From 148991bcd567cfd0515cdae873f0004ebe6c7376 Mon Sep 17 00:00:00 2001
From: Fredy Wijaya <fredyw@google.com>
Date: Mon, 15 Jul 2024 15:07:10 +0000
Subject: [PATCH] Add an option to set the UDP socket send buffer size

Signed-off-by: Fredy Wijaya <fredyw@google.com>
---
 mobile/library/cc/engine_builder.cc      | 14 +++++++++++
 mobile/library/cc/engine_builder.h       |  5 ++++
 mobile/test/cc/unit/envoy_config_test.cc | 31 ++++++++++++++++++++++++
 3 files changed, 50 insertions(+)

diff --git a/mobile/library/cc/engine_builder.cc b/mobile/library/cc/engine_builder.cc
index a59e6c3c7b8bb..c639761173fb7 100644
--- a/mobile/library/cc/engine_builder.cc
+++ b/mobile/library/cc/engine_builder.cc
@@ -245,6 +245,11 @@ EngineBuilder& EngineBuilder::setSocketReceiveBufferSize(int32_t size) {
   return *this;
 }
 
+EngineBuilder& EngineBuilder::setUdpSocketSendBufferSize(int32_t size) {
+  udp_socket_send_buffer_size_ = size;
+  return *this;
+}
+
 EngineBuilder& EngineBuilder::enableDrainPostDnsRefresh(bool drain_post_dns_refresh_on) {
   enable_drain_post_dns_refresh_ = drain_post_dns_refresh_on;
   return *this;
@@ -734,6 +739,15 @@ std::unique_ptr<envoy::config::bootstrap::v3::Bootstrap> EngineBuilder::generate
     rcv_buf_sock_opt->set_int_value(socket_receive_buffer_size_);
     rcv_buf_sock_opt->set_description(
         absl::StrCat("SO_RCVBUF = ", socket_receive_buffer_size_, " bytes"));
+
+    envoy::config::core::v3::SocketOption* udp_snd_buf_sock_opt =
+        base_cluster->mutable_upstream_bind_config()->add_socket_options();
+    udp_snd_buf_sock_opt->set_name(SO_SNDBUF);
+    udp_snd_buf_sock_opt->set_level(SOL_SOCKET);
+    udp_snd_buf_sock_opt->set_int_value(udp_socket_send_buffer_size_);
+    udp_snd_buf_sock_opt->mutable_type()->mutable_datagram();
+    udp_snd_buf_sock_opt->set_description(
+        absl::StrCat("SO_SNDBUF = ", udp_socket_send_buffer_size_, " bytes"));
     // Set the network service type on iOS, if supplied.
 #if defined(__APPLE__)
     if (ios_network_service_type_ > 0) {
diff --git a/mobile/library/cc/engine_builder.h b/mobile/library/cc/engine_builder.h
index 5d94d71aee6ce..e0ed01d2b2029 100644
--- a/mobile/library/cc/engine_builder.h
+++ b/mobile/library/cc/engine_builder.h
@@ -69,6 +69,7 @@ class EngineBuilder {
   // Sets whether to use GRO for upstream UDP sockets (QUIC/HTTP3).
   EngineBuilder& setUseGroIfAvailable(bool use_gro_if_available);
   EngineBuilder& setSocketReceiveBufferSize(int32_t size);
+  EngineBuilder& setUdpSocketSendBufferSize(int32_t size);
   EngineBuilder& enforceTrustChainVerification(bool trust_chain_verification_on);
   EngineBuilder& setUpstreamTlsSni(std::string sni);
   EngineBuilder& enablePlatformCertificatesValidation(bool platform_certificates_validation_on);
@@ -183,6 +184,10 @@ class EngineBuilder {
   // This is the same value Cronet uses for QUIC:
   // https://source.chromium.org/chromium/chromium/src/+/main:net/quic/quic_context.h;drc=ccfe61524368c94b138ddf96ae8121d7eb7096cf;l=87
   int32_t socket_receive_buffer_size_ = 1024 * 1024; // 1MB
+  // This is the same value Cronet uses for QUIC:
+  // https://source.chromium.org/chromium/chromium/src/+/main:net/quic/quic_session_pool.cc;l=790-793;drc=7f04a8e033c23dede6beae129cd212e6d4473d72
+  // https://source.chromium.org/chromium/chromium/src/+/main:net/third_party/quiche/src/quiche/quic/core/quic_constants.h;l=43-47;drc=34ad7f3844f882baf3d31a6bc6e300acaa0e3fc8
+  int32_t udp_socket_send_buffer_size_ = 1452 * 20;
 };
 
 using EngineBuilderSharedPtr = std::shared_ptr<EngineBuilder>;
diff --git a/mobile/test/cc/unit/envoy_config_test.cc b/mobile/test/cc/unit/envoy_config_test.cc
index 9fabb192676a4..bf5add3cc4ede 100644
--- a/mobile/test/cc/unit/envoy_config_test.cc
+++ b/mobile/test/cc/unit/envoy_config_test.cc
@@ -360,6 +360,37 @@ TEST(TestConfig, SocketReceiveBufferSize) {
   EXPECT_EQ(rcv_buf_option->level(), SOL_SOCKET);
   EXPECT_EQ(rcv_buf_option->int_value(), 1024 * 1024 /* 1 MB */);
 }
+
+TEST(TestConfig, UdpSocketSendBufferSize) {
+  EngineBuilder engine_builder;
+  engine_builder.enableHttp3(true);
+
+  std::unique_ptr<Bootstrap> bootstrap = engine_builder.generateBootstrap();
+  Cluster const* base_cluster = nullptr;
+  for (const Cluster& cluster : bootstrap->static_resources().clusters()) {
+    if (cluster.name() == "base") {
+      base_cluster = &cluster;
+      break;
+    }
+  }
+
+  // The base H3 cluster should always be found.
+  ASSERT_THAT(base_cluster, NotNull());
+
+  SocketOption const* snd_buf_option = nullptr;
+  for (const SocketOption& sock_opt : base_cluster->upstream_bind_config().socket_options()) {
+    if (sock_opt.name() == SO_SNDBUF) {
+      snd_buf_option = &sock_opt;
+      break;
+    }
+  }
+
+  // When using an H3 cluster, the UDP send buffer size option should always be set.
+  ASSERT_THAT(snd_buf_option, NotNull());
+  EXPECT_EQ(snd_buf_option->level(), SOL_SOCKET);
+  EXPECT_TRUE(snd_buf_option->type().has_datagram());
+  EXPECT_EQ(snd_buf_option->int_value(), 1452 * 20);
+}
 #endif
 
 TEST(TestConfig, EnablePlatformCertificatesValidation) {