Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/tools/socktap/rpc_link.cpp

@@ -0,0 +1,112 @@
+#include "rpc_link.hpp"
+#include "vanetza/rpc/link_layer_client.hpp"
+#include "vanetza/rpc/logger.hpp"
+#include <vanetza/access/ethertype.hpp>
+#include <iostream>
+
+namespace {
+
+class RpcLinkLayerLogger : public vanetza::rpc::Logger
+{
+public:
+    void error(const char* module, const char* message) override
+    {
+        std::cerr << "RPC error at " << module << ": " << message << "\n";
+    }
+
+    void debug(const char* module, const char* message) override
+    {
+        if (print_debug_) {
+           std::cout << "RPC debug(" << module << "): " << message << "\n";
+        }
+    }
+
+    void enable_debug(bool debug)
+    {
+        print_debug_ = debug;
+    }
+
+private:
+    bool print_debug_ = false;
+};
+
+RpcLinkLayerLogger logger;
+
+} // namespace
+
+RpcLinkLayer::RpcLinkLayer(boost::asio::io_context& io, boost::asio::ip::tcp::socket socket) :
+    io_(io),
+    event_port_(io),
+    event_loop_(event_port_),
+    asio_stream_(std::move(socket)),
+    wait_scope_(event_loop_),
+    client_(event_port_.getTimer(), asio_stream_, &logger)
+{
+    auto id = client_.identify().then([](const vanetza::rpc::LinkLayerClient::Identity& identity) -> kj::Promise<void> {
+        std::cout << "Connected to RPC server id=" << identity.id << " version=" << identity.version << "\n";
+        if (!identity.info.empty()) {
+          std::cout << "RPC server's info: " << identity.info << "\n";
+        }
+        return kj::READY_NOW;
+    });
+    client_.add_task(kj::mv(id));
+}
+
+RpcLinkLayer::~RpcLinkLayer() noexcept
+{
+}
+
+void RpcLinkLayer::set_source_address(const vanetza::MacAddress& addr)
+{
+    client_.set_source_address(addr);
+}
+
+void RpcLinkLayer::request(const vanetza::access::DataRequest& request, std::unique_ptr<vanetza::ChunkPacket> packet)
+{
+    client_.request(request, std::move(packet));
+}
+
+void RpcLinkLayer::indicate(IndicationCallback callback)
+{
+    if (callback) {
+        auto wrapper = [callback, this](vanetza::rpc::LinkLayerClient::Indication&& indication) {
+            boost::asio::post(io_, [callback, indication]() mutable {
+                vanetza::EthernetHeader eth_hdr;
+                eth_hdr.destination = indication.destination;
+                eth_hdr.source = indication.source;
+                eth_hdr.type = vanetza::access::ethertype::GeoNetworking;
+                callback(std::move(indication.packet), eth_hdr);
+            });
+        };
+        client_.indicate(std::move(wrapper));
+    } else {
+        client_.indicate(nullptr);
+    }
+}
+
+void RpcLinkLayer::radio_technology(const std::string& technology)
+{
+    if (technology == "ITS-G5") {
+        client_.configure(vanetza::rpc::LinkLayerClient::Technology::ITS_G5);
+    } else if (technology == "LTE-V2X" || technology == "C-V2X") {
+        client_.configure(vanetza::rpc::LinkLayerClient::Technology::LTE_V2X);
+    } else if (!technology.empty()) {
+        std::cerr << "Unknown radio technology '" << technology << "'. RPC link layer omits radio-specific fields.\n";
+    }
+}
+
+void RpcLinkLayer::enable_debug(bool debug)
+{
+    logger.enable_debug(debug);
+}
+
+void RpcLinkLayer::add_options(boost::program_options::options_description& options)
+{
+    namespace po = boost::program_options;
+    options.add_options()
+        ("rpc-host", po::value<std::string>()->default_value("localhost"), "RPC host address")
+        ("rpc-port", po::value<unsigned>()->default_value(23057), "RPC port number")
+        ("rpc-radio-technology", po::value<std::string>()->default_value(""), "radio technology of RPC link layer (ITS-G5 | LTE-V2X)")
+        ("rpc-debug", po::bool_switch()->default_value(false), "RPC debug output")
+    ;
+}