conn: handle initial error packet correctly

If we haven't completed the hashshake the server will not be aware of our
capabilities and so its will packets behave as if we have none. This is necessary to
correcly parse an initial error packet which never contains an SQL State field even
if the client capabilities will eventually contain CLIENT_PROTOCOL_41.

https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_connection_phase.html

Signed-off-by: Petros Angelatos <[email protected]>

Author: petrosagg

src/conn/mod.rs

@@ -102,6 +102,7 @@ struct ConnInner {
     status: StatusFlags,
     last_ok_packet: Option<OkPacket<'static>>,
     last_err_packet: Option<mysql_common::packets::ServerError<'static>>,
+    handshake_complete: bool,
     pool: Option<Pool>,
     pending_result: std::result::Result<Option<PendingResult>, ServerError>,
     tx_status: TxStatus,
@@ -147,6 +148,7 @@ impl ConnInner {
             status: StatusFlags::empty(),
             last_ok_packet: None,
             last_err_packet: None,
+            handshake_complete: false,
             stream: None,
             is_mariadb: false,
             version: (0, 0, 0),
@@ -585,6 +587,7 @@ impl Conn {
         handshake_response.serialize(buf.as_mut());
 
         self.write_packet(buf).await?;
+        self.inner.handshake_complete = true;
         Ok(())
     }
 
@@ -789,7 +792,19 @@ impl Conn {
         if let Ok(ok_packet) = ok_packet {
             self.handle_ok(ok_packet.into_owned());
         } else {
-            let err_packet = ParseBuf(packet).parse::<ErrPacket>(self.capabilities());
+            // If we haven't completed the handshake the server will not be aware of our
+            // capabilities and so it will behave as if we have none. In particular, the error
+            // packet will not contain a SQL State field even if our capabilities do contain the
+            // `CLIENT_PROTOCOL_41` flag. Therefore it is necessary to parse an incoming packet
+            // with no capability assumptions if we have not completed the handshake.
+            //
+            // https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_connection_phase.html
+            let capabilities = if self.inner.handshake_complete {
+                self.capabilities()
+            } else {
+                CapabilityFlags::empty()
+            };
+            let err_packet = ParseBuf(packet).parse::<ErrPacket>(capabilities);
             if let Ok(err_packet) = err_packet {
                 self.handle_err(err_packet)?;
                 return Ok(true);