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 int     if_queued = 0;                  /* Number of packets queued so far */
  11
  12 struct  mbuf if_fastq;                  /* fast queue (for interactive data) */
  13 struct  mbuf if_batchq;                 /* queue for non-interactive data */
  14 struct  mbuf *next_m;                   /* Pointer to next mbuf to output */
  15
  16 #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
  17
  18 static void
  19 ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)
  20 {
  21         ifm->ifs_next = ifmhead->ifs_next;
  22         ifmhead->ifs_next = ifm;
  23         ifm->ifs_prev = ifmhead;
  24         ifm->ifs_next->ifs_prev = ifm;
  25 }
  26
  27 static void
  28 ifs_remque(struct mbuf *ifm)
  29 {
  30         ifm->ifs_prev->ifs_next = ifm->ifs_next;
  31         ifm->ifs_next->ifs_prev = ifm->ifs_prev;
  32 }
  33
  34 void
  35 if_init(void)
  36 {
  37         if_fastq.ifq_next = if_fastq.ifq_prev = &if_fastq;
  38         if_batchq.ifq_next = if_batchq.ifq_prev = &if_batchq;
  39         //      sl_compress_init(&comp_s);
  40         next_m = &if_batchq;
  41 }
  42
  43 #if 0
  44 /*
  45  * This shouldn't be needed since the modem is blocking and
  46  * we don't expect any signals, but what the hell..
  47  */
  48 inline int
  49 writen(fd, bptr, n)
  50         int fd;
  51         char *bptr;
  52         int n;
  53 {
  54         int ret;
  55         int total;
  56
  57         /* This should succeed most of the time */
  58         ret = send(fd, bptr, n,0);
  59         if (ret == n || ret <= 0)
  60            return ret;
  61
  62         /* Didn't write everything, go into the loop */
  63         total = ret;
  64         while (n > total) {
  65                 ret = send(fd, bptr+total, n-total,0);
  66                 if (ret <= 0)
  67                    return ret;
  68                 total += ret;
  69         }
  70         return total;
  71 }
  72
  73 /*
  74  * if_input - read() the tty, do "top level" processing (ie: check for any escapes),
  75  * and pass onto (*ttyp->if_input)
  76  *
  77  * XXXXX Any zeros arriving by themselves are NOT placed into the arriving packet.
  78  */
  79 #define INBUFF_SIZE 2048 /* XXX */
  80 void
  81 if_input(ttyp)
  82         struct ttys *ttyp;
  83 {
  84         u_char if_inbuff[INBUFF_SIZE];
  85         int if_n;
  86
  87         DEBUG_CALL("if_input");
  88         DEBUG_ARG("ttyp = %lx", (long)ttyp);
  89
  90         if_n = recv(ttyp->fd, (char *)if_inbuff, INBUFF_SIZE,0);
  91
  92         DEBUG_MISC((dfd, " read %d bytes\n", if_n));
  93
  94         if (if_n <= 0) {
  95                 if (if_n == 0 || (errno != EINTR && errno != EAGAIN)) {
  96                         if (ttyp->up)
  97                            link_up--;
  98                         tty_detached(ttyp, 0);
  99                 }
 100                 return;
 101         }
 102         if (if_n == 1) {
 103                 if (*if_inbuff == '0') {
 104                         ttyp->ones = 0;
 105                         if (++ttyp->zeros >= 5)
 106                            slirp_exit(0);
 107                         return;
 108                 }
 109                 if (*if_inbuff == '1') {
 110                         ttyp->zeros = 0;
 111                         if (++ttyp->ones >= 5)
 112                            tty_detached(ttyp, 0);
 113                         return;
 114                 }
 115         }
 116         ttyp->ones = ttyp->zeros = 0;
 117
 118         (*ttyp->if_input)(ttyp, if_inbuff, if_n);
 119 }
 120 #endif
 121
 122 /*
 123  * if_output: Queue packet into an output queue.
 124  * There are 2 output queue's, if_fastq and if_batchq.
 125  * Each output queue is a doubly linked list of double linked lists
 126  * of mbufs, each list belonging to one "session" (socket).  This
 127  * way, we can output packets fairly by sending one packet from each
 128  * session, instead of all the packets from one session, then all packets
 129  * from the next session, etc.  Packets on the if_fastq get absolute
 130  * priority, but if one session hogs the link, it gets "downgraded"
 131  * to the batchq until it runs out of packets, then it'll return
 132  * to the fastq (eg. if the user does an ls -alR in a telnet session,
 133  * it'll temporarily get downgraded to the batchq)
 134  */
 135 void
 136 if_output(struct socket *so, struct mbuf *ifm)
 137 {
 138         struct mbuf *ifq;
 139         int on_fastq = 1;
 140
 141         DEBUG_CALL("if_output");
 142         DEBUG_ARG("so = %lx", (long)so);
 143         DEBUG_ARG("ifm = %lx", (long)ifm);
 144
 145         /*
 146          * First remove the mbuf from m_usedlist,
 147          * since we're gonna use m_next and m_prev ourselves
 148          * XXX Shouldn't need this, gotta change dtom() etc.
 149          */
 150         if (ifm->m_flags & M_USEDLIST) {
 151                 remque(ifm);
 152                 ifm->m_flags &= ~M_USEDLIST;
 153         }
 154
 155         /*
 156          * See if there's already a batchq list for this session.
 157          * This can include an interactive session, which should go on fastq,
 158          * but gets too greedy... hence it'll be downgraded from fastq to batchq.
 159          * We mustn't put this packet back on the fastq (or we'll send it out of order)
 160          * XXX add cache here?
 161          */
 162         for (ifq = if_batchq.ifq_prev; ifq != &if_batchq; ifq = ifq->ifq_prev) {
 163                 if (so == ifq->ifq_so) {
 164                         /* A match! */
 165                         ifm->ifq_so = so;
 166                         ifs_insque(ifm, ifq->ifs_prev);
 167                         goto diddit;
 168                 }
 169         }
 170
 171         /* No match, check which queue to put it on */
 172         if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
 173                 ifq = if_fastq.ifq_prev;
 174                 on_fastq = 1;
 175                 /*
 176                  * Check if this packet is a part of the last
 177                  * packet's session
 178                  */
 179                 if (ifq->ifq_so == so) {
 180                         ifm->ifq_so = so;
 181                         ifs_insque(ifm, ifq->ifs_prev);
 182                         goto diddit;
 183                 }
 184         } else
 185                 ifq = if_batchq.ifq_prev;
 186
 187         /* Create a new doubly linked list for this session */
 188         ifm->ifq_so = so;
 189         ifs_init(ifm);
 190         insque(ifm, ifq);
 191
 192 diddit:
 193         ++if_queued;
 194
 195         if (so) {
 196                 /* Update *_queued */
 197                 so->so_queued++;
 198                 so->so_nqueued++;
 199                 /*
 200                  * Check if the interactive session should be downgraded to
 201                  * the batchq.  A session is downgraded if it has queued 6
 202                  * packets without pausing, and at least 3 of those packets
 203                  * have been sent over the link
 204                  * (XXX These are arbitrary numbers, probably not optimal..)
 205                  */
 206                 if (on_fastq && ((so->so_nqueued >= 6) &&
 207                                  (so->so_nqueued - so->so_queued) >= 3)) {
 208
 209                         /* Remove from current queue... */
 210                         remque(ifm->ifs_next);
 211
 212                         /* ...And insert in the new.  That'll teach ya! */
 213                         insque(ifm->ifs_next, &if_batchq);
 214                 }
 215         }
 216
 217 #ifndef FULL_BOLT
 218         /*
 219          * This prevents us from malloc()ing too many mbufs
 220          */
 221         if (link_up) {
 222                 /* if_start will check towrite */
 223                 if_start();
 224         }
 225 #endif
 226 }
 227
 228 /*
 229  * Send a packet
 230  * We choose a packet based on it's position in the output queues;
 231  * If there are packets on the fastq, they are sent FIFO, before
 232  * everything else.  Otherwise we choose the first packet from the
 233  * batchq and send it.  the next packet chosen will be from the session
 234  * after this one, then the session after that one, and so on..  So,
 235  * for example, if there are 3 ftp session's fighting for bandwidth,
 236  * one packet will be sent from the first session, then one packet
 237  * from the second session, then one packet from the third, then back
 238  * to the first, etc. etc.
 239  */
 240 void
 241 if_start(void)
 242 {
 243         struct mbuf *ifm, *ifqt;
 244
 245         DEBUG_CALL("if_start");
 246
 247         if (if_queued == 0)
 248            return; /* Nothing to do */
 249
 250  again:
 251         /* check if we can really output */
 252         if (!slirp_can_output())
 253             return;
 254
 255         /*
 256          * See which queue to get next packet from
 257          * If there's something in the fastq, select it immediately
 258          */
 259         if (if_fastq.ifq_next != &if_fastq) {
 260                 ifm = if_fastq.ifq_next;
 261         } else {
 262                 /* Nothing on fastq, see if next_m is valid */
 263                 if (next_m != &if_batchq)
 264                    ifm = next_m;
 265                 else
 266                    ifm = if_batchq.ifq_next;
 267
 268                 /* Set which packet to send on next iteration */
 269                 next_m = ifm->ifq_next;
 270         }
 271         /* Remove it from the queue */
 272         ifqt = ifm->ifq_prev;
 273         remque(ifm);
 274         --if_queued;
 275
 276         /* If there are more packets for this session, re-queue them */
 277         if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
 278                 insque(ifm->ifs_next, ifqt);
 279                 ifs_remque(ifm);
 280         }
 281
 282         /* Update so_queued */
 283         if (ifm->ifq_so) {
 284                 if (--ifm->ifq_so->so_queued == 0)
 285                    /* If there's no more queued, reset nqueued */
 286                    ifm->ifq_so->so_nqueued = 0;
 287         }
 288
 289         /* Encapsulate the packet for sending */
 290         if_encap((uint8_t *)ifm->m_data, ifm->m_len);
 291
 292         m_free(ifm);
 293
 294         if (if_queued)
 295            goto again;
 296 }