global: begin modularization

device/ip.go

@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package device
+
+import (
+	"net"
+)
+
+const (
+	IPv4offsetTotalLength = 2
+	IPv4offsetSrc         = 12
+	IPv4offsetDst         = IPv4offsetSrc + net.IPv4len
+)
+
+const (
+	IPv6offsetPayloadLength = 4
+	IPv6offsetSrc           = 8
+	IPv6offsetDst           = IPv6offsetSrc + net.IPv6len
+)