From fa06f0cdacaa58ca20f6c99d351d209e6d731a04 Mon Sep 17 00:00:00 2001
From: Nathael Pajani <nathael.pajani@ed3l.fr>
Date: Wed, 6 Mar 2019 01:31:26 +0100
Subject: [PATCH] MQTT protocol support going on, adding connack packet check.
 Compiles but still untested.

---
 include/lib/protocols/mqtt.h | 17 +++++++++++++----
 lib/protocols/mqtt.c         | 31 +++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/include/lib/protocols/mqtt.h b/include/lib/protocols/mqtt.h
index c2c458f..3ea54d2 100644
--- a/include/lib/protocols/mqtt.h
+++ b/include/lib/protocols/mqtt.h
@@ -37,6 +37,8 @@
  * This code only handles the packet encoding and decoding according to the MQTT specification and
  * provides usage information in order to respect the protocol flow, but does not provide the communication
  * parts of the protocol, which should be application specific.
+ * This lets the application designer choose between any of the possible MQTT flow available, from single
+ * "in-flight" message window to a single server to multiple servers and complex message queues.
  * 
  */
 
@@ -116,8 +118,8 @@ struct mqtt_connect_pkt {
 };
 
 /* Create MQTT connect packet
- * This function must be called in order to connectte the connect MQTT packet used to
- * connect to the server.
+ * This function must be called in order to create the connect MQTT packet used to connect to the
+ * server.
  * The client must send a connect packet whenever the server does not acknoledge a publish,
  * subscribe, unsubscribe, or ping packet, or when the server explicitely closes the connection.
  *
@@ -140,6 +142,7 @@ enum MQTT_connack_return_codes {
 	MQTT_CONNACK_REFUSED_SERVER_UNAVAILABLE = 3,
 	MQTT_CONNACK_REFUSED_BAD_USER_NAME_OR_PASSWORD = 4,
 	MQTT_CONNACK_REFUSED_NOT_AUTHORIZED = 5,
+	MQTT_CONNACK_MAX,
 };
 
 /* MQTT connack packet */
@@ -154,8 +157,14 @@ struct mqtt_connack_response_pkt {
  * the server accepts the connection and has a stored session for this client id */
 #define MQTT_CONNACK_SESSION_PRESENT  (0x01 << 0)
 
-/* Check and Decode MQTT connack packet */
-int mqtt_unpackconnack_response_pkt(uint8_t* buf, uint8_t buf_size);
+/* Check MQTT connack packet
+ * This function may get called to check a supposed connect acknowledge packet.
+ * The function checks for conformance to the MQTT protocol and returns 0 if the packet is valid and
+ * the server accepted the connection.
+ * The function returns -EPROTO in case of invalid connack packet or -EREMOTEIO in case of connection
+ * refused by the server (ret_code is then valid in the packet).
+ */
+int mqtt_check_connack_response_pkt(struct mqtt_connack_response_pkt* pkt);
 
 /***************************************************************************** */
 /* publish and puback packets */
diff --git a/lib/protocols/mqtt.c b/lib/protocols/mqtt.c
index 861fecd..690ba9e 100644
--- a/lib/protocols/mqtt.c
+++ b/lib/protocols/mqtt.c
@@ -195,3 +195,34 @@ int mqtt_pack_connect_packet(struct mqtt_connect_pkt* pkt, uint8_t* buf, uint32_
 }
 
 
+/***************************************************************************** */
+/* Check MQTT connack packet
+ * This function may get called to check a supposed connect acknowledge packet.
+ * The function checks for conformance to the MQTT protocol and returns 0 if the packet is valid,
+ * regardless of the retrun code value.
+ * The function returns -EPROTO in case of protocol error.
+ */
+int mqtt_check_connack_response_pkt(struct mqtt_connack_response_pkt* pkt)
+{
+	if (pkt->control != (MQTT_CONTROL_CONNACK << 4)) {
+		return -EPROTO;
+	}
+	if (pkt->rem_len != 2) {
+		return -EPROTO;
+	}
+	if (pkt->flags & 0xFE) {
+		return -EPROTO;
+	}
+	if (pkt->ret_code >= MQTT_CONNACK_MAX) {
+		return -EPROTO;
+	}
+	if (pkt->ret_code != 0) {
+		return -EREMOTEIO;
+	}
+	return 0;
+}
+
+
+
+/***************************************************************************** */
+
-- 
2.43.0