  * There are 2 output queue's, if_fastq and if_batchq.
  38  * Each output queue is a doubly linked list of double linked lists
  39  * of mbufs, each list belonging to one "session" (socket).  This
  40  * way, we can output packets fairly by sending one packet from each
  41  * session, instead of all the packets from one session, then all packets
  42  * from the next session, etc.  Packets on the if_fastq get absolute
  43  * priority, but if one session hogs the link, it gets "downgraded"
  44  * to the batchq until it runs out of packets, then it'll return
  45  * to the fastq (eg. if the user does an ls -alR in a telnet session,
  46  * it'll temporarily get downgraded to the batchq)
  47  */
  48 void
  49 if_output(struct socket *so, struct mbuf *ifm)
  50 {
  51         Slirp *slirp = ifm->slirp;
  52         struct mbuf *ifq;
  53         int on_fastq = 1;
  54
  55         DEBUG_CALL("if_output");
  56         DEBUG_ARG("so = %p", so);
  57         DEBUG_ARG("ifm = %p", ifm);
  58
  59         /*
  60          * First remove the mbuf from m_usedlist,
  61          * since we're gonna use m_next and m_prev ourselves
  62          * XXX Shouldn't need this, gotta change dtom() etc.
  63          */
  64         if (ifm->m_flags & M_USEDLIST) {
  65                 remque(ifm);
  66                 ifm->m_flags &= ~M_USEDLIST;
  67         }
  68
  69         /*
  70          * See if there's already a batchq list for this session.
  71          * This can include an interactive session, which should go on fastq,
  72          * but gets too greedy... hence it'll be downgraded from fastq to batchq.
  73          * We mustn't put this packet back on the fastq (or we'll send it out of order)
  74          * XXX add cache here?
  75          */
  76         if (so) {
  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
  89         /* No match, check which queue to put it on */
  90         if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
  91                 ifq = (struct mbuf *) slirp->if_fastq.qh_rlink;
  92                 on_fastq = 1;
  93                 /*
  94                  * Check if this packet is a part of the last
  95                  * packet's session
  96                  */
  97                 if (ifq->ifq_so == so) {
  98                         ifm->ifq_so = so;
  99                         ifs_insque(ifm, ifq->ifs_prev);
 100                         goto diddit;
 101                 }
 102         } else {
 103                 ifq = (struct mbuf *) slirp->if_batchq.qh_rlink;
 104         }
 105
 106         /* Create a new doubly linked list for this session */
 107         ifm->ifq_so = so;
 108         ifs_init(ifm);
 109         insque(ifm, ifq);
 110
 111 diddit:
 112         if (so) {
 113                 /* Update *_queued */
 114                 so->so_queued++;
 115                 so->so_nqueued++;
 116                 /*
 117                  * Check if the interactive session should be downgraded to
 118                  * the batchq.  A session is downgraded if it has queued 6
 119                  * packets without pausing, and at least 3 of those packets
 120                  * have been sent over the link
 121                  * (XXX These are arbitrary numbers, probably not optimal..)
 122                  */
 123                 if (on_fastq && ((so->so_nqueued >= 6) &&
 124                                  (so->so_nqueued - so->so_queued) >= 3)) {
 125
 126                         /* Remove from current queue... */
 127                         remque(ifm->ifs_next);
 128
 129                         /* ...And insert in the new.  That'll teach ya! */
 130                         insque(ifm->ifs_next, &slirp->if_batchq);
 131                 }
 132         }
 133
 134 #ifndef FULL_BOLT
 135         /*
 136          * This prevents us from malloc()ing too many mbufs
 137          */
 138         if_start(ifm->slirp);
 139 #endif
 140 }
 141
 142 /*
 143  * Send one packet from each session.
 144  * If there are packets on the fastq, they are sent FIFO, before
 145  * everything else.  Then we choose the first packet from each
 146  * batchq session (socket) and send it.
 147  * For example, if there are 3 ftp sessions fighting for bandwidth,
 148  * one packet will be sent from the first session, then one packet
 149  * from the second session, then one packet from the third.
 150  */
 151 void if_start(Slirp *slirp)
 152 {
 153     uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 154     bool from_batchq = false;
 155     struct mbuf *ifm, *ifm_next, *ifqt;
 156
 157     DEBUG_CALL("if_start");
 158
 159     if (slirp->if_start_busy) {
 160         return;
 161     }
 162     slirp->if_start_busy = true;
 163
 164     struct mbuf *batch_head = NULL;
 165     if (slirp->if_batchq.qh_link != &slirp->if_batchq) {
 166         batch_head = (struct mbuf *) slirp->if_batchq.qh_link;
 167     }
 168
 169     if (slirp->if_fastq.qh_link != &slirp->if_fastq) {
 170         ifm_next = (struct mbuf *) slirp->if_fastq.qh_link;
 171     } else if (batch_head) {
 172         /* Nothing on fastq, pick up from batchq */
 173         ifm_next = batch_head;
 174         from_batchq = true;
 175     } else {
 176         ifm_next = NULL;
 177     }
 178
 179     while (ifm_next) {
 180         ifm = ifm_next;
 181
 182         ifm_next = ifm->ifq_next;
 183         if ((struct quehead *) ifm_next == &slirp->if_fastq) {
 184             /* No more packets in fastq, switch to batchq */
 185             ifm_next = batch_head;
 186             from_batchq = true;
 187         }
 188         if ((struct quehead *) ifm_next == &slirp->if_batchq) {
 189             /* end of batchq */
 190             ifm_next = NULL;
 191         }
 192
 193         /* Try to send packet unless it already expired */
 194         if (ifm->expiration_date >= now && !if_encap(slirp, ifm)) {
 195             /* Packet is delayed due to pending ARP or NDP resolution */
 196             continue;
 197         }
 198
 199         /* Remove it from the queue */
 200         ifqt = ifm->ifq_prev;
 201         remque(ifm);
 202
 203         /* If there are more packets for this session, re-queue them */
 204         if (ifm->ifs_next != ifm) {
 205             struct mbuf *next = ifm->ifs_next;
 206
 207             insque(next, ifqt);
 208             ifs_remque(ifm);
 209             if (!from_batchq) {
 210                 ifm_next = next;
 211             }
 212         }
 213
 214         /* Update so_queued */
 215         if (ifm->ifq_so && --ifm->ifq_so->so_queued == 0) {
 216             /* If there's no more queued, reset nqueued */
 217             ifm->ifq_so->so_nqueued = 0;
 218         }
 219
 220         m_free(ifm);
 221     }
 222
 223     slirp->if_start_busy = false;
 224 }