Annotation of qemu/slirp/if.c, revision 1.1.1.1

1.1       root        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:         /* 14 for ethernet + 40 */
                     56:         if_maxlinkhdr = 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: }

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