feat(stats): add host_netinfo networking information stats family

Introduce host_netinfo stats family to hold information regarding host
networking. At the moment, it only provides ipv4 and ipv6 addresses
list for each interface available on the host. The naming schema for
the introduced stats is
falco.host_netinfo.interfaces.<ifname>.protocols.<ipv4|ipv6>.addresses.

Signed-off-by: Leonardo Di Giovanna <leonardodigiovanna1@gmail.com>

userspace/falco/stats_writer.cpp

@@ -309,6 +309,75 @@ stats_writer::collector::collector(const std::shared_ptr<stats_writer>& writer)
 {
 }
 
+std::string merge_strings(const std::vector<std::string>& v, const std::string& delim) {
+	if(v.empty())
+	{
+		return "";
+	}
+	std::stringstream ss;
+	std::copy(v.cbegin(), v.cend(), std::ostream_iterator<std::string>(ss, delim.c_str()));
+	const std::string s_str = ss.str();
+	return s_str.substr(0, s_str.size() - delim.size());
+}
+
+void add_netinfo_metrics_output_fields(
+	nlohmann::json& output_fields,
+	const std::shared_ptr<sinsp>& inspector)
+{
+	const auto ipv4_ifinfo = inspector->get_ifaddr_list().get_ipv4_list();
+	const auto ipv6_ifinfo = inspector->get_ifaddr_list().get_ipv6_list();
+
+	// For each interface name, collect the corresponding list of IPv4/IPv6 addresses
+	std::map<std::string, std::vector<std::string>> ifnames_to_ipv4_addresses;
+	std::map<std::string, std::vector<std::string>> ifnames_to_ipv6_addresses;
+
+	for (const auto& ifinfo : *ipv4_ifinfo)
+	{
+		if(ifinfo.m_name == "lo")
+		{
+			return;
+		}
+
+		auto it = ifnames_to_ipv4_addresses.find(ifinfo.m_name);
+		auto address = ifinfo.addr_to_string();
+		if (it == ifnames_to_ipv4_addresses.end())
+		{
+			ifnames_to_ipv4_addresses.emplace(ifinfo.m_name, std::vector{address});
+			return;
+		}
+		it->second.emplace_back(address);
+	}
+
+	for (const auto& ifinfo : *ipv6_ifinfo)
+	{
+		if(ifinfo.m_name == "lo")
+		{
+			return;
+		}
+
+		auto it = ifnames_to_ipv6_addresses.find(ifinfo.m_name);
+		auto address = ifinfo.addr_to_string();
+		if (it == ifnames_to_ipv6_addresses.end())
+		{
+			ifnames_to_ipv6_addresses.emplace(ifinfo.m_name, std::vector{address});
+			return;
+		}
+		it->second.emplace_back(address);
+	}
+
+	for (const auto& item : ifnames_to_ipv4_addresses) {
+		auto metric_name = "falco.host_netinfo.interfaces." + item.first + ".protocols.ipv4.addresses";
+		auto addresses = merge_strings(item.second, ",");
+		output_fields.emplace(metric_name, addresses);
+	}
+
+	for (const auto& item : ifnames_to_ipv6_addresses) {
+		auto metric_name = "falco.host_netinfo.interfaces." + item.first + ".protocols.ipv6.addresses";
+		auto addresses = merge_strings(item.second, ",");
+		output_fields.emplace(metric_name, addresses);
+	}
+}
+
 void stats_writer::collector::get_metrics_output_fields_wrapper(
 		nlohmann::json& output_fields,
 		const std::shared_ptr<sinsp>& inspector,
@@ -358,6 +427,8 @@ void stats_writer::collector::get_metrics_output_fields_wrapper(
 		output_fields[metric_name_file_sha256] = item.second;
 	}
 
+	add_netinfo_metrics_output_fields(output_fields, inspector);
+
 #endif
 	output_fields["evt.source"] = src;
 	for (size_t i = 0; i < sizeof(all_driver_engines) / sizeof(const char*); i++)