Expose metadata limits and annotation info to filter stack

BUILD

@@ -4245,6 +4245,7 @@ grpc_cc_library(
         "//src/core:hpack_constants",
         "//src/core:match",
         "//src/core:metadata_batch",
+        "//src/core:metadata_info",
         "//src/core:parsed_metadata",
         "//src/core:random_early_detection",
         "//src/core:slice",
@@ -4422,6 +4423,7 @@ grpc_cc_library(
         "//src/core:max_concurrent_streams_policy",
         "//src/core:memory_quota",
         "//src/core:metadata_batch",
+        "//src/core:metadata_info",
         "//src/core:ping_abuse_policy",
         "//src/core:ping_callbacks",
         "//src/core:ping_rate_policy",

src/core/BUILD

@@ -128,6 +128,20 @@ grpc_cc_library(
     deps = ["//:gpr_platform"],
 )
 
+grpc_cc_library(
+    name = "metadata_info",
+    srcs = ["lib/transport/metadata_info.cc"],
+    hdrs = ["lib/transport/metadata_info.h"],
+    deps = [
+        "channel_args",
+        "hpack_constants",
+        "metadata_batch",
+        "slice",
+        "//:gpr_platform",
+        "//:grpc_base",
+    ],
+)
+
 grpc_cc_library(
     name = "experiments",
     srcs = [

src/core/ext/transport/chttp2/transport/chttp2_transport.cc

@@ -106,6 +106,7 @@
 #include "src/core/lib/transport/error_utils.h"
 #include "src/core/lib/transport/http2_errors.h"
 #include "src/core/lib/transport/metadata_batch.h"
+#include "src/core/lib/transport/metadata_info.h"
 #include "src/core/lib/transport/status_conversion.h"
 #include "src/core/lib/transport/transport.h"
 
@@ -116,8 +117,6 @@
 #define DEFAULT_CONNECTION_WINDOW_TARGET (1024 * 1024)
 #define MAX_WINDOW 0x7fffffffu
 #define MAX_WRITE_BUFFER_SIZE (64 * 1024 * 1024)
-#define DEFAULT_MAX_HEADER_LIST_SIZE (16 * 1024)
-#define DEFAULT_MAX_HEADER_LIST_SIZE_SOFT_LIMIT (8 * 1024)
 
 #define KEEPALIVE_TIME_BACKOFF_MULTIPLIER 2
 
@@ -525,21 +524,8 @@ static void read_channel_args(grpc_chttp2_transport* t,
           .GetDurationFromIntMillis(GRPC_ARG_HTTP_TARPIT_MAX_DURATION_MS)
           .value_or(grpc_core::Duration::Seconds(1))
           .millis();
-
-  const int soft_limit =
-      channel_args.GetInt(GRPC_ARG_MAX_METADATA_SIZE).value_or(-1);
-  if (soft_limit < 0) {
-    // Set soft limit to 0.8 * hard limit if this is larger than
-    // `DEFAULT_MAX_HEADER_LIST_SIZE_SOFT_LIMIT` and
-    // `GRPC_ARG_MAX_METADATA_SIZE` is not set.
-    t->max_header_list_size_soft_limit = std::max(
-        DEFAULT_MAX_HEADER_LIST_SIZE_SOFT_LIMIT,
-        static_cast<int>(
-            0.8 * channel_args.GetInt(GRPC_ARG_ABSOLUTE_MAX_METADATA_SIZE)
-                      .value_or(-1)));
-  } else {
-    t->max_header_list_size_soft_limit = soft_limit;
-  }
+  t->max_header_list_size_soft_limit =
+      grpc_core::GetSoftLimitFromChannelArgs(channel_args);
 
   int value;
   if (!is_client) {
@@ -557,22 +543,8 @@ static void read_channel_args(grpc_chttp2_transport* t,
   if (value >= 0) {
     t->settings.mutable_local().SetHeaderTableSize(value);
   }
-  value = channel_args.GetInt(GRPC_ARG_ABSOLUTE_MAX_METADATA_SIZE).value_or(-1);
-  if (value >= 0) {
-    t->settings.mutable_local().SetMaxHeaderListSize(value);
-  } else {
-    // Set value to 1.25 * soft limit if this is larger than
-    // `DEFAULT_MAX_HEADER_LIST_SIZE` and
-    // `GRPC_ARG_ABSOLUTE_MAX_METADATA_SIZE` is not set.
-    const int soft_limit =
-        channel_args.GetInt(GRPC_ARG_MAX_METADATA_SIZE).value_or(-1);
-    const int value = (soft_limit >= 0 && soft_limit < (INT_MAX / 1.25))
-                          ? static_cast<int>(soft_limit * 1.25)
-                          : soft_limit;
-    if (value > DEFAULT_MAX_HEADER_LIST_SIZE) {
-      t->settings.mutable_local().SetMaxHeaderListSize(value);
-    }
-  }
+  t->settings.mutable_local().SetMaxHeaderListSize(
+      grpc_core::GetHardLimitFromChannelArgs(channel_args));
   value = channel_args.GetInt(GRPC_ARG_HTTP2_MAX_FRAME_SIZE).value_or(-1);
   if (value >= 0) {
     t->settings.mutable_local().SetMaxFrameSize(value);

src/core/ext/transport/chttp2/transport/hpack_parser.cc

@@ -52,6 +52,7 @@
 #include "src/core/lib/slice/slice.h"
 #include "src/core/lib/slice/slice_refcount.h"
 #include "src/core/lib/surface/validate_metadata.h"
+#include "src/core/lib/transport/metadata_info.h"
 #include "src/core/lib/transport/parsed_metadata.h"
 
 // IWYU pragma: no_include <type_traits>
@@ -1076,55 +1077,6 @@ Slice HPackParser::String::Take() {
   GPR_UNREACHABLE_CODE(return Slice());
 }
 
-class HPackParser::MetadataSizeEncoder {
- public:
-  explicit MetadataSizeEncoder(std::string& summary) : summary_(summary) {}
-
-  void Encode(const Slice& key, const Slice& value) {
-    AddToSummary(key.as_string_view(), value.size());
-  }
-
-  template <typename Key, typename Value>
-  void Encode(Key, const Value& value) {
-    AddToSummary(Key::key(), EncodedSizeOfKey(Key(), value));
-  }
-
- private:
-  void AddToSummary(absl::string_view key,
-                    size_t value_length) GPR_ATTRIBUTE_NOINLINE {
-    absl::StrAppend(&summary_, key, ":",
-                    hpack_constants::SizeForEntry(key.size(), value_length),
-                    ",");
-  }
-  std::string& summary_;
-};
-
-class HPackParser::MetadataSizesAnnotation
-    : public CallTracerAnnotationInterface::Annotation {
- public:
-  MetadataSizesAnnotation(grpc_metadata_batch* metadata_buffer,
-                          uint64_t soft_limit, uint64_t hard_limit)
-      : CallTracerAnnotationInterface::Annotation(
-            CallTracerAnnotationInterface::AnnotationType::kMetadataSizes),
-        metadata_buffer_(metadata_buffer),
-        soft_limit_(soft_limit),
-        hard_limit_(hard_limit) {}
-
-  std::string ToString() const override {
-    std::string metadata_annotation =
-        absl::StrCat("gRPC metadata soft_limit:", soft_limit_,
-                     ",hard_limit:", hard_limit_, ",");
-    MetadataSizeEncoder encoder(metadata_annotation);
-    metadata_buffer_->Encode(&encoder);
-    return metadata_annotation;
-  }
-
- private:
-  grpc_metadata_batch* metadata_buffer_;
-  uint64_t soft_limit_;
-  uint64_t hard_limit_;
-};
-
 // PUBLIC INTERFACE
 
 HPackParser::HPackParser() = default;

src/core/ext/transport/chttp2/transport/hpack_parser.h

@@ -123,8 +123,6 @@ class HPackParser {
   // Helper classes: see implementation
   class Parser;
   class Input;
-  class MetadataSizeEncoder;
-  class MetadataSizesAnnotation;
 
   // Helper to parse a string and turn it into a slice with appropriate memory
   // management characteristics

src/core/lib/transport/metadata_info.cc

@@ -0,0 +1,53 @@
+// Copyright 2023 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/core/lib/transport/metadata_info.h"
+
+#include "src/core/lib/slice/slice.h"
+
+namespace grpc_core {
+
+class MetadataSizesAnnotation::MetadataSizeEncoder {
+ public:
+  explicit MetadataSizeEncoder(std::string& summary) : summary_(summary) {}
+
+  void Encode(const Slice& key, const Slice& value) {
+    AddToSummary(key.as_string_view(), value.size());
+  }
+
+  template <typename Key, typename Value>
+  void Encode(Key, const Value& value) {
+    AddToSummary(Key::key(), EncodedSizeOfKey(Key(), value));
+  }
+
+ private:
+  void AddToSummary(absl::string_view key,
+                    size_t value_length) GPR_ATTRIBUTE_NOINLINE {
+    absl::StrAppend(&summary_, key, ":",
+                    hpack_constants::SizeForEntry(key.size(), value_length),
+                    ",");
+  }
+  std::string& summary_;
+};
+
+std::string MetadataSizesAnnotation::ToString() const {
+  std::string metadata_annotation =
+      absl::StrCat("gRPC metadata soft_limit:", soft_limit_,
+                   ",hard_limit:", hard_limit_, ",");
+  MetadataSizeEncoder encoder(metadata_annotation);
+  metadata_buffer_->Encode(&encoder);
+  return metadata_annotation;
+}
+
+}  // namespace grpc_core