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/vanetza/geonet/basic_header.cpp

@@ -0,0 +1,71 @@
+#include <vanetza/geonet/basic_header.hpp>
+#include <vanetza/geonet/data_request.hpp>
+#include <vanetza/geonet/serialization.hpp>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+constexpr std::size_t BasicHeader::length_bytes;
+
+BasicHeader::BasicHeader() :
+    version(0),
+    next_header(NextHeaderBasic::Any),
+    reserved(0),
+    hop_limit(0)
+{
+}
+
+BasicHeader::BasicHeader(const MIB& mib) :
+    version(mib.itsGnProtocolVersion),
+    next_header(NextHeaderBasic::Any),
+    reserved(0),
+    lifetime(mib.itsGnDefaultPacketLifetime),
+    hop_limit(mib.itsGnDefaultHopLimit)
+{
+}
+
+BasicHeader::BasicHeader(const DataRequest& request, const MIB& mib) :
+    BasicHeader(mib)
+{
+    if (mib.itsGnSecurity) {
+        next_header = NextHeaderBasic::Secured;
+    } else {
+        next_header = NextHeaderBasic::Common;
+    }
+
+    lifetime = request.maximum_lifetime;
+    hop_limit = request.max_hop_limit;
+}
+
+BasicHeader::BasicHeader(const ShbDataRequest& request, const MIB& mib) :
+    BasicHeader(static_cast<const DataRequest&>(request), mib)
+{
+    hop_limit = 1;
+}
+
+void serialize(const BasicHeader& hdr, OutputArchive& ar)
+{
+    uint8_t versionAndNextHeader = hdr.version.raw();
+    versionAndNextHeader <<= 4;
+    versionAndNextHeader |= static_cast<uint8_t>(hdr.next_header) & 0x0f;
+    serialize(host_cast(versionAndNextHeader), ar);
+    serialize(host_cast(hdr.reserved), ar);
+    serialize(hdr.lifetime, ar);
+    serialize(host_cast(hdr.hop_limit), ar);
+}
+
+void deserialize(BasicHeader& hdr, InputArchive& ar)
+{
+    uint8_t versionAndNextHeader;
+    deserialize(versionAndNextHeader, ar);
+    hdr.version = versionAndNextHeader >> 4;
+    hdr.next_header = static_cast<NextHeaderBasic>(versionAndNextHeader & 0x0f);
+    deserialize(hdr.reserved, ar);
+    deserialize(hdr.lifetime, ar);
+    deserialize(hdr.hop_limit, ar);
+}
+
+} // namespace geonet
+} // namespace vanetza