Incorrect SSID bits handling fix

Core/Inc/ax25.h

@@ -29,6 +29,28 @@ along with VP-Digi.  If not, see <http://www.gnu.org/licenses/>.
 //for AX.25 329 bytes is the theoretical max size assuming 2-byte Control, 1-byte PID, 256-byte info field and 8 digi address fields
 #define AX25_FRAME_MAX_SIZE (329) //single frame max length
 
+/**
+ * @brief Extract SSID from SSID byte in AX.25 frame
+ * @param byte Byte containing SSID
+ * @return Decoded SSID (0-15)
+ */
+#define EXTRACT_SSID(byte) (((byte) >> 1) & 0xF)
+
+/**
+ * @brief H-bit (has been repeated) mask
+ */
+#define H_BIT_MASK 0x80
+
+/**
+ * @brief Reserved bits in AX.25 SSID
+ */
+#define SSID_RESERVED_MASK 0x60
+
+/**
+ * @brief C-bit (end of path) mask
+ */
+#define C_BIT_MASK 0x1
+
 enum Ax25RxStage
 {
 	RX_STAGE_IDLE = 0,

Core/Src/beacon.c

@@ -49,7 +49,7 @@ void BeaconSend(uint8_t number)
 	for(uint8_t i = 0; i < sizeof(GeneralConfig.call); i++) //add source address
 		buf[idx++] = GeneralConfig.call[i];
 
-	buf[idx++] = ((GeneralConfig.callSsid << 1) + 0b01100000); //add source ssid
+	buf[idx++] = ((GeneralConfig.callSsid << 1) | SSID_RESERVED_MASK); //add source ssid
 
 	if(BeaconConfig[number].path[0] > 0) //this BeaconConfig has some path set
 	{
@@ -60,7 +60,7 @@ void BeaconSend(uint8_t number)
 				buf[idx] = BeaconConfig[number].path[i]; //copy path
 				if((i == 6) || (i == 13)) //it was and ssid
 				{
-					buf[idx] = ((buf[idx] << 1) + 0b01100000); //add appropriate bits for ssid
+					buf[idx] = ((buf[idx] << 1) | SSID_RESERVED_MASK); //add appropriate bits for ssid
 				}
 				idx++;
 			}
@@ -68,7 +68,7 @@ void BeaconSend(uint8_t number)
 				break; //end here
 		}
 	}
-	buf[idx - 1] |= 1; //add c-bit on the last element
+	buf[idx - 1] |= C_BIT_MASK; //add c-bit on the last element
 	buf[idx++] = 0x03; //control
 	buf[idx++] = 0xF0; //pid
 	for(uint8_t i = 0; i < strlen((char*)BeaconConfig[number].data); i++)

Core/Src/common.c

@@ -101,7 +101,7 @@ static void sendTNC2ToUart(Uart *uart, uint8_t *from, uint16_t len)
 		}
 	}
 
-	uint8_t ssid = ((from[13] >> 1) & 0b00001111); //store ssid
+	uint8_t ssid = EXTRACT_SSID(from[13]); //store ssid
 	if(ssid > 0) //SSID >0
 	{
 		UartSendByte(uart, '-'); //add -
@@ -117,7 +117,7 @@ static void sendTNC2ToUart(Uart *uart, uint8_t *from, uint16_t len)
 			UartSendByte(uart, from[i] >> 1);
 		}
 	}
-	ssid = ((from[6] >> 1) & 0b00001111); //store ssid
+	ssid = EXTRACT_SSID(from[6]); //store ssid
 
 	if(ssid > 0) //SSID >0
 	{
@@ -141,20 +141,20 @@ static void sendTNC2ToUart(Uart *uart, uint8_t *from, uint16_t len)
         		}
         	}
 
-            ssid = ((from[nextPathEl + 6] >> 1) & 0b00001111); //store ssid
+            ssid = EXTRACT_SSID(from[nextPathEl + 6]); //store ssid
         	if(ssid > 0) //SSID >0
         	{
         		UartSendByte(uart, '-'); //add -
         		UartSendNumber(uart, ssid);
         	}
-            if((from[nextPathEl + 6] & 0x80)) //h-bit in ssid
+            if((from[nextPathEl + 6] & H_BIT_MASK)) //h-bit in ssid
             	UartSendByte(uart, '*'); //add *
 
             nextPathEl += 7; //next path element
             if(nextPathEl > 56) //too many path elements
             	break;
         }
-        while((from[nextPathEl - 1] & 1) == 0); //loop until the c-bit is found
+        while((from[nextPathEl - 1] & C_BIT_MASK) == 0); //loop until the c-bit is found
 
     }
 

Core/Src/digipeater.c

@@ -210,7 +210,7 @@ static void makeFrame(uint8_t *frame, uint16_t elStart, uint16_t len, uint32_t h
     	if(!filterFrameCheck(&frame[7], alias)) //push source callsign through the filter
     		return;
     }
-    uint8_t ssid = (frame[elStart + 6] >> 1) - 48; //store SSID (N)
+    uint8_t ssid = EXTRACT_SSID(frame[elStart + 6]); //store SSID (N)
 
 
     if(alias < 8)
@@ -241,8 +241,8 @@ static void makeFrame(uint8_t *frame, uint16_t elStart, uint16_t len, uint32_t h
     		for(uint8_t i = 0; i < sizeof(GeneralConfig.call); i++) //replace with own call
     			buffer[elStart + i] = GeneralConfig.call[i];
 
-    		buffer[elStart + 6] &= 1; //clear everything but path end bit
-    		buffer[elStart + 6] |= ((GeneralConfig.callSsid << 1) + 0b11100000); //insert ssid and h-bit
+    		buffer[elStart + 6] &= C_BIT_MASK; //clear everything but path end bit
+    		buffer[elStart + 6] |= ((GeneralConfig.callSsid << 1) | H_BIT_MASK | SSID_RESERVED_MASK); //insert ssid and h-bit
     	}
     }
     else //standard n-N alias
@@ -263,7 +263,7 @@ static void makeFrame(uint8_t *frame, uint16_t elStart, uint16_t len, uint32_t h
     		for(uint8_t i = 0; i < sizeof(GeneralConfig.call); i++) //insert own call
     			buffer[(*index)++] = GeneralConfig.call[i];
 
-    		buffer[(*index)++] = ((GeneralConfig.callSsid << 1) + 0b11100000); //insert ssid and h-bit
+    		buffer[(*index)++] = ((GeneralConfig.callSsid << 1) | H_BIT_MASK | SSID_RESERVED_MASK); //insert ssid and h-bit
     		shift = 7; //additional shift when own call is inserted
     	}
 
@@ -274,9 +274,9 @@ static void makeFrame(uint8_t *frame, uint16_t elStart, uint16_t len, uint32_t h
     	}
 
 		buffer[elStart + shift + 6] -= 2; //decrement SSID in alias (2 because ssid is shifted left by 1)
-		if((buffer[elStart + shift + 6] & 0b11110) == 0) //if SSID is 0
+		if(EXTRACT_SSID(buffer[elStart + shift + 6]) == 0) //if SSID is 0
 		{
-			buffer[elStart + shift + 6] += 0x80; //add h-bit
+			buffer[elStart + shift + 6] |= H_BIT_MASK; //add h-bit
 		}
 
     }
@@ -314,7 +314,7 @@ void DigiDigipeat(uint8_t *frame, uint16_t len)
 		return;
 
     uint16_t t = 13; //start from first byte that can contain path end bit
-    while((frame[t] & 1) == 0) //look for path end
+    while((frame[t] & C_BIT_MASK) == 0) //look for path end
     {
     	if((t + 7) >= len)
     		return;
@@ -347,7 +347,7 @@ void DigiDigipeat(uint8_t *frame, uint16_t len)
     }
 
 
-    while((frame[t] & 0x80) == 0) //look for h-bit
+    while((frame[t] & H_BIT_MASK) == 0) //look for h-bit
     {
         if(t == 13)
         {
@@ -357,7 +357,7 @@ void DigiDigipeat(uint8_t *frame, uint16_t len)
     }
     t++; //now t is the index for the first byte in path element we want to process
 
-    uint8_t ssid = ((frame[t + 6] >> 1) - 0b00110000); //current path element SSID
+    uint8_t ssid = EXTRACT_SSID(frame[t + 6]); //current path element SSID
 
     uint8_t err = 0;
 
@@ -416,7 +416,7 @@ void DigiDigipeat(uint8_t *frame, uint16_t len)
 
         if(err == 0) //alias matching, check further
         {
-            uint8_t n = ((frame[t + j] >> 1) - 48); //get n from alias (e.g. WIDEn-N) - N is in ssid variable
+            uint8_t n = ((frame[t + j] >> 1) - '0'); //get n from alias (e.g. WIDEn-N) - N is in ssid variable
 
             //every path must meet several requirements
             //say we have a WIDEn-N path. Then:

lwfec

@@ -1 +1 @@
-Subproject commit c4b8bbf1ff6fa1b3f6fa1a584eab6fb42732a91b
+Subproject commit 97d1753fda01372fe45b3c3b8ca6d28f1eddab98