#include <net/if.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

static void show_interface_broadaddr(int fd, const char *name) {
	struct ifreq ifreq;
	char host[128];
	memset(&ifreq, 0, sizeof ifreq);
	strncpy(ifreq.ifr_name, name, IFNAMSIZ);

	if (ioctl(fd, SIOCGIFBRDADDR, &ifreq) != 0) {
		fprintf(stderr, "Could not find interface named %s\n", name);
		return; /* ignore */
	}

	getnameinfo(&ifreq.ifr_broadaddr, sizeof(ifreq.ifr_broadaddr), host, sizeof(host), 0, 0, NI_NUMERICHOST);
	printf("%-24s%s\n", name, host);
}

static void list_interfaces(int fd) {
	struct ifreq *ifreq;
	struct ifconf ifconf;
	char buf[16384];
	unsigned i;
	size_t len;

	ifconf.ifc_len = sizeof(buf);
	ifconf.ifc_buf = buf;

	if (ioctl(fd, SIOCGIFCONF, &ifconf) != 0) {
		perror("ioctl(SIOCGIFCONF)");
		exit(EXIT_FAILURE);
	}

	printf("Listing all interfaces:\n");
	ifreq = ifconf.ifc_req;
	i = 0;
	while (i < ifconf.ifc_len) {
#ifndef linux
		len = IFNAMSIZ + ifreq->ifr_addr.sa_len;
#else
		len = sizeof(struct ifreq);
#endif

		printf("%s\n", ifreq->ifr_name);

		ifreq = (struct ifreq *)((char *)ifreq + len);
		i += len;
	}
}

int main(int argc, char **argv) {
	int sock;

	sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (sock < 0) {
		perror("socket()");
		exit(EXIT_FAILURE);
	}

	if (argc == 1) {
		list_interfaces(sock);
	} else if (argc == 2) {
		show_interface_broadaddr(sock, argv[1]);
	}

	close(sock);

	return EXIT_SUCCESS;
}