xref: /openbsd-src/lib/libpcap/inet.c (revision 13c7aa11c65ab3d585b6c4ba96f70495be495c46)
1 /*	$OpenBSD: inet.c,v 1.8 1998/07/14 00:14:01 deraadt Exp $	*/
2 
3 /*
4  * Copyright (c) 1994, 1995, 1996
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by the Computer Systems
18  *	Engineering Group at Lawrence Berkeley Laboratory.
19  * 4. Neither the name of the University nor of the Laboratory may be used
20  *    to endorse or promote products derived from this software without
21  *    specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  */
35 
36 #ifndef lint
37 static char rcsid[] =
38     "@(#) Header: inet.c,v 1.16 96/06/23 14:28:22 leres Exp (LBL)";
39 #endif
40 
41 #include <sys/param.h>
42 #include <sys/file.h>
43 #include <sys/ioctl.h>
44 #include <sys/socket.h>
45 #ifdef HAVE_SYS_SOCKIO_H
46 #include <sys/sockio.h>
47 #endif
48 
49 #ifdef __STDC__
50 struct mbuf;
51 struct rtentry;
52 #endif
53 
54 #include <net/if.h>
55 #include <netinet/in.h>
56 
57 #include <ctype.h>
58 #include <errno.h>
59 #include <memory.h>
60 #include <stdio.h>
61 #include <stdlib.h>
62 #include <string.h>
63 #include <unistd.h>
64 #include <pcap.h>
65 
66 #ifdef HAVE_OS_PROTO_H
67 #include "os-proto.h"
68 #endif
69 
70 #include "pcap-int.h"
71 
72 /* Not all systems have IFF_LOOPBACK */
73 #ifdef IFF_LOOPBACK
74 #define ISLOOPBACK(p) ((p)->ifr_flags & IFF_LOOPBACK)
75 #else
76 #define ISLOOPBACK(p) (strcmp((p)->ifr_name, "lo0") == 0)
77 #endif
78 
79 /*
80  * Return the name of a network interface attached to the system, or NULL
81  * if none can be found.  The interface must be configured up; the
82  * lowest unit number is preferred; loopback is ignored.
83  */
84 char *
85 pcap_lookupdev(errbuf)
86 	register char *errbuf;
87 {
88 	register int fd, minunit, n;
89 	register char *cp, *ibuf = NULL;
90 	register struct ifreq *ifrp, *ifend, *ifnext, *mp;
91 	struct ifconf ifc;
92 	struct ifreq ifr;
93 	static char device[sizeof(ifrp->ifr_name) + 1];
94 	int len = 8192;
95 
96 	fd = socket(AF_INET, SOCK_DGRAM, 0);
97 	if (fd < 0) {
98 		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE, "socket: %s",
99 		    pcap_strerror(errno));
100 		return (NULL);
101 	}
102 	while (1) {
103 		ifc.ifc_len = len;
104 		ifc.ifc_buf = ibuf = realloc(ibuf, len);
105 		if (ibuf == NULL) {
106 			close(fd);
107 			return (NULL);
108 		}
109 		if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0) {
110 			(void)close(fd);
111 			free(ibuf);
112 			return (NULL);
113 		}
114 		if (ifc.ifc_len + sizeof(ifr) < len)
115 			break;
116 		len *= 2;
117 	}
118 
119 	ifrp = (struct ifreq *)ibuf;
120 	ifend = (struct ifreq *)((char *)ibuf + ifc.ifc_len);
121 
122 	mp = NULL;
123 	minunit = 666;
124 	for (; ifrp < ifend; ifrp = ifnext) {
125 #if BSD - 0 >= 199006
126 		n = ifrp->ifr_addr.sa_len + sizeof(ifrp->ifr_name);
127 		if (n < sizeof(*ifrp))
128 			ifnext = ifrp + 1;
129 		else
130 			ifnext = (struct ifreq *)((char *)ifrp + n);
131 		if (ifrp->ifr_addr.sa_family != AF_INET)
132 			continue;
133 #else
134 		ifnext = ifrp + 1;
135 #endif
136 		/*
137 		 * Need a template to preserve address info that is
138 		 * used below to locate the next entry.  (Otherwise,
139 		 * SIOCGIFFLAGS stomps over it because the requests
140 		 * are returned in a union.)
141 		 */
142 		strncpy(ifr.ifr_name, ifrp->ifr_name, sizeof(ifr.ifr_name));
143 		if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifr) < 0) {
144 			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
145 			    "SIOCGIFFLAGS: %s", pcap_strerror(errno));
146 			(void)close(fd);
147 			free(ibuf);
148 			return (NULL);
149 		}
150 
151 		/* Must be up and not the loopback */
152 		if ((ifr.ifr_flags & IFF_UP) == 0 || ISLOOPBACK(&ifr))
153 			continue;
154 
155 		for (cp = ifrp->ifr_name; !isdigit(*cp); ++cp)
156 			continue;
157 		n = atoi(cp);
158 		if (n < minunit) {
159 			minunit = n;
160 			mp = ifrp;
161 		}
162 	}
163 	free(ibuf);
164 	(void)close(fd);
165 	if (mp == NULL) {
166 		(void)strcpy(errbuf, "no suitable device found");
167 		return (NULL);
168 	}
169 
170 	(void)strncpy(device, mp->ifr_name, sizeof(device) - 1);
171 	device[sizeof(device) - 1] = '\0';
172 	return (device);
173 }
174 
175 int
176 pcap_lookupnet(device, netp, maskp, errbuf)
177 	register char *device;
178 	register bpf_u_int32 *netp, *maskp;
179 	register char *errbuf;
180 {
181 	register int fd;
182 	register struct sockaddr_in *sin;
183 	struct ifreq ifr;
184 
185 	fd = socket(AF_INET, SOCK_DGRAM, 0);
186 	if (fd < 0) {
187 		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE, "socket: %s",
188 		    pcap_strerror(errno));
189 		return (-1);
190 	}
191 	memset(&ifr, 0, sizeof(ifr));
192 #ifdef linux
193 	/* XXX Work around Linux kernel bug */
194 	ifr.ifr_addr.sa_family = AF_INET;
195 #endif
196 	(void)strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
197 	if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) < 0) {
198 		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE, "SIOCGIFADDR: %s: %s",
199 		    device, pcap_strerror(errno));
200 		(void)close(fd);
201 		return (-1);
202 	}
203 	sin = (struct sockaddr_in *)&ifr.ifr_addr;
204 	*netp = sin->sin_addr.s_addr;
205 	if (ioctl(fd, SIOCGIFNETMASK, (char *)&ifr) < 0) {
206 		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE, "SIOCGIFNETMASK: %s: %s",
207 		    device, pcap_strerror(errno));
208 		(void)close(fd);
209 		return (-1);
210 	}
211 	(void)close(fd);
212 	*maskp = sin->sin_addr.s_addr;
213 	if (*maskp == 0) {
214 		if (IN_CLASSA(*netp))
215 			*maskp = IN_CLASSA_NET;
216 		else if (IN_CLASSB(*netp))
217 			*maskp = IN_CLASSB_NET;
218 		else if (IN_CLASSC(*netp))
219 			*maskp = IN_CLASSC_NET;
220 		else {
221 			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
222 			    "inet class for 0x%x unknown", *netp);
223 			return (-1);
224 		}
225 	}
226 	*netp &= *maskp;
227 	return (0);
228 }
229