/*
 * Send to an UDP socket with a pad destination option.
 *
 * Francis Dupont <fdupont@isc.org> January 2020
 */

#include <sys/param.h>
#include <sys/socket.h>

#ifdef __APPLE__
#define __APPLE_USE_RFC_3542
#endif

#include <netinet/in.h>
#include <netinet/ip6.h>

#include <arpa/inet.h>

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

struct sockaddr_in6 sin6;
int s;
socklen_t slen;
char src[INET6_ADDRSTRLEN];
uint8_t dstopt[8];
struct ip6_opt *opt;
uint8_t pack[8000];
int cc;


int
main(int argc, char *argv[])
{
	if (argc != 2)
		errx(1, "usage: %s <dst>", argv[0]);

	memset(&sin6, 0, sizeof(sin6));
	sin6.sin6_family = AF_INET6;
#ifdef BSD
	sin6.sin6_len = sizeof(sin6);
#endif
	sin6.sin6_port = htons(12345);
	if (inet_pton(AF_INET6, argv[1], &sin6.sin6_addr) != 1)
		err(1, "inet_pton(%s)", argv[1]);
	s = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
	if (s < 0)
		err(1, "socket");
	if (connect(s, (struct sockaddr *)&sin6, sizeof(sin6)) < 0)
		err(1, "connect");
	memset(&sin6, 0, sizeof(sin6));
	slen = sizeof(sin6);
	if (getsockname(s, (struct sockaddr *)&sin6, &slen) < 0)
		err(1, "getsockname");
	if (sin6.sin6_family != AF_INET6)
		errx(1, "bad family %d", (int)sin6.sin6_family);
	if (inet_ntop(sin6.sin6_family, &sin6.sin6_addr, src,
		      sizeof(src)) == NULL)
		err(1, "inet_ntop");
	memset(&dstopt, 0, sizeof(dstopt));
	opt = (struct ip6_opt *)&dstopt[sizeof(struct ip6_ext)];
	opt->ip6o_type = IP6OPT_PADN;
	opt->ip6o_len = 4;
	if (setsockopt(s, IPPROTO_IPV6, IPV6_DSTOPTS, dstopt,
		       sizeof(dstopt)) < 0)
		err(1, "setsockopt(IPV6_DSTOPTS)");
	for (;;) {
		memset(pack, 0, sizeof(pack));
		printf("send %s -> %s:\n", src, argv[1]);
		cc = read(0, pack, sizeof(pack));
		if (cc < 0)
			err(1, "read");
		if (cc == 0)
			exit(0);
		if (send(s, pack, cc, 0) < 0)
			err(1, "send");
	}
	errx(1, "exit loop");
}