dns_filter: make DNS format commands available at config initialization

Signed-off-by: Anton Kanugalawattage <antondilon@gmail.com>

u

Signed-off-by: Anton Kanugalawattage <antondilon@gmail.com>

Author: AntonKanug

source/extensions/filters/udp/dns_filter/BUILD

@@ -14,13 +14,15 @@ envoy_cc_library(
     srcs = [
         "dns_filter.cc",
         "dns_filter_access_log.cc",
+        "dns_filter_command_parser_factory.cc",
         "dns_filter_resolver.cc",
         "dns_filter_utils.cc",
         "dns_parser.cc",
     ],
     hdrs = [
         "dns_filter.h",
         "dns_filter_access_log.h",
+        "dns_filter_command_parser_factory.h",
         "dns_filter_constants.h",
         "dns_filter_resolver.h",
         "dns_filter_utils.h",
@@ -35,6 +37,7 @@ envoy_cc_library(
         "//envoy/network:dns_interface",
         "//envoy/network:filter_interface",
         "//envoy/network:listener_interface",
+        "//envoy/registry",
         "//source/common/buffer:buffer_lib",
         "//source/common/common:empty_string",
         "//source/common/common:radix_tree_lib",

source/extensions/filters/udp/dns_filter/dns_filter.cc

@@ -10,7 +10,6 @@
 #include "source/common/network/dns_resolver/dns_factory_util.h"
 #include "source/common/protobuf/message_validator_impl.h"
 #include "source/common/protobuf/utility.h"
-#include "source/extensions/filters/udp/dns_filter/dns_filter_access_log.h"
 #include "source/extensions/filters/udp/dns_filter/dns_filter_utils.h"
 
 namespace Envoy {
@@ -198,12 +197,10 @@ DnsFilterEnvoyConfig::DnsFilterEnvoyConfig(
     max_pending_lookups_ = 0;
   }
 
-  // Initialize access logs with DNS-specific command parser
+  // Initialize access logs. DNS-specific command parser is now registered as a built-in formatter.
   for (const auto& log_config : config.access_log()) {
-    std::vector<Formatter::CommandParserPtr> command_parsers;
-    command_parsers.push_back(createDnsFilterCommandParser());
     AccessLog::InstanceSharedPtr current_access_log =
-        AccessLog::AccessLogFactory::fromProto(log_config, context, std::move(command_parsers));
+        AccessLog::AccessLogFactory::fromProto(log_config, context);
     access_logs_.push_back(current_access_log);
   }
 }

source/extensions/filters/udp/dns_filter/dns_filter_command_parser_factory.cc

@@ -0,0 +1,22 @@
+#include "source/extensions/filters/udp/dns_filter/dns_filter_command_parser_factory.h"
+#include "source/extensions/filters/udp/dns_filter/dns_filter_access_log.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace UdpFilters {
+namespace DnsFilter {
+
+std::string DnsFilterCommandParserFactory::name() const {
+  return "envoy.built_in_formatters.dns_filter";
+}
+
+Formatter::CommandParserPtr DnsFilterCommandParserFactory::createCommandParser() const {
+  return createDnsFilterCommandParser();
+}
+
+REGISTER_FACTORY(DnsFilterCommandParserFactory, Formatter::BuiltInCommandParserFactory);
+
+} // namespace DnsFilter
+} // namespace UdpFilters
+} // namespace Extensions
+} // namespace Envoy

source/extensions/filters/udp/dns_filter/dns_filter_command_parser_factory.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "envoy/formatter/substitution_formatter_base.h"
+#include "envoy/registry/registry.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace UdpFilters {
+namespace DnsFilter {
+
+/**
+ * Factory for DNS filter command parser that handles DNS-specific format commands.
+ * This factory is registered as a built-in formatter to ensure DNS-specific tags
+ * are available during config initialization.
+ */
+class DnsFilterCommandParserFactory : public Formatter::BuiltInCommandParserFactory {
+public:
+  DnsFilterCommandParserFactory() = default;
+
+  std::string name() const override;
+  Formatter::CommandParserPtr createCommandParser() const override;
+};
+
+DECLARE_FACTORY(DnsFilterCommandParserFactory);
+
+} // namespace DnsFilter
+} // namespace UdpFilters
+} // namespace Extensions
+} // namespace Envoy