* Copyright 2009, Axel Dörfler, axeld@pinc-software.de.
* Distributed under the terms of the MIT License.
*/
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/socket.h>
static int
open_tcp_socket()
{
int fd = socket(AF_INET, SOCK_STREAM, 0);
if (fd < 0)
return -1;
fcntl(fd, F_SETFL, O_NONBLOCK);
return fd;
}
static void
init_sockaddr(struct sockaddr_in& address, unsigned ipAddress, unsigned port)
{
memset(&address, 0, sizeof(sockaddr_in));
address.sin_family = AF_INET;
address.sin_port = htons(port);
address.sin_addr.s_addr = htonl(ipAddress);
}
static int
tcp_pair(int pair[])
{
pair[0] = pair[1] = -1;
int listenSocket = open_tcp_socket();
if (listenSocket < 0)
return -1;
sockaddr_in listenAddress;
sockaddr_in peerAddress;
sockaddr_in address;
socklen_t length;
init_sockaddr(listenAddress, INADDR_LOOPBACK, 0);
if (bind(listenSocket, (sockaddr*)&listenAddress, sizeof(sockaddr_in)) != 0)
goto error;
length = sizeof(sockaddr_in);
if (getsockname(listenSocket, (sockaddr*)&listenAddress, &length) != 0)
goto error;
if (listen(listenSocket, 5) != 0)
goto error;
pair[0] = open_tcp_socket();
if (pair[0] < 0)
goto error;
init_sockaddr(address, INADDR_LOOPBACK, ntohs(listenAddress.sin_port));
if (connect(pair[0], (sockaddr*)&address, sizeof(sockaddr_in)) != 0
&& errno != EINPROGRESS)
goto error;
if (errno == EINPROGRESS) {
struct timeval tv;
tv.tv_sec = 100000;
tv.tv_usec = 0;
fd_set set;
FD_ZERO(&set);
FD_SET(pair[0], &set);
if (select(pair[0] + 1, NULL, &set, NULL, &tv) < 0)
fprintf(stderr, "write select() failed: %s\n", strerror(errno));
}
length = sizeof(sockaddr_in);
if (getsockname(pair[0], (sockaddr*)&address, &length) != 0)
goto error;
while (true) {
pair[1] = accept(listenSocket, (sockaddr*)&peerAddress, &length);
if (pair[1] >= 0)
break;
if (errno != EAGAIN && errno != EWOULDBLOCK && errno != ETIMEDOUT)
goto error;
struct timeval tv;
tv.tv_sec = 100000;
tv.tv_usec = 0;
fd_set set;
FD_ZERO(&set);
FD_SET(listenSocket, &set);
if (select(listenSocket + 1, &set, NULL, NULL, &tv) < 0)
fprintf(stderr, "read select() failed: %s\n", strerror(errno));
}
if (peerAddress.sin_port != address.sin_port)
goto error;
close(listenSocket);
return 0;
error:
close(listenSocket);
for (int i = 0; i < 2; i++) {
if (pair[i] >= 0)
close(pair[i]);
}
return -1;
}
int
main(int argc, char** argv)
{
int pair[2];
if (tcp_pair(pair) == 0) {
close(pair[0]);
close(pair[1]);
} else
fprintf(stderr, "pair failed: %s\n", strerror(errno));
return 0;
}
