La clave para hacer que el reenvío de puertos libssh2 funcione fue descubrir que básicamente solo le proporciona los datos que ingresaron a ese puerto. En realidad, debe enviar los datos a un puerto local que abra:
(Tenga en cuenta que este código aún no se ha completado, no se ha verificado ningún error y el resultado no es correcto, pero da un esquema general de cómo lograr esto.)
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
}
PS Para que esto funcione, se necesitan las últimas compilaciones SVN de libssh2. Hubo errores en versiones anteriores que impedían el uso de reenvío de puertos.
Parece que está pidiendo un puerto de reenvío, pero su función se titula claramente como "reverse_port_forward". ¿Este código de ejemplo trae un puerto local a un puerto de servidor, o un puerto de servidor a un puerto local? – Ralphleon