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 "qemu/osdep.h"
  25 #include "slirp.h"
  26
  27 #if defined(_WIN32)
  28 /* Windows ntohl() returns an u_long value.
  29  * Add a type cast to match the format strings. */
  30 # define ntohl(n) ((uint32_t)ntohl(n))
  31 #endif
  32
  33 /* XXX: only DHCP is supported */
  34
  35 #define LEASE_TIME (24 * 3600)
  36
  37 static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  38
  39 #define DPRINTF(fmt, ...) DEBUG_CALL(fmt, ##__VA_ARGS__)
  40
  41 static BOOTPClient *get_new_addr(Slirp *slirp, struct in_addr *paddr,
  42                                  const uint8_t *macaddr)
  43 {
  44     BOOTPClient *bc;
  45     int i;
  46
  47     for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  48         bc = &slirp->bootp_clients[i];
  49         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
  50             goto found;
  51     }
  52     return NULL;
  53  found:
  54     bc = &slirp->bootp_clients[i];
  55     bc->allocated = 1;
  56     paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  57     return bc;
  58 }
  59
  60 static BOOTPClient *request_addr(Slirp *slirp, const struct in_addr *paddr,
  61                                  const uint8_t *macaddr)
  62 {
  63     uint32_t req_addr = ntohl(paddr->s_addr);
  64     uint32_t dhcp_addr = ntohl(slirp->vdhcp_startaddr.s_addr);
  65     BOOTPClient *bc;
  66
  67     if (req_addr >= dhcp_addr &&
  68         req_addr < (dhcp_addr + NB_BOOTP_CLIENTS)) {
  69         bc = &slirp->bootp_clients[req_addr - dhcp_addr];
  70         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
  71             bc->allocated = 1;
  72             return bc;
  73         }
  74     }
  75     return NULL;
  76 }
  77
  78 static BOOTPClient *find_addr(Slirp *slirp, struct in_addr *paddr,
  79                               const uint8_t *macaddr)
  80 {
  81     BOOTPClient *bc;
  82     int i;
  83
  84     for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  85         if (!memcmp(macaddr, slirp->bootp_clients[i].macaddr, 6))
  86             goto found;
  87     }
  88     return NULL;
  89  found:
  90     bc = &slirp->bootp_clients[i];
  91     bc->allocated = 1;
  92     paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  93     return bc;
  94 }
  95
  96 static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
  97                         struct in_addr *preq_addr)
  98 {
  99     const uint8_t *p, *p_end;
 100     int len, tag;
 101
 102     *pmsg_type = 0;
 103     preq_addr->s_addr = htonl(0L);
 104
 105     p = bp->bp_vend;
 106     p_end = p + DHCP_OPT_LEN;
 107     if (memcmp(p, rfc1533_cookie, 4) != 0)
 108         return;
 109     p += 4;
 110     while (p < p_end) {
 111         tag = p[0];
 112         if (tag == RFC1533_PAD) {
 113             p++;
 114         } else if (tag == RFC1533_END) {
 115             break;
 116         } else {
 117             p++;
 118             if (p >= p_end)
 119                 break;
 120             len = *p++;
 121             if (p + len > p_end) {
 122                 break;
 123             }
 124             DPRINTF("dhcp: tag=%d len=%d\n", tag, len);
 125
 126             switch(tag) {
 127             case RFC2132_MSG_TYPE:
 128                 if (len >= 1)
 129                     *pmsg_type = p[0];
 130                 break;
 131             case RFC2132_REQ_ADDR:
 132                 if (len >= 4) {
 133                     memcpy(&(preq_addr->s_addr), p, 4);
 134                 }
 135                 break;
 136             default:
 137                 break;
 138             }
 139             p += len;
 140         }
 141     }
 142     if (*pmsg_type == DHCPREQUEST && preq_addr->s_addr == htonl(0L) &&
 143         bp->bp_ciaddr.s_addr) {
 144         memcpy(&(preq_addr->s_addr), &bp->bp_ciaddr, 4);
 145     }
 146 }
 147
 148 static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
 149 {
 150     BOOTPClient *bc = NULL;
 151     struct mbuf *m;
 152     struct bootp_t *rbp;
 153     struct sockaddr_in saddr, daddr;
 154     struct in_addr preq_addr;
 155     int dhcp_msg_type, val;
 156     uint8_t *q;
 157     uint8_t *end;
 158     uint8_t client_ethaddr[ETH_ALEN];
 159
 160     /* extract exact DHCP msg type */
 161     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
 162     DPRINTF("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
 163     if (preq_addr.s_addr != htonl(0L))
 164         DPRINTF(" req_addr=%08" PRIx32 "\n", ntohl(preq_addr.s_addr));
 165     else {
 166         DPRINTF("\n");
 167     }
 168
 169     if (dhcp_msg_type == 0)
 170         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 171
 172     if (dhcp_msg_type != DHCPDISCOVER &&
 173         dhcp_msg_type != DHCPREQUEST)
 174         return;
 175
 176     /* Get client's hardware address from bootp request */
 177     memcpy(client_ethaddr, bp->bp_hwaddr, ETH_ALEN);
 178
 179     m = m_get(slirp);
 180     if (!m) {
 181         return;
 182     }
 183     m->m_data += IF_MAXLINKHDR;
 184     rbp = (struct bootp_t *)m->m_data;
 185     m->m_data += sizeof(struct udpiphdr);
 186     memset(rbp, 0, sizeof(struct bootp_t));
 187
 188     if (dhcp_msg_type == DHCPDISCOVER) {
 189         if (preq_addr.s_addr != htonl(0L)) {
 190             bc = request_addr(slirp, &preq_addr, client_ethaddr);
 191             if (bc) {
 192                 daddr.sin_addr = preq_addr;
 193             }
 194         }
 195         if (!bc) {
 196          new_addr:
 197             bc = get_new_addr(slirp, &daddr.sin_addr, client_ethaddr);
 198             if (!bc) {
 199                 DPRINTF("no address left\n");
 200                 return;
 201             }
 202         }
 203         memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
 204     } else if (preq_addr.s_addr != htonl(0L)) {
 205         bc = request_addr(slirp, &preq_addr, client_ethaddr);
 206         if (bc) {
 207             daddr.sin_addr = preq_addr;
 208             memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
 209         } else {
 210             /* DHCPNAKs should be sent to broadcast */
 211             daddr.sin_addr.s_addr = 0xffffffff;
 212         }
 213     } else {
 214         bc = find_addr(slirp, &daddr.sin_addr, bp->bp_hwaddr);
 215         if (!bc) {
 216             /* if never assigned, behaves as if it was already
 217                assigned (windows fix because it remembers its address) */
 218             goto new_addr;
 219         }
 220     }
 221
 222     /* Update ARP table for this IP address */
 223     arp_table_add(slirp, daddr.sin_addr.s_addr, client_ethaddr);
 224
 225     saddr.sin_addr = slirp->vhost_addr;
 226     saddr.sin_port = htons(BOOTP_SERVER);
 227
 228     daddr.sin_port = htons(BOOTP_CLIENT);
 229
 230     rbp->bp_op = BOOTP_REPLY;
 231     rbp->bp_xid = bp->bp_xid;
 232     rbp->bp_htype = 1;
 233     rbp->bp_hlen = 6;
 234     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, ETH_ALEN);
 235
 236     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 237     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 238
 239     q = rbp->bp_vend;
 240     end = (uint8_t *)&rbp[1];
 241     memcpy(q, rfc1533_cookie, 4);
 242     q += 4;
 243
 244     if (bc) {
 245         DPRINTF("%s addr=%08" PRIx32 "\n",
 246                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 247                 ntohl(daddr.sin_addr.s_addr));
 248
 249         if (dhcp_msg_type == DHCPDISCOVER) {
 250             *q++ = RFC2132_MSG_TYPE;
 251             *q++ = 1;
 252             *q++ = DHCPOFFER;
 253         } else /* DHCPREQUEST */ {
 254             *q++ = RFC2132_MSG_TYPE;
 255             *q++ = 1;
 256             *q++ = DHCPACK;
 257         }
 258
 259         if (slirp->bootp_filename)
 260             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 261                      slirp->bootp_filename);
 262
 263         *q++ = RFC2132_SRV_ID;
 264         *q++ = 4;
 265         memcpy(q, &saddr.sin_addr, 4);
 266         q += 4;
 267
 268         *q++ = RFC1533_NETMASK;
 269         *q++ = 4;
 270         memcpy(q, &slirp->vnetwork_mask, 4);
 271         q += 4;
 272
 273         if (!slirp->restricted) {
 274             *q++ = RFC1533_GATEWAY;
 275             *q++ = 4;
 276             memcpy(q, &saddr.sin_addr, 4);
 277             q += 4;
 278
 279             *q++ = RFC1533_DNS;
 280             *q++ = 4;
 281             memcpy(q, &slirp->vnameserver_addr, 4);
 282             q += 4;
 283         }
 284
 285         *q++ = RFC2132_LEASE_TIME;
 286         *q++ = 4;
 287         val = htonl(LEASE_TIME);
 288         memcpy(q, &val, 4);
 289         q += 4;
 290
 291         if (*slirp->client_hostname) {
 292             val = strlen(slirp->client_hostname);
 293             if (q + val + 2 >= end) {
 294                 g_warning("DHCP packet size exceeded, "
 295                     "omitting host name option.");
 296             } else {
 297                 *q++ = RFC1533_HOSTNAME;
 298                 *q++ = val;
 299                 memcpy(q, slirp->client_hostname, val);
 300                 q += val;
 301             }
 302         }
 303
 304         if (slirp->vdomainname) {
 305             val = strlen(slirp->vdomainname);
 306             if (q + val + 2 >= end) {
 307                 g_warning("DHCP packet size exceeded, "
 308                     "omitting domain name option.");
 309             } else {
 310                 *q++ = RFC1533_DOMAINNAME;
 311                 *q++ = val;
 312                 memcpy(q, slirp->vdomainname, val);
 313                 q += val;
 314             }
 315         }
 316
 317         if (slirp->tftp_server_name) {
 318             val = strlen(slirp->tftp_server_name);
 319             if (q + val + 2 >= end) {
 320                 g_warning("DHCP packet size exceeded, "
 321                     "omitting tftp-server-name option.");
 322             } else {
 323                 *q++ = RFC2132_TFTP_SERVER_NAME;
 324                 *q++ = val;
 325                 memcpy(q, slirp->tftp_server_name, val);
 326                 q += val;
 327             }
 328         }
 329
 330         if (slirp->vdnssearch) {
 331             val = slirp->vdnssearch_len;
 332             if (q + val >= end) {
 333                 g_warning("DHCP packet size exceeded, "
 334                     "omitting domain-search option.");
 335             } else {
 336                 memcpy(q, slirp->vdnssearch, val);
 337                 q += val;
 338             }
 339         }
 340     } else {
 341         static const char nak_msg[] = "requested address not available";
 342
 343         DPRINTF("nak'ed addr=%08" PRIx32 "\n", ntohl(preq_addr.s_addr));
 344
 345         *q++ = RFC2132_MSG_TYPE;
 346         *q++ = 1;
 347         *q++ = DHCPNAK;
 348
 349         *q++ = RFC2132_MESSAGE;
 350         *q++ = sizeof(nak_msg) - 1;
 351         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 352         q += sizeof(nak_msg) - 1;
 353     }
 354     assert(q < end);
 355     *q = RFC1533_END;
 356
 357     daddr.sin_addr.s_addr = 0xffffffffu;
 358
 359     m->m_len = sizeof(struct bootp_t) -
 360         sizeof(struct ip) - sizeof(struct udphdr);
 361     udp_output(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 362 }
 363
 364 void bootp_input(struct mbuf *m)
 365 {
 366     struct bootp_t *bp = mtod(m, struct bootp_t *);
 367
 368     if (bp->bp_op == BOOTP_REQUEST) {
 369         bootp_reply(m->slirp, bp);
 370     }
 371 }