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