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 NB_ADDR 16
  29
  30 #define START_ADDR 15
  31
  32 #define LEASE_TIME (24 * 3600)
  33
  34 typedef struct {
  35     uint8_t allocated;
  36     uint8_t macaddr[6];
  37 } BOOTPClient;
  38
  39 static BOOTPClient bootp_clients[NB_ADDR];
  40
  41 const char *bootp_filename;
  42
  43 static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  44
  45 #ifdef DEBUG
  46 #define dprintf(fmt, ...) \
  47 if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); }
  48 #else
  49 #define dprintf(fmt, ...)
  50 #endif
  51
  52 static BOOTPClient *get_new_addr(struct in_addr *paddr)
  53 {
  54     BOOTPClient *bc;
  55     int i;
  56
  57     for(i = 0; i < NB_ADDR; i++) {
  58         if (!bootp_clients[i].allocated)
  59             goto found;
  60     }
  61     return NULL;
  62  found:
  63     bc = &bootp_clients[i];
  64     bc->allocated = 1;
  65     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
  66     return bc;
  67 }
  68
  69 static BOOTPClient *request_addr(const struct in_addr *paddr,
  70                                  const uint8_t *macaddr)
  71 {
  72     uint32_t req_addr = ntohl(paddr->s_addr);
  73     uint32_t spec_addr = ntohl(special_addr.s_addr);
  74     BOOTPClient *bc;
  75
  76     if (req_addr >= (spec_addr | START_ADDR) &&
  77         req_addr < (spec_addr | (NB_ADDR + START_ADDR))) {
  78         bc = &bootp_clients[(req_addr & 0xff) - START_ADDR];
  79         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
  80             bc->allocated = 1;
  81             return bc;
  82         }
  83     }
  84     return NULL;
  85 }
  86
  87 static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr)
  88 {
  89     BOOTPClient *bc;
  90     int i;
  91
  92     for(i = 0; i < NB_ADDR; i++) {
  93         if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
  94             goto found;
  95     }
  96     return NULL;
  97  found:
  98     bc = &bootp_clients[i];
  99     bc->allocated = 1;
 100     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
 101     return bc;
 102 }
 103
 104 static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
 105                         const struct in_addr **preq_addr)
 106 {
 107     const uint8_t *p, *p_end;
 108     int len, tag;
 109
 110     *pmsg_type = 0;
 111     *preq_addr = NULL;
 112
 113     p = bp->bp_vend;
 114     p_end = p + DHCP_OPT_LEN;
 115     if (memcmp(p, rfc1533_cookie, 4) != 0)
 116         return;
 117     p += 4;
 118     while (p < p_end) {
 119         tag = p[0];
 120         if (tag == RFC1533_PAD) {
 121             p++;
 122         } else if (tag == RFC1533_END) {
 123             break;
 124         } else {
 125             p++;
 126             if (p >= p_end)
 127                 break;
 128             len = *p++;
 129             dprintf("dhcp: tag=%d len=%d\n", tag, len);
 130
 131             switch(tag) {
 132             case RFC2132_MSG_TYPE:
 133                 if (len >= 1)
 134                     *pmsg_type = p[0];
 135                 break;
 136             case RFC2132_REQ_ADDR:
 137                 if (len >= 4)
 138                     *preq_addr = (struct in_addr *)p;
 139                 break;
 140             default:
 141                 break;
 142             }
 143             p += len;
 144         }
 145     }
 146     if (*pmsg_type == DHCPREQUEST && !*preq_addr && bp->bp_ciaddr.s_addr) {
 147         *preq_addr = &bp->bp_ciaddr;
 148     }
 149 }
 150
 151 static void bootp_reply(const struct bootp_t *bp)
 152 {
 153     BOOTPClient *bc = NULL;
 154     struct mbuf *m;
 155     struct bootp_t *rbp;
 156     struct sockaddr_in saddr, daddr;
 157     struct in_addr dns_addr;
 158     const struct in_addr *preq_addr;
 159     int dhcp_msg_type, val;
 160     uint8_t *q;
 161
 162     /* extract exact DHCP msg type */
 163     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
 164     dprintf("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
 165     if (preq_addr)
 166         dprintf(" req_addr=%08x\n", ntohl(preq_addr->s_addr));
 167     else
 168         dprintf("\n");
 169
 170     if (dhcp_msg_type == 0)
 171         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 172
 173     if (dhcp_msg_type != DHCPDISCOVER &&
 174         dhcp_msg_type != DHCPREQUEST)
 175         return;
 176     /* XXX: this is a hack to get the client mac address */
 177     memcpy(client_ethaddr, bp->bp_hwaddr, 6);
 178
 179     if ((m = m_get()) == NULL)
 180         return;
 181     m->m_data += IF_MAXLINKHDR;
 182     rbp = (struct bootp_t *)m->m_data;
 183     m->m_data += sizeof(struct udpiphdr);
 184     memset(rbp, 0, sizeof(struct bootp_t));
 185
 186     if (dhcp_msg_type == DHCPDISCOVER) {
 187         if (preq_addr) {
 188             bc = request_addr(preq_addr, client_ethaddr);
 189             if (bc) {
 190                 daddr.sin_addr = *preq_addr;
 191             }
 192         }
 193         if (!bc) {
 194          new_addr:
 195             bc = get_new_addr(&daddr.sin_addr);
 196             if (!bc) {
 197                 dprintf("no address left\n");
 198                 return;
 199             }
 200         }
 201         memcpy(bc->macaddr, client_ethaddr, 6);
 202     } else if (preq_addr) {
 203         bc = request_addr(preq_addr, client_ethaddr);
 204         if (bc) {
 205             daddr.sin_addr = *preq_addr;
 206             memcpy(bc->macaddr, client_ethaddr, 6);
 207         } else {
 208             daddr.sin_addr.s_addr = 0;
 209         }
 210     } else {
 211         bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
 212         if (!bc) {
 213             /* if never assigned, behaves as if it was already
 214                assigned (windows fix because it remembers its address) */
 215             goto new_addr;
 216         }
 217     }
 218
 219     saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
 220     saddr.sin_port = htons(BOOTP_SERVER);
 221
 222     daddr.sin_port = htons(BOOTP_CLIENT);
 223
 224     rbp->bp_op = BOOTP_REPLY;
 225     rbp->bp_xid = bp->bp_xid;
 226     rbp->bp_htype = 1;
 227     rbp->bp_hlen = 6;
 228     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
 229
 230     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 231     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 232
 233     q = rbp->bp_vend;
 234     memcpy(q, rfc1533_cookie, 4);
 235     q += 4;
 236
 237     if (bc) {
 238         dprintf("%s addr=%08x\n",
 239                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 240                 ntohl(daddr.sin_addr.s_addr));
 241
 242         if (dhcp_msg_type == DHCPDISCOVER) {
 243             *q++ = RFC2132_MSG_TYPE;
 244             *q++ = 1;
 245             *q++ = DHCPOFFER;
 246         } else /* DHCPREQUEST */ {
 247             *q++ = RFC2132_MSG_TYPE;
 248             *q++ = 1;
 249             *q++ = DHCPACK;
 250         }
 251
 252         if (bootp_filename)
 253             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 254                      bootp_filename);
 255
 256         *q++ = RFC2132_SRV_ID;
 257         *q++ = 4;
 258         memcpy(q, &saddr.sin_addr, 4);
 259         q += 4;
 260
 261         *q++ = RFC1533_NETMASK;
 262         *q++ = 4;
 263         *q++ = 0xff;
 264         *q++ = 0xff;
 265         *q++ = 0xff;
 266         *q++ = 0x00;
 267
 268         if (!slirp_restrict) {
 269             *q++ = RFC1533_GATEWAY;
 270             *q++ = 4;
 271             memcpy(q, &saddr.sin_addr, 4);
 272             q += 4;
 273
 274             *q++ = RFC1533_DNS;
 275             *q++ = 4;
 276             dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
 277             memcpy(q, &dns_addr, 4);
 278             q += 4;
 279         }
 280
 281         *q++ = RFC2132_LEASE_TIME;
 282         *q++ = 4;
 283         val = htonl(LEASE_TIME);
 284         memcpy(q, &val, 4);
 285         q += 4;
 286
 287         if (*slirp_hostname) {
 288             val = strlen(slirp_hostname);
 289             *q++ = RFC1533_HOSTNAME;
 290             *q++ = val;
 291             memcpy(q, slirp_hostname, val);
 292             q += val;
 293         }
 294     } else {
 295         static const char nak_msg[] = "requested address not available";
 296
 297         dprintf("nak'ed addr=%08x\n", ntohl(preq_addr->s_addr));
 298
 299         *q++ = RFC2132_MSG_TYPE;
 300         *q++ = 1;
 301         *q++ = DHCPNAK;
 302
 303         *q++ = RFC2132_MESSAGE;
 304         *q++ = sizeof(nak_msg) - 1;
 305         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 306         q += sizeof(nak_msg) - 1;
 307     }
 308     *q++ = RFC1533_END;
 309
 310     daddr.sin_addr.s_addr = 0xffffffffu;
 311
 312     m->m_len = sizeof(struct bootp_t) -
 313         sizeof(struct ip) - sizeof(struct udphdr);
 314     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 315 }
 316
 317 void bootp_input(struct mbuf *m)
 318 {
 319     struct bootp_t *bp = mtod(m, struct bootp_t *);
 320
 321     if (bp->bp_op == BOOTP_REQUEST) {
 322         bootp_reply(bp);
 323     }
 324 }