Add interface for easy protocol implementation

This commit adds a protocol interface to the server, its purpose is to manage TCP connections and the various third-party protocols.

More specifically, ProtoHandleConnection() takes care of exchanging the packets between the local and remote endpoint; the protocol implementation only has to parse them and act accordingly.

The interface knows which protocol is the connection for by calling IsPacketForMe(), a function implemented for each protocol.

src/Cedar/Proto.h

@@ -0,0 +1,44 @@
+#ifndef PROTO_H
+#define PROTO_H
+
+// OpenVPN sends 2 bytes, thus this is the buffer size.
+// If another protocol requires more bytes to be detected, the buffer size must be increased.
+#define PROTO_CHECK_BUFFER_SIZE	2
+
+#define PROTO_TCP_BUFFER_SIZE	(128 * 1024)
+
+#define PROTO_MODE_TCP			1
+#define PROTO_MODE_UDP			2
+
+typedef struct PROTO_IMPL
+{
+	bool (*Init)(void **param, CEDAR *cedar, INTERRUPT_MANAGER *im, SOCK_EVENT *se);
+	void (*Free)(void *param);
+	char *(*Name)();
+	UINT (*SupportedModes)();
+	bool (*IsPacketForMe)(const UCHAR *data, const UINT size);
+	bool (*ProcessData)(void *param, TCP_RAW_DATA *received_data, FIFO *data_to_send);
+	void (*BufferLimit)(void *param, const bool reached);
+	bool (*IsOk)(void *param);
+	UINT (*EstablishedSessions)(void *param);
+} PROTO_IMPL;
+
+typedef struct PROTO
+{
+	PROTO_IMPL *impl;
+} PROTO;
+
+int ProtoCompare(void *p1, void *p2);
+
+void ProtoInit();
+void ProtoFree();
+
+bool ProtoAdd(PROTO_IMPL *impl);
+
+UINT ProtoNum();
+PROTO *ProtoGet(const UINT index);
+PROTO *ProtoDetect(SOCK *sock);
+
+bool ProtoHandleConnection(CEDAR *cedar, SOCK *sock);
+
+#endif