Header to metadata filter (#2436) (#3633)

Add support for extracting dynamic metadata from requests. This can then
be used as static metadata would be used (e.g.: for subset load balancer
metadata matches, logging, etc).

Risk Level: Low
Testing: unit-test
Docs Changes: Basic docs.
Release Notes: N/A

Signed-off-by: Raul Gutierrez Segales <rgs@pinterest.com>

Mirrored from https://github.com/envoyproxy/envoy @ 827c0a548ab38d55debe00587ee27253786befad

docs/BUILD

@@ -32,6 +32,7 @@ proto_library(
         "//envoy/config/filter/http/ext_authz/v2alpha:ext_authz",
         "//envoy/config/filter/http/fault/v2:fault",
         "//envoy/config/filter/http/gzip/v2:gzip",
+        "//envoy/config/filter/http/header_to_metadata/v2:header_to_metadata",
         "//envoy/config/filter/http/health_check/v2:health_check",
         "//envoy/config/filter/http/ip_tagging/v2:ip_tagging",
         "//envoy/config/filter/http/lua/v2:lua",

envoy/config/filter/http/header_to_metadata/v2/BUILD

@@ -0,0 +1,9 @@
+load("//bazel:api_build_system.bzl", "api_proto_library")
+
+licenses(["notice"])  # Apache 2
+
+api_proto_library(
+    name = "header_to_metadata",
+    srcs = ["header_to_metadata.proto"],
+    deps = [],
+)

envoy/config/filter/http/header_to_metadata/v2/header_to_metadata.proto

@@ -0,0 +1,69 @@
+syntax = "proto3";
+
+package envoy.config.filter.http.header_to_metadata.v2;
+option go_package = "v2";
+
+import "validate/validate.proto";
+
+// [#protodoc-title: Header-To-Metadata Filter]
+//
+// The configuration for transforming headers into metadata. This is useful
+// for matching load balancer subsets, logging, etc.
+//
+// Header to Metadata :ref:`configuration overview <config_http_filters_header_to_metadata>`.
+
+message Config {
+  enum ValueType {
+    STRING = 0;
+    NUMBER = 1;
+  }
+
+  message KeyValuePair {
+    // The namespace — if this is empty, the filter's namespace will be used.
+    string metadata_namespace = 1;
+
+    // The key to use within the namespace.
+    string key = 2 [(validate.rules).string.min_bytes = 1];
+
+    // The value to pair with the given key.
+    //
+    // When used for a `on_header_present` case, if value is non-empty it'll be used
+    // instead of the header value. If both are empty, no metadata is added.
+    //
+    // When used for a `on_header_missing` case, a non-empty value must be provided
+    // otherwise no metadata is added.
+    string value = 3;
+
+    // The value's type — defaults to string.
+    ValueType type = 4;
+  }
+
+  // A Rule defines what metadata to apply when a header is present or missing.
+  message Rule {
+    // The header that triggers this rule — required.
+    string header = 1 [(validate.rules).string.min_bytes = 1];
+
+    // If the header is present, apply this metadata KeyValuePair.
+    //
+    // If the value in the KeyValuePair is non-empty, it'll be used instead
+    // of the header value.
+    KeyValuePair on_header_present = 2;
+
+    // If the header is not present, apply this metadata KeyValuePair.
+    //
+    // The value in the KeyValuePair must be set, since it'll be used in lieu
+    // of the missing header value.
+    KeyValuePair on_header_missing = 3;
+
+    // Whether or not to remove the header after a rule is applied.
+    //
+    // This prevents headers from leaking.
+    bool remove = 4;
+  }
+
+  // The list of rules to apply to requests.
+  repeated Rule request_rules = 1;
+
+  // The list of rules to apply to responses.
+  repeated Rule response_rules = 2;
+}

envoy/config/filter/network/http_connection_manager/v2/http_connection_manager.proto

@@ -298,6 +298,7 @@ message HttpFilter {
   // * :ref:`envoy.grpc_json_transcoder <config_http_filters_grpc_json_transcoder>`
   // * :ref:`envoy.grpc_web <config_http_filters_grpc_web>`
   // * :ref:`envoy.health_check <config_http_filters_health_check>`
+  // * :ref:`envoy.header_to_metadata <config_http_filters_header_to_metadata>`
   // * :ref:`envoy.ip_tagging <config_http_filters_ip_tagging>`
   // * :ref:`envoy.lua <config_http_filters_lua>`
   // * :ref:`envoy.rate_limit <config_http_filters_rate_limit>`

test/validate/BUILD

@@ -18,6 +18,7 @@ api_cc_test(
         "//envoy/config/filter/http/buffer/v2:buffer",
         "//envoy/config/filter/http/fault/v2:fault",
         "//envoy/config/filter/http/gzip/v2:gzip",
+        "//envoy/config/filter/http/header_to_metadata/v2:header_to_metadata",
         "//envoy/config/filter/http/health_check/v2:health_check",
         "//envoy/config/filter/http/ip_tagging/v2:ip_tagging",
         "//envoy/config/filter/http/lua/v2:lua",

test/validate/pgv_test.cc

@@ -15,6 +15,7 @@
 #include "envoy/config/filter/http/fault/v2/fault.pb.validate.h"
 #include "envoy/config/filter/http/gzip/v2/gzip.pb.validate.h"
 #include "envoy/config/filter/http/health_check/v2/health_check.pb.validate.h"
+#include "envoy/config/filter/http/header_to_metadata/v2/header_to_metadata.pb.validate.h"
 #include "envoy/config/filter/http/ip_tagging/v2/ip_tagging.pb.validate.h"
 #include "envoy/config/filter/http/lua/v2/lua.pb.validate.h"
 #include "envoy/config/filter/http/router/v2/router.pb.validate.h"