Import checksumming from scapy

bin/checksum_from_scapy.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+
+# Code copied from /usr/lib/python3/dist-packages/scapy/utils.py
+
+
+if struct.pack("H",1) == b"\x00\x01": # big endian
+    def checksum(pkt):
+        if len(pkt) % 2 == 1:
+            pkt += b"\0"
+        s = sum(array.array("H", pkt))
+        s = (s >> 16) + (s & 0xffff)
+        s += s >> 16
+        s = ~s
+        return s & 0xffff
+else:
+    def checksum(pkt):
+        if len(pkt) % 2 == 1:
+            pkt += b"\0"
+        s = sum(array.array("H", pkt))
+        s = (s >> 16) + (s & 0xffff)
+        s += s >> 16
+        s = ~s
+        return (((s>>8)&0xff)|s<<8) & 0xffff