/*
 * Copyright (c) 2001 Nicholas W. Sayer. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <dlfcn.h>
#include <stdio.h>
#include <errno.h>
#include <strings.h>

#if (defined(__unix__) || defined(unix)) && !defined(USG)
#include <sys/param.h>
#endif

#define NUMSOCK (1024) /* Maximum number of supported sockets */

enum status {
	NEED_INIT,
	INACTIVE,
	ACTIVE
};
static enum status active = NEED_INIT;

static int sock_type[NUMSOCK];

static int (*R_socket)();
static int (*R_connect)();
static int (*R_close)();
static int (*R_getaddrinfo)();
static struct hostent *(*R_gethostbyname)();

static void initlib() {
	void *handle;
	int i;

	active = INACTIVE;

	for(i = 0; i < NUMSOCK; i++)
		sock_type[i] = -1;

#ifdef BSD
	handle = dlopen("/usr/lib/libc.so", RTLD_LAZY);
#elif defined(LINUX)
	handle = dlopen("/lib/libc.so", RTLD_LAZY);
#else
#error "Unknown operating system"
#endif
	if (handle == NULL)
		return;

#define SET_UP(x,y) if ((x = dlsym(handle, y)) == NULL) return

	SET_UP(R_socket, "socket");
	SET_UP(R_connect, "connect");
	SET_UP(R_close, "close");

	/* If we got here, everything worked. We are ready to go */
	active = ACTIVE;

}

/*
 * Socket needs to do nothing more than make a note of the 2nd argument
 * if the socket is AF_INET
 */
int socket(int family, int type, int proto) {
	int sock;

	if (active == NEED_INIT)
		initlib();

	if (active == ACTIVE && family == PF_INET
		&& getenv("NATPT_PREFIX") != NULL) {
		family = PF_INET6;	
		sock = R_socket(family, type, proto);
		if (sock < 0)
			return sock;
		if (sock > NUMSOCK) {
			R_close(sock);
			errno = EAGAIN;
			return -1;
		}
		sock_type[sock] = type;
		return sock;
	} else
		return R_socket(family, type, proto);
}

/*
 * If the socket had its 2nd argument noted before, then we need
 * to look up any previously cached information we got from
 * gethostbyname and make connections to the real addresses
 * instead. If we connect successfully, we dup2() over the old
 * (user-supplied) socket.
 */
int connect(int s, const struct sockaddr *name, socklen_t namelen) {
	int i;
	char *prefix;
	struct sockaddr_in6 new_addr;

	if (active == NEED_INIT)
		initlib();

	if (active == INACTIVE)
		return R_connect(s, name, namelen);
	if (s < 0 || s >= NUMSOCK) /* ignore rather than core */
		return R_connect(s, name, namelen);
	if (sock_type[s] < 0) /* if, for instance, it is AF_UNIX */
		return R_connect(s, name, namelen);
	if ((prefix = getenv("NATPT_PREFIX")) == NULL)
		return R_connect(s, name, namelen);

	bzero(&new_addr, sizeof(struct sockaddr_in6));
	new_addr.sin6_len = sizeof(struct sockaddr_in6);
	new_addr.sin6_family = PF_INET6;

	if (inet_pton(AF_INET6, prefix, &(new_addr.sin6_addr.s6_addr)) != 1)
		return R_connect(s, name, namelen);

	for(i = 0; i < sizeof(in_addr_t); i++)
		new_addr.sin6_addr.s6_addr[i + 12] =
			((unsigned char *)&((struct sockaddr_in *)name)->sin_addr.s_addr)[i];

	new_addr.sin6_port = ((struct sockaddr_in *)name)->sin_port;

	return R_connect(s, &new_addr, sizeof(new_addr));
}

int
close(int s) {
	int out;

	if (active == NEED_INIT)
		initlib();

	if (s >= 0 && s < NUMSOCK)
		sock_type[s] = -1;

	return R_close(s);
}