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