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