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
get_new_addr(struct in_addr * paddr,const uint8_t * macaddr)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
request_addr(const struct in_addr * paddr,const uint8_t * macaddr)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
find_addr(struct in_addr * paddr,const uint8_t * macaddr)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
dhcp_decode(const struct bootp_t * bp,int * pmsg_type,const struct in_addr ** preq_addr)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
bootp_reply(const struct bootp_t * bp)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
bootp_input(struct mbuf * m)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 }
327