inet.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 154 行

/*
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * SCCSID: @(#)inet.c	4.3	ULTRIX	2/4/91
 * Based on:
static  char rcsid[] =
    "@(#)$Header: inet.c,v 1.6 90/11/14 20:58:45 mccanne Exp $ (LBL)";
 */

#include <stdio.h>
#include <ctype.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>

#include <net/if.h>
#include <netinet/in.h>

#include "interface.h"

/* Not all systems have IFF_LOOPBACK */
#ifdef IFF_LOOPBACK
#define ISLOOPBACK(p) ((p)->ifr_flags & IFF_LOOPBACK)
#else
#define ISLOOPBACK(p) (strcmp((p)->ifr_name, "lo0") == 0)
#endif

/*
 * Return the name of a network interface attached to the system, or 0
 * if none can be found.  The interface must be configured up; the
 * lowest unit number is preferred; loopback is ignored.
 */
char *
lookup_device()
{
	struct ifreq ibuf[8], *ifrp, *ifend, *mp;
	struct ifconf ifc;
	int fd;
	int minunit, n;
	char *cp;
	static char device[sizeof(ifrp->ifr_name)];

	fd = socket(AF_INET, SOCK_DGRAM, 0);
	if (fd < 0) {
		perror("tcpdump: lookup_device(): socket");
		exit(1);
	}
	ifc.ifc_len = sizeof ibuf;
	ifc.ifc_buf = (caddr_t)ibuf;

	if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0 ||
	    ifc.ifc_len < sizeof(struct ifreq)) {
		perror("tcpdump: lookup_device(): ioctl");
		exit(1);
	}

	ifrp = ibuf;
	ifend = (struct ifreq *)((char *)ibuf + ifc.ifc_len);
	
	mp = 0;
	minunit = 666;
	for (; ifrp < ifend && minunit > 0; ++ifrp) {
		if (ioctl(fd, SIOCGIFFLAGS, (char *)ifrp) < 0) {
			perror("tcpdump: lookup_device(): SIOCGIFFLAGS");
			exit(1);
		}

		if ((ifrp->ifr_flags & IFF_UP) == 0 || ISLOOPBACK(ifrp))
			continue;
		for (cp = ifrp->ifr_name; !isdigit(*cp); ++cp)
			;
		n = atoi(cp);
		if (n < minunit) {
			minunit = n;
			mp = ifrp;
		}
	}
	close(fd);
	if (mp == 0)
		return 0;
	
	(void)strcpy(device, mp->ifr_name);
	return device;
}

/*
 * Get the netmask of an IP address.  This routine is used if
 * SIOCGIFNETMASK doesn't work.
 */
static u_long
ipaddrtonetmask(addr)
	u_long addr;
{
	if (IN_CLASSA(addr))
		return IN_CLASSA_NET;
	if (IN_CLASSB(addr))
		return IN_CLASSB_NET;
	if (IN_CLASSC(addr))
		return IN_CLASSC_NET;
	error("unknown IP address class: %08X", addr);
	/* NOTREACHED */
}

void
lookup_net(device, netp, maskp)
	char *device;
	u_long *netp;
	u_long *maskp;
{
	int fd;
	struct ifreq ifr;
	struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;

	/* Use data gram socket to get IP address. */
	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		perror("tcpdump: socket");
		exit(1);
	}
	(void)strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
	if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) < 0) {
		perror("tcpdump: SIOCGIFADDR");
		exit(1);
	}
	*netp = sin->sin_addr.s_addr;
	if (ioctl(fd, SIOCGIFNETMASK, (char *)&ifr) < 0) {
		perror("tcpdump: SIOCGIFADDR");
		exit(1);
	}
	*maskp = sin->sin_addr.s_addr;
	if (*maskp == 0)
		*maskp = ipaddrtonetmask(*netp);
	*netp &= *maskp;
	(void)close(fd);
}