should work on hardcoded port (not tested)

src/CMakeLists.txt

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.9...3.24 FATAL_ERROR)
+
+project(solanaceae)
+
+#########################################
+
+add_library(solanaceae_tox_upnp
+	./solanaceae/tox_upnp.hpp
+	./solanaceae/tox_upnp.cpp
+)
+
+target_include_directories(solanaceae_tox_upnp PUBLIC .)
+target_compile_features(solanaceae_tox_upnp PUBLIC cxx_std_17)
+target_link_libraries(solanaceae_tox_upnp PUBLIC
+	miniupnpc::miniupnpc
+)
+

src/solanaceae/tox_upnp.cpp

@@ -0,0 +1,114 @@
+#include "./tox_upnp.hpp"
+
+#include <miniupnpc.h>
+#include <upnpcommands.h>
+#include <upnperrors.h>
+
+#include <chrono>
+
+#include <iostream>
+
+ToxUPnP::ToxUPnP(void) {
+	// get tox port
+
+	// start upnp thread
+	_thread = std::thread([this](void) {
+		int seconds_since_last {60*10};
+		bool last_mapping_succ {false};
+		while (!_quit) {
+			if (seconds_since_last < 60*10) {
+				std::this_thread::sleep_for(std::chrono::seconds(1));
+				seconds_since_last++;
+				continue;
+			}
+			seconds_since_last = 0;
+			last_mapping_succ = false;
+
+			// first get available devices
+			int error {0};
+			std::cerr << "TUPNP: starting search\n";
+			auto* devices = upnpDiscover(2000, nullptr, nullptr, UPNP_LOCAL_PORT_ANY, 0, 2, &error);
+			if (error != 0 || devices == nullptr) {
+				std::cerr << "TUPNP error: no device found\n";
+				continue;
+			}
+
+			std::cerr << "TUPNP: discovered devices:\n";
+			for (auto* d = devices; d != nullptr; d = d->pNext) {
+				std::cerr << "  " << d->descURL << " " << d->st << " " << d->usn << "\n";
+			}
+
+			UPNPUrls urls;
+			IGDdatas data;
+			char lanaddr[64] = "unset";
+			auto res = UPNP_GetValidIGD(devices, &urls, &data, lanaddr, sizeof(lanaddr));
+
+			if (res != 1) {
+				std::cerr << "TUPNP error: no valid connected IGD has been found\n";
+				continue;
+			}
+
+			std::cerr << "TUPNP: valid IGD found, local ip: " << lanaddr << "\n";
+
+			const auto port_string = std::to_string(_local_port);
+			auto map_ret = UPNP_AddPortMapping(
+				urls.controlURL,
+				data.first.servicetype,
+				port_string.c_str(),
+				port_string.c_str(),
+				lanaddr,
+				"Tomato UPnP Tox UDP port forwarding",
+				"UDP",
+				nullptr,
+				"900" // lease duration in seconds
+			);
+
+			if (map_ret != UPNPCOMMAND_SUCCESS) {
+				std::cerr << "TUPNP error: adding port mapping failed " << strupnperror(map_ret) << "\n";
+				continue;
+			}
+
+			char intClient[40] {};
+			char intPort[6] {};
+			char duration[16] {};
+			auto getmap_ret = UPNP_GetSpecificPortMappingEntry(
+				urls.controlURL,
+				data.first.servicetype,
+				port_string.c_str(),
+				"UDP",
+				nullptr,
+				intClient,
+				intPort,
+				nullptr,
+				nullptr,
+				duration
+			);
+
+			if (getmap_ret != UPNPCOMMAND_SUCCESS) {
+				std::cerr << "TUPNP error: getting port mapping failed " << strupnperror(getmap_ret) << "\n";
+
+				// potentially succ ???
+				last_mapping_succ = true;
+				continue;
+			}
+
+			std::cerr << "TUPNP: mapping active external :" << port_string << " is redirected to internal " << intClient << ":" << intPort << " (for " << duration << "s)\n";
+			// potentially succ
+			last_mapping_succ = true;
+
+			FreeUPNPUrls(&urls);
+			freeUPNPDevlist(devices);
+		}
+
+		// remove mapping here?
+	});
+}
+
+ToxUPnP::~ToxUPnP(void) {
+	_quit = true;
+
+	if (_thread.joinable()) {
+		_thread.join();
+	}
+}
+

src/solanaceae/tox_upnp.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <cstdint>
+#include <atomic>
+#include <thread>
+
+class ToxUPnP {
+	// TODO: ToxI& _t;
+
+	uint16_t _local_port {33445};
+
+	std::atomic_bool _quit {false};
+	std::thread _thread;
+
+	public:
+		ToxUPnP(void);
+		~ToxUPnP(void);
+};
+