Kernel: Start fleshing out an UDP implementation.

Kernel/UDP.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <Kernel/IPv4.h>
+
+class [[gnu::packed]] UDPPacket {
+public:
+    UDPPacket() { }
+    ~UDPPacket() { }
+
+    word source_port() const { return m_source_port; }
+    void set_source_port(word port) { m_source_port = port; }
+
+    word destination_port() const { return m_destination_port; }
+    void set_destination_port(word port) { m_destination_port = port; }
+
+    word length() const { return m_length; }
+    void set_length(word length) { m_length = length; }
+
+    word checksum() const { return m_checksum; }
+    void set_checksum(word checksum) { m_checksum = checksum; }
+
+    const void* payload() const { return this + 1; }
+    void* payload() { return this + 1; }
+
+private:
+    NetworkOrdered<word> m_source_port;
+    NetworkOrdered<word> m_destination_port;
+    NetworkOrdered<word> m_length;
+    NetworkOrdered<word> m_checksum;
+};
+
+static_assert(sizeof(UDPPacket) == 8);