Incoming handshake version not accepted

[Javieracost]

When I try to connect from Ogmios via socket, Dolos logs the following warning:
WARN serve: dolos::serve::o7s_unix: error on incoming connection error=handshake version not accepted

Environment

• Dolos version: 0.20.0
• Ogmios version: v6.11.2
• Connection method: Unix socket

Expected behavior

Dolos should accept Ogmios’ handshake and establish the connection successfully.

Actual behavior

Dolos rejects the incoming connection and logs the mentioned warning.

Possible cause

It looks like Ogmios bumped its network protocol version to match the latest Haskell node, and Dolos hasn’t caught up yet. (ref.)
Edit: Testing with Ogmios v6.10 and 6.9 produces the same result 😕

[Javieracost]

After the kind of debugging that makes you question your life choices I found the exact cause of the handshake failure between Dolos v0.20.0 (and v0.22.0), and newer Ogmios versions.

Key Findings:

Dolos (actually Pallas) N2C Server Capabilities:
When a client connects, Dolos advertises it supports N2C protocol versions 10 to 16:

server: [
    (32784, VersionData(764824073, Some(false))), // N2C V16
    ...
    (32778, VersionData(764824073, None))        // N2C V10
]

Ogmios Client Proposals (Failing Versions - e.g., v6.9.0, v6.10.x, v6.11.2, nightly):
Newer Ogmios versions propose a set of N2C versions that do not overlap with what Dolos supports. In particular Ogmios proposes:

client: [
    (32786, VersionData(764824073, Some(false))), // N2C V18
    (32785, VersionData(764824073, Some(false)))  // N2C V17
]

Since there's no intersection between the server's offered versions (max V16) and the client's proposed versions (V17, V18), the handshake is rejected with no version intersect found.

Solution

Ogmios Client Proposals (Successful Version - v6.8.0):
By downgrading Ogmios to v6.8.0, the connection was successful. This is because Ogmios v6.8.0 proposes a list of N2C versions that includes versions supported by Dolos. The handshake successfully negotiated and agreed upon N2C V16:

DEBUG serve: pallas_network::miniprotocols::handshake::server: accepting hs with (32784, VersionData(764824073, Some(false)))

The issue is a straightforward N2C protocol version incompatibility. Dolos (via its version of Pallas) supports up to N2C V16. Ogmios versions from v6.9.0 onwards appear to have dropped support for proposing N2C V16 (and older) in their default handshake, instead opting to propose N2C V17 and V18.

Hope this helps :)

[mpizenberg]

Thanks for the issue and answer. I got the same problem.