LXR qemu/slirp/bootp.c

   1/*
   2 * QEMU BOOTP/DHCP server
   3 *
   4 * Copyright (c) 2004 Fabrice Bellard
   5 *
   6 * Permission is hereby granted, free of charge, to any person obtaining a copy
   7 * of this software and associated documentation files (the "Software"), to deal
   8 * in the Software without restriction, including without limitation the rights
   9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 * copies of the Software, and to permit persons to whom the Software is
  11 * furnished to do so, subject to the following conditions:
  12 *
  13 * The above copyright notice and this permission notice shall be included in
  14 * all copies or substantial portions of the Software.
  15 *
  16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 * THE SOFTWARE.
  23 */
  24#include <slirp.h>
  25
  26/* XXX: only DHCP is supported */
  27
  28#define LEASE_TIME (24 * 3600)
  29
  30static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  31
  32#ifdef DEBUG
  33#define DPRINTF(fmt, ...) \
  34do if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); } while (0)
  35#else
  36#define DPRINTF(fmt, ...) do{}while(0)
  37#endif
  38
  39static BOOTPClient *get_new_addr(Slirp *slirp, struct in_addr *paddr,
  40                                 const uint8_t *macaddr)
  41{
  42    BOOTPClient *bc;
  43    int i;
  44
  45    for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  46        bc = &slirp->bootp_clients[i];
  47        if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
  48            goto found;
  49    }
  50    return NULL;
  51 found:
  52    bc = &slirp->bootp_clients[i];
  53    bc->allocated = 1;
  54    paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  55    return bc;
  56}
  57
  58static BOOTPClient *request_addr(Slirp *slirp, const struct in_addr *paddr,
  59                                 const uint8_t *macaddr)
  60{
  61    uint32_t req_addr = ntohl(paddr->s_addr);
  62    uint32_t dhcp_addr = ntohl(slirp->vdhcp_startaddr.s_addr);
  63    BOOTPClient *bc;
  64
  65    if (req_addr >= dhcp_addr &&
  66        req_addr < (dhcp_addr + NB_BOOTP_CLIENTS)) {
  67        bc = &slirp->bootp_clients[req_addr - dhcp_addr];
  68        if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
  69            bc->allocated = 1;
  70            return bc;
  71        }
  72    }
  73    return NULL;
  74}
  75
  76static BOOTPClient *find_addr(Slirp *slirp, struct in_addr *paddr,
  77                              const uint8_t *macaddr)
  78{
  79    BOOTPClient *bc;
  80    int i;
  81
  82    for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  83        if (!memcmp(macaddr, slirp->bootp_clients[i].macaddr, 6))
  84            goto found;
  85    }
  86    return NULL;
  87 found:
  88    bc = &slirp->bootp_clients[i];
  89    bc->allocated = 1;
  90    paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  91    return bc;
  92}
  93
  94static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
  95                        struct in_addr *preq_addr)
  96{
  97    const uint8_t *p, *p_end;
  98    int len, tag;
  99
 100    *pmsg_type = 0;
 101    preq_addr->s_addr = htonl(0L);
 102
 103    p = bp->bp_vend;
 104    p_end = p + DHCP_OPT_LEN;
 105    if (memcmp(p, rfc1533_cookie, 4) != 0)
 106        return;
 107    p += 4;
 108    while (p < p_end) {
 109        tag = p[0];
 110        if (tag == RFC1533_PAD) {
 111            p++;
 112        } else if (tag == RFC1533_END) {
 113            break;
 114        } else {
 115            p++;
 116            if (p >= p_end)
 117                break;
 118            len = *p++;
 119            DPRINTF("dhcp: tag=%d len=%d\n", tag, len);
 120
 121            switch(tag) {
 122            case RFC2132_MSG_TYPE:
 123                if (len >= 1)
 124                    *pmsg_type = p[0];
 125                break;
 126            case RFC2132_REQ_ADDR:
 127                if (len >= 4) {
 128                    memcpy(&(preq_addr->s_addr), p, 4);
 129                }
 130                break;
 131            default:
 132                break;
 133            }
 134            p += len;
 135        }
 136    }
 137    if (*pmsg_type == DHCPREQUEST && preq_addr->s_addr == htonl(0L) &&
 138        bp->bp_ciaddr.s_addr) {
 139        memcpy(&(preq_addr->s_addr), &bp->bp_ciaddr, 4);
 140    }
 141}
 142
 143static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
 144{
 145    BOOTPClient *bc = NULL;
 146    struct mbuf *m;
 147    struct bootp_t *rbp;
 148    struct sockaddr_in saddr, daddr;
 149    struct in_addr preq_addr;
 150    int dhcp_msg_type, val;
 151    uint8_t *q;
 152    uint8_t client_ethaddr[ETH_ALEN];
 153
 154    /* extract exact DHCP msg type */
 155    dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
 156    DPRINTF("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
 157    if (preq_addr.s_addr != htonl(0L))
 158        DPRINTF(" req_addr=%08x\n", ntohl(preq_addr.s_addr));
 159    else
 160        DPRINTF("\n");
 161
 162    if (dhcp_msg_type == 0)
 163        dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 164
 165    if (dhcp_msg_type != DHCPDISCOVER &&
 166        dhcp_msg_type != DHCPREQUEST)
 167        return;
 168
 169    /* Get client's hardware address from bootp request */
 170    memcpy(client_ethaddr, bp->bp_hwaddr, ETH_ALEN);
 171
 172    m = m_get(slirp);
 173    if (!m) {
 174        return;
 175    }
 176    m->m_data += IF_MAXLINKHDR;
 177    rbp = (struct bootp_t *)m->m_data;
 178    m->m_data += sizeof(struct udpiphdr);
 179    memset(rbp, 0, sizeof(struct bootp_t));
 180
 181    if (dhcp_msg_type == DHCPDISCOVER) {
 182        if (preq_addr.s_addr != htonl(0L)) {
 183            bc = request_addr(slirp, &preq_addr, client_ethaddr);
 184            if (bc) {
 185                daddr.sin_addr = preq_addr;
 186            }
 187        }
 188        if (!bc) {
 189         new_addr:
 190            bc = get_new_addr(slirp, &daddr.sin_addr, client_ethaddr);
 191            if (!bc) {
 192                DPRINTF("no address left\n");
 193                return;
 194            }
 195        }
 196        memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
 197    } else if (preq_addr.s_addr != htonl(0L)) {
 198        bc = request_addr(slirp, &preq_addr, client_ethaddr);
 199        if (bc) {
 200            daddr.sin_addr = preq_addr;
 201            memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
 202        } else {
 203            /* DHCPNAKs should be sent to broadcast */
 204            daddr.sin_addr.s_addr = 0xffffffff;
 205        }
 206    } else {
 207        bc = find_addr(slirp, &daddr.sin_addr, bp->bp_hwaddr);
 208        if (!bc) {
 209            /* if never assigned, behaves as if it was already
 210               assigned (windows fix because it remembers its address) */
 211            goto new_addr;
 212        }
 213    }
 214
 215    /* Update ARP table for this IP address */
 216    arp_table_add(slirp, daddr.sin_addr.s_addr, client_ethaddr);
 217
 218    saddr.sin_addr = slirp->vhost_addr;
 219    saddr.sin_port = htons(BOOTP_SERVER);
 220
 221    daddr.sin_port = htons(BOOTP_CLIENT);
 222
 223    rbp->bp_op = BOOTP_REPLY;
 224    rbp->bp_xid = bp->bp_xid;
 225    rbp->bp_htype = 1;
 226    rbp->bp_hlen = 6;
 227    memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, ETH_ALEN);
 228
 229    rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 230    rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 231
 232    q = rbp->bp_vend;
 233    memcpy(q, rfc1533_cookie, 4);
 234    q += 4;
 235
 236    if (bc) {
 237        DPRINTF("%s addr=%08x\n",
 238                (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 239                ntohl(daddr.sin_addr.s_addr));
 240
 241        if (dhcp_msg_type == DHCPDISCOVER) {
 242            *q++ = RFC2132_MSG_TYPE;
 243            *q++ = 1;
 244            *q++ = DHCPOFFER;
 245        } else /* DHCPREQUEST */ {
 246            *q++ = RFC2132_MSG_TYPE;
 247            *q++ = 1;
 248            *q++ = DHCPACK;
 249        }
 250
 251        if (slirp->bootp_filename)
 252            snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 253                     slirp->bootp_filename);
 254
 255        *q++ = RFC2132_SRV_ID;
 256        *q++ = 4;
 257        memcpy(q, &saddr.sin_addr, 4);
 258        q += 4;
 259
 260        *q++ = RFC1533_NETMASK;
 261        *q++ = 4;
 262        memcpy(q, &slirp->vnetwork_mask, 4);
 263        q += 4;
 264
 265        if (!slirp->restricted) {
 266            *q++ = RFC1533_GATEWAY;
 267            *q++ = 4;
 268            memcpy(q, &saddr.sin_addr, 4);
 269            q += 4;
 270
 271            *q++ = RFC1533_DNS;
 272            *q++ = 4;
 273            memcpy(q, &slirp->vnameserver_addr, 4);
 274            q += 4;
 275        }
 276
 277        *q++ = RFC2132_LEASE_TIME;
 278        *q++ = 4;
 279        val = htonl(LEASE_TIME);
 280        memcpy(q, &val, 4);
 281        q += 4;
 282
 283        if (*slirp->client_hostname) {
 284            val = strlen(slirp->client_hostname);
 285            *q++ = RFC1533_HOSTNAME;
 286            *q++ = val;
 287            memcpy(q, slirp->client_hostname, val);
 288            q += val;
 289        }
 290
 291        if (slirp->vdnssearch) {
 292            size_t spaceleft = sizeof(rbp->bp_vend) - (q - rbp->bp_vend);
 293            val = slirp->vdnssearch_len;
 294            if (val + 1 > spaceleft) {
 295                g_warning("DHCP packet size exceeded, "
 296                    "omitting domain-search option.");
 297            } else {
 298                memcpy(q, slirp->vdnssearch, val);
 299                q += val;
 300            }
 301        }
 302    } else {
 303        static const char nak_msg[] = "requested address not available";
 304
 305        DPRINTF("nak'ed addr=%08x\n", ntohl(preq_addr.s_addr));
 306
 307        *q++ = RFC2132_MSG_TYPE;
 308        *q++ = 1;
 309        *q++ = DHCPNAK;
 310
 311        *q++ = RFC2132_MESSAGE;
 312        *q++ = sizeof(nak_msg) - 1;
 313        memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 314        q += sizeof(nak_msg) - 1;
 315    }
 316    *q = RFC1533_END;
 317
 318    daddr.sin_addr.s_addr = 0xffffffffu;
 319
 320    m->m_len = sizeof(struct bootp_t) -
 321        sizeof(struct ip) - sizeof(struct udphdr);
 322    udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 323}
 324
 325void bootp_input(struct mbuf *m)
 326{
 327    struct bootp_t *bp = mtod(m, struct bootp_t *);
 328
 329    if (bp->bp_op == BOOTP_REQUEST) {
 330        bootp_reply(m->slirp, bp);
 331    }
 332}
 333