bugfix in parsePacket(): accept short artnet packets (#5588) for 16_x

* bugfix in parsePacket(): accept short artnet packets
* add min artnet packet size check and fix indentation

---------

Co-authored-by: Frank Möhle <91616163+softhack007@users.noreply.github.com>

Author: DedeHai

wled00/src/dependencies/e131/ESPAsyncE131.cpp

@@ -99,33 +99,37 @@ bool ESPAsyncE131::initMulticast(uint16_t port, uint16_t universe, uint8_t n) {
 
 void ESPAsyncE131::parsePacket(AsyncUDPPacket _packet) {
   bool error = false;
-  uint8_t protocol = P_E131;
+  uint8_t protocol = P_ARTNET;
   const size_t pktLen = _packet.length();
 
   e131_packet_t *sbuff = reinterpret_cast<e131_packet_t *>(_packet.data());
 
   // E1.31 packet identifier (ACN_ID = "ASC-E1.17"), need at least 16 bytes to safely read acn_id (offset 4, length 12).
   if (pktLen >= 16) {
-    if (memcmp(sbuff->acn_id, ESPAsyncE131::ACN_ID, sizeof(sbuff->acn_id)))
-      protocol = P_ARTNET;
+    if (!memcmp(sbuff->acn_id, ESPAsyncE131::ACN_ID, sizeof(sbuff->acn_id)))
+      protocol = P_E131;
   }
 
 	if (protocol == P_ARTNET) {
-		if (memcmp(sbuff->art_id, ESPAsyncE131::ART_ID, sizeof(sbuff->art_id)))
-			error = true; //not "Art-Net"
-		if (sbuff->art_opcode != ARTNET_OPCODE_OPDMX && sbuff->art_opcode != ARTNET_OPCODE_OPPOLL)
-			error = true; //not a DMX or poll packet
-	} else { //E1.31 error handling
-		if (htonl(sbuff->root_vector) != ESPAsyncE131::VECTOR_ROOT)
-			error = true;
-		if (htonl(sbuff->frame_vector) != ESPAsyncE131::VECTOR_FRAME)
-			error = true;
-		if (sbuff->dmp_vector != ESPAsyncE131::VECTOR_DMP)
-			error = true;
-		if (sbuff->property_values[0] != 0)
-			error = true;
-	} 
-  
+    if (pktLen < 10) {
+      error = true; // Need at least Art-Net ID (8) + opcode (2)
+    } else {
+      if (memcmp(sbuff->art_id, ESPAsyncE131::ART_ID, sizeof(sbuff->art_id)))
+        error = true; //not "Art-Net"
+      if (sbuff->art_opcode != ARTNET_OPCODE_OPDMX && sbuff->art_opcode != ARTNET_OPCODE_OPPOLL)
+        error = true; //not a DMX or poll packet
+    }
+  } else { //E1.31 error handling
+    if (htonl(sbuff->root_vector) != ESPAsyncE131::VECTOR_ROOT)
+      error = true;
+    if (htonl(sbuff->frame_vector) != ESPAsyncE131::VECTOR_FRAME)
+      error = true;
+    if (sbuff->dmp_vector != ESPAsyncE131::VECTOR_DMP)
+      error = true;
+    if (sbuff->property_values[0] != 0)
+      error = true;
+  }
+
   if (error && _packet.localPort() == DDP_DEFAULT_PORT) { //DDP packet
     error = false;
     protocol = P_DDP;