- Vlad Grachov brought the new function called

libssh2_session_block_directions() which returns a bitmask for what
  directions the connection blocks. It is to be used applications that use
  non-blocking sockets and when a libssh2 function returns
  LIBSSH2_ERROR_EAGAIN this function can be used to figure out in which
  direction the socket would block and thus it can wait for the socket to
  again be ready for communication in that direction before it calls libssh2
  again.

src/libssh2_priv.h

@@ -705,6 +705,7 @@ struct _LIBSSH2_SESSION
     int socket_fd;
     int socket_block;
     int socket_state;
+    int socket_block_directions;
 
     /* Error tracking */
     char *err_msg;