Use a larger read buffer on the client to accommodate servers that ignore a small max_receive_size during the handshake

Summary: If the client sets a small max_udp_payload_size (<1280), some servers ignore it and end up sending larger packets anyway. Currently, our client transport sets its read buffer to the size of the max_udp_payload_size it sent in the handshake, and ends up truncating any incoming packets that are longer than that. Using a larger read buffer enables reading these packets successfully even though the server is violating the max_udp_payload_size parameter.

Reviewed By: lnicco, kvtsoy

Differential Revision: D85821409

fbshipit-source-id: 8257b3367cde8e8a7c7a888beb243ed93e950a19

Author: jbeshay

quic/client/QuicClientTransport.cpp

@@ -34,8 +34,10 @@ void QuicClientTransport::onNotifyDataAvailable(
     QuicAsyncUDPSocket& sock) noexcept {
   auto self = this->shared_from_this();
   CHECK(conn_) << "trying to receive packets without a connection";
-  auto readBufferSize =
-      conn_->transportSettings.maxRecvPacketSize * numGROBuffers_;
+  auto readBufferSize = std::max(
+                            conn_->transportSettings.maxRecvPacketSize,
+                            uint64_t(kDefaultUDPReadBufferSize)) *
+      numGROBuffers_;
   const uint16_t numPackets = conn_->transportSettings.maxRecvBatchSize;
 
   const size_t readAllocSize =

quic/client/QuicClientTransportLite.cpp

@@ -1880,8 +1880,10 @@ void QuicClientTransportLite::onNotifyDataAvailable(
     QuicAsyncUDPSocket& sock) noexcept {
   auto self = this->shared_from_this();
   CHECK(conn_) << "trying to receive packets without a connection";
-  auto readBufferSize =
-      conn_->transportSettings.maxRecvPacketSize * numGROBuffers_;
+  auto readBufferSize = std::max(
+                            conn_->transportSettings.maxRecvPacketSize,
+                            uint64_t(kDefaultUDPReadBufferSize)) *
+      numGROBuffers_;
 
   const size_t readAllocSize =
       conn_->transportSettings.readCoalescingSize > kDefaultUDPSendPacketLen