getif_name.c

/* 
 * name: getif_name.c
 * this file is part of the "Net-Injector" project. It defines the getif_name_by_ip() function
 * Adapted from Salvatore Sanfilippo <antirez@invece.org>
 * license: This software is under GPL license
 * date: 04 17 2003
 * rev: 0.8
*/ 

#include "neti.h"


int getif_name_by_ip(char *ifname, u_int32_t *inet_ip){
	
	int sock;
	struct ifconf	ifc;
	struct ifreq	ibuf[16], ifr, *ifrp, *ifend;
	struct sockaddr_in if_sockaddr;
	
	if ( (sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		fprintf(stderr, "Error : (getif_name) socket(AF_INET, SOCK_DGRAM, 0) !\n");
		return EXIT_FAILURE;
	}

	memset(ibuf, 0, sizeof(struct ifreq)*16);
	ifc.ifc_len = sizeof ibuf;
	ifc.ifc_buf = (caddr_t) ibuf;

	/* gets interfaces list */
	if ( ioctl(sock, SIOCGIFCONF, (char*)&ifc) == -1 ||
	    ifc.ifc_len < sizeof(struct ifreq)		) {
		fprintf(stderr, "Error : (getif_name) ioctl(SIOCGIFCONF) !\n");
		close(sock);
		return EXIT_FAILURE;
	}

	/* ifrp points to buffer and ifend points to buffer's end */
	ifrp = ibuf;
	ifend = (struct ifreq*) ((char*)ibuf + ifc.ifc_len);

	for (; ifrp < ifend; ifrp++) {
		strncpy(ifr.ifr_name, ifrp->ifr_name, sizeof(ifr.ifr_name));

		if ( ioctl(sock, SIOCGIFFLAGS, (char*)&ifr) == -1) {
			fprintf(stderr, "Error : (getif_name) ioctl(SIOCGIFFLAGS) !\n");
			continue;
		}

		/* Check if down */
		if ( !(ifr.ifr_flags & IFF_UP) ) continue;

		/* Get the interface address */
		if (ioctl(sock, SIOCGIFADDR, (char*)&ifr) == -1) {
			fprintf(stderr, "Error : (getif_name) ioctl(SIOCGIFADDR) !\n");
			continue;
		}
		
		/* Copy it */
		memcpy(&if_sockaddr, &ifr.ifr_addr, sizeof(struct sockaddr_in));
		
		/* Check if it is what we are locking for */
		if (if_sockaddr.sin_addr.s_addr != *inet_ip) continue;
		
		/* interface found, save if name */
		strncpy(ifname, ifr.ifr_name, 32);				
		close(sock);
		return EXIT_SUCCESS;
	}
close(sock);
return EXIT_FAILURE;
}