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 LEASE_TIME (24 * 3600)
  31
  32 typedef struct {
  33     uint8_t allocated;
  34     uint8_t macaddr[6];
  35 } BOOTPClient;
  36
  37 static BOOTPClient bootp_clients[NB_ADDR];
  38
  39 char *bootp_filename;
  40
  41 static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  42
  43 #ifdef DEBUG
  44 #define dprintf(fmt, ...) \
  45 do if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); } while (0)
  46 #else
  47 #define dprintf(fmt, ...)
  48 #endif
  49
  50 static BOOTPClient *get_new_addr(struct in_addr *paddr,
  51                                  const uint8_t *macaddr)
  52 {
  53     BOOTPClient *bc;
  54     int i;
  55
  56     for(i = 0; i < NB_ADDR; i++) {
  57         bc = &bootp_clients[i];
  58         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
  59             goto found;
  60     }
  61     return NULL;
  62  found:
  63     bc = &bootp_clients[i];
  64     bc->allocated = 1;
  65     paddr->s_addr = vdhcp_startaddr.s_addr + htonl(i);
  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 dhcp_addr = ntohl(vdhcp_startaddr.s_addr);
  74     BOOTPClient *bc;
  75
  76     if (req_addr >= dhcp_addr &&
  77         req_addr < (dhcp_addr + NB_ADDR)) {
  78         bc = &bootp_clients[req_addr - dhcp_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 = vdhcp_startaddr.s_addr + htonl(i);
 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     const struct in_addr *preq_addr;
 158     int dhcp_msg_type, val;
 159     uint8_t *q;
 160
 161     /* extract exact DHCP msg type */
 162     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
 163     dprintf("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
 164     if (preq_addr)
 165         dprintf(" req_addr=%08x\n", ntohl(preq_addr->s_addr));
 166     else
 167         dprintf("\n");
 168
 169     if (dhcp_msg_type == 0)
 170         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 171
 172     if (dhcp_msg_type != DHCPDISCOVER &&
 173         dhcp_msg_type != DHCPREQUEST)
 174         return;
 175     /* XXX: this is a hack to get the client mac address */
 176     memcpy(client_ethaddr, bp->bp_hwaddr, 6);
 177
 178     if ((m = m_get()) == NULL)
 179         return;
 180     m->m_data += IF_MAXLINKHDR;
 181     rbp = (struct bootp_t *)m->m_data;
 182     m->m_data += sizeof(struct udpiphdr);
 183     memset(rbp, 0, sizeof(struct bootp_t));
 184
 185     if (dhcp_msg_type == DHCPDISCOVER) {
 186         if (preq_addr) {
 187             bc = request_addr(preq_addr, client_ethaddr);
 188             if (bc) {
 189                 daddr.sin_addr = *preq_addr;
 190             }
 191         }
 192         if (!bc) {
 193          new_addr:
 194             bc = get_new_addr(&daddr.sin_addr, client_ethaddr);
 195             if (!bc) {
 196                 dprintf("no address left\n");
 197                 return;
 198             }
 199         }
 200         memcpy(bc->macaddr, client_ethaddr, 6);
 201     } else if (preq_addr) {
 202         bc = request_addr(preq_addr, client_ethaddr);
 203         if (bc) {
 204             daddr.sin_addr = *preq_addr;
 205             memcpy(bc->macaddr, client_ethaddr, 6);
 206         } else {
 207             daddr.sin_addr.s_addr = 0;
 208         }
 209     } else {
 210         bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
 211         if (!bc) {
 212             /* if never assigned, behaves as if it was already
 213                assigned (windows fix because it remembers its address) */
 214             goto new_addr;
 215         }
 216     }
 217
 218     saddr.sin_addr = 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, 6);
 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 (bootp_filename)
 252             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 253                      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, &vnetwork_mask, 4);
 263         q += 4;
 264
 265         if (!slirp_restrict) {
 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, &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_hostname) {
 284             val = strlen(slirp_hostname);
 285             *q++ = RFC1533_HOSTNAME;
 286             *q++ = val;
 287             memcpy(q, slirp_hostname, val);
 288             q += val;
 289         }
 290     } else {
 291         static const char nak_msg[] = "requested address not available";
 292
 293         dprintf("nak'ed addr=%08x\n", ntohl(preq_addr->s_addr));
 294
 295         *q++ = RFC2132_MSG_TYPE;
 296         *q++ = 1;
 297         *q++ = DHCPNAK;
 298
 299         *q++ = RFC2132_MESSAGE;
 300         *q++ = sizeof(nak_msg) - 1;
 301         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 302         q += sizeof(nak_msg) - 1;
 303     }
 304     *q++ = RFC1533_END;
 305
 306     daddr.sin_addr.s_addr = 0xffffffffu;
 307
 308     m->m_len = sizeof(struct bootp_t) -
 309         sizeof(struct ip) - sizeof(struct udphdr);
 310     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 311 }
 312
 313 void bootp_input(struct mbuf *m)
 314 {
 315     struct bootp_t *bp = mtod(m, struct bootp_t *);
 316
 317     if (bp->bp_op == BOOTP_REQUEST) {
 318         bootp_reply(bp);
 319     }
 320 }