Be explicit about use of protobuf version 2

[oskarth]

Problem

Protobuf2 and 3 are different protocols with different semantics. From reading the specs, it is not obvious which version is used. The same is true looking at the docs site https://docs.libp2p.io/concepts/protocols/

Looking at e.g. https://github.com/libp2p/go-libp2p/blob/master/p2p/protocol/identify/pb/identify.proto#L1 one can infer that protobuf2 is used.

Potential solutions

1. Docs site should be explicit about use of protobuf2 unless otherwise mentioned
2. It could be mentioned in the beginning of each spec
3. It could be mentioned in a meta spec (e.g. lifecycle document, or style guide)
4. syntax = "proto2"; could be added to every protobuf field in line

As an example, at Status we specify proto3 in the main spec once: https://specs.status.im/spec/1#protobuf

Notes and related links

• https://github.com/status-im/nim-protobuf-serialization/issues/4
• https://developers.google.com/protocol-buffers/docs/proto?hl=en#optional
• https://developers.google.com/protocol-buffers/docs/proto3?hl=en#default

[sinkingsugar]

I'd like to point out also that 2 implementations of the noise spec are using proto3 Not strictly connected to this issue but to not forget, keep track and investigate.

• go: https://github.com/libp2p/go-libp2p-noise/blob/master/pb/payload.proto#L1
• rust: https://github.com/libp2p/rust-libp2p/blob/cc3438ec378c653cbfda9f73585687bdad45a92f/protocols/noise/src/io/handshake/payload.proto#L1

[oskarth]

Closed in https://github.com/libp2p/specs/pull/282