1 /* $FreeBSD$ */
2
3 /*
4 * ip.c (C) 1995-1998 Darren Reed
5 *
6 * See the IPFILTER.LICENCE file for details on licencing.
7 */
8 #if !defined(lint)
9 static const char sccsid[] = "%W% %G% (C)1995";
10 static const char rcsid[] = "@(#)$Id$";
11 #endif
12 #include <sys/param.h>
13 #include <sys/types.h>
14 #include <netinet/in_systm.h>
15 #include <sys/socket.h>
16 #include <net/if.h>
17 #include <netinet/in.h>
18 #include <netinet/ip.h>
19 #include <sys/param.h>
20 # include <net/route.h>
21 # include <netinet/if_ether.h>
22 # include <netinet/ip_var.h>
23 #include <errno.h>
24 #include <stdio.h>
25 #include <stdlib.h>
26 #include <unistd.h>
27 #include <string.h>
28 #include "ipsend.h"
29
30
31 static char *ipbuf = NULL, *ethbuf = NULL;
32
33
chksum(buf,len)34 u_short chksum(buf,len)
35 u_short *buf;
36 int len;
37 {
38 u_long sum = 0;
39 int nwords = len >> 1;
40
41 for(; nwords > 0; nwords--)
42 sum += *buf++;
43 sum = (sum>>16) + (sum & 0xffff);
44 sum += (sum >>16);
45 return (~sum);
46 }
47
48
send_ether(nfd,buf,len,gwip)49 int send_ether(nfd, buf, len, gwip)
50 int nfd, len;
51 char *buf;
52 struct in_addr gwip;
53 {
54 static struct in_addr last_gw;
55 static char last_arp[6] = { 0, 0, 0, 0, 0, 0};
56 ether_header_t *eh;
57 char *s;
58 int err;
59
60 if (!ethbuf)
61 ethbuf = (char *)calloc(1, 65536+1024);
62 s = ethbuf;
63 eh = (ether_header_t *)s;
64
65 bcopy((char *)buf, s + sizeof(*eh), len);
66 if (gwip.s_addr == last_gw.s_addr)
67 {
68 bcopy(last_arp, (char *) &eh->ether_dhost, 6);
69 }
70 else if (arp((char *)&gwip, (char *) &eh->ether_dhost) == -1)
71 {
72 perror("arp");
73 return -2;
74 }
75 eh->ether_type = htons(ETHERTYPE_IP);
76 last_gw.s_addr = gwip.s_addr;
77 err = sendip(nfd, s, sizeof(*eh) + len);
78 return err;
79 }
80
81
82 /*
83 */
send_ip(nfd,mtu,ip,gwip,frag)84 int send_ip(nfd, mtu, ip, gwip, frag)
85 int nfd, mtu;
86 ip_t *ip;
87 struct in_addr gwip;
88 int frag;
89 {
90 static struct in_addr last_gw, local_ip;
91 static char local_arp[6] = { 0, 0, 0, 0, 0, 0};
92 static char last_arp[6] = { 0, 0, 0, 0, 0, 0};
93 static u_short id = 0;
94 ether_header_t *eh;
95 ip_t ipsv;
96 int err, iplen;
97
98 if (!ipbuf)
99 {
100 ipbuf = (char *)malloc(65536);
101 if (!ipbuf)
102 {
103 perror("malloc failed");
104 return -2;
105 }
106 }
107
108 eh = (ether_header_t *)ipbuf;
109
110 bzero((char *) &eh->ether_shost, sizeof(eh->ether_shost));
111 if (last_gw.s_addr && (gwip.s_addr == last_gw.s_addr))
112 {
113 bcopy(last_arp, (char *) &eh->ether_dhost, 6);
114 }
115 else if (arp((char *)&gwip, (char *) &eh->ether_dhost) == -1)
116 {
117 perror("arp");
118 return -2;
119 }
120 bcopy((char *) &eh->ether_dhost, last_arp, sizeof(last_arp));
121 eh->ether_type = htons(ETHERTYPE_IP);
122
123 bcopy((char *)ip, (char *)&ipsv, sizeof(*ip));
124 last_gw.s_addr = gwip.s_addr;
125 iplen = ip->ip_len;
126 ip->ip_len = htons(iplen);
127 if (!(frag & 2)) {
128 if (!IP_V(ip))
129 IP_V_A(ip, IPVERSION);
130 if (!ip->ip_id)
131 ip->ip_id = htons(id++);
132 if (!ip->ip_ttl)
133 ip->ip_ttl = 60;
134 }
135
136 if (ip->ip_src.s_addr != local_ip.s_addr) {
137 (void) arp((char *)&ip->ip_src, (char *) &local_arp);
138 bcopy(local_arp, (char *) &eh->ether_shost,sizeof(last_arp));
139 local_ip = ip->ip_src;
140 } else
141 bcopy(local_arp, (char *) &eh->ether_shost, 6);
142
143 if (!frag || (sizeof(*eh) + iplen < mtu))
144 {
145 ip->ip_sum = 0;
146 ip->ip_sum = chksum((u_short *)ip, IP_HL(ip) << 2);
147
148 bcopy((char *)ip, ipbuf + sizeof(*eh), iplen);
149 err = sendip(nfd, ipbuf, sizeof(*eh) + iplen);
150 }
151 else
152 {
153 /*
154 * Actually, this is bogus because we're putting all IP
155 * options in every packet, which isn't always what should be
156 * done. Will do for now.
157 */
158 ether_header_t eth;
159 char optcpy[48], ol;
160 char *s;
161 int i, sent = 0, ts, hlen, olen;
162
163 hlen = IP_HL(ip) << 2;
164 if (mtu < (hlen + 8)) {
165 fprintf(stderr, "mtu (%d) < ip header size (%d) + 8\n",
166 mtu, hlen);
167 fprintf(stderr, "can't fragment data\n");
168 return -2;
169 }
170 ol = (IP_HL(ip) << 2) - sizeof(*ip);
171 for (i = 0, s = (char*)(ip + 1); ol > 0; )
172 if (*s == IPOPT_EOL) {
173 optcpy[i++] = *s;
174 break;
175 } else if (*s == IPOPT_NOP) {
176 s++;
177 ol--;
178 } else
179 {
180 olen = (int)(*(u_char *)(s + 1));
181 ol -= olen;
182 if (IPOPT_COPIED(*s))
183 {
184 bcopy(s, optcpy + i, olen);
185 i += olen;
186 s += olen;
187 }
188 }
189 if (i)
190 {
191 /*
192 * pad out
193 */
194 while ((i & 3) && (i & 3) != 3)
195 optcpy[i++] = IPOPT_NOP;
196 if ((i & 3) == 3)
197 optcpy[i++] = IPOPT_EOL;
198 }
199
200 bcopy((char *)eh, (char *)ð, sizeof(eth));
201 s = (char *)ip + hlen;
202 iplen = ntohs(ip->ip_len) - hlen;
203 ip->ip_off |= htons(IP_MF);
204
205 while (1)
206 {
207 if ((sent + (mtu - hlen)) >= iplen)
208 {
209 ip->ip_off ^= htons(IP_MF);
210 ts = iplen - sent;
211 }
212 else
213 ts = (mtu - hlen);
214 ip->ip_off &= htons(0xe000);
215 ip->ip_off |= htons(sent >> 3);
216 ts += hlen;
217 ip->ip_len = htons(ts);
218 ip->ip_sum = 0;
219 ip->ip_sum = chksum((u_short *)ip, hlen);
220 bcopy((char *)ip, ipbuf + sizeof(*eh), hlen);
221 bcopy(s + sent, ipbuf + sizeof(*eh) + hlen, ts - hlen);
222 err = sendip(nfd, ipbuf, sizeof(*eh) + ts);
223
224 bcopy((char *)ð, ipbuf, sizeof(eth));
225 sent += (ts - hlen);
226 if (!(ntohs(ip->ip_off) & IP_MF))
227 break;
228 else if (!(ip->ip_off & htons(0x1fff)))
229 {
230 hlen = i + sizeof(*ip);
231 IP_HL_A(ip, (sizeof(*ip) + i) >> 2);
232 bcopy(optcpy, (char *)(ip + 1), i);
233 }
234 }
235 }
236
237 bcopy((char *)&ipsv, (char *)ip, sizeof(*ip));
238 return err;
239 }
240
241
242 /*
243 * send a tcp packet.
244 */
send_tcp(nfd,mtu,ip,gwip)245 int send_tcp(nfd, mtu, ip, gwip)
246 int nfd, mtu;
247 ip_t *ip;
248 struct in_addr gwip;
249 {
250 static tcp_seq iss = 2;
251 tcphdr_t *t, *t2;
252 int thlen, i, iplen, hlen;
253 u_32_t lbuf[20];
254 ip_t *ip2;
255
256 iplen = ip->ip_len;
257 hlen = IP_HL(ip) << 2;
258 t = (tcphdr_t *)((char *)ip + hlen);
259 ip2 = (struct ip *)lbuf;
260 t2 = (tcphdr_t *)((char *)ip2 + hlen);
261 thlen = TCP_OFF(t) << 2;
262 if (!thlen)
263 thlen = sizeof(tcphdr_t);
264 bzero((char *)ip2, sizeof(*ip2) + sizeof(*t2));
265 ip->ip_p = IPPROTO_TCP;
266 ip2->ip_p = ip->ip_p;
267 ip2->ip_src = ip->ip_src;
268 ip2->ip_dst = ip->ip_dst;
269 bcopy((char *)ip + hlen, (char *)t2, thlen);
270
271 if (!t2->th_win)
272 t2->th_win = htons(4096);
273 iss += 63;
274
275 i = sizeof(struct tcpiphdr) / sizeof(long);
276
277 if ((t2->th_flags == TH_SYN) && !ntohs(ip->ip_off) &&
278 (lbuf[i] != htonl(0x020405b4))) {
279 lbuf[i] = htonl(0x020405b4);
280 bcopy((char *)ip + hlen + thlen, (char *)ip + hlen + thlen + 4,
281 iplen - thlen - hlen);
282 thlen += 4;
283 }
284 TCP_OFF_A(t2, thlen >> 2);
285 ip2->ip_len = htons(thlen);
286 ip->ip_len = hlen + thlen;
287 t2->th_sum = 0;
288 t2->th_sum = chksum((u_short *)ip2, thlen + sizeof(ip_t));
289
290 bcopy((char *)t2, (char *)ip + hlen, thlen);
291 return send_ip(nfd, mtu, ip, gwip, 1);
292 }
293
294
295 /*
296 * send a udp packet.
297 */
send_udp(nfd,mtu,ip,gwip)298 int send_udp(nfd, mtu, ip, gwip)
299 int nfd, mtu;
300 ip_t *ip;
301 struct in_addr gwip;
302 {
303 struct tcpiphdr *ti;
304 int thlen;
305 u_long lbuf[20];
306
307 ti = (struct tcpiphdr *)lbuf;
308 bzero((char *)ti, sizeof(*ti));
309 thlen = sizeof(udphdr_t);
310 ti->ti_pr = ip->ip_p;
311 ti->ti_src = ip->ip_src;
312 ti->ti_dst = ip->ip_dst;
313 bcopy((char *)ip + (IP_HL(ip) << 2),
314 (char *)&ti->ti_sport, sizeof(udphdr_t));
315
316 ti->ti_len = htons(thlen);
317 ip->ip_len = (IP_HL(ip) << 2) + thlen;
318 ti->ti_sum = 0;
319 ti->ti_sum = chksum((u_short *)ti, thlen + sizeof(ip_t));
320
321 bcopy((char *)&ti->ti_sport,
322 (char *)ip + (IP_HL(ip) << 2), sizeof(udphdr_t));
323 return send_ip(nfd, mtu, ip, gwip, 1);
324 }
325
326
327 /*
328 * send an icmp packet.
329 */
send_icmp(nfd,mtu,ip,gwip)330 int send_icmp(nfd, mtu, ip, gwip)
331 int nfd, mtu;
332 ip_t *ip;
333 struct in_addr gwip;
334 {
335 struct icmp *ic;
336
337 ic = (struct icmp *)((char *)ip + (IP_HL(ip) << 2));
338
339 ic->icmp_cksum = 0;
340 ic->icmp_cksum = chksum((u_short *)ic, sizeof(struct icmp));
341
342 return send_ip(nfd, mtu, ip, gwip, 1);
343 }
344
345
send_packet(nfd,mtu,ip,gwip)346 int send_packet(nfd, mtu, ip, gwip)
347 int nfd, mtu;
348 ip_t *ip;
349 struct in_addr gwip;
350 {
351 switch (ip->ip_p)
352 {
353 case IPPROTO_TCP :
354 return send_tcp(nfd, mtu, ip, gwip);
355 case IPPROTO_UDP :
356 return send_udp(nfd, mtu, ip, gwip);
357 case IPPROTO_ICMP :
358 return send_icmp(nfd, mtu, ip, gwip);
359 default :
360 return send_ip(nfd, mtu, ip, gwip, 1);
361 }
362 }
363