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, ...)
  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                         const 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 = NULL;
 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                     *preq_addr = (struct in_addr *)p;
 129                 break;
 130             default:
 131                 break;
 132             }
 133             p += len;
 134         }
 135     }
 136     if (*pmsg_type == DHCPREQUEST && !*preq_addr && bp->bp_ciaddr.s_addr) {
 137         *preq_addr = &bp->bp_ciaddr;
 138     }
 139 }
 140
 141 static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
 142 {
 143     BOOTPClient *bc = NULL;
 144     struct mbuf *m;
 145     struct bootp_t *rbp;
 146     struct sockaddr_in saddr, daddr;
 147     const struct in_addr *preq_addr;
 148     int dhcp_msg_type, val;
 149     uint8_t *q;
 150
 151     /* extract exact DHCP msg type */
 152     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
 153     dprintf("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
 154     if (preq_addr)
 155         dprintf(" req_addr=%08x\n", ntohl(preq_addr->s_addr));
 156     else
 157         dprintf("\n");
 158
 159     if (dhcp_msg_type == 0)
 160         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 161
 162     if (dhcp_msg_type != DHCPDISCOVER &&
 163         dhcp_msg_type != DHCPREQUEST)
 164         return;
 165     /* XXX: this is a hack to get the client mac address */
 166     memcpy(slirp->client_ethaddr, bp->bp_hwaddr, 6);
 167
 168     m = m_get(slirp);
 169     if (!m) {
 170         return;
 171     }
 172     m->m_data += IF_MAXLINKHDR;
 173     rbp = (struct bootp_t *)m->m_data;
 174     m->m_data += sizeof(struct udpiphdr);
 175     memset(rbp, 0, sizeof(struct bootp_t));
 176
 177     if (dhcp_msg_type == DHCPDISCOVER) {
 178         if (preq_addr) {
 179             bc = request_addr(slirp, preq_addr, slirp->client_ethaddr);
 180             if (bc) {
 181                 daddr.sin_addr = *preq_addr;
 182             }
 183         }
 184         if (!bc) {
 185          new_addr:
 186             bc = get_new_addr(slirp, &daddr.sin_addr, slirp->client_ethaddr);
 187             if (!bc) {
 188                 dprintf("no address left\n");
 189                 return;
 190             }
 191         }
 192         memcpy(bc->macaddr, slirp->client_ethaddr, 6);
 193     } else if (preq_addr) {
 194         bc = request_addr(slirp, preq_addr, slirp->client_ethaddr);
 195         if (bc) {
 196             daddr.sin_addr = *preq_addr;
 197             memcpy(bc->macaddr, slirp->client_ethaddr, 6);
 198         } else {
 199             daddr.sin_addr.s_addr = 0;
 200         }
 201     } else {
 202         bc = find_addr(slirp, &daddr.sin_addr, bp->bp_hwaddr);
 203         if (!bc) {
 204             /* if never assigned, behaves as if it was already
 205                assigned (windows fix because it remembers its address) */
 206             goto new_addr;
 207         }
 208     }
 209
 210     saddr.sin_addr = slirp->vhost_addr;
 211     saddr.sin_port = htons(BOOTP_SERVER);
 212
 213     daddr.sin_port = htons(BOOTP_CLIENT);
 214
 215     rbp->bp_op = BOOTP_REPLY;
 216     rbp->bp_xid = bp->bp_xid;
 217     rbp->bp_htype = 1;
 218     rbp->bp_hlen = 6;
 219     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
 220
 221     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 222     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 223
 224     q = rbp->bp_vend;
 225     memcpy(q, rfc1533_cookie, 4);
 226     q += 4;
 227
 228     if (bc) {
 229         dprintf("%s addr=%08x\n",
 230                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 231                 ntohl(daddr.sin_addr.s_addr));
 232
 233         if (dhcp_msg_type == DHCPDISCOVER) {
 234             *q++ = RFC2132_MSG_TYPE;
 235             *q++ = 1;
 236             *q++ = DHCPOFFER;
 237         } else /* DHCPREQUEST */ {
 238             *q++ = RFC2132_MSG_TYPE;
 239             *q++ = 1;
 240             *q++ = DHCPACK;
 241         }
 242
 243         if (slirp->bootp_filename)
 244             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 245                      slirp->bootp_filename);
 246
 247         *q++ = RFC2132_SRV_ID;
 248         *q++ = 4;
 249         memcpy(q, &saddr.sin_addr, 4);
 250         q += 4;
 251
 252         *q++ = RFC1533_NETMASK;
 253         *q++ = 4;
 254         memcpy(q, &slirp->vnetwork_mask, 4);
 255         q += 4;
 256
 257         if (!slirp->restricted) {
 258             *q++ = RFC1533_GATEWAY;
 259             *q++ = 4;
 260             memcpy(q, &saddr.sin_addr, 4);
 261             q += 4;
 262
 263             *q++ = RFC1533_DNS;
 264             *q++ = 4;
 265             memcpy(q, &slirp->vnameserver_addr, 4);
 266             q += 4;
 267         }
 268
 269         *q++ = RFC2132_LEASE_TIME;
 270         *q++ = 4;
 271         val = htonl(LEASE_TIME);
 272         memcpy(q, &val, 4);
 273         q += 4;
 274
 275         if (*slirp->client_hostname) {
 276             val = strlen(slirp->client_hostname);
 277             *q++ = RFC1533_HOSTNAME;
 278             *q++ = val;
 279             memcpy(q, slirp->client_hostname, val);
 280             q += val;
 281         }
 282     } else {
 283         static const char nak_msg[] = "requested address not available";
 284
 285         dprintf("nak'ed addr=%08x\n", ntohl(preq_addr->s_addr));
 286
 287         *q++ = RFC2132_MSG_TYPE;
 288         *q++ = 1;
 289         *q++ = DHCPNAK;
 290
 291         *q++ = RFC2132_MESSAGE;
 292         *q++ = sizeof(nak_msg) - 1;
 293         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 294         q += sizeof(nak_msg) - 1;
 295     }
 296     *q++ = RFC1533_END;
 297
 298     daddr.sin_addr.s_addr = 0xffffffffu;
 299
 300     m->m_len = sizeof(struct bootp_t) -
 301         sizeof(struct ip) - sizeof(struct udphdr);
 302     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 303 }
 304
 305 void bootp_input(struct mbuf *m)
 306 {
 307     struct bootp_t *bp = mtod(m, struct bootp_t *);
 308
 309     if (bp->bp_op == BOOTP_REQUEST) {
 310         bootp_reply(m->slirp, bp);
 311     }
 312 }