dgram.c

#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>

static int str_to_sockaddr(struct sockaddr_storage *ss, const char *addr,
			   const char *port)
{
	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ss;
	struct sockaddr_in *sin = (struct sockaddr_in *)ss;
	int ret;

	memset(ss, 0, sizeof(*ss));
	ret = inet_pton(AF_INET6, addr, &sin6->sin6_addr);
	if (ret == 1) {
		sin6->sin6_family = AF_INET6;
		sin6->sin6_port = htons(atoi(port));
		return 0;
	}

	ret = inet_pton(AF_INET, addr, &sin->sin_addr);
	if (ret == 1) {
		sin->sin_family = AF_INET;
		sin->sin_port = htons(atoi(port));
		return 0;
	}

	return -EINVAL;
}

static void str_to_sockaddr_ipv4_mp6(struct sockaddr_storage *ss,
				     const char *addr, const char *port)
{
	char tmp[INET6_ADDRSTRLEN];

	snprintf(tmp, sizeof(tmp), "::ffff:%s", addr);
	str_to_sockaddr(ss, tmp, port);
}

int main(int argc, char *argv[])
{
	struct sockaddr_storage src, dst;
	int fd, err;
	ssize_t ret;

	if (argc != 5) {
		fprintf(stderr, "Usage: %s [iface] [src] [dst] [dport]\n", argv[0]);
		return 1;
	}

	err = str_to_sockaddr(&src, argv[2], "0");
	if (err < 0) {
		fprintf(stderr, "Invalid source address: %s\n", argv[2]);
		return 1;
	}

	err = str_to_sockaddr(&dst, argv[3], argv[4]);
	if (err < 0) {
		fprintf(stderr, "Invalid destination address: %s\n", argv[3]);
		return 1;
	}

	if (src.ss_family != dst.ss_family) {
		if (src.ss_family == AF_INET)
			str_to_sockaddr_ipv4_mp6(&src, argv[2], "0");
		else
			str_to_sockaddr_ipv4_mp6(&dst, argv[3], argv[4]);
	}

	fd = socket(src.ss_family, SOCK_DGRAM, 0);
	if (fd < 0) {
		perror("socket");
		return 1;
	}

	err = setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, argv[1], strlen(argv[1]));
	if (err < 0) {
		perror("setsockopt");
		close(fd);
		return 1;
	}

	err = bind(fd, (struct sockaddr *)&src, sizeof(src));
	if (err < 0) {
		perror("bind");
		close(fd);
		return 1;
	}

repeat:
	ret = sendto(fd, "Test", 5, 0, (struct sockaddr *)&dst, sizeof(dst));
	if (ret < 0) {
		perror("sendto");
		close(fd);
		return 1;
	}
	printf("Sent %zd bytes\n", ret);
	sleep(1);
	goto repeat;
}