/* myip.c : PUBLIC DOMAIN - Jon Mayo - August 22, 2006
 * - You may remove any comments you wish, modify this code any way you wish,
 *   and distribute any way you wish.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * Updated: August 4, 2020 */

/* finds all network interfaces and shows a little information about them.
 * some operating systems list interfaces multiple times because of different
 * flags, modes, etc. if you want to use this code you should be aware that
 * duplicate interfaces is a possibility */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <ifaddrs.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define MYIP_MAX_IGNORED 2

/* filter these IPs from the listings */
static struct sockaddr_storage ignored[MYIP_MAX_IGNORED];
static unsigned ignored_len = 0;

static void *
get_addr(struct sockaddr *sa, size_t *addr_len_out)
{
	if (sa->sa_family == AF_INET) {
		if (addr_len_out)
			*addr_len_out = sizeof(struct in_addr);
		return &((struct sockaddr_in*)sa)->sin_addr;
	} else if (sa->sa_family == AF_INET6) {
		if (addr_len_out)
			*addr_len_out = sizeof(struct in6_addr);
		return &((struct sockaddr_in6*)sa)->sin6_addr;
	} else {
		if (addr_len_out)
			*addr_len_out = 0;
		return NULL; // unknown family
	}
}

static int
add_ignored(int family, const char *addrstr)
{
	if (ignored_len >= MYIP_MAX_IGNORED)
		return -1; // too many items

	struct sockaddr_storage *ss = &ignored[ignored_len];
	memset(ss, 0, sizeof(*ss));

	ss->ss_family = family;
	void *addr = get_addr((struct sockaddr*)ss, NULL);
	inet_pton(family, addrstr, addr);

	ignored_len++;

	return 0;
}

static int
is_ignored(struct sockaddr *sa)
{
	unsigned i;
	struct sockaddr_storage *ig;
	size_t addrlen;
	void *my_addr = get_addr(sa, &addrlen);

	for (i = 0, ig = ignored; i < ignored_len; i++, ig++) {
		if (sa->sa_family == ig->ss_family) {
			void *ig_addr = get_addr((struct sockaddr*)ig, NULL);
			if (memcmp(my_addr, ig_addr, addrlen) == 0)
				return 1; /* match */
		}
	}

	return 0; /* no match - not ignored */
}

static int
match_addrs(int family_match, void (*show)(struct sockaddr *sa, socklen_t sa_len))
{
	struct ifaddrs *a, *curr;

	if (getifaddrs(&a)) {
		perror("getifaddrs()");
		return -1;
	}

	for (curr = a; curr; curr = curr->ifa_next) {
		int family = curr->ifa_addr->sa_family;

		if (family == family_match) {
			socklen_t len = family == AF_INET ? sizeof(struct sockaddr_in) : family == AF_INET6 ? sizeof(struct sockaddr_in6) : sizeof(struct sockaddr_storage);
			show(curr->ifa_addr, len);
		}
	}

	freeifaddrs(a);

	return 0;
}

static void
show_addr(struct sockaddr *sa, socklen_t sa_len)
{
	char addrstr[128];

	if (is_ignored(sa)) {
		return; // ignored
	}
	getnameinfo(sa, sa_len, addrstr, sizeof(addrstr), 0, 0, NI_NUMERICHOST);

	printf("%s ", addrstr);
}

static int
collect_ipv4(void)
{
	return match_addrs(AF_INET, show_addr);
}

static int
collect_ipv6(void)
{
	return match_addrs(AF_INET6, show_addr);
}

int
main()
{
	add_ignored(AF_INET, "127.0.0.1");
	add_ignored(AF_INET6, "::1");

	if (collect_ipv4())
		return EXIT_FAILURE;
	// putchar('\n');
	if (collect_ipv6())
		return EXIT_FAILURE;
	putchar('\n');

	return EXIT_SUCCESS;
}