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 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, args...) \
  47 if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ## args); fflush(dfd); }
  48 #else
  49 #define dprintf(fmt, args...)
  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 *find_addr(struct in_addr *paddr, const uint8_t *macaddr)
  70 {
  71     BOOTPClient *bc;
  72     int i;
  73
  74     for(i = 0; i < NB_ADDR; i++) {
  75         if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
  76             goto found;
  77     }
  78     return NULL;
  79  found:
  80     bc = &bootp_clients[i];
  81     bc->allocated = 1;
  82     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
  83     return bc;
  84 }
  85
  86 static void dhcp_decode(const uint8_t *buf, int size,
  87                         int *pmsg_type)
  88 {
  89     const uint8_t *p, *p_end;
  90     int len, tag;
  91
  92     *pmsg_type = 0;
  93
  94     p = buf;
  95     p_end = buf + size;
  96     if (size < 5)
  97         return;
  98     if (memcmp(p, rfc1533_cookie, 4) != 0)
  99         return;
 100     p += 4;
 101     while (p < p_end) {
 102         tag = p[0];
 103         if (tag == RFC1533_PAD) {
 104             p++;
 105         } else if (tag == RFC1533_END) {
 106             break;
 107         } else {
 108             p++;
 109             if (p >= p_end)
 110                 break;
 111             len = *p++;
 112             dprintf("dhcp: tag=0x%02x len=%d\n", tag, len);
 113
 114             switch(tag) {
 115             case RFC2132_MSG_TYPE:
 116                 if (len >= 1)
 117                     *pmsg_type = p[0];
 118                 break;
 119             default:
 120                 break;
 121             }
 122             p += len;
 123         }
 124     }
 125 }
 126
 127 static void bootp_reply(struct bootp_t *bp)
 128 {
 129     BOOTPClient *bc;
 130     struct mbuf *m;
 131     struct bootp_t *rbp;
 132     struct sockaddr_in saddr, daddr;
 133     struct in_addr dns_addr;
 134     int dhcp_msg_type, val;
 135     uint8_t *q;
 136
 137     /* extract exact DHCP msg type */
 138     dhcp_decode(bp->bp_vend, DHCP_OPT_LEN, &dhcp_msg_type);
 139     dprintf("bootp packet op=%d msgtype=%d\n", bp->bp_op, dhcp_msg_type);
 140
 141     if (dhcp_msg_type == 0)
 142         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
 143
 144     if (dhcp_msg_type != DHCPDISCOVER &&
 145         dhcp_msg_type != DHCPREQUEST)
 146         return;
 147     /* XXX: this is a hack to get the client mac address */
 148     memcpy(client_ethaddr, bp->bp_hwaddr, 6);
 149
 150     if ((m = m_get()) == NULL)
 151         return;
 152     m->m_data += if_maxlinkhdr;
 153     rbp = (struct bootp_t *)m->m_data;
 154     m->m_data += sizeof(struct udpiphdr);
 155     memset(rbp, 0, sizeof(struct bootp_t));
 156
 157     if (dhcp_msg_type == DHCPDISCOVER) {
 158     new_addr:
 159         bc = get_new_addr(&daddr.sin_addr);
 160         if (!bc) {
 161             dprintf("no address left\n");
 162             return;
 163         }
 164         memcpy(bc->macaddr, client_ethaddr, 6);
 165     } else {
 166         bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
 167         if (!bc) {
 168             /* if never assigned, behaves as if it was already
 169                assigned (windows fix because it remembers its address) */
 170             goto new_addr;
 171         }
 172     }
 173
 174     if (bootp_filename)
 175         snprintf(rbp->bp_file, sizeof(rbp->bp_file), "%s", bootp_filename);
 176
 177     dprintf("offered addr=%08x\n", ntohl(daddr.sin_addr.s_addr));
 178
 179     saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
 180     saddr.sin_port = htons(BOOTP_SERVER);
 181
 182     daddr.sin_port = htons(BOOTP_CLIENT);
 183
 184     rbp->bp_op = BOOTP_REPLY;
 185     rbp->bp_xid = bp->bp_xid;
 186     rbp->bp_htype = 1;
 187     rbp->bp_hlen = 6;
 188     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
 189
 190     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
 191     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
 192
 193     q = rbp->bp_vend;
 194     memcpy(q, rfc1533_cookie, 4);
 195     q += 4;
 196
 197     if (dhcp_msg_type == DHCPDISCOVER) {
 198         *q++ = RFC2132_MSG_TYPE;
 199         *q++ = 1;
 200         *q++ = DHCPOFFER;
 201     } else if (dhcp_msg_type == DHCPREQUEST) {
 202         *q++ = RFC2132_MSG_TYPE;
 203         *q++ = 1;
 204         *q++ = DHCPACK;
 205     }
 206
 207     if (dhcp_msg_type == DHCPDISCOVER ||
 208         dhcp_msg_type == DHCPREQUEST) {
 209         *q++ = RFC2132_SRV_ID;
 210         *q++ = 4;
 211         memcpy(q, &saddr.sin_addr, 4);
 212         q += 4;
 213
 214         *q++ = RFC1533_NETMASK;
 215         *q++ = 4;
 216         *q++ = 0xff;
 217         *q++ = 0xff;
 218         *q++ = 0xff;
 219         *q++ = 0x00;
 220
 221         *q++ = RFC1533_GATEWAY;
 222         *q++ = 4;
 223         memcpy(q, &saddr.sin_addr, 4);
 224         q += 4;
 225
 226         *q++ = RFC1533_DNS;
 227         *q++ = 4;
 228         dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
 229         memcpy(q, &dns_addr, 4);
 230         q += 4;
 231
 232         *q++ = RFC2132_LEASE_TIME;
 233         *q++ = 4;
 234         val = htonl(LEASE_TIME);
 235         memcpy(q, &val, 4);
 236         q += 4;
 237
 238         if (*slirp_hostname) {
 239             val = strlen(slirp_hostname);
 240             *q++ = RFC1533_HOSTNAME;
 241             *q++ = val;
 242             memcpy(q, slirp_hostname, val);
 243             q += val;
 244         }
 245     }
 246     *q++ = RFC1533_END;
 247
 248     m->m_len = sizeof(struct bootp_t) -
 249         sizeof(struct ip) - sizeof(struct udphdr);
 250     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 251 }
 252
 253 void bootp_input(struct mbuf *m)
 254 {
 255     struct bootp_t *bp = mtod(m, struct bootp_t *);
 256
 257     if (bp->bp_op == BOOTP_REQUEST) {
 258         bootp_reply(bp);
 259     }
 260 }