getifaddrs_test.c

#include <stdio.h>
#include <stdlib.h>
/* The following include files for the network interface. */
#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <net/if_dl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if_types.h>
/* For "toupper". */
#include <ctype.h>
/* For "strerror". */
#include <string.h>
/* For "errno". */
#include <errno.h>

/* Print an internet address. */

void
print_ip (const char * name, struct ifaddrs * ifaddrs_ptr, void * addr_ptr) {
	if (addr_ptr) {
	/* This constant is defined in <netinet/in.h>. */
	char address[INET6_ADDRSTRLEN];

	inet_ntop (ifaddrs_ptr->ifa_addr->sa_family,
		   addr_ptr,
		   address, sizeof (address));

	/* The "toupper" capitalizes the first letter. */
	printf ("%c%s: <%s>\n", toupper (name[0]), name + 1, address);
	}
	else {
		printf ("No %s\n", name);
	}
}

/* Get a pointer to the address structure from a sockaddr. */

void *
get_addr_ptr (struct sockaddr * sockaddr_ptr) {
	void * addr_ptr = 0;
	if (sockaddr_ptr->sa_family == AF_INET) {
		addr_ptr = &((struct sockaddr_in *)  sockaddr_ptr)->sin_addr;
	}
	else if (sockaddr_ptr->sa_family == AF_INET6) {
		addr_ptr = &((struct sockaddr_in6 *) sockaddr_ptr)->sin6_addr;
	}
	return addr_ptr;
}

/* Print the internet address. */

void
print_internet_address (struct ifaddrs * ifaddrs_ptr) {
	void * addr_ptr;
	if (! ifaddrs_ptr->ifa_addr) {
		return;
	}
	addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_addr);
	print_ip ("internet address", ifaddrs_ptr, addr_ptr);
}

/* Print the netmask. */

void
print_netmask (struct ifaddrs * ifaddrs_ptr) {
	void * addr_ptr;
	if (! ifaddrs_ptr->ifa_netmask) {
		return;
	}
	addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_netmask);
	print_ip ("netmask", ifaddrs_ptr, addr_ptr);
}

/* Print the mac address. */

void
print_mac_address (const char * mac_address) {
	int mac_addr_offset;

	printf ("Mac address: ");
	for (mac_addr_offset = 0; mac_addr_offset < 6; mac_addr_offset++) {
		unsigned char byte;
				            
		byte = (unsigned char) mac_address[mac_addr_offset];
		printf ("%02x", byte);
		if (mac_addr_offset != 5) {
			printf (":");
		}
	}
	printf ("\n");
}

/* Adapted from http://othermark.livejournal.com/3005.html */

void
print_af_link (struct ifaddrs * ifaddrs_ptr) {
	struct sockaddr_dl * sdl;

	sdl = (struct sockaddr_dl *) ifaddrs_ptr->ifa_addr;

	/* The types "IFT_ETHER" and so on are defined in
	*        <net/if_types.h>. */

	if (sdl->sdl_type == IFT_ETHER) {
		print_mac_address (LLADDR (sdl));
	}
	else if (sdl->sdl_type == IFT_LOOP) {
		printf ("Loopback.\n");
	}
//			    else if (sdl->sdl_type == IFT_USB) {
//				    	printf ("USB interface.\n");
//					    }
	else {
		printf ("Link of type %d\n", sdl->sdl_type);
	}
}

void
print_internet_interface (struct ifaddrs * ifaddrs_ptr) {
	print_internet_address (ifaddrs_ptr);
	print_netmask (ifaddrs_ptr);

	/* P2P interface destination */
	if (ifaddrs_ptr->ifa_dstaddr) {
		void * addr_ptr;

		addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_dstaddr);
		print_ip ("destination address", ifaddrs_ptr, addr_ptr);
	}

	/* Interface broadcast address */
	if (ifaddrs_ptr->ifa_broadaddr) {
		void * addr_ptr;

		addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_broadaddr);
		print_ip ("broadcast address", ifaddrs_ptr, addr_ptr);
	}
}

/* Adapted from
 *    http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/index.jsp?topic=/apis/getifaddrs.htm */
void
print_ifaddrs (struct ifaddrs * ifaddrs_ptr) {
	while (ifaddrs_ptr) {
		printf ("Name: %s; Flags: 0x%x; ",
		ifaddrs_ptr->ifa_name, ifaddrs_ptr->ifa_flags);

		/* Decide what to do based on the family. */
		if (ifaddrs_ptr->ifa_addr->sa_family == AF_INET) {
			/* AF_INET is defined in <sys/socket.h>. */
			printf ("Family: AF_INET\n");
			print_internet_interface (ifaddrs_ptr);
		}
		else if (ifaddrs_ptr->ifa_addr->sa_family == AF_INET6) {
			printf ("Family: AF_INET6\n");
			print_internet_interface (ifaddrs_ptr);
		}
		else if (ifaddrs_ptr->ifa_addr->sa_family == AF_LINK) {
			printf ("Family: AF_LINK\n");
			print_af_link (ifaddrs_ptr);
		}
		else {
			printf ("Unknown family");
		}

		/* Print a line between this entry and the next. */

		printf ("\n");
		ifaddrs_ptr = ifaddrs_ptr->ifa_next;
	}
}

int main ()
{
	struct ifaddrs * ifaddrs_ptr;
	int status;
	status = getifaddrs (& ifaddrs_ptr);
	if (status == -1) {
		fprintf (stderr, "Error in 'getifaddrs': %d (%s)\n",
			 errno, strerror (errno));
		exit (1);
	}
	print_ifaddrs (ifaddrs_ptr);
	/* Free the memory associated with "ifaddrs_ptr". */
	freeifaddrs (ifaddrs_ptr);
	return 0;
}