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
  30 static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  31
  32 #ifdef DEBUG
  33 #define DPRINTF(fmt, ...) \
  34 do 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
  39 static 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
  58 static 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
  76 static 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
  94 static 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
 143 static 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
 325 void 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 }