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                                  const uint8_t *macaddr)
  54 {
  55     BOOTPClient *bc;
  56     int i;
  57
  58     for(i = 0; i < NB_ADDR; i++) {
  59         bc = &bootp_clients[i];
  60         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
  61             goto found;
  62     }
  63     return NULL;
  64  found:
  65     bc = &bootp_clients[i];
  66     bc->allocated = 1;
  67     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
  68     return bc;
  69 }
  70
  71 static BOOTPClient *request_addr(const struct in_addr *paddr,
  72                                  const uint8_t *macaddr)
  73 {
  74     uint32_t req_addr = ntohl(paddr->s_addr);
  75     uint32_t spec_addr = ntohl(special_addr.s_addr);
  76     BOOTPClient *bc;
  77
  78     if (req_addr >= (spec_addr | START_ADDR) &&
  79         req_addr < (spec_addr | (NB_ADDR + START_ADDR))) {
  80         bc = &bootp_clients[(req_addr & 0xff) - START_ADDR];
  81         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
  82             bc->allocated = 1;
  83             return bc;
  84         }
  85     }
  86     return NULL;
  87 }
  88
  89 static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr)
  90 {
  91     BOOTPClient *bc;
  92     int i;
  93
  94     for(i = 0; i < NB_ADDR; i++) {
  95         if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
  96             goto found;
  97     }
  98     return NULL;
  99  found:
 100     bc = &bootp_clients[i];
 101     bc->allocated = 1;
 102     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
 103     return bc;
 104 }
 105
 106 static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
 107                         const struct in_addr **preq_addr)
 108 {
 109     const uint8_t *p, *p_end;
 110     int len, tag;
 111
 112     *pmsg_type = 0;
 113     *preq_addr = NULL;
 114
 115     p = bp->bp_vend;
 116     p_end = p + DHCP_OPT_LEN;
 117     if (memcmp(p, rfc1533_cookie, 4) != 0)
 118         return;
 119     p += 4;
 120     while (p < p_end) {
 121         tag = p[0];
 122         if (tag == RFC1533_PAD) {
 123             p++;
 124         } else if (tag == RFC1533_END) {
 125             break;
 126         } else {
 127             p++;
 128             if (p >= p_end)
 129                 break;
 130             len = *p++;
 131             dprintf("dhcp: tag=%d len=%d\n", tag, len);
 132
 133             switch(tag) {
 134             case RFC2132_MSG_TYPE:
 135                 if (len >= 1)
 136                     *pmsg_type = p[0];
 137                 break;
 138             case RFC2132_REQ_ADDR:
 139                 if (len >= 4)
 140                     *preq_addr = (struct in_addr *)p;
 141                 break;
 142             default:
 143                 break;
 144             }
 145             p += len;
 146         }
 147     }
 148     if (*pmsg_type == DHCPREQUEST && !*preq_addr && bp->bp_ciaddr.s_addr) {
 149         *preq_addr = &bp->bp_ciaddr;
 150     }
 151 }
 152
 153 static void bootp_reply(const struct bootp_t *bp)
 154 {
 155     BOOTPClient *bc = NULL;
 156     struct mbuf *m;
 157     struct bootp_t *rbp;
 158     struct sockaddr_in saddr, daddr;
 159     struct in_addr dns_addr;
 160     const struct in_addr *preq_addr;
 161     int dhcp_msg_type, val;
 162     uint8_t *q;
 163
 164     /* extract exact DHCP msg type */
 165     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
 166     dprintf("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
 167     if (preq_addr)
 168         dprintf(" req_addr=%08x\n", ntohl(preq_addr->s_addr));
 169     else
 170         dprintf("\n");
 171
 172     if (dhcp_msg_type == 0)
 173         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 174
 175     if (dhcp_msg_type != DHCPDISCOVER &&
 176         dhcp_msg_type != DHCPREQUEST)
 177         return;
 178     /* XXX: this is a hack to get the client mac address */
 179     memcpy(client_ethaddr, bp->bp_hwaddr, 6);
 180
 181     if ((m = m_get()) == NULL)
 182         return;
 183     m->m_data += IF_MAXLINKHDR;
 184     rbp = (struct bootp_t *)m->m_data;
 185     m->m_data += sizeof(struct udpiphdr);
 186     memset(rbp, 0, sizeof(struct bootp_t));
 187
 188     if (dhcp_msg_type == DHCPDISCOVER) {
 189         if (preq_addr) {
 190             bc = request_addr(preq_addr, client_ethaddr);
 191             if (bc) {
 192                 daddr.sin_addr = *preq_addr;
 193             }
 194         }
 195         if (!bc) {
 196          new_addr:
 197             bc = get_new_addr(&daddr.sin_addr, client_ethaddr);
 198             if (!bc) {
 199                 dprintf("no address left\n");
 200                 return;
 201             }
 202         }
 203         memcpy(bc->macaddr, client_ethaddr, 6);
 204     } else if (preq_addr) {
 205         bc = request_addr(preq_addr, client_ethaddr);
 206         if (bc) {
 207             daddr.sin_addr = *preq_addr;
 208             memcpy(bc->macaddr, client_ethaddr, 6);
 209         } else {
 210             daddr.sin_addr.s_addr = 0;
 211         }
 212     } else {
 213         bc = find_addr(&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     saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
 222     saddr.sin_port = htons(BOOTP_SERVER);
 223
 224     daddr.sin_port = htons(BOOTP_CLIENT);
 225
 226     rbp->bp_op = BOOTP_REPLY;
 227     rbp->bp_xid = bp->bp_xid;
 228     rbp->bp_htype = 1;
 229     rbp->bp_hlen = 6;
 230     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
 231
 232     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 233     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 234
 235     q = rbp->bp_vend;
 236     memcpy(q, rfc1533_cookie, 4);
 237     q += 4;
 238
 239     if (bc) {
 240         dprintf("%s addr=%08x\n",
 241                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 242                 ntohl(daddr.sin_addr.s_addr));
 243
 244         if (dhcp_msg_type == DHCPDISCOVER) {
 245             *q++ = RFC2132_MSG_TYPE;
 246             *q++ = 1;
 247             *q++ = DHCPOFFER;
 248         } else /* DHCPREQUEST */ {
 249             *q++ = RFC2132_MSG_TYPE;
 250             *q++ = 1;
 251             *q++ = DHCPACK;
 252         }
 253
 254         if (bootp_filename)
 255             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 256                      bootp_filename);
 257
 258         *q++ = RFC2132_SRV_ID;
 259         *q++ = 4;
 260         memcpy(q, &saddr.sin_addr, 4);
 261         q += 4;
 262
 263         *q++ = RFC1533_NETMASK;
 264         *q++ = 4;
 265         *q++ = 0xff;
 266         *q++ = 0xff;
 267         *q++ = 0xff;
 268         *q++ = 0x00;
 269
 270         if (!slirp_restrict) {
 271             *q++ = RFC1533_GATEWAY;
 272             *q++ = 4;
 273             memcpy(q, &saddr.sin_addr, 4);
 274             q += 4;
 275
 276             *q++ = RFC1533_DNS;
 277             *q++ = 4;
 278             dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
 279             memcpy(q, &dns_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_hostname) {
 290             val = strlen(slirp_hostname);
 291             *q++ = RFC1533_HOSTNAME;
 292             *q++ = val;
 293             memcpy(q, slirp_hostname, val);
 294             q += val;
 295         }
 296     } else {
 297         static const char nak_msg[] = "requested address not available";
 298
 299         dprintf("nak'ed addr=%08x\n", ntohl(preq_addr->s_addr));
 300
 301         *q++ = RFC2132_MSG_TYPE;
 302         *q++ = 1;
 303         *q++ = DHCPNAK;
 304
 305         *q++ = RFC2132_MESSAGE;
 306         *q++ = sizeof(nak_msg) - 1;
 307         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 308         q += sizeof(nak_msg) - 1;
 309     }
 310     *q++ = RFC1533_END;
 311
 312     daddr.sin_addr.s_addr = 0xffffffffu;
 313
 314     m->m_len = sizeof(struct bootp_t) -
 315         sizeof(struct ip) - sizeof(struct udphdr);
 316     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 317 }
 318
 319 void bootp_input(struct mbuf *m)
 320 {
 321     struct bootp_t *bp = mtod(m, struct bootp_t *);
 322
 323     if (bp->bp_op == BOOTP_REQUEST) {
 324         bootp_reply(bp);
 325     }
 326 }