decode protobuf within a protobuf in lua plugin

edit

I have a http2 packet with grpc+protobuf content.

The protobuf inside grpc has a byte array field which itself is a protobuf.

I have written a lua post-dissector which find offset and length of this byte array and calls protobuf dissector on it as follows:

        pinfo.private["pb_msg_type"] = "message," .. probmsgtype
        Dissector.get("protobuf"):call(tvb, pinfo, subtree)

i am seeing following error: Protocol Buffers: pbuf.pbufmsgtype [Packet size limited during capture: ProtoBuf truncated]

I verified that length of buffer and content is alright.

i doubt some field in http2 header messing it up.

Any ideas?