Function outbound_sasl 

pub async fn outbound_sasl<S>(
    stream: &mut S,
    creds: &SaslCredentials,
    server_name: &str,
    client_id: &str,
    frame_max: ClientFrameMax,
) -> Result<SaslSession, OutboundSaslError>
where
    S: AsyncRead + AsyncWrite + Unpin + Send + ?Sized,

Run the outbound SASL handshake to completion over stream.

This function sends ApiVersions v0, then SaslHandshake with the mechanism in creds at the version that the broker lists, then drives the mechanism-specific SaslAuthenticate round-trips, as Kafka’s SaslClientAuthenticator does. The requests use Kafka’s reserved SASL correlation ids. server_name is the broker’s canonical hostname. Only the GSSAPI path uses it, to build the target SPN (service_name/server_name). The function returns once the broker has accepted the credentials. The same stream is then usable for normal Kafka RPCs.

Errors

Returns OutboundSaslError on I/O failure, codec failure, or a non-zero broker SASL error code.