getifname.c

/* getifname.c -- network interface handling
 * Copyright(C) 1999,2000,2001 Salvatore Sanfilippo <antirez@invece.org>
 * Copyright(C) 2001 by Nicolas Jombart <Nicolas.Jombart@hsc.fr>
 * This code is under the GPL license */

/* BSD support thanks to Nicolas Jombart <Nicolas.Jombart@hsc.fr> */

/* $Id: getifname.c,v 1.3 2003/10/22 10:41:00 antirez Exp $ */

#include <stdio.h>		/* perror */
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>		/* struct sockaddr_in */
#include <arpa/inet.h>		/* inet_ntoa */
#include <net/if.h>
#include <unistd.h>		/* close */
#include <stdlib.h>

#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) || \
    defined(__bsdi__) || defined(__APPLE__)
#include <ifaddrs.h>
#include <net/route.h>
#endif /* defined(__*BSD__) */

#include "hping2.h"
#include "globals.h"

#if !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__) && \
    !defined(__linux__) && !defined(__sun__) && !defined(__bsdi__) && \
    !defined(__APPLE__)
#error Sorry, interface code not implemented.
#endif

#ifdef __sun__
#include <sys/sockio.h>
#include <net/route.h>
#include <net/if_dl.h>
#endif

#if (defined OSTYPE_LINUX) || (defined __sun__)
int get_if_name(void)
{
	int fd;
	struct ifconf	ifc;
	struct ifreq	ibuf[16],
			ifr,
			*ifrp,
			*ifend;
	struct sockaddr_in sa;
	struct sockaddr_in output_if_addr;
	int known_output_if = 0;

	/* Try to get the output interface address according to
	 * the OS routing table */
	if (ifname[0] == '\0') {
		if (get_output_if(&remote, &output_if_addr) == 0) {
			known_output_if = 1;
			if (opt_debug)
				printf("DEBUG: Output interface address: %s\n",
					inet_ntoa(sa.sin_addr));
		} else {
			fprintf(stderr, "Warning: Unable to guess the output "
					"interface\n");
		}
	}

	if ( (fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		perror("[get_if_name] socket(AF_INET, SOCK_DGRAM, 0)");
		return -1;
	}

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

	/* gets interfaces list */
	if ( ioctl(fd, SIOCGIFCONF, (char*)&ifc) == -1 ||
	     ifc.ifc_len < sizeof(struct ifreq)		) {
		perror("[get_if_name] ioctl(SIOCGIFCONF)");
		close(fd);
		return -1;
	}

	/* 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++) {
		strlcpy(ifr.ifr_name, ifrp->ifr_name, sizeof(ifr.ifr_name));

		if ( ioctl(fd, SIOCGIFFLAGS, (char*)&ifr) == -1) {
			if (opt_debug)
				perror("DEBUG: [get_if_name] ioctl(SIOCGIFFLAGS)");
			continue;
		}

		if (opt_debug)
			printf("DEBUG: if %s: ", ifr.ifr_name);

		/* Down interface? */
		if ( !(ifr.ifr_flags & IFF_UP) )
		{
			if (opt_debug)
				printf("DOWN\n");
			continue;
		}

		if (known_output_if) {
			/* Get the interface address */
			if (ioctl(fd, SIOCGIFADDR, (char*)&ifr) == -1) {
				perror("[get_if_name] ioctl(SIOCGIFADDR)");
				continue;
			}
			/* Copy it */
			memcpy(&sa, &ifr.ifr_addr,
				sizeof(struct sockaddr_in));
			/* Check if it is what we are locking for */
			if (sa.sin_addr.s_addr !=
			    output_if_addr.sin_addr.s_addr) {
				if (opt_debug)
					printf("The address doesn't match\n");
				continue;
			}
		} else if (ifname[0] != '\0' && !strstr(ifr.ifr_name, ifname)) {
			if (opt_debug)
				printf("Don't Match (but seems to be UP)\n");
			continue;
		}

		if (opt_debug)
			printf("OK\n");

		/* interface found, save if name */
		strlcpy(ifname, ifr.ifr_name, 1024);

		/* get if address */
		if ( ioctl(fd, SIOCGIFADDR, (char*)&ifr) == -1) {
			perror("DEBUG: [get_if_name] ioctl(SIOCGIFADDR)");
			exit(1);
		}

		/* save if address */
		memcpy(&sa, &ifr.ifr_addr,
			sizeof(struct sockaddr_in));
		strlcpy(ifstraddr, inet_ntoa(sa.sin_addr), 1024);

		/* get if mtu */
		if ( ioctl(fd, SIOCGIFMTU, (char*)&ifr) == -1) {
			perror("Warning: [get_if_name] ioctl(SIOCGIFMTU)");
			fprintf(stderr, "Using a fixed MTU of 1500\n");
			h_if_mtu = 1500;
		}
		else
		{
#ifdef __sun__
			/* somehow solaris is braidamaged in wrt ifr_mtu */
			h_if_mtu = ifr.ifr_metric;
#else
			h_if_mtu = ifr.ifr_mtu;
#endif
		}
		close(fd);
		return 0;
	}
	/* interface not found, use 'lo' */
	strlcpy(ifname, "lo", 1024);
	strlcpy(ifstraddr, "127.0.0.1", 1024);
	h_if_mtu = 1500;

	close(fd);
	return 0;
}

#elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \
      defined(__bsdi__) || defined(__APPLE__)

/* return interface informations :
   - from the specified (-I) interface
   - from the routing table
   - or at least from the first UP interface found
*/
int get_if_name(void)
{
	/* variable declarations */
	struct ifaddrs		*ifap, *ifa;
	char			current_if_name[24];
	char			saved_ifname[24];
	struct sockaddr_in	output_if_addr;
#ifdef __NetBSD__
	int s;
	struct ifreq ifr;
#endif  /* __NetBSD__ */

	if (getifaddrs(&ifap) < 0)
		perror("getifaddrs");

	saved_ifname[0] = 0;

	/* lookup desired interface */
	if(ifname[0] == 0) {
		/* find gateway interface from kernel */
                if (get_output_if(&remote, &output_if_addr) == 0) {
                        if (opt_debug)
                                printf("DEBUG: Output interface address: %s\n",
                                        inet_ntoa(output_if_addr.sin_addr));
			/* Put something in saved_ifname in order to tell
			   that the output adress is known */
			saved_ifname[0] = 'X'; saved_ifname[1] = 0;
                } else {
                        fprintf(stderr, "Warning: Unable to guess the output "
                                        "interface\n");
                }
	}
	else {
		/* use the forced interface name */
		strlcpy(saved_ifname,ifname,24);
	}

	/* get interface information */
        for (ifa = ifap; ifa; ifa = ifa->ifa_next) {

		if (opt_debug) printf("\n DEBUG: if %s: ", ifa->ifa_name);

		/* print if the data structure is null or not */
		if (ifa->ifa_data) {
			if(opt_debug) printf("DEBUG: (struct DATA) "); }
		else
			if(opt_debug) printf("DEBUG: (struct DATA is NULL) ");

		if (!(ifa->ifa_flags & IFF_UP)) {       /* if down */
			if (opt_debug)
				printf("DEBUG: DOWN");
			continue; 
		}

		if ((ifa->ifa_flags & IFF_LOOPBACK)&&
		    (strncmp(saved_ifname,"lo0",3))) {  /* if loopback */
			if (opt_debug)
				printf("DEBUG: LOOPBACK, SKIPPED");
			continue;
		}

		if (ifa->ifa_addr->sa_family == AF_LINK) {
			if (opt_debug)
				printf("DEBUG: AF_LINK ");
			strlcpy(ifname,ifa->ifa_name,1024);
			strlcpy(current_if_name,ifa->ifa_name,24);

/* I don't know why NetBSD behavior is not the same */
#ifdef __NetBSD__
			memset( &ifr, 0, sizeof(ifr));
			strlcpy(ifr.ifr_name, ifa->ifa_name, sizeof(ifr.ifr_name));
			if( sizeof(ifr.ifr_addr) >= ifa->ifa_addr->sa_len )
				memcpy(&ifr.ifr_addr, ifa->ifa_addr, 
				       ifa->ifa_addr->sa_len);
			if( (s = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
				perror("[get_if_name] socket");
				return -1;
			}
			if (ioctl(s, SIOCGIFMTU, (caddr_t)&ifr) < 0) h_if_mtu = 0;
			else h_if_mtu = ifr.ifr_mtu;
			close(s);
#else
			if( ifa->ifa_data )
				h_if_mtu = ((struct if_data *)ifa->ifa_data)->ifi_mtu;
			else {
				h_if_mtu = 1500;
				fprintf(stderr, "Warning: fixing MTU to 1500 !\n");
                        }
#endif /* __NetBSD__ */
			continue;
		}

		if (ifa->ifa_addr->sa_family == AF_INET6) {
			if (opt_debug)
				printf("AF_INET6 ");
			continue;
		}

		if (ifa->ifa_addr->sa_family == AF_INET) {
			if (opt_debug)
				printf("AF_INET ");

			if(strncmp(ifa->ifa_name,current_if_name,24))
				continue; /* error */

			if(opt_debug) printf("OK\n");

			strlcpy(ifstraddr,
			        inet_ntoa(((struct sockaddr_in *)ifa->ifa_addr)->sin_addr),
				          1024);
			
			if( (saved_ifname[0] == 0) ||
                            (!strncmp(ifa->ifa_name, saved_ifname, 24)) || 
			    (((struct sockaddr_in *)ifa->ifa_addr)->sin_addr.s_addr ==
			       output_if_addr.sin_addr.s_addr) )
				break; /* asked if found or first UP interface */
		}

		/* interface not found, use hardcoded 'lo' */
		strlcpy(ifname, "lo0", 1024);
		strlcpy(ifstraddr, "127.0.0.1", 1024);
		h_if_mtu = 1500;
	}

	freeifaddrs(ifap);
	return 0;
}

#endif /* __*BSD__ */

/* Try to obtain the IP address of the output interface according
 * to the OS routing table. Derived from R.Stevens */
int get_output_if(struct sockaddr_in *dest, struct sockaddr_in *ifip)
{
	socklen_t len;
	int sock_rt, on=1;
	struct sockaddr_in iface_out;
 
	memset(&iface_out, 0, sizeof(iface_out));
	sock_rt = socket(AF_INET, SOCK_DGRAM, 0 );

	dest->sin_port = htons(11111);
	if (setsockopt(sock_rt, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on))
            == -1) {
		if (opt_debug)
			perror("DEBUG: [get_output_if] setsockopt(SOL_SOCKET, "
			       "SO_BROADCAST");
		close(sock_rt);
		return -1;
	}
  
	if (connect(sock_rt, (struct sockaddr*)dest, sizeof(struct sockaddr_in))
	    == -1 ) {
		if (opt_debug)
			perror("DEBUG: [get_output_if] connect");
		close(sock_rt);
		return -1;
	}

	len = sizeof(iface_out);
	if (getsockname(sock_rt, (struct sockaddr *)&iface_out, &len) == -1 ) {
		if (opt_debug)
			perror("DEBUG: [get_output_if] getsockname");
		close(sock_rt);
		return -1;
	}
	close(sock_rt);
	if (iface_out.sin_addr.s_addr == 0)
		return 1;
	memcpy(ifip, &iface_out, sizeof(struct sockaddr_in));
        return 0;
}