Add callback to accept forwarded-tcpip requests

Signed-off-by: Adley Phu <aphu@janestreet.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

include/libssh/callbacks.h

@@ -139,6 +139,26 @@ typedef ssh_channel (*ssh_channel_open_request_x11_callback) (ssh_session sessio
 typedef ssh_channel (*ssh_channel_open_request_auth_agent_callback) (ssh_session session,
       void *userdata);
 
+/**
+ * @brief Handles an SSH new channel open "forwarded-tcpip" request. This
+ * happens when the server forwards an incoming TCP connection on a port it was
+ * previously requested to listen on. This is a client-side API
+ * @param session current session handler
+ * @param destination_address the address that the TCP connection connected to
+ * @param destination_port the port that the TCP connection connected to
+ * @param originator_address the originator IP address
+ * @param originator_port the originator port
+ * @param userdata Userdata to be passed to the callback function.
+ * @returns a valid ssh_channel handle if the request is to be allowed
+ * @returns NULL if the request should not be allowed
+ * @warning The channel pointer returned by this callback must be closed by the
+ * application.
+ */
+typedef ssh_channel (*ssh_channel_open_request_forwarded_tcpip_callback) (ssh_session session,
+      const char *destination_address, int destination_port,
+      const char *originator_address, int originator_port,
+      void *userdata);
+
 /**
  * The structure to replace libssh functions with appropriate callbacks.
  */
@@ -172,6 +192,11 @@ struct ssh_callbacks_struct {
   /** This function will be called when an incoming "auth-agent" request is received.
    */
   ssh_channel_open_request_auth_agent_callback channel_open_request_auth_agent_function;
+  /**
+   * This function will be called when an incoming "forwarded-tcpip"
+   * request is received.
+   */
+  ssh_channel_open_request_forwarded_tcpip_callback channel_open_request_forwarded_tcpip_function;
 };
 typedef struct ssh_callbacks_struct *ssh_callbacks;