Summary

When iterating through the hello response, mongoc_server_description_handle_hello does not set the bson_error_t on the server description if the type check on any fields fails. This causes further errors down the line due to _cluster_fetch_stream_single returning the server description's error if it selects a server with a type of MONGOC_SERVER_UNKNOWN. Since this error is not set, any operation that calls fails with an unknown error.

Environment

Versions starting with 1.22.0 are affected when connecting to a mongohoused. In my case, connecting to mongohoused returned a hello response which contained a connectionId with type int64, whereas libmongoc expects int32 for a connectionId.

How to Reproduce

The hello response that triggered this behaviour is as follows:

{ 
  "ok" : { "$numberInt" : "1" }, 
  "ismaster" : true, 
  "maxBsonObjectSize" : { "$numberInt" : "16777216" }, 
  "maxMessageSizeBytes" : { "$numberInt" : "48000000" }, 
  "maxWriteBatchSize" : { "$numberInt" : "100000" }, 
  "logicalSessionTimeoutMinutes" : { "$numberInt" : "30" }, 
  "connectionId" : { "$numberLong" : "565160423" }, 
  "minWireVersion" : { "$numberInt" : "0" }, 
  "maxWireVersion" : { "$numberInt" : "15" }, 
  "readOnly" : false 
}

Expected behaviour

When setting the server description's type to unknown, the associated bson_error_t should contain a reason for why the server was marked as unknown. This is not the case for validation failures in the hello response.