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/ethernet_device.cpp

@@ -0,0 +1,73 @@
+#include "ethernet_device.hpp"
+#include <boost/asio/ip/address.hpp>
+#include <algorithm>
+#include <cstring>
+#include <system_error>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <net/if.h>
+#include <sys/ioctl.h>
+#include <ifaddrs.h>
+
+static void initialize(ifreq& request, const char* interface_name)
+{
+    std::memset(&request, 0, sizeof(ifreq));
+    std::strncpy(request.ifr_name, interface_name, IF_NAMESIZE);
+    request.ifr_name[IF_NAMESIZE - 1] = '\0';
+}
+
+EthernetDevice::EthernetDevice(const char* devname) :
+    inet_socket_(::socket(AF_INET, SOCK_DGRAM, 0)),
+    interface_name_(devname)
+{
+    if (!inet_socket_) {
+        throw std::system_error(errno, std::system_category());
+    }
+}
+
+EthernetDevice::~EthernetDevice()
+{
+    if (inet_socket_ >= 0)
+        ::close(inet_socket_);
+
+}
+
+EthernetDevice::protocol::endpoint EthernetDevice::endpoint(int family) const
+{
+    sockaddr_ll socket_address = {};
+    socket_address.sll_family = family;
+    socket_address.sll_protocol = htons(ETH_P_ALL);
+    socket_address.sll_ifindex = index();
+    return protocol::endpoint(&socket_address, sizeof(sockaddr_ll));
+}
+
+int EthernetDevice::index() const
+{
+    ifreq data;
+    initialize(data, interface_name_.c_str());
+    ::ioctl(inet_socket_, SIOCGIFINDEX, &data);
+    return data.ifr_ifindex;
+}
+
+vanetza::MacAddress EthernetDevice::address() const
+{
+    ifreq data;
+    initialize(data, interface_name_.c_str());
+    ::ioctl(inet_socket_, SIOCGIFHWADDR, &data);
+
+    vanetza::MacAddress addr;
+    std::copy_n(data.ifr_hwaddr.sa_data, addr.octets.size(), addr.octets.data());
+    return addr;
+}
+
+boost::asio::ip::address_v4 EthernetDevice::ip() const
+{
+    ifreq data;
+    initialize(data, interface_name_.c_str());
+    ::ioctl(inet_socket_, SIOCGIFADDR, &data);
+
+    char host[NI_MAXHOST] = { 0 };
+    ::getnameinfo(&data.ifr_addr, sizeof(sockaddr), host, NI_MAXHOST, nullptr, 0, NI_NUMERICHOST);
+
+    return boost::asio::ip::make_address_v4(host);
+}