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 "qemu/osdep.h"
  25 #include <slirp.h>
  26
  27 #if defined(_WIN32)
  28 /* Windows ntohl() returns an u_long value.
  29  * Add a type cast to match the format strings. */
  30 # define ntohl(n) ((uint32_t)ntohl(n))
  31 #endif
  32
  33 /* XXX: only DHCP is supported */
  34
  35 #define LEASE_TIME (24 * 3600)
  36
  37 static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  38
  39 #ifdef DEBUG
  40 #define DPRINTF(fmt, ...) \
  41 do if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); } while (0)
  42 #else
  43 #define DPRINTF(fmt, ...) do{}while(0)
  44 #endif
  45
  46 static BOOTPClient *get_new_addr(Slirp *slirp, struct in_addr *paddr,
  47                                  const uint8_t *macaddr)
  48 {
  49     BOOTPClient *bc;
  50     int i;
  51
  52     for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  53         bc = &slirp->bootp_clients[i];
  54         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
  55             goto found;
  56     }
  57     return NULL;
  58  found:
  59     bc = &slirp->bootp_clients[i];
  60     bc->allocated = 1;
  61     paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  62     return bc;
  63 }
  64
  65 static BOOTPClient *request_addr(Slirp *slirp, const struct in_addr *paddr,
  66                                  const uint8_t *macaddr)
  67 {
  68     uint32_t req_addr = ntohl(paddr->s_addr);
  69     uint32_t dhcp_addr = ntohl(slirp->vdhcp_startaddr.s_addr);
  70     BOOTPClient *bc;
  71
  72     if (req_addr >= dhcp_addr &&
  73         req_addr < (dhcp_addr + NB_BOOTP_CLIENTS)) {
  74         bc = &slirp->bootp_clients[req_addr - dhcp_addr];
  75         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
  76             bc->allocated = 1;
  77             return bc;
  78         }
  79     }
  80     return NULL;
  81 }
  82
  83 static BOOTPClient *find_addr(Slirp *slirp, struct in_addr *paddr,
  84                               const uint8_t *macaddr)
  85 {
  86     BOOTPClient *bc;
  87     int i;
  88
  89     for(i = 0; i < NB_BOOTP_CLIENTS; i++) {
  90         if (!memcmp(macaddr, slirp->bootp_clients[i].macaddr, 6))
  91             goto found;
  92     }
  93     return NULL;
  94  found:
  95     bc = &slirp->bootp_clients[i];
  96     bc->allocated = 1;
  97     paddr->s_addr = slirp->vdhcp_startaddr.s_addr + htonl(i);
  98     return bc;
  99 }
 100
 101 static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
 102                         struct in_addr *preq_addr)
 103 {
 104     const uint8_t *p, *p_end;
 105     int len, tag;
 106
 107     *pmsg_type = 0;
 108     preq_addr->s_addr = htonl(0L);
 109
 110     p = bp->bp_vend;
 111     p_end = p + DHCP_OPT_LEN;
 112     if (memcmp(p, rfc1533_cookie, 4) != 0)
 113         return;
 114     p += 4;
 115     while (p < p_end) {
 116         tag = p[0];
 117         if (tag == RFC1533_PAD) {
 118             p++;
 119         } else if (tag == RFC1533_END) {
 120             break;
 121         } else {
 122             p++;
 123             if (p >= p_end)
 124                 break;
 125             len = *p++;
 126             DPRINTF("dhcp: tag=%d len=%d\n", tag, len);
 127
 128             switch(tag) {
 129             case RFC2132_MSG_TYPE:
 130                 if (len >= 1)
 131                     *pmsg_type = p[0];
 132                 break;
 133             case RFC2132_REQ_ADDR:
 134                 if (len >= 4) {
 135                     memcpy(&(preq_addr->s_addr), p, 4);
 136                 }
 137                 break;
 138             default:
 139                 break;
 140             }
 141             p += len;
 142         }
 143     }
 144     if (*pmsg_type == DHCPREQUEST && preq_addr->s_addr == htonl(0L) &&
 145         bp->bp_ciaddr.s_addr) {
 146         memcpy(&(preq_addr->s_addr), &bp->bp_ciaddr, 4);
 147     }
 148 }
 149
 150 static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
 151 {
 152     BOOTPClient *bc = NULL;
 153     struct mbuf *m;
 154     struct bootp_t *rbp;
 155     struct sockaddr_in saddr, daddr;
 156     struct in_addr preq_addr;
 157     int dhcp_msg_type, val;
 158     uint8_t *q;
 159     uint8_t client_ethaddr[ETH_ALEN];
 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.s_addr != htonl(0L))
 165         DPRINTF(" req_addr=%08" PRIx32 "\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
 176     /* Get client's hardware address from bootp request */
 177     memcpy(client_ethaddr, bp->bp_hwaddr, ETH_ALEN);
 178
 179     m = m_get(slirp);
 180     if (!m) {
 181         return;
 182     }
 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.s_addr != htonl(0L)) {
 190             bc = request_addr(slirp, &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(slirp, &daddr.sin_addr, client_ethaddr);
 198             if (!bc) {
 199                 DPRINTF("no address left\n");
 200                 return;
 201             }
 202         }
 203         memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
 204     } else if (preq_addr.s_addr != htonl(0L)) {
 205         bc = request_addr(slirp, &preq_addr, client_ethaddr);
 206         if (bc) {
 207             daddr.sin_addr = preq_addr;
 208             memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
 209         } else {
 210             /* DHCPNAKs should be sent to broadcast */
 211             daddr.sin_addr.s_addr = 0xffffffff;
 212         }
 213     } else {
 214         bc = find_addr(slirp, &daddr.sin_addr, bp->bp_hwaddr);
 215         if (!bc) {
 216             /* if never assigned, behaves as if it was already
 217                assigned (windows fix because it remembers its address) */
 218             goto new_addr;
 219         }
 220     }
 221
 222     /* Update ARP table for this IP address */
 223     arp_table_add(slirp, daddr.sin_addr.s_addr, client_ethaddr);
 224
 225     saddr.sin_addr = slirp->vhost_addr;
 226     saddr.sin_port = htons(BOOTP_SERVER);
 227
 228     daddr.sin_port = htons(BOOTP_CLIENT);
 229
 230     rbp->bp_op = BOOTP_REPLY;
 231     rbp->bp_xid = bp->bp_xid;
 232     rbp->bp_htype = 1;
 233     rbp->bp_hlen = 6;
 234     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, ETH_ALEN);
 235
 236     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 237     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 238
 239     q = rbp->bp_vend;
 240     memcpy(q, rfc1533_cookie, 4);
 241     q += 4;
 242
 243     if (bc) {
 244         DPRINTF("%s addr=%08" PRIx32 "\n",
 245                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
 246                 ntohl(daddr.sin_addr.s_addr));
 247
 248         if (dhcp_msg_type == DHCPDISCOVER) {
 249             *q++ = RFC2132_MSG_TYPE;
 250             *q++ = 1;
 251             *q++ = DHCPOFFER;
 252         } else /* DHCPREQUEST */ {
 253             *q++ = RFC2132_MSG_TYPE;
 254             *q++ = 1;
 255             *q++ = DHCPACK;
 256         }
 257
 258         if (slirp->bootp_filename)
 259             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
 260                      slirp->bootp_filename);
 261
 262         *q++ = RFC2132_SRV_ID;
 263         *q++ = 4;
 264         memcpy(q, &saddr.sin_addr, 4);
 265         q += 4;
 266
 267         *q++ = RFC1533_NETMASK;
 268         *q++ = 4;
 269         memcpy(q, &slirp->vnetwork_mask, 4);
 270         q += 4;
 271
 272         if (!slirp->restricted) {
 273             *q++ = RFC1533_GATEWAY;
 274             *q++ = 4;
 275             memcpy(q, &saddr.sin_addr, 4);
 276             q += 4;
 277
 278             *q++ = RFC1533_DNS;
 279             *q++ = 4;
 280             memcpy(q, &slirp->vnameserver_addr, 4);
 281             q += 4;
 282         }
 283
 284         *q++ = RFC2132_LEASE_TIME;
 285         *q++ = 4;
 286         val = htonl(LEASE_TIME);
 287         memcpy(q, &val, 4);
 288         q += 4;
 289
 290         if (*slirp->client_hostname) {
 291             val = strlen(slirp->client_hostname);
 292             *q++ = RFC1533_HOSTNAME;
 293             *q++ = val;
 294             memcpy(q, slirp->client_hostname, val);
 295             q += val;
 296         }
 297
 298         if (slirp->vdnssearch) {
 299             size_t spaceleft = sizeof(rbp->bp_vend) - (q - rbp->bp_vend);
 300             val = slirp->vdnssearch_len;
 301             if (val + 1 > spaceleft) {
 302                 g_warning("DHCP packet size exceeded, "
 303                     "omitting domain-search option.");
 304             } else {
 305                 memcpy(q, slirp->vdnssearch, val);
 306                 q += val;
 307             }
 308         }
 309     } else {
 310         static const char nak_msg[] = "requested address not available";
 311
 312         DPRINTF("nak'ed addr=%08" PRIx32 "\n", ntohl(preq_addr.s_addr));
 313
 314         *q++ = RFC2132_MSG_TYPE;
 315         *q++ = 1;
 316         *q++ = DHCPNAK;
 317
 318         *q++ = RFC2132_MESSAGE;
 319         *q++ = sizeof(nak_msg) - 1;
 320         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
 321         q += sizeof(nak_msg) - 1;
 322     }
 323     *q = RFC1533_END;
 324
 325     daddr.sin_addr.s_addr = 0xffffffffu;
 326
 327     m->m_len = sizeof(struct bootp_t) -
 328         sizeof(struct ip) - sizeof(struct udphdr);
 329     udp_output(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 330 }
 331
 332 void bootp_input(struct mbuf *m)
 333 {
 334     struct bootp_t *bp = mtod(m, struct bootp_t *);
 335
 336     if (bp->bp_op == BOOTP_REQUEST) {
 337         bootp_reply(m->slirp, bp);
 338     }
 339 }