How to propagate context for a custom network protocol?

[abailly]

We are using open telemetry-rust as part of the Amaru project whose purpose is to build a Cardano node. This node is part of a network which uses a custom TCP-based protocol upon which we have no control and which does not have provision for any kind of extra field or baggage. However, the so-called block diffusion protocol is built in such a way that it should be possible to define locally a Context from messages' content with a unique identifier therefore enabling propagation of context.

What I am trying to do is to:

• When a new message is received, create a custom Context with a unique identifier (the block id)
• Use that context for all spans created within a single node
• Ensure correlation of traces across nodes when they reference the same unique identifier (block id)

It's not clear to me how to do this as all the examples of Propagator I found are based on injection/extraction of data to/from network messages. Any help would be much appreciated.