qemu/slirp/bootp.c
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   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
  37static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
  38
  39#ifdef DEBUG
  40#define DPRINTF(fmt, ...) \
  41do 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
  46static 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
  65static 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
  83static 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
 101static 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
 150static 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
 332void 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}
 340