NegotiateProtocolVersion incorrect field naming

[Eugeny]

Despite what the docs describe, the actual protocol version field in NegotiateProtocolVersion carries a packed full version (e.g. 0x00030000) and not just the minor part

[sunng87]

Hi @Eugeny , could you provide more information? The only usage of NegotiateProtocolVersion is here https://github.com/sunng87/pgwire/blob/master/src/api/auth/mod.rs#L279 and it should use the minor part of protocol version

[Eugeny]

Sure! A real Postgres 18.4 includes the full version number in that field - see this example capture.

The full NegotiateProtocolVersion message:

The version number field (0x00030000):

So judging by this, protocol_negotiation would build an incompatible packet compared to the real server - unless the clients are ignoring the higher bits

[Eugeny]

Postgres server source:

• Message encoding: https://github.com/postgres/postgres/blob/master/src/backend/tcop/backend_startup.c#L965
• FrontendProtocol is set via PG_PROTOCOL which is full version packed into an i32: https://github.com/postgres/postgres/blob/89eafad297a9b01ad77cfc1ab93a433e0af894b0/src/include/libpq/pqcomm.h#L89-L95

[sunng87]

I see. Thank you for the information. I might follow a out-of-date docs when implementing this. Will create a fix for this soon.

[Eugeny]

No worries and thanks for this crate! The official docs actually say "minor version" as well - but it turns out to actually be more than that

[sunng87]

Released in 0.40.1

[sunng87]

Just talked with postgres developer, the "minor version" stands for "major+minor" in postgres context, like "18.4" is a minor version. The doc is correct about this.