2.0.0-p353/lib/ruby/gems/2.0.0/gems/ffi-1.9.6/lib/ffi/library.rb:261:in `attach_function': Function 'sftp_reply_handle' not found in [libssh.so] (FFI::NotFoundError)
This seems to be caused by the sftp_reply_* functions not being exported via the LIBSSH_API C macro.