使libssh2端口转发工作的关键是发现它基本上只提供了进入该端口的数据。你必须打开一个本地端口来发送数据:
(请注意,这段代码还没有完成,没有错误检查,线程生成也不正确,但它给出了如何完成此操作的概要。)
void reverse_port_forward(CMainDlg* dlg, addrinfo * hubaddr, std::string username, std::string password, int port)
{
int iretval;
unsigned long mode = 1;
int last_socket_err = 0;
int other_port = 0;
fd_set read_set, write_set;
SOCKET sshsock = socket(AF_INET, SOCK_STREAM, 0);
iretval = connect(sshsock, hubaddr->ai_addr, hubaddr->ai_addrlen);
if (iretval != 0)
::PostQuitMessage(0);
LIBSSH2_SESSION * session = NULL;
session = libssh2_session_init();
iretval = libssh2_session_startup(session, sshsock);
if (iretval)
::PostQuitMessage(0);
iretval = libssh2_userauth_password(session, username.c_str(), password.c_str());
dlg->m_track_status(dlg, 1, 0, "Authorized");
LIBSSH2_LISTENER* listener = NULL;
listener = libssh2_channel_forward_listen_ex(session, "127.0.0.1", port, &other_port, 1);
if (!listener)
::PostQuitMessage(0);
LIBSSH2_CHANNEL* channel = NULL;
ioctlsocket(sshsock, FIONBIO, &mode);
libssh2_session_set_blocking(session, 0); // non-blocking
int err = LIBSSH2_ERROR_EAGAIN;
while (err == LIBSSH2_ERROR_EAGAIN)
{
channel = libssh2_channel_forward_accept(listener);
if (channel) break;
err = libssh2_session_last_errno(session);
boost::this_thread::yield();
}
if (channel)
{
char buf[MAX_BUF_LEN];
char* chunk;
long bytes_read = 0;
long bytes_written = 0;
int total_set = 0;
timeval wait;
wait.tv_sec = 0;
wait.tv_usec = 2000;
sockaddr_in localhost;
localhost.sin_family = AF_INET;
localhost.sin_addr.s_addr = inet_addr("127.0.0.1");
localhost.sin_port = htons(5900);
SOCKET local_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
ioctlsocket(local_sock, FIONBIO, &mode);
iretval = connect(local_sock, (sockaddr*) &localhost, sizeof(localhost) );
if (iretval == SOCKET_ERROR)
iretval = WSAGetLastError();
while (1)
{
bytes_read = libssh2_channel_read(channel, buf, MAX_BUF_LEN);
if (bytes_read >= 0){
FD_ZERO(&read_set);
FD_ZERO(&write_set);
FD_SET(local_sock, &write_set);
// wait until the socket can be written to
while (select(0, &read_set, &write_set, NULL, &wait) < 1)
boost::this_thread::yield();
if (FD_ISSET(local_sock, &write_set))
{
FD_CLR(local_sock, &write_set);
chunk = buf;
// everything may not get written in this call because we're non blocking. So
// keep writing more data until we've emptied the buffer pointer.
while ((bytes_written = send(local_sock, chunk, bytes_read, 0)) < bytes_read)
{
// if it couldn't write anything because the buffer is full, bytes_written
// will be negative which won't help our pointer math much
if (bytes_written > 0)
{
chunk = buf + bytes_written;
bytes_read -= bytes_written;
if (bytes_read == 0)
break;
}
FD_ZERO(&read_set);
FD_ZERO(&write_set);
FD_SET(local_sock, &write_set);
// wait until the socket can be written to
while (select(0, &read_set, &write_set, NULL, &wait) < 1)
boost::this_thread::yield();
}
}
}
FD_ZERO(&read_set);
FD_ZERO(&write_set);
FD_SET(local_sock, &read_set);
select(0, &read_set, &write_set, NULL, &wait);
if (FD_ISSET(local_sock, &read_set))
{
FD_CLR(local_sock, &read_set);
bytes_read = recv(local_sock, buf, MAX_BUF_LEN, 0);
if (bytes_read >= 0)
{
while ((bytes_written = libssh2_channel_write_ex(channel, 0, buf, bytes_read)) == LIBSSH2_ERROR_EAGAIN)
boost::this_thread::yield();
}
}
boost::this_thread::yield();
} // while
} // if channel
}
