Adapt the byte order to the system configuration

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

squinnondation/squinnondation.py

@@ -4,6 +4,7 @@
 import curses
 import re
 import socket
+import sys
 from argparse import ArgumentParser
 from enum import Enum
 from ipaddress import IPv6Address
@@ -119,9 +120,16 @@ class TLV:
         return 2 + self.length
 
     @staticmethod
-    def tlv_classes():
+    def tlv_classes() -> list:
         return [Pad1TLV, PadNTLV, HelloTLV, NeighbourTLV, DataTLV, AckTLV, GoAwayTLV, WarningTLV]
 
+    @staticmethod
+    def network_order() -> str:
+        """
+        The network byte order is always inverted as the host network byte order.
+        """
+        return "little" if sys.byteorder == "big" else "big"
+
 
 class Pad1TLV(TLV):
     """
@@ -139,7 +147,7 @@ class Pad1TLV(TLV):
         """
         The TLV is empty.
         """
-        return self.type.to_bytes(1, "big")
+        return self.type.to_bytes(1, TLV.network_order())
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
         # TODO Add some easter eggs
@@ -162,7 +170,7 @@ class PadNTLV(TLV):
     mbz: bytes
 
     def validate_data(self) -> bool:
-        if self.mbz != int(0).to_bytes(self.length, "big"):
+        if self.mbz != int(0).to_bytes(self.length, TLV.network_order()):
             raise ValueError("The body of a PadN TLV is not filled with zeros.")
         return True
 
@@ -178,7 +186,8 @@ class PadNTLV(TLV):
         """
         Construct the byte array filled by zeros.
         """
-        return self.type.to_bytes(1, "big") + self.length.to_bytes(1, "big") + self.mbz[:self.length]
+        return self.type.to_bytes(1, TLV.network_order()) + self.length.to_bytes(1, TLV.network_order()) \
+            + self.mbz[:self.length]
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
         # TODO Add some easter eggs
@@ -200,14 +209,15 @@ class HelloTLV(TLV):
     def unmarshal(self, raw_data: bytes) -> None:
         self.type = raw_data[0]
         self.length = raw_data[1]
-        self.source_id = int.from_bytes(raw_data[2:10], "big")
+        self.source_id = int.from_bytes(raw_data[2:10], TLV.network_order())
         if self.is_long:
-            self.dest_id = int.from_bytes(raw_data[10:18], "big")
+            self.dest_id = int.from_bytes(raw_data[10:18], TLV.network_order())
 
     def marshal(self) -> bytes:
-        data = self.type.to_bytes(1, "big") + self.length.to_bytes(1, "big") + self.source_id.to_bytes(8, "big")
+        data = self.type.to_bytes(1, TLV.network_order()) + self.length.to_bytes(1, TLV.network_order()) \
+            + self.source_id.to_bytes(8, TLV.network_order())
         if self.dest_id:
-            data += self.dest_id.to_bytes(8, "big")
+            data += self.dest_id.to_bytes(8, TLV.network_order())
         return data
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
@@ -230,13 +240,13 @@ class NeighbourTLV(TLV):
         self.type = raw_data[0]
         self.length = raw_data[1]
         self.ip_address = IPv6Address(raw_data[2:18])
-        self.port = int.from_bytes(raw_data[18:20], "big")
+        self.port = int.from_bytes(raw_data[18:20], TLV.network_order())
 
     def marshal(self) -> bytes:
-        return self.type.to_bytes(1, "big") + \
+        return self.type.to_bytes(1, TLV.network_order()) + \
-            self.length.to_bytes(1, "big") + \
+            self.length.to_bytes(1, TLV.network_order()) + \
             self.ip_address.packed + \
-            self.port.to_bytes(2, "big")
+            self.port.to_bytes(2, TLV.network_order())
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
         # TODO Implement NeighbourTLV
@@ -254,15 +264,15 @@ class DataTLV(TLV):
     def unmarshal(self, raw_data: bytes) -> None:
         self.type = raw_data[0]
         self.length = raw_data[1]
-        self.sender_id = int.from_bytes(raw_data[2:10], "big")
+        self.sender_id = int.from_bytes(raw_data[2:10], TLV.network_order())
-        self.nonce = int.from_bytes(raw_data[10:14], "big")
+        self.nonce = int.from_bytes(raw_data[10:14], TLV.network_order())
         self.data = raw_data[14:self.tlv_length]
 
     def marshal(self) -> bytes:
-        return self.type.to_bytes(1, "big") + \
+        return self.type.to_bytes(1, TLV.network_order()) + \
-            self.length.to_bytes(1, "big") + \
+            self.length.to_bytes(1, TLV.network_order()) + \
-            self.sender_id.to_bytes(8, "big") + \
+            self.sender_id.to_bytes(8, TLV.network_order()) + \
-            self.nonce.to_bytes(4, "big") + \
+            self.nonce.to_bytes(4, TLV.network_order()) + \
             self.data
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
@@ -292,14 +302,14 @@ class AckTLV(TLV):
     def unmarshal(self, raw_data: bytes) -> None:
         self.type = raw_data[0]
         self.length = raw_data[1]
-        self.sender_id = int.from_bytes(raw_data[2:10], "big")
+        self.sender_id = int.from_bytes(raw_data[2:10], TLV.network_order())
-        self.nonce = int.from_bytes(raw_data[10:14], "big")
+        self.nonce = int.from_bytes(raw_data[10:14], TLV.network_order())
 
     def marshal(self) -> bytes:
-        return self.type.to_bytes(1, "big") + \
+        return self.type.to_bytes(1, TLV.network_order()) + \
-            self.length.to_bytes(1, "big") + \
+            self.length.to_bytes(1, TLV.network_order()) + \
-            self.sender_id.to_bytes(8, "big") + \
+            self.sender_id.to_bytes(8, TLV.network_order()) + \
-            self.nonce.to_bytes(4, "big")
+            self.nonce.to_bytes(4, TLV.network_order())
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
         # TODO Implement AckTLV
@@ -325,9 +335,9 @@ class GoAwayTLV(TLV):
         self.message = raw_data[3:self.length - 1].decode("UTF-8")
 
     def marshal(self) -> bytes:
-        return self.type.to_bytes(1, "big") + \
+        return self.type.to_bytes(1, TLV.network_order()) + \
-            self.length.to_bytes(1, "big") + \
+            self.length.to_bytes(1, TLV.network_order()) + \
-            self.code.value.to_bytes(1, "big") + \
+            self.code.value.to_bytes(1, TLV.network_order()) + \
             self.message.encode("UTF-8")[:self.length - 1]
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
@@ -347,8 +357,8 @@ class WarningTLV(TLV):
         self.message = raw_data[2:self.length].decode("UTF-8")
 
     def marshal(self) -> bytes:
-        return self.type.to_bytes(1, "big") + \
+        return self.type.to_bytes(1, TLV.network_order()) + \
-            self.length.to_bytes(1, "big") + \
+            self.length.to_bytes(1, TLV.network_order()) + \
             self.message.encode("UTF-8")[:self.length]
 
     def handle(self, squirrel: "Squirrel", sender: "Hazelnut") -> None:
@@ -387,7 +397,7 @@ class Packet:
         pkt = Packet()
         pkt.magic = data[0]
         pkt.version = data[1]
-        pkt.body_length = int.from_bytes(data[2:4], byteorder="big")
+        pkt.body_length = int.from_bytes(data[2:4], byteorder=TLV.network_order())
         pkt.body = []
         read_bytes = 0
         while read_bytes <= min(len(data) - 4, pkt.body_length):
@@ -407,9 +417,9 @@ class Packet:
         """
         Compute the byte array data associated to the packet.
         """
-        data = self.magic.to_bytes(1, "big")
+        data = self.magic.to_bytes(1, TLV.network_order())
-        data += self.version.to_bytes(1, "big")
+        data += self.version.to_bytes(1, TLV.network_order())
-        data += self.body_length.to_bytes(2, "big")
+        data += self.body_length.to_bytes(2, TLV.network_order())
         data += b"".join(tlv.marshal() for tlv in self.body)
         return data