arp.c revision 31183 
1/*
2 * arp.c (C) 1995-1997 Darren Reed
3 *
4 * Redistribution and use in source and binary forms are permitted
5 * provided that this notice is preserved and due credit is given
6 * to the original author and the contributors.
7 */
8#if !defined(lint)
9static const char sccsid[] = "@(#)arp.c	1.4 1/11/96 (C)1995 Darren Reed";
10static const char rcsid[] = "@(#)$Id: arp.c,v 2.0.2.6 1997/09/28 07:13:25 darrenr Exp $";
11#endif
12#include <stdio.h>
13#include <errno.h>
14#include <sys/types.h>
15#include <sys/socket.h>
16#if !defined(ultrix) && !defined(hpux)
17#include <sys/sockio.h>
18#endif
19#include <sys/ioctl.h>
20#include <netdb.h>
21#include <netinet/in.h>
22#include <net/if.h>
23#ifndef	ultrix
24#include <net/if_arp.h>
25#endif
26#include <netinet/in.h>
27#include <netinet/ip_var.h>
28#include <netinet/tcp.h>
29#include "ipsend.h"
30
31
32/*
33 * lookup host and return
34 * its IP address in address
35 * (4 bytes)
36 */
37int	resolve(host, address)
38char	*host, *address;
39{
40        struct	hostent	*hp;
41        u_long	add;
42
43	add = inet_addr(host);
44	if (add == -1)
45	    {
46		if (!(hp = gethostbyname(host)))
47		    {
48			fprintf(stderr, "unknown host: %s\n", host);
49			return -1;
50		    }
51		bcopy((char *)hp->h_addr, (char *)address, 4);
52		return 0;
53	}
54	bcopy((char*)&add, address, 4);
55	return 0;
56}
57
58/*
59 * ARP for the MAC address corresponding
60 * to the IP address.  This taken from
61 * some BSD program, I cant remember which.
62 */
63int	arp(ip, ether)
64char	*ip;
65char	*ether;
66{
67	static	int	sfd = -1;
68	static	char	ethersave[6], ipsave[4];
69	struct	arpreq	ar;
70	struct	sockaddr_in	*sin, san;
71	struct	hostent	*hp;
72	int	fd;
73
74	if (!bcmp(ipsave, ip, 4)) {
75		bcopy(ethersave, ether, 6);
76		return 0;
77	}
78	fd = -1;
79	bzero((char *)&ar, sizeof(ar));
80	sin = (struct sockaddr_in *)&ar.arp_pa;
81	sin->sin_family = AF_INET;
82	bcopy(ip, (char *)&sin->sin_addr.s_addr, 4);
83#ifndef	hpux
84	if ((hp = gethostbyaddr(ip, 4, AF_INET)))
85		if (!(ether_hostton(hp->h_name, ether)))
86			goto savearp;
87#endif
88
89	if (sfd == -1)
90		if ((sfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
91		    {
92			perror("arp: socket");
93			return -1;
94		    }
95tryagain:
96	if (ioctl(sfd, SIOCGARP, (caddr_t)&ar) == -1)
97	    {
98		if (fd == -1)
99		    {
100			bzero((char *)&san, sizeof(san));
101			san.sin_family = AF_INET;
102			san.sin_port = htons(1);
103			bcopy(ip, &san.sin_addr.s_addr, 4);
104			fd = socket(AF_INET, SOCK_DGRAM, 0);
105			(void) sendto(fd, ip, 4, 0,
106				      (struct sockaddr *)&san, sizeof(san));
107			sleep(1);
108			(void) close(fd);
109			goto tryagain;
110		    }
111		fprintf(stderr, "(%s):", inet_ntoa(sin->sin_addr));
112		if (errno != ENXIO)
113			perror("SIOCGARP");
114		return -1;
115	    }
116
117	bcopy(ar.arp_ha.sa_data, ether, 6);
118savearp:
119	bcopy(ether, ethersave, 6);
120	bcopy(ip, ipsave, 4);
121	return 0;
122}
123