netif.c

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/*
 * Collect information about network interface.
 *
 * Copyright (c) 2004, by:      Jian Shen
 *    All rights reserved.      Peking University, China
 *                             <[e-mail]>
 *
 * This file may be used subject to the terms and conditions of the
 * GNU Library General Public License Version 2, or any later version
 * at your option, as published by the Free Software Foundation.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 *
 */

#include "netif.h"

#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <netinet/in.h>
#include <arpa/inet.h>

static char *get_name(char *name, char *p)
{
    while (isspace(*p))
		p++;
    while (*p) {
		if (isspace(*p))
			break;
		if (*p == ':') {	/* could be an alias */
			char *dot = p, *dotname = name;
			*name++ = *p++;
			while (isdigit(*p))
				*name++ = *p++;
			if (*p != ':') {	/* it wasn't, backup */
				p = dot;
				name = dotname;
			}
			if (*p == '\0')
				return NULL;
			p++;
			break;
		}
		*name++ = *p++;
    }
    *name++ = '\0';
    return p;
}

int get_if_addr(char* ifname, struct netif* newif)
{
    struct ifreq ifr;
    int fd;
	
	fd = socket(AF_INET, SOCK_DGRAM, 0);
	if(fd < 0) {
		perror("socket");
		return -1;
	}

	strcpy(ifr.ifr_name, ifname);
	ifr.ifr_addr.sa_family = AF_INET;
	if(ioctl(fd, SIOCGIFADDR, &ifr) == 0) {

		strcpy(newif->name, ifname);
		newif->ipaddr = ifr.ifr_addr;

		strcpy(ifr.ifr_name, ifname);
		if(ioctl(fd, SIOCGIFBRDADDR, &ifr) == 0) {
			newif->broadaddr = ifr.ifr_broadaddr;
		}else {
			close(fd);
			return -1;
		}

		close(fd);
		return 0;
	}else {
		close(fd);
		return -1;
	}
}

int get_netif()
{
	FILE *fp;
	char buf[512];

	int num_of_netif = 0;
	int i;

	fp = fopen("/proc/net/dev", "r");
	if(!fp) {
		fprintf(stderr, "Failed to open /proc/net/dev");
		return -1;
	}

    fgets(buf, sizeof(buf), fp);	/* eat line */
    fgets(buf, sizeof(buf), fp);

	i = 0;
    while (fgets(buf, sizeof(buf), fp)) {
		char *s, name[10];
		s = get_name(name, buf);

		if(s) {
			if(strcmp(name, "lo") == 0)
				continue;

			struct netif newif;
			if(get_if_addr(name, &newif) == 0) {
				if_table[i] = newif;
				i++;
			}
		}
    }

	num_of_netif = i;

	fclose(fp);

	return num_of_netif;

}