1 /*
2 Perl ARP Extension
3 Lookup the MAC address of an ip address
4 BSD code
5
6 Programmed by Bastian Ballmann
7 Last update: 20.09.2006
8
9 This program is free software; you can redistribute
10 it and/or modify it under the terms of the
11 GNU General Public License version 2 as published
12 by the Free Software Foundation.
13
14 This program is distributed in the hope that it will
15 be useful, but WITHOUT ANY WARRANTY; without even
16 the implied warranty of MERCHANTABILITY or FITNESS
17 FOR A PARTICULAR PURPOSE.
18 See the GNU General Public License for more details.
19 */
20
21 #include <sys/file.h>
22 #include <sys/socket.h>
23 #include <net/if_dl.h>
24 #include <net/route.h>
25 #include <net/if_arp.h>
26 #include <net/if.h>
27 #include <netinet/in.h>
28 #include <netinet/if_ether.h>
29 #include <arpa/inet.h>
30 #include <sys/sysctl.h>
31 #include <sys/types.h>
32 #include <stdio.h>
33 #include <stdlib.h>
34 #include <string.h>
35 #include "arp.h"
36
37 #define ROUNDUP(a) \
38 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
39
arp_lookup_bsd(const char * dev,const char * ip,char * mac)40 int arp_lookup_bsd(const char *dev, const char *ip, char *mac)
41 {
42 int mib[6];
43 size_t needed;
44 char *lim, *buf, *next;
45
46 if ( (mac == NULL) || (dev == NULL) || (ip == NULL) )
47 return -1;
48
49 strncpy(mac,"unknown", HEX_HW_ADDR_LEN);
50 mac[HEX_HW_ADDR_LEN-1] = '\0';
51
52 mib[0] = CTL_NET;
53 mib[1] = PF_ROUTE;
54 mib[2] = 0;
55 mib[3] = AF_INET;
56 mib[4] = NET_RT_FLAGS;
57 mib[5] = RTF_LLINFO;
58
59 /* Retrieve routing table */
60
61 if(sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
62 {
63 perror("route-sysctl-estimate");
64 exit(1);
65 }
66
67 if((buf = malloc(needed)) == NULL)
68 {
69 perror("malloc");
70 exit(1);
71 }
72
73 if(sysctl(mib, 6, buf, &needed, NULL, 0) < 0)
74 {
75 perror("retrieval of routing table");
76 exit(1);
77 }
78
79 lim = buf + needed;
80 next = buf;
81
82 /* Search for the requested ip */
83 while (next < lim)
84 {
85 struct rt_msghdr *rtm = (struct rt_msghdr *)next;
86 struct sockaddr_inarp *sinarp = (struct sockaddr_inarp *)(rtm + 1);
87 struct sockaddr_dl *sdl = (struct sockaddr_dl *)((char *)sinarp + ROUNDUP(sinarp->sin_len));
88
89 if( (sdl->sdl_alen) && (!strcmp(ip,inet_ntoa(sinarp->sin_addr))) )
90 {
91 sprintf(mac,"%s", ether_ntoa((struct ether_addr *)LLADDR(sdl)));
92 }
93
94 next += rtm->rtm_msglen;
95 }
96
97 free(buf);
98 return(0);
99 }
100