From 983f02ea1bbbbe9fc85b9971e054d2a1e6391342 Mon Sep 17 00:00:00 2001
From: JimMoen <LnJimMoen@outlook.com>
Date: Tue, 25 Jun 2024 20:37:54 +0800
Subject: [PATCH] refactor: separate CONNECT flags validation funcs

---
 apps/emqx/src/emqx_frame.erl | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/apps/emqx/src/emqx_frame.erl b/apps/emqx/src/emqx_frame.erl
index 4b4a2d5cf..873311ed4 100644
--- a/apps/emqx/src/emqx_frame.erl
+++ b/apps/emqx/src/emqx_frame.erl
@@ -284,28 +284,18 @@ parse_connect(FrameBin, StrictMode) ->
     end,
     parse_connect2(ProtoName, Rest, StrictMode).
 
-% Note: return malformed if reserved flag is not 0.
 parse_connect2(
     ProtoName,
     <<BridgeTag:4, ProtoVer:4, UsernameFlag:1, PasswordFlag:1, WillRetainB:1, WillQoS:2,
         WillFlagB:1, CleanStart:1, Reserved:1, KeepAlive:16/big, Rest2/binary>>,
     StrictMode
 ) ->
-    case Reserved of
-        0 -> ok;
-        1 -> ?PARSE_ERR(reserved_connect_flag)
-    end,
-    WillFlag = bool(WillFlagB),
-    WillRetain = bool(WillRetainB),
-    case WillFlag of
-        %% MQTT-v3.1.1-[MQTT-3.1.2-13], MQTT-v5.0-[MQTT-3.1.2-11]
-        false when WillQoS > 0 -> ?PARSE_ERR(invalid_will_qos);
-        %% MQTT-v3.1.1-[MQTT-3.1.2-14], MQTT-v5.0-[MQTT-3.1.2-12]
-        true when WillQoS > 2 -> ?PARSE_ERR(invalid_will_qos);
-        %% MQTT-v3.1.1-[MQTT-3.1.2-15], MQTT-v5.0-[MQTT-3.1.2-13]
-        false when WillRetain -> ?PARSE_ERR(invalid_will_retain);
-        _ -> ok
-    end,
+    _ = validate_connect_reserved(Reserved),
+    _ = validate_connect_will(
+        WillFlag = bool(WillFlagB),
+        WillRetain = bool(WillRetainB),
+        WillQoS
+    ),
     {Properties, Rest3} = parse_properties(Rest2, ProtoVer, StrictMode),
     {ClientId, Rest4} = parse_utf8_string_with_cause(Rest3, StrictMode, invalid_clientid),
     ConnPacket = #mqtt_packet_connect{
@@ -1133,6 +1123,18 @@ validate_subqos([3 | _]) -> ?PARSE_ERR(bad_subqos);
 validate_subqos([_ | T]) -> validate_subqos(T);
 validate_subqos([]) -> ok.
 
+%% MQTT-v3.1.1-[MQTT-3.1.2-3], MQTT-v5.0-[MQTT-3.1.2-3]
+validate_connect_reserved(0) -> ok;
+validate_connect_reserved(1) -> ?PARSE_ERR(reserved_connect_flag).
+
+%% MQTT-v3.1.1-[MQTT-3.1.2-13], MQTT-v5.0-[MQTT-3.1.2-11]
+validate_connect_will(false, _, WillQos) when WillQos > 0 -> ?PARSE_ERR(invalid_will_qos);
+%% MQTT-v3.1.1-[MQTT-3.1.2-14], MQTT-v5.0-[MQTT-3.1.2-12]
+validate_connect_will(true, _, WillQoS) when WillQoS > 2 -> ?PARSE_ERR(invalid_will_qos);
+%% MQTT-v3.1.1-[MQTT-3.1.2-15], MQTT-v5.0-[MQTT-3.1.2-13]
+validate_connect_will(false, WillRetain, _) when WillRetain -> ?PARSE_ERR(invalid_will_retain);
+validate_connect_will(_, _, _) -> ok.
+
 bool(0) -> false;
 bool(1) -> true.