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 #ifdef DEBUG
  39 #define DPRINTF(fmt, ...) \
  40 do if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); } while (0)
  41 #else
  42 #define DPRINTF(fmt, ...) do{}while(0)
  43 #endif
  44
  45 static BOOTPClient *get_new_addr(Slirp *slirp, struct in_addr *paddr,
  46                                  const uint8_t *macaddr)
  47 {
  48     BOOTPClient *bc;
  49     int i;
  50
  51     for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  52         bc = &slirp->bootp_clients[i];
  53         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
  54             goto found;
  55     }
  56     return NULL;
  57  found:
  58     bc = &slirp->bootp_clients[i];
  59     bc->allocated = 1;
  60     paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  61     return bc;
  62 }
  63
  64 static BOOTPClient *request_addr(Slirp *slirp, const struct in_addr *paddr,
  65                                  const uint8_t *macaddr)
  66 {
  67     uint32_t req_addr = ntohl(paddr->s_addr);
  68     uint32_t dhcp_addr = ntohl(slirp->vdhcp_startaddr.s_addr);
  69     BOOTPClient *bc;
  70
  71     if (req_addr >= dhcp_addr &&
  72         req_addr < (dhcp_addr + NB_BOOTP_CLIENTS)) {
  73         bc = &slirp->bootp_clients[req_addr - dhcp_addr];
  74         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
  75             bc->allocated = 1;
  76             return bc;
  77         }
  78     }
  79     return NULL;
  80 }
  81
  82 static BOOTPClient *find_addr(Slirp *slirp, struct in_addr *paddr,
  83                               const uint8_t *macaddr)
  84 {
  85     BOOTPClient *bc;
  86     int i;
  87
  88     for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  89         if (!memcmp(macaddr, slirp->bootp_clients[i].macaddr, 6))
  90             goto found;
  91     }
  92     return NULL;
  93  found:
  94     bc = &slirp->bootp_clients[i];
  95     bc->allocated = 1;
  96     paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  97     return bc;
  98 }
  99
 100 static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
 101                         struct in_addr *preq_addr)
 102 {
 103     const uint8_t *p, *p_end;
 104     int len, tag;
 105
 106     *pmsg_type = 0;
 107     preq_addr->s_addr = htonl(0L);
 108
 109     p = bp->bp_vend;
 110     p_end = p + DHCP_OPT_LEN;
 111     if (memcmp(p, rfc1533_cookie, 4) != 0)
 112         return;
 113     p += 4;
 114     while (p < p_end) {
 115         tag = p[0];
 116         if (tag == RFC1533_PAD) {
 117             p++;
 118         } else if (tag == RFC1533_END) {
 119             break;
 120         } else {
 121             p++;
 122             if (p >= p_end)
 123                 break;
 124             len = *p++;
 125             DPRINTF("dhcp: tag=%d len=%d\n", tag, len);
 126
 127             switch(tag) {
 128             case RFC2132_MSG_TYPE:
 129                 if (len >= 1)
 130                     *pmsg_type = p[0];
 131                 break;
 132             case RFC2132_REQ_ADDR:
 133                 if (len >= 4) {
 134                     memcpy(&(preq_addr->s_addr), p, 4);
 135                 }
 136                 break;
 137             default:
 138                 break;
 139             }
 140             p += len;
 141         }
 142     }
 143     if (*pmsg_type == DHCPREQUEST && preq_addr->s_addr == htonl(0L) &&
 144         bp->bp_ciaddr.s_addr) {
 145         memcpy(&(preq_addr->s_addr), &bp->bp_ciaddr, 4);
 146     }
 147 }
 148
 149 static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
 150 {
 151     BOOTPClient *bc = NULL;
 152     struct mbuf *m;
 153     struct bootp_t *rbp;
 154     struct sockaddr_in saddr, daddr;
 155     struct in_addr preq_addr;
 156     int dhcp_msg_type, val;
 157     uint8_t *q;
 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     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     memcpy(q, rfc1533_cookie, 4);
 240     q += 4;
 241
 242     if (bc) {
 243         DPRINTF("%s addr=%08" PRIx32 "\n",
 244                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 245                 ntohl(daddr.sin_addr.s_addr));
 246
 247         if (dhcp_msg_type == DHCPDISCOVER) {
 248             *q++ = RFC2132_MSG_TYPE;
 249             *q++ = 1;
 250             *q++ = DHCPOFFER;
 251         } else /* DHCPREQUEST */ {
 252             *q++ = RFC2132_MSG_TYPE;
 253             *q++ = 1;
 254             *q++ = DHCPACK;
 255         }
 256
 257         if (slirp->bootp_filename)
 258             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 259                      slirp->bootp_filename);
 260
 261         *q++ = RFC2132_SRV_ID;
 262         *q++ = 4;
 263         memcpy(q, &saddr.sin_addr, 4);
 264         q += 4;
 265
 266         *q++ = RFC1533_NETMASK;
 267         *q++ = 4;
 268         memcpy(q, &slirp->vnetwork_mask, 4);
 269         q += 4;
 270
 271         if (!slirp->restricted) {
 272             *q++ = RFC1533_GATEWAY;
 273             *q++ = 4;
 274             memcpy(q, &saddr.sin_addr, 4);
 275             q += 4;
 276
 277             *q++ = RFC1533_DNS;
 278             *q++ = 4;
 279             memcpy(q, &slirp->vnameserver_addr, 4);
 280             q += 4;
 281         }
 282
 283         *q++ = RFC2132_LEASE_TIME;
 284         *q++ = 4;
 285         val = htonl(LEASE_TIME);
 286         memcpy(q, &val, 4);
 287         q += 4;
 288
 289         if (*slirp->client_hostname) {
 290             val = strlen(slirp->client_hostname);
 291             *q++ = RFC1533_HOSTNAME;
 292             *q++ = val;
 293             memcpy(q, slirp->client_hostname, val);
 294             q += val;
 295         }
 296
 297         if (slirp->vdnssearch) {
 298             size_t spaceleft = sizeof(rbp->bp_vend) - (q - rbp->bp_vend);
 299             val = slirp->vdnssearch_len;
 300             if (val + 1 > spaceleft) {
 301                 g_warning("DHCP packet size exceeded, "
 302                     "omitting domain-search option.");
 303             } else {
 304                 memcpy(q, slirp->vdnssearch, val);
 305                 q += val;
 306             }
 307         }
 308     } else {
 309         static const char nak_msg[] = "requested address not available";
 310
 311         DPRINTF("nak'ed addr=%08" PRIx32 "\n", ntohl(preq_addr.s_addr));
 312
 313         *q++ = RFC2132_MSG_TYPE;
 314         *q++ = 1;
 315         *q++ = DHCPNAK;
 316
 317         *q++ = RFC2132_MESSAGE;
 318         *q++ = sizeof(nak_msg) - 1;
 319         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 320         q += sizeof(nak_msg) - 1;
 321     }
 322     *q = RFC1533_END;
 323
 324     daddr.sin_addr.s_addr = 0xffffffffu;
 325
 326     m->m_len = sizeof(struct bootp_t) -
 327         sizeof(struct ip) - sizeof(struct udphdr);
 328     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 329 }
 330
 331 void bootp_input(struct mbuf *m)
 332 {
 333     struct bootp_t *bp = mtod(m, struct bootp_t *);
 334
 335     if (bp->bp_op == BOOTP_REQUEST) {
 336         bootp_reply(m->slirp, bp);
 337     }
 338 }