From 7f548110ffc4e3e8a7881270963e4f1deb20b630 Mon Sep 17 00:00:00 2001
From: Olaf Baumert <olaf.baumert@axpo-systems.com>
Date: Tue, 3 Jun 2025 11:04:25 +0000
Subject: [PATCH] feat: Add automatic decimal AS number conversion for SCION AS
 entries

- Implement scion_as_to_decimal() function in both add-as and add-as-batch scripts
- Automatically converts SCION AS format (ISD:AS:Instance) to decimal when in BGP range
- Handles both ISD:AS:Instance format and colon-separated hex format
- Follows SCION AS numbering specification from https://github.com/scionproto/scion/wiki/ISD-and-AS-numbering
---
 add-as       | 43 +++++++++++++++++++++++--------------------
 add-as-batch | 43 +++++++++++++++++++++++--------------------
 2 files changed, 46 insertions(+), 40 deletions(-)

diff --git a/add-as b/add-as
index e00975c..6f9c296 100755
--- a/add-as
+++ b/add-as
@@ -12,34 +12,37 @@ def scion_as_to_decimal(as_id):
     if ':' not in as_id:
         return as_id
     
-    # Parse SCION format (ISD:AS:Instance or AS parts in hex)
+    # Parse SCION format
     parts = as_id.split(':')
     
-    # For ISD:AS:Instance format, extract the AS part
-    if len(parts) == 3:
-        # ISD:AS:Instance format - AS is the middle part
+    # Check if this looks like ISD:AS:Instance format (first part is single digit ISD)
+    if len(parts) == 3 and len(parts[0]) == 1 and parts[0].isdigit():
+        # ISD:AS:Instance format - convert the AS part (middle) and instance (last)
         try:
-            # Convert hex AS to decimal
+            # AS is 16-bit hex, instance is 16-bit hex
+            # Combine them as 32-bit number: AS << 16 | Instance
             as_num = int(parts[1], 16)
-            if 0 <= as_num <= 0xFFFFFFFF:  # BGP AS range
-                return str(as_num)
+            instance = int(parts[2], 16)
+            total = (as_num << 16) | instance
+            
+            if 0 <= total <= 0xFFFFFFFF:  # BGP AS range
+                return str(total)
         except ValueError:
             pass
         return ""
     
-    # For colon-separated hex format (e.g., 0:1:f)
-    if len(parts) <= 3:
-        try:
-            # Convert each hex part and combine
-            total = 0
-            for i, part in enumerate(parts):
-                total = total * 65536 + int(part, 16)
-            
-            # Check if in BGP AS range
-            if 0 <= total <= 0xFFFFFFFF:  # 2^32 - 1
-                return str(total)
-        except ValueError:
-            pass
+    # For standard colon-separated hex format (e.g., 0:1:f)
+    # Each part is up to 16 bits
+    try:
+        total = 0
+        for part in parts:
+            total = (total << 16) + int(part, 16)
+        
+        # Check if in BGP AS range
+        if 0 <= total <= 0xFFFFFFFF:  # 2^32 - 1
+            return str(total)
+    except ValueError:
+        pass
     
     return ""
 
diff --git a/add-as-batch b/add-as-batch
index 871d20c..0c56d58 100755
--- a/add-as-batch
+++ b/add-as-batch
@@ -17,34 +17,37 @@ def scion_as_to_decimal(as_id):
     if ':' not in as_id:
         return as_id
     
-    # Parse SCION format (ISD:AS:Instance or AS parts in hex)
+    # Parse SCION format
     parts = as_id.split(':')
     
-    # For ISD:AS:Instance format, extract the AS part
-    if len(parts) == 3:
-        # ISD:AS:Instance format - AS is the middle part
+    # Check if this looks like ISD:AS:Instance format (first part is single digit ISD)
+    if len(parts) == 3 and len(parts[0]) == 1 and parts[0].isdigit():
+        # ISD:AS:Instance format - convert the AS part (middle) and instance (last)
         try:
-            # Convert hex AS to decimal
+            # AS is 16-bit hex, instance is 16-bit hex
+            # Combine them as 32-bit number: AS << 16 | Instance
             as_num = int(parts[1], 16)
-            if 0 <= as_num <= 0xFFFFFFFF:  # BGP AS range
-                return str(as_num)
+            instance = int(parts[2], 16)
+            total = (as_num << 16) | instance
+            
+            if 0 <= total <= 0xFFFFFFFF:  # BGP AS range
+                return str(total)
         except ValueError:
             pass
         return ""
     
-    # For colon-separated hex format (e.g., 0:1:f)
-    if len(parts) <= 3:
-        try:
-            # Convert each hex part and combine
-            total = 0
-            for i, part in enumerate(parts):
-                total = total * 65536 + int(part, 16)
-            
-            # Check if in BGP AS range
-            if 0 <= total <= 0xFFFFFFFF:  # 2^32 - 1
-                return str(total)
-        except ValueError:
-            pass
+    # For standard colon-separated hex format (e.g., 0:1:f)
+    # Each part is up to 16 bits
+    try:
+        total = 0
+        for part in parts:
+            total = (total << 16) + int(part, 16)
+        
+        # Check if in BGP AS range
+        if 0 <= total <= 0xFFFFFFFF:  # 2^32 - 1
+            return str(total)
+    except ValueError:
+        pass
     
     return ""