arp.c revision 53024 
1/*
2 * arp.c (C) 1995-1998 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 2.1 1999/08/04 17:31:03 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#include <netinet/if_ether.h>
24#ifndef	ultrix
25#include <net/if_arp.h>
26#endif
27#include <netinet/in.h>
28#include <netinet/ip_var.h>
29#include <netinet/tcp.h>
30#include "ipsend.h"
31#include "iplang/iplang.h"
32
33
34/*
35 * lookup host and return
36 * its IP address in address
37 * (4 bytes)
38 */
39int	resolve(host, address)
40char	*host, *address;
41{
42        struct	hostent	*hp;
43        u_long	add;
44
45	add = inet_addr(host);
46	if (add == -1)
47	    {
48		if (!(hp = gethostbyname(host)))
49		    {
50			fprintf(stderr, "unknown host: %s\n", host);
51			return -1;
52		    }
53		bcopy((char *)hp->h_addr, (char *)address, 4);
54		return 0;
55	}
56	bcopy((char*)&add, address, 4);
57	return 0;
58}
59
60/*
61 * ARP for the MAC address corresponding
62 * to the IP address.  This taken from
63 * some BSD program, I cant remember which.
64 */
65int	arp(ip, ether)
66char	*ip;
67char	*ether;
68{
69	static	int	sfd = -1;
70	static	char	ethersave[6], ipsave[4];
71	struct	arpreq	ar;
72	struct	sockaddr_in	*sin, san;
73	struct	hostent	*hp;
74	int	fd;
75
76#ifdef	IPSEND
77	if (arp_getipv4(ip, ether) == 0)
78		return 0;
79#endif
80	if (!bcmp(ipsave, ip, 4)) {
81		bcopy(ethersave, ether, 6);
82		return 0;
83	}
84	fd = -1;
85	bzero((char *)&ar, sizeof(ar));
86	sin = (struct sockaddr_in *)&ar.arp_pa;
87	sin->sin_family = AF_INET;
88	bcopy(ip, (char *)&sin->sin_addr.s_addr, 4);
89#ifndef	hpux
90	if ((hp = gethostbyaddr(ip, 4, AF_INET)))
91		if (!(ether_hostton(hp->h_name, ether)))
92			goto savearp;
93#endif
94
95	if (sfd == -1)
96		if ((sfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
97		    {
98			perror("arp: socket");
99			return -1;
100		    }
101tryagain:
102	if (ioctl(sfd, SIOCGARP, (caddr_t)&ar) == -1)
103	    {
104		if (fd == -1)
105		    {
106			bzero((char *)&san, sizeof(san));
107			san.sin_family = AF_INET;
108			san.sin_port = htons(1);
109			bcopy(ip, &san.sin_addr.s_addr, 4);
110			fd = socket(AF_INET, SOCK_DGRAM, 0);
111			(void) sendto(fd, ip, 4, 0,
112				      (struct sockaddr *)&san, sizeof(san));
113			sleep(1);
114			(void) close(fd);
115			goto tryagain;
116		    }
117		fprintf(stderr, "(%s):", inet_ntoa(sin->sin_addr));
118		if (errno != ENXIO)
119			perror("SIOCGARP");
120		return -1;
121	    }
122
123	bcopy(ar.arp_ha.sa_data, ether, 6);
124savearp:
125	bcopy(ether, ethersave, 6);
126	bcopy(ip, ipsave, 4);
127	return 0;
128}
129