1 /*
2 sniff.c
3
4 Dug Song <dugsong@anzen.com>
5
6 Copyright (c) 1999 Anzen Computing. All rights reserved.
7
8 Redistribution and use in source and binary forms, with or without
9 modification, are permitted provided that the following conditions
10 are met:
11
12 1. Redistributions of source code must retain the above copyright
13 notice, this list of conditions and the following disclaimer.
14 2. Redistributions in binary form must reproduce the above copyright
15 notice, this list of conditions and the following disclaimer in the
16 documentation and/or other materials provided with the distribution.
17 3. All advertising materials mentioning features or use of this software
18 must display the following acknowledgement:
19 This product includes software developed by Anzen Computing.
20 4. Neither the name of Anzen Computing nor the names of its
21 contributors may be used to endorse or promote products derived
22 from this software without specific prior written permission.
23
24 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
25 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
26 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
28 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
30 GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
32 IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
33 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
34 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35
36 $Id: sniff.c,v 1.25 1999/07/30 13:02:35 dugsong Exp $
37 */
38
39 #include "config.h"
40
41 #ifdef STDC_HEADERS
42 #include <stdio.h>
43 #endif
44 #ifdef HAVE_UNISTD_H
45 #include <sys/param.h>
46 #endif
47 #include <pcap.h>
48 #include <libnet.h>
49 #include "sniff.h"
50
51 pcap_t *sniff_pd;
52 int sniff_ll_len;
53
54 int
sniff_init(char * intf,char * ebuf)55 sniff_init(char *intf, char *ebuf)
56 {
57 char *dev, filter[BUFSIZ];
58 struct link_int *llif;
59 struct ether_addr *llmac;
60 u_long llip;
61 u_int net, mask;
62 struct bpf_program fcode;
63
64 /* Get interface. */
65 if (intf) dev = intf;
66 else if (!(dev = pcap_lookupdev(ebuf)))
67 return 0;
68
69 /* Get interface IP and MAC address and link layer header length. */
70 if (!(llif = libnet_open_link_interface(dev, ebuf)))
71 return 0;
72
73 if (!(llip = libnet_get_ipaddr(llif, dev, ebuf)))
74 return 0;
75
76 if (!(llmac = libnet_get_hwaddr(llif, dev, ebuf)))
77 return 0;
78
79 libnet_close_link_interface(llif);
80
81 llip = ntohl(llip);
82
83 if (!llif->linkoffset)
84 sniff_ll_len = 14; /* XXX - assume Ethernet, if libnet fails us here. */
85 else
86 sniff_ll_len = llif->linkoffset;
87
88 /* Generate packet filter. We aren't sniffing in promiscuous mode,
89 but be specific in case someone else is. */
90 snprintf(filter, sizeof(filter),
91 "ip and ether dst %x:%x:%x:%x:%x:%x and not dst %s and not ip broadcast",
92 llmac->ether_addr_octet[0], llmac->ether_addr_octet[1],
93 llmac->ether_addr_octet[2], llmac->ether_addr_octet[3],
94 llmac->ether_addr_octet[4], llmac->ether_addr_octet[5],
95 libnet_host_lookup(llip, 0));
96 #ifdef DEBUG
97 fprintf(stderr, "fragrouter: %s\n", filter);
98 #endif /* DEBUG */
99
100 /* Open interface for sniffing, don't set promiscuous mode. */
101 if (pcap_lookupnet(dev, &net, &mask, ebuf) == -1)
102 return 0;
103
104 if (!(sniff_pd = pcap_open_live(dev, 2048, 0, 1024, ebuf)))
105 return 0;
106
107 if (pcap_compile(sniff_pd, &fcode, filter, 1, mask) < 0) {
108 strcpy(ebuf, pcap_geterr(sniff_pd));
109 return 0;
110 }
111 if (pcap_setfilter(sniff_pd, &fcode) == -1) {
112 strcpy(ebuf, pcap_geterr(sniff_pd));
113 return 0;
114 }
115 #ifdef DEBUG
116 fprintf(stderr, "fragrouter: sniffing on %s\n", dev);
117 #endif /* DEBUG */
118
119 return 1;
120 }
121
122 void
sniff_loop(sniff_handler attack)123 sniff_loop(sniff_handler attack)
124 {
125 struct pcap_pkthdr pkthdr;
126 struct ip *iph;
127 u_char *pkt;
128 int len;
129
130 for (;;) {
131 if ((pkt = (char *)pcap_next(sniff_pd, &pkthdr)) != NULL) {
132 iph = (struct ip *)(pkt + sniff_ll_len);
133
134 len = ntohs(iph->ip_len);
135 if (len > pkthdr.len)
136 len = pkthdr.len;
137
138 attack(pkt + sniff_ll_len, len);
139 }
140 }
141 }
142