Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/vanetza/geonet/cbf_counter.hpp

@@ -0,0 +1,113 @@
+#ifndef CBF_COUNTER_HPP_QTMUOGJS
+#define CBF_COUNTER_HPP_QTMUOGJS
+
+#include <vanetza/common/clock.hpp>
+#include <vanetza/geonet/cbf_packet_identifier.hpp>
+#include <vanetza/geonet/soft_state_map.hpp>
+#include <cstddef>
+#include <unordered_map>
+
+namespace vanetza
+{
+
+// forward declaration
+class Runtime;
+
+namespace geonet
+{
+
+/**
+ * Interface for duplicate packet counters.
+ * This is used by the Contention Based Forwarding (CBF) packet buffer.
+ */
+class CbfCounter
+{
+public:
+    using id_type = CbfPacketIdentifier;
+    using counter_type = std::size_t;
+
+    /**
+     * Packet has been added to buffer
+     * \param id packet identifier
+     */
+    virtual void add(const id_type& id) = 0;
+
+    /**
+     * Packet has been removed from buffer.
+     * \param id packet identifier
+     */
+    virtual void remove(const id_type& id) = 0;
+
+    /**
+     * Increment packet counter by one
+     * \param id packet identifier
+     */
+    virtual void increment(const id_type& id) = 0;
+
+    /**
+     * Retrieve counter value
+     * \param id packet identifier
+     */
+    virtual counter_type counter(const id_type& id) const = 0;
+
+    virtual ~CbfCounter() = default;
+};
+
+
+/**
+ * Immortal CBF counters, i.e. they never expire.
+ * \note Be aware, memory consumption is constantly growing of this implemenation!
+ */
+class CbfCounterImmortal : public virtual CbfCounter
+{
+public:
+    void add(const id_type&) override;
+    void remove(const id_type&) override {}
+    void increment(const id_type&) override;
+    counter_type counter(const id_type&) const override;
+
+protected:
+    std::unordered_map<id_type, counter_type> m_counters;
+};
+
+/**
+ * Remembers only counter values for packets currently contending, i.e. stored in CBF buffer.
+ * \note This is the ADVANCED routing behaviour of EN 302 636-4-1 v1.2.1
+ */
+class CbfCounterContending : public virtual CbfCounter, private CbfCounterImmortal
+{
+public:
+    void add(const id_type&) override;
+    void remove(const id_type&) override;
+};
+
+/**
+ * Fading CBF counters
+ *
+ * Counters are removed from the internal table only after expiry, i.e. they are soft-state.
+ * This fixes some serious GN flooding due to ADVANCED routing, see CbfCounterContending.
+ */
+class CbfCounterFading : public virtual CbfCounter
+{
+public:
+    /*
+     * Initialize fading counters
+     * \param rt runtime used for soft-state behaviour
+     * \param lifetime newly added counters are initialized with this lifetime
+     */
+    CbfCounterFading(Runtime&, Clock::duration lifetime);
+
+    void add(const id_type&) override;
+    void remove(const id_type&) override {}
+    void increment(const id_type&) override;
+    counter_type counter(const id_type&) const override;
+
+private:
+    SoftStateMap<id_type, counter_type> m_counters;
+};
+
+} // namespace geonet
+} // namespace vanetza
+
+#endif /* CBF_COUNTER_HPP_QTMUOGJS */
+