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

void md5_set(int sock, int family,
	     const char *host, unsigned short port, const char *password)
{
	struct tcp_md5sig md5sig;
	int s;
	memset(&md5sig, 0, sizeof(md5sig));

	if (family == AF_INET6) {
		struct sockaddr_in6 sin6 = {
			.sin6_family = family,
			.sin6_port = htons(port),
		};

		if (strchr(host, ':') == NULL) {
			/* convert V4 address to mapped */
			sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
			s = inet_pton(AF_INET, host,
				      &sin6.sin6_addr.s6_addr32[3]);
			if (s == 0)
				fprintf(stderr, "%s: not in IPV4 format\n",
					host);
		} else {
			s = inet_pton(AF_INET6, host, &sin6.sin6_addr);
			if (s == 0)
				fprintf(stderr, "%s: not in IPV6 format\n",
					host);
		}
		memcpy(&md5sig.tcpm_addr, &sin6, sizeof(sin6));
	} else {
		struct sockaddr_in sin = {
			.sin_family = family,
			.sin_port = htons(port),
		};

		s = inet_pton(AF_INET, host, &sin.sin_addr);
		if (s == 0)
			fprintf(stderr, "%s: not in IPV4 format\n", host);
		memcpy(&md5sig.tcpm_addr, &sin, sizeof(sin));
	}

	if (s <= 0)
		exit(EXIT_FAILURE);

	memcpy(md5sig.tcpm_key, password, md5sig.tcpm_keylen =
	       strlen(password));
	if (setsockopt(sock, IPPROTO_TCP, TCP_MD5SIG, &md5sig, sizeof(md5sig)) <
	    0)
		perror("setsockopt (TCP_MD5SIG)");
}

static void usage(void)
{
	fprintf(stderr, "Usage: server port [host port passwd]\n");
	exit(EXIT_FAILURE);
}

int main(int argc, char *argv[])
{
	struct addrinfo *result, *rp;
	int sfd, s, cc;
	static struct addrinfo hints = {
		.ai_family = AF_UNSPEC,
		.ai_flags = AI_PASSIVE,
		.ai_socktype = SOCK_STREAM,
	};
	char buf[BUFSIZ];

	if (argc > 1 && argv[1][0] == '-') {
		if (strcmp(argv[1], "-4") == 0) {
			hints.ai_family = AF_INET;
		} else if (strcmp(argv[1], "-6") == 0) {
			hints.ai_family = AF_INET6;
		} else
			usage();
		--argc, ++argv;
	}
	if (argc < 2)
		usage();

	s = getaddrinfo(NULL, argv[1], &hints, &result);
	if (s != 0) {
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
		exit(EXIT_FAILURE);
	}

	for (rp = result; rp != NULL; rp = rp->ai_next) {
		sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
		if (sfd == -1) {
			perror("socket");
			continue;
		}

		if (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0)
			break;	/* Success */

		perror("bind");
		close(sfd);
	}

	if (rp == NULL) {	/* No address succeeded */
		fprintf(stderr, "Could not bind\n");
		exit(EXIT_FAILURE);
	}
	if (listen(sfd, 5) < 0)
		perror("listen");

	if (argc > 2)
		md5_set(sfd, rp->ai_family, argv[2], atoi(argv[3]), argv[4]);
	freeaddrinfo(result);	/* No longer needed */

	for (;;) {
		struct sockaddr_storage peer_addr;
		socklen_t peer_addr_len = sizeof(peer_addr);
		char host[NI_MAXHOST], service[NI_MAXSERV];

		int afd =
		    accept(sfd, (struct sockaddr *)&peer_addr, &peer_addr_len);
		if (afd < 0) {
			perror("accept");
			return 1;
		}

		s = getnameinfo((struct sockaddr *)&peer_addr,
				peer_addr_len, host, NI_MAXHOST,
				service, NI_MAXSERV, NI_NUMERICSERV);
		if (s == 0)
			printf("Connect from %s:%s\n", host, service);
		else
			fprintf(stderr, "getnameinfo: %s\n", gai_strerror(s));

		if (fork() == 0) {
			close(sfd);
			while ((cc = read(afd, buf, sizeof(buf))) > 0)
				if (write(afd, buf, cc) != cc)
					break;
			if (cc < 0)
				perror("read");
			else
				printf("eof\n");
			exit(0);
		}
		close(afd);
	}
}