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_mtu, if_mru;
  11 int if_comp;
  12 int if_maxlinkhdr;
  13 int     if_queued = 0;                  /* Number of packets queued so far */
  14 int     if_thresh = 10;                 /* Number of packets queued before we start sending
  15                                          * (to prevent allocing too many mbufs) */
  16
  17 struct  mbuf if_fastq;                  /* fast queue (for interactive data) */
  18 struct  mbuf if_batchq;                 /* queue for non-interactive data */
  19 struct  mbuf *next_m;                   /* Pointer to next mbuf to output */
  20
  21 #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
  22
  23 void
  24 ifs_insque(ifm, ifmhead)
  25         struct mbuf *ifm, *ifmhead;
  26 {
  27         ifm->ifs_next = ifmhead->ifs_next;
  28         ifmhead->ifs_next = ifm;
  29         ifm->ifs_prev = ifmhead;
  30         ifm->ifs_next->ifs_prev = ifm;
  31 }
  32
  33 void
  34 ifs_remque(ifm)
  35         struct mbuf *ifm;
  36 {
  37         ifm->ifs_prev->ifs_next = ifm->ifs_next;
  38         ifm->ifs_next->ifs_prev = ifm->ifs_prev;
  39 }
  40
  41 void
  42 if_init()
  43 {
  44 #if 0
  45         /*
  46          * Set if_maxlinkhdr to 48 because it's 40 bytes for TCP/IP,
  47          * and 8 bytes for PPP, but need to have it on an 8byte boundary
  48          */
  49 #ifdef USE_PPP
  50         if_maxlinkhdr = 48;
  51 #else
  52         if_maxlinkhdr = 40;
  53 #endif
  54 #else
  55         /* 2 for alignment, 14 for ethernet, 40 for TCP/IP */
  56         if_maxlinkhdr = 2 + 14 + 40;
  57 #endif
  58         if_mtu = 1500;
  59         if_mru = 1500;
  60         if_comp = IF_AUTOCOMP;
  61         if_fastq.ifq_next = if_fastq.ifq_prev = &if_fastq;
  62         if_batchq.ifq_next = if_batchq.ifq_prev = &if_batchq;
  63         //      sl_compress_init(&comp_s);
  64         next_m = &if_batchq;
  65 }
  66
  67 #if 0
  68 /*
  69  * This shouldn't be needed since the modem is blocking and
  70  * we don't expect any signals, but what the hell..
  71  */
  72 inline int
  73 writen(fd, bptr, n)
  74         int fd;
  75         char *bptr;
  76         int n;
  77 {
  78         int ret;
  79         int total;
  80
  81         /* This should succeed most of the time */
  82         ret = send(fd, bptr, n,0);
  83         if (ret == n || ret <= 0)
  84            return ret;
  85
  86         /* Didn't write everything, go into the loop */
  87         total = ret;
  88         while (n > total) {
  89                 ret = send(fd, bptr+total, n-total,0);
  90                 if (ret <= 0)
  91                    return ret;
  92                 total += ret;
  93         }
  94         return total;
  95 }
  96
  97 /*
  98  * if_input - read() the tty, do "top level" processing (ie: check for any escapes),
  99  * and pass onto (*ttyp->if_input)
 100  *
 101  * XXXXX Any zeros arriving by themselves are NOT placed into the arriving packet.
 102  */
 103 #define INBUFF_SIZE 2048 /* XXX */
 104 void
 105 if_input(ttyp)
 106         struct ttys *ttyp;
 107 {
 108         u_char if_inbuff[INBUFF_SIZE];
 109         int if_n;
 110
 111         DEBUG_CALL("if_input");
 112         DEBUG_ARG("ttyp = %lx", (long)ttyp);
 113
 114         if_n = recv(ttyp->fd, (char *)if_inbuff, INBUFF_SIZE,0);
 115
 116         DEBUG_MISC((dfd, " read %d bytes\n", if_n));
 117
 118         if (if_n <= 0) {
 119                 if (if_n == 0 || (errno != EINTR && errno != EAGAIN)) {
 120                         if (ttyp->up)
 121                            link_up--;
 122                         tty_detached(ttyp, 0);
 123                 }
 124                 return;
 125         }
 126         if (if_n == 1) {
 127                 if (*if_inbuff == '0') {
 128                         ttyp->ones = 0;
 129                         if (++ttyp->zeros >= 5)
 130                            slirp_exit(0);
 131                         return;
 132                 }
 133                 if (*if_inbuff == '1') {
 134                         ttyp->zeros = 0;
 135                         if (++ttyp->ones >= 5)
 136                            tty_detached(ttyp, 0);
 137                         return;
 138                 }
 139         }
 140         ttyp->ones = ttyp->zeros = 0;
 141
 142         (*ttyp->if_input)(ttyp, if_inbuff, if_n);
 143 }
 144 #endif
 145
 146 /*
 147  * if_output: Queue packet into an output queue.
 148  * There are 2 output queue's, if_fastq and if_batchq.
 149  * Each output queue is a doubly linked list of double linked lists
 150  * of mbufs, each list belonging to one "session" (socket).  This
 151  * way, we can output packets fairly by sending one packet from each
 152  * session, instead of all the packets from one session, then all packets
 153  * from the next session, etc.  Packets on the if_fastq get absolute
 154  * priority, but if one session hogs the link, it gets "downgraded"
 155  * to the batchq until it runs out of packets, then it'll return
 156  * to the fastq (eg. if the user does an ls -alR in a telnet session,
 157  * it'll temporarily get downgraded to the batchq)
 158  */
 159 void
 160 if_output(so, ifm)
 161         struct socket *so;
 162         struct mbuf *ifm;
 163 {
 164         struct mbuf *ifq;
 165         int on_fastq = 1;
 166
 167         DEBUG_CALL("if_output");
 168         DEBUG_ARG("so = %lx", (long)so);
 169         DEBUG_ARG("ifm = %lx", (long)ifm);
 170
 171         /*
 172          * First remove the mbuf from m_usedlist,
 173          * since we're gonna use m_next and m_prev ourselves
 174          * XXX Shouldn't need this, gotta change dtom() etc.
 175          */
 176         if (ifm->m_flags & M_USEDLIST) {
 177                 remque(ifm);
 178                 ifm->m_flags &= ~M_USEDLIST;
 179         }
 180
 181         /*
 182          * See if there's already a batchq list for this session.
 183          * This can include an interactive session, which should go on fastq,
 184          * but gets too greedy... hence it'll be downgraded from fastq to batchq.
 185          * We mustn't put this packet back on the fastq (or we'll send it out of order)
 186          * XXX add cache here?
 187          */
 188         for (ifq = if_batchq.ifq_prev; ifq != &if_batchq; ifq = ifq->ifq_prev) {
 189                 if (so == ifq->ifq_so) {
 190                         /* A match! */
 191                         ifm->ifq_so = so;
 192                         ifs_insque(ifm, ifq->ifs_prev);
 193                         goto diddit;
 194                 }
 195         }
 196
 197         /* No match, check which queue to put it on */
 198         if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
 199                 ifq = if_fastq.ifq_prev;
 200                 on_fastq = 1;
 201                 /*
 202                  * Check if this packet is a part of the last
 203                  * packet's session
 204                  */
 205                 if (ifq->ifq_so == so) {
 206                         ifm->ifq_so = so;
 207                         ifs_insque(ifm, ifq->ifs_prev);
 208                         goto diddit;
 209                 }
 210         } else
 211                 ifq = if_batchq.ifq_prev;
 212
 213         /* Create a new doubly linked list for this session */
 214         ifm->ifq_so = so;
 215         ifs_init(ifm);
 216         insque(ifm, ifq);
 217
 218 diddit:
 219         ++if_queued;
 220
 221         if (so) {
 222                 /* Update *_queued */
 223                 so->so_queued++;
 224                 so->so_nqueued++;
 225                 /*
 226                  * Check if the interactive session should be downgraded to
 227                  * the batchq.  A session is downgraded if it has queued 6
 228                  * packets without pausing, and at least 3 of those packets
 229                  * have been sent over the link
 230                  * (XXX These are arbitrary numbers, probably not optimal..)
 231                  */
 232                 if (on_fastq && ((so->so_nqueued >= 6) &&
 233                                  (so->so_nqueued - so->so_queued) >= 3)) {
 234
 235                         /* Remove from current queue... */
 236                         remque(ifm->ifs_next);
 237
 238                         /* ...And insert in the new.  That'll teach ya! */
 239                         insque(ifm->ifs_next, &if_batchq);
 240                 }
 241         }
 242
 243 #ifndef FULL_BOLT
 244         /*
 245          * This prevents us from malloc()ing too many mbufs
 246          */
 247         if (link_up) {
 248                 /* if_start will check towrite */
 249                 if_start();
 250         }
 251 #endif
 252 }
 253
 254 /*
 255  * Send a packet
 256  * We choose a packet based on it's position in the output queues;
 257  * If there are packets on the fastq, they are sent FIFO, before
 258  * everything else.  Otherwise we choose the first packet from the
 259  * batchq and send it.  the next packet chosen will be from the session
 260  * after this one, then the session after that one, and so on..  So,
 261  * for example, if there are 3 ftp session's fighting for bandwidth,
 262  * one packet will be sent from the first session, then one packet
 263  * from the second session, then one packet from the third, then back
 264  * to the first, etc. etc.
 265  */
 266 void
 267 if_start(void)
 268 {
 269         struct mbuf *ifm, *ifqt;
 270
 271         DEBUG_CALL("if_start");
 272
 273         if (if_queued == 0)
 274            return; /* Nothing to do */
 275
 276  again:
 277         /* check if we can really output */
 278         if (!slirp_can_output())
 279             return;
 280
 281         /*
 282          * See which queue to get next packet from
 283          * If there's something in the fastq, select it immediately
 284          */
 285         if (if_fastq.ifq_next != &if_fastq) {
 286                 ifm = if_fastq.ifq_next;
 287         } else {
 288                 /* Nothing on fastq, see if next_m is valid */
 289                 if (next_m != &if_batchq)
 290                    ifm = next_m;
 291                 else
 292                    ifm = if_batchq.ifq_next;
 293
 294                 /* Set which packet to send on next iteration */
 295                 next_m = ifm->ifq_next;
 296         }
 297         /* Remove it from the queue */
 298         ifqt = ifm->ifq_prev;
 299         remque(ifm);
 300         --if_queued;
 301
 302         /* If there are more packets for this session, re-queue them */
 303         if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
 304                 insque(ifm->ifs_next, ifqt);
 305                 ifs_remque(ifm);
 306         }
 307
 308         /* Update so_queued */
 309         if (ifm->ifq_so) {
 310                 if (--ifm->ifq_so->so_queued == 0)
 311                    /* If there's no more queued, reset nqueued */
 312                    ifm->ifq_so->so_nqueued = 0;
 313         }
 314
 315         /* Encapsulate the packet for sending */
 316         if_encap(ifm->m_data, ifm->m_len);
 317
 318         m_free(ifm);
 319
 320         if (if_queued)
 321            goto again;
 322 }