feat: implement RNS transport (Smol Mail 1.2) over microReticulum

shim/udp_interface.h

@@ -0,0 +1,64 @@
+/*
+ * UDP interface for the bunshin RNS shim, adapted from microReticulum's
+ * examples/common/udp_interface (Apache-2.0). The example version hardcodes
+ * compile-time defaults; this one takes its endpoints from the caller, and
+ * with no forward target configured it sends to the source address of the
+ * last datagram received, so a listen-only server can answer any client.
+ */
+#pragma once
+
+#include <microReticulum/Interface.h>
+#include <microReticulum/Bytes.h>
+#include <microReticulum/Type.h>
+
+#ifdef ARDUINO
+#include <WiFi.h>
+#include <WiFiUdp.h>
+#else
+#include <netinet/in.h>
+#endif
+
+#include <stdint.h>
+#include <string>
+
+class UDPInterface : public RNS::InterfaceImpl {
+
+public:
+	static const uint32_t BITRATE_GUESS = 10*1000*1000;
+
+	UDPInterface(const char* name,
+	             const std::string& local_host, int local_port,
+	             const std::string& remote_host, int remote_port);
+	virtual ~UDPInterface();
+
+	virtual bool start();
+	virtual void stop();
+	virtual void loop();
+
+	virtual inline std::string toString() const { return "UDPInterface[" + _name + "/" + _local_host + ":" + std::to_string(_local_port) + "]"; }
+
+protected:
+	virtual bool send_outgoing(const RNS::Bytes& data);
+	void on_incoming(const RNS::Bytes& data);
+
+private:
+	RNS::Bytes _buffer;
+
+	std::string _local_host;
+	int _local_port;
+	std::string _remote_host;
+	int _remote_port;
+
+	bool _forward_configured = false;
+
+#ifdef ARDUINO
+	WiFiUDP udp;
+#else
+	int _socket = -1;
+	in_addr_t _local_address = INADDR_ANY;
+	in_addr_t _remote_address = INADDR_NONE;
+	sockaddr_in _last_src_addr = {};
+	bool _have_src = false;
+#endif
+
+};