Revert PMTU and size-enforced packet builder

Differential Revision: D23283619

fbshipit-source-id: b7fe31871dad5711016234a2d10ae84edc4fd24c

quic/QuicConstants.h

@@ -38,8 +38,8 @@ constexpr uint16_t kDefaultMaxUDPPayload = 1452;
 // maximum QUIC packet size.
 constexpr uint16_t kMinMaxUDPPayload = 1200;
 
-// How many bytes to reduce from udpSendPacketLen when socket write leads
+// How many bytes to reduce from udpSendPacketLen when socket write leads to
-// to EMSGSIZE.
+// EMSGSIZE.
 constexpr uint16_t kDefaultMsgSizeBackOffSize = 50;
 
 // Size of read buffer we provide to AsyncUDPSocket. The packet size cannot be

quic/api/test/QuicBatchWriterTest.cpp

@@ -590,7 +590,7 @@ TEST_P(QuicBatchWriterTest, InplaceWriterBufResidueCheck) {
   auto bufAccessor =
       std::make_unique<SimpleBufAccessor>(conn_.udpSendPacketLen * batchSize);
   conn_.bufAccessor = bufAccessor.get();
-  updateUdpSendPacketLen(conn_, 1000);
+  conn_.udpSendPacketLen = 1000;
   auto batchWriter = quic::BatchWriterFactory::makeBatchWriter(
       sock,
       quic::QuicBatchingMode::BATCHING_MODE_GSO,

quic/api/test/QuicPacketSchedulerTest.cpp

@@ -862,7 +862,7 @@ TEST_F(QuicPacketSchedulerTest, CloningSchedulerWithInplaceBuilderFullPacket) {
 TEST_F(QuicPacketSchedulerTest, CloneLargerThanOriginalPacket) {
   QuicClientConnectionState conn(
       FizzClientQuicHandshakeContext::Builder().build());
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   conn.streamManager->setMaxLocalBidirectionalStreams(10);
   conn.flowControlState.peerAdvertisedMaxOffset = 100000;
   conn.flowControlState.peerAdvertisedInitialMaxStreamOffsetBidiRemote = 100000;

quic/api/test/QuicTransportFunctionsTest.cpp

@@ -1087,7 +1087,7 @@ TEST_F(QuicTransportFunctionsTest, TestUpdateConnectionConnWindowUpdate) {
 
 TEST_F(QuicTransportFunctionsTest, WriteQuicDataToSocketWithCC) {
   auto conn = createConn();
-  updateUdpSendPacketLen(*conn, 30);
+  conn->udpSendPacketLen = 30;
   auto mockCongestionController =
       std::make_unique<NiceMock<MockCongestionController>>();
   auto rawCongestionController = mockCongestionController.get();
@@ -1162,7 +1162,7 @@ TEST_F(QuicTransportFunctionsTest, WriteQuicDataToSocketLimitTest) {
       std::make_unique<NiceMock<MockCongestionController>>();
   auto rawCongestionController = mockCongestionController.get();
   conn->congestionController = std::move(mockCongestionController);
-  updateUdpSendPacketLen(*conn, aead->getCipherOverhead() + 50);
+  conn->udpSendPacketLen = aead->getCipherOverhead() + 50;
 
   EventBase evb;
   auto socket =
@@ -2124,7 +2124,7 @@ TEST_F(QuicTransportFunctionsTest, WriteLimitBytRttFraction) {
 
 TEST_F(QuicTransportFunctionsTest, CongestionControlWritableBytesRoundUp) {
   auto conn = createConn();
-  updateUdpSendPacketLen(*conn, 2000);
+  conn->udpSendPacketLen = 2000;
   auto mockCongestionController =
       std::make_unique<NiceMock<MockCongestionController>>();
   auto rawCongestionController = mockCongestionController.get();
@@ -2217,7 +2217,7 @@ TEST_F(QuicTransportFunctionsTest, HandshakeConfirmedDropCipher) {
 
 TEST_F(QuicTransportFunctionsTest, ProbeWriteNewFunctionalFrames) {
   auto conn = createConn();
-  updateUdpSendPacketLen(*conn, 1200);
+  conn->udpSendPacketLen = 1200;
   EventBase evb;
   auto sock = std::make_unique<NiceMock<folly::test::MockAsyncUDPSocket>>(&evb);
   auto rawSocket = sock.get();

quic/api/test/QuicTransportTest.cpp

@@ -3034,7 +3034,7 @@ TEST_F(QuicTransportTest, PacingWillBurstFirst) {
 TEST_F(QuicTransportTest, AlreadyScheduledPacingNoWrite) {
   transport_->setPacingTimer(TimerHighRes::newTimer(&evb_, 1ms));
   auto& conn = transport_->getConnectionState();
-  updateUdpSendPacketLen(conn, 100);
+  conn.udpSendPacketLen = 100;
   auto mockCongestionController =
       std::make_unique<NiceMock<MockCongestionController>>();
   auto rawCongestionController = mockCongestionController.get();

quic/client/QuicClientTransport.cpp

@@ -1423,21 +1423,17 @@ void QuicClientTransport::addNewPeerAddress(folly::SocketAddress peerAddress) {
   CHECK(peerAddress.isInitialized());
 
   if (happyEyeballsEnabled_) {
-    updateUdpSendPacketLen(
+    conn_->udpSendPacketLen = std::min(
-        *conn_,
-        std::min(
         conn_->udpSendPacketLen,
-            (peerAddress.getFamily() == AF_INET6
+        (peerAddress.getFamily() == AF_INET6 ? kDefaultV6UDPSendPacketLen
-                 ? kDefaultV6UDPSendPacketLen
+                                             : kDefaultV4UDPSendPacketLen));
-                 : kDefaultV4UDPSendPacketLen)));
     happyEyeballsAddPeerAddress(*conn_, peerAddress);
     return;
   }
 
-  updateUdpSendPacketLen(
+  conn_->udpSendPacketLen = peerAddress.getFamily() == AF_INET6
-      *conn_,
+      ? kDefaultV6UDPSendPacketLen
-      peerAddress.getFamily() == AF_INET6 ? kDefaultV6UDPSendPacketLen
+      : kDefaultV4UDPSendPacketLen;
-                                          : kDefaultV4UDPSendPacketLen);
   conn_->originalPeerAddress = peerAddress;
   conn_->peerAddress = std::move(peerAddress);
 }

quic/client/state/ClientStateMachine.cpp

@@ -43,8 +43,6 @@ std::unique_ptr<QuicClientConnectionState> undoAllClientStateForRetry(
   newConn->originalPeerAddress = conn->originalPeerAddress;
   newConn->peerAddress = conn->peerAddress;
   newConn->udpSendPacketLen = conn->udpSendPacketLen;
-  newConn->peerMaxPacketSize = conn->peerMaxPacketSize;
-  newConn->currentPMTU = conn->currentPMTU;
   newConn->supportedVersions = conn->supportedVersions;
   newConn->transportSettings = conn->transportSettings;
   newConn->initialWriteCipher = std::move(conn->initialWriteCipher);
@@ -153,13 +151,12 @@ void processServerInitialParams(
   }
   conn.peerAckDelayExponent =
       ackDelayExponent.value_or(kDefaultAckDelayExponent);
-
   // TODO: udpSendPacketLen should also be limited by PMTU
   if (conn.transportSettings.canIgnorePathMTU) {
     if (*packetSize > kDefaultMaxUDPPayload) {
       *packetSize = kDefaultUDPSendPacketLen;
     }
-    updateUdpSendPacketLen(conn, *packetSize);
+    conn.udpSendPacketLen = *packetSize;
   }
 
   // Currently no-op for a client; it doesn't issue connection ids
@@ -238,7 +235,7 @@ void updateTransportParamsFromCachedEarlyParams(
     const CachedServerTransportParameters& transportParams) {
   conn.peerIdleTimeout = std::chrono::milliseconds(transportParams.idleTimeout);
   if (conn.transportSettings.canIgnorePathMTU) {
-    updateUdpSendPacketLen(conn, transportParams.maxRecvPacketSize);
+    conn.udpSendPacketLen = transportParams.maxRecvPacketSize;
   }
   conn.flowControlState.peerAdvertisedMaxOffset =
       transportParams.initialMaxData;

quic/codec/QuicPacketBuilder.cpp

@@ -286,94 +286,6 @@ Buf StatelessResetPacketBuilder::buildPacket() && {
   return std::move(data_);
 }
 
-RegularSizeEnforcedPacketBuilder::RegularSizeEnforcedPacketBuilder(
-    Packet packet,
-    uint64_t enforcedSize,
-    uint32_t cipherOverhead)
-    : packet_(std::move(packet.packet)),
-      header_(std::move(packet.header)),
-      body_(std::move(packet.body)),
-      bodyAppender_(body_.get(), kAppenderGrowthSize),
-      enforcedSize_(enforcedSize),
-      cipherOverhead_(cipherOverhead) {}
-
-bool RegularSizeEnforcedPacketBuilder::canBuildPacket() const noexcept {
-  // We only force size of packets with short header, because d6d probes always
-  // have short headers and there's no other situations for this type of builder
-  const ShortHeader* shortHeader = packet_.header.asShort();
-  // We also don't want to send packets longer than kDefaultMaxUDPPayload
-  return shortHeader && enforcedSize_ <= kDefaultMaxUDPPayload &&
-      (body_->computeChainDataLength() + header_->computeChainDataLength() +
-           cipherOverhead_ <
-       enforcedSize_);
-}
-
-PacketBuilderInterface::Packet
-RegularSizeEnforcedPacketBuilder::buildPacket() && {
-  // Store counters on the stack to overhead from function calls
-  size_t extraDataWritten = 0;
-  size_t bodyLength = body_->computeChainDataLength();
-  size_t headerLength = header_->computeChainDataLength();
-  while (extraDataWritten + bodyLength + headerLength + cipherOverhead_ <
-         enforcedSize_) {
-    QuicInteger paddingType(static_cast<uint8_t>(FrameType::PADDING));
-    paddingType.encode([&](auto val) { bodyAppender_.writeBE(val); });
-    extraDataWritten++;
-  }
-  return Packet(std::move(packet_), std::move(header_), std::move(body_));
-}
-
-InplaceSizeEnforcedPacketBuilder::InplaceSizeEnforcedPacketBuilder(
-    BufAccessor& bufAccessor,
-    Packet packet,
-    uint64_t enforcedSize,
-    uint32_t cipherOverhead)
-    : bufAccessor_(bufAccessor),
-      iobuf_(bufAccessor_.obtain()),
-      packet_(std::move(packet.packet)),
-      header_(std::move(packet.header)),
-      body_(std::move(packet.body)),
-      enforcedSize_(enforcedSize),
-      cipherOverhead_(cipherOverhead) {}
-
-bool InplaceSizeEnforcedPacketBuilder::canBuildPacket() const noexcept {
-  const ShortHeader* shortHeader = packet_.header.asShort();
-  size_t encryptedPacketSize =
-      header_->length() + body_->length() + cipherOverhead_;
-  size_t delta = enforcedSize_ - encryptedPacketSize;
-  return shortHeader && enforcedSize_ <= kDefaultMaxUDPPayload &&
-      encryptedPacketSize < enforcedSize_ && iobuf_->tailroom() >= delta;
-}
-
-PacketBuilderInterface::Packet
-InplaceSizeEnforcedPacketBuilder::buildPacket() && {
-  // Create bodyWriter
-  size_t encryptedPacketSize =
-      header_->length() + body_->length() + cipherOverhead_;
-  size_t paddingSize = enforcedSize_ - encryptedPacketSize;
-  BufWriter bodyWriter(*iobuf_, paddingSize);
-
-  // Store counters on the stack to overhead from function calls
-  size_t extraDataWritten = 0;
-  size_t bodyLength = body_->computeChainDataLength();
-  size_t headerLength = header_->computeChainDataLength();
-  while (extraDataWritten + bodyLength + headerLength + cipherOverhead_ <
-         enforcedSize_) {
-    QuicInteger paddingType(static_cast<uint8_t>(FrameType::PADDING));
-    paddingType.encode([&](auto val) { bodyWriter.writeBE(val); });
-    extraDataWritten++;
-  }
-
-  PacketBuilderInterface::Packet builtPacket(
-      std::move(packet_),
-      std::move(header_),
-      folly::IOBuf::wrapBuffer(body_->data(), iobuf_->tail() - body_->data()));
-
-  // Release internal iobuf
-  bufAccessor_.release(std::move(iobuf_));
-  return builtPacket;
-}
-
 VersionNegotiationPacketBuilder::VersionNegotiationPacketBuilder(
     ConnectionId sourceConnectionId,
     ConnectionId destinationConnectionId,

quic/codec/QuicPacketBuilder.h

@@ -255,88 +255,6 @@ class RegularQuicPacketBuilder final : public PacketBuilderInterface {
   folly::Optional<PacketNumEncodingResult> packetNumberEncoding_;
 };
 
-/**
- * A less involving interface for packet builder, this enables polymorphism
- * for wrapper-like packet builders (e.g. RegularSizeEnforcedPacketBuilder).
- */
-class WrapperPacketBuilderInterface {
- public:
-  using Packet = PacketBuilderInterface::Packet;
-
-  virtual ~WrapperPacketBuilderInterface() = default;
-
-  FOLLY_NODISCARD virtual bool canBuildPacket() const noexcept = 0;
-
-  virtual Packet buildPacket() && = 0;
-};
-
-/**
- * This builder will enforce the packet size by appending padding frames for
- * chained memory. This means appending IOBuf at the end of the chain. The
- * caller should ensure canBuildPacket() returns true before constructing the
- * builder.
- */
-class RegularSizeEnforcedPacketBuilder : public WrapperPacketBuilderInterface {
- public:
-  using Packet = PacketBuilderInterface::Packet;
-
-  explicit RegularSizeEnforcedPacketBuilder(
-      Packet packet,
-      uint64_t enforcedSize,
-      uint32_t cipherOverhead);
-
-  /**
-   * Returns true when packet has short header, and that enforced size >
-   * current packet size + cipher overhead, otherwise false
-   */
-  FOLLY_NODISCARD bool canBuildPacket() const noexcept override;
-
-  Packet buildPacket() && override;
-
- private:
-  RegularQuicWritePacket packet_;
-  Buf header_;
-  Buf body_;
-  BufAppender bodyAppender_;
-  uint64_t enforcedSize_;
-  uint32_t cipherOverhead_;
-};
-
-/**
- * This builder will enforce the packet size by appending padding frames for
- * continuous memory. This means pushing padding frame directly to the current
- * tail offset. The caller should ensure canBuildPacket() returns true before
- * constructing the builder.
- */
-class InplaceSizeEnforcedPacketBuilder : public WrapperPacketBuilderInterface {
- public:
-  using Packet = PacketBuilderInterface::Packet;
-
-  explicit InplaceSizeEnforcedPacketBuilder(
-      BufAccessor& bufAccessor,
-      Packet packet,
-      uint64_t enforcedSize,
-      uint32_t cipherOverhead);
-
-  /**
-   * Returns true when packet has short header, and that enforced size> current
-   * packet size + cipher oveahead and that iobuf has enough tailroom,
-   * otherwise false
-   */
-  FOLLY_NODISCARD bool canBuildPacket() const noexcept override;
-
-  Packet buildPacket() && override;
-
- private:
-  BufAccessor& bufAccessor_;
-  Buf iobuf_;
-  RegularQuicWritePacket packet_;
-  Buf header_;
-  Buf body_;
-  uint64_t enforcedSize_;
-  uint32_t cipherOverhead_;
-};
-
 class VersionNegotiationPacketBuilder {
  public:
   explicit VersionNegotiationPacketBuilder(

quic/codec/test/QuicPacketBuilderTest.cpp

@@ -109,7 +109,7 @@ class QuicPacketBuilderTest : public TestWithParam<TestFlavor> {
     folly::assume_unreachable();
   }
 
- protected:
+ private:
   std::unique_ptr<BufAccessor> simpleBufAccessor_;
 };
 
@@ -277,67 +277,6 @@ TEST_P(QuicPacketBuilderTest, ShortHeaderRegularPacket) {
   EXPECT_EQ(pktNum, decodedHeader.getPacketSequenceNum());
 }
 
-TEST_P(QuicPacketBuilderTest, EnforcePacketSizeWithCipherOverhead) {
-  auto connId = getTestConnectionId();
-  PacketNum pktNum = 222;
-
-  PacketNum largestAckedPacketNum = 0;
-  size_t cipherOverhead = 2;
-  uint64_t enforcedSize = 1400;
-  auto aead = std::make_unique<NiceMock<MockAead>>();
-  auto aead_ = aead.get();
-  EXPECT_CALL(*aead_, _inplaceEncrypt(_, _, _))
-      .WillRepeatedly(Invoke([&](auto& buf, auto, auto) {
-        auto overhead = folly::IOBuf::create(1000);
-        overhead->append(cipherOverhead);
-        auto clone = buf->clone();
-        clone->prependChain(std::move(overhead));
-        return std::move(clone);
-      }));
-
-  auto builder = testBuilderProvider(
-      GetParam(),
-      kDefaultUDPSendPacketLen,
-      ShortHeader(ProtectionType::KeyPhaseZero, connId, pktNum),
-      largestAckedPacketNum,
-      2000);
-  builder->accountForCipherOverhead(cipherOverhead);
-  builder->encodePacketHeader();
-
-  // write out at least one frame
-  writeFrame(PaddingFrame(), *builder);
-  EXPECT_TRUE(builder->canBuildPacket());
-  auto builtOut = std::move(*builder).buildPacket();
-
-  auto param = GetParam();
-  if (param == TestFlavor::Regular) {
-    EXPECT_EQ(builtOut.body->isManagedOne(), true);
-    RegularSizeEnforcedPacketBuilder sizeEnforcedBuilder(
-        std::move(builtOut), enforcedSize, cipherOverhead);
-    EXPECT_TRUE(sizeEnforcedBuilder.canBuildPacket());
-    auto out = std::move(sizeEnforcedBuilder).buildPacket();
-    EXPECT_EQ(
-        out.header->computeChainDataLength() +
-            out.body->computeChainDataLength(),
-        enforcedSize - cipherOverhead);
-    auto buf = packetToBuf(out, aead_);
-    EXPECT_EQ(buf->computeChainDataLength(), enforcedSize);
-
-  } else {
-    EXPECT_EQ(builtOut.body->isManagedOne(), false);
-    InplaceSizeEnforcedPacketBuilder sizeEnforcedBuilder(
-        *simpleBufAccessor_, std::move(builtOut), enforcedSize, cipherOverhead);
-    EXPECT_TRUE(sizeEnforcedBuilder.canBuildPacket());
-    auto out = std::move(sizeEnforcedBuilder).buildPacket();
-    EXPECT_EQ(
-        out.header->computeChainDataLength() +
-            out.body->computeChainDataLength(),
-        enforcedSize - cipherOverhead);
-    auto buf = packetToBuf(out, aead_);
-    EXPECT_EQ(buf->computeChainDataLength(), enforcedSize);
-  }
-}
-
 TEST_P(QuicPacketBuilderTest, ShortHeaderWithNoFrames) {
   auto connId = getTestConnectionId();
   PacketNum pktNum = 222;

quic/congestion_control/test/BbrTest.cpp

@@ -25,7 +25,7 @@ class BbrTest : public Test {};
 
 TEST_F(BbrTest, InitStates) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   BbrCongestionController bbr(conn);
   EXPECT_EQ(CongestionControlType::BBR, bbr.type());
   EXPECT_FALSE(bbr.inRecovery());
@@ -39,7 +39,7 @@ TEST_F(BbrTest, Recovery) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
   auto qLogger = std::make_shared<FileQLogger>(VantagePoint::Client);
   conn.qLogger = qLogger;
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   conn.transportSettings.initCwndInMss = 500; // Make a really large initCwnd
   BbrCongestionController bbr(conn);
   // Make a huge inflight so we don't underflow anything
@@ -121,7 +121,7 @@ TEST_F(BbrTest, Recovery) {
 
 TEST_F(BbrTest, StartupCwnd) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   BbrCongestionController bbr(conn);
   auto mockRttSampler = std::make_unique<MockMinRttSampler>();
   auto mockBandwidthSampler = std::make_unique<MockBandwidthSampler>();
@@ -147,7 +147,7 @@ TEST_F(BbrTest, StartupCwnd) {
 
 TEST_F(BbrTest, LeaveStartup) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   BbrCongestionController bbr(conn);
   auto mockBandwidthSampler = std::make_unique<MockBandwidthSampler>();
   auto rawBandwidthSampler = mockBandwidthSampler.get();
@@ -203,7 +203,7 @@ TEST_F(BbrTest, LeaveStartup) {
 
 TEST_F(BbrTest, RemoveInflightBytes) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   BbrCongestionController bbr(conn);
   auto writableBytesAfterInit = bbr.getWritableBytes();
   bbr.onPacketSent(makeTestingWritePacket(0, 1000, 1000));
@@ -214,7 +214,7 @@ TEST_F(BbrTest, RemoveInflightBytes) {
 
 TEST_F(BbrTest, ProbeRtt) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   BbrCongestionController bbr(conn);
   auto mockBandwidthSampler = std::make_unique<MockBandwidthSampler>();
   auto rawBandwidthSampler = mockBandwidthSampler.get();
@@ -376,7 +376,7 @@ TEST_F(BbrTest, AckAggregation) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
   auto qLogger = std::make_shared<FileQLogger>(VantagePoint::Client);
   conn.qLogger = qLogger;
-  updateUdpSendPacketLen(conn, 1000);
+  conn.udpSendPacketLen = 1000;
   BbrCongestionController bbr(conn);
   auto mockBandwidthSampler = std::make_unique<MockBandwidthSampler>();
   auto mockRttSampler = std::make_unique<MockMinRttSampler>();

quic/congestion_control/test/CongestionControlFunctionsTest.cpp

@@ -10,7 +10,6 @@
 
 #include <folly/portability/GTest.h>
 #include <quic/QuicConstants.h>
-#include <quic/state/QuicStateFunctions.h>
 #include <quic/state/StateData.h>
 
 using namespace testing;
@@ -22,7 +21,7 @@ class CongestionControlFunctionsTest : public Test {};
 
 TEST_F(CongestionControlFunctionsTest, CalculatePacingRate) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1);
+  conn.udpSendPacketLen = 1;
   conn.transportSettings.minBurstPackets = 1;
   conn.transportSettings.pacingTimerTickInterval = 10ms;
   std::chrono::microseconds rtt(1000 * 100);
@@ -40,7 +39,7 @@ TEST_F(CongestionControlFunctionsTest, CalculatePacingRate) {
 
 TEST_F(CongestionControlFunctionsTest, MinPacingRate) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1);
+  conn.udpSendPacketLen = 1;
   conn.transportSettings.pacingTimerTickInterval = 1ms;
   auto result = calculatePacingRate(
       conn, 100, conn.transportSettings.minCwndInMss, 100ms);
@@ -52,7 +51,7 @@ TEST_F(CongestionControlFunctionsTest, MinPacingRate) {
 
 TEST_F(CongestionControlFunctionsTest, SmallCwnd) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1);
+  conn.udpSendPacketLen = 1;
   conn.transportSettings.minBurstPackets = 1;
   conn.transportSettings.pacingTimerTickInterval = 1ms;
   auto result = calculatePacingRate(
@@ -63,7 +62,7 @@ TEST_F(CongestionControlFunctionsTest, SmallCwnd) {
 
 TEST_F(CongestionControlFunctionsTest, RttSmallerThanInterval) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 1);
+  conn.udpSendPacketLen = 1;
   conn.transportSettings.minBurstPackets = 1;
   conn.transportSettings.pacingTimerTickInterval = 10ms;
   auto result =

quic/congestion_control/test/CubicHystartTest.cpp

@@ -19,7 +19,7 @@ class CubicHystartTest : public Test {};
 
 TEST_F(CubicHystartTest, SendAndAck) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 100);
+  conn.udpSendPacketLen = 100;
   Cubic cubic(conn);
   auto initCwnd = cubic.getWritableBytes();
   // Packet 0 is sent:
@@ -54,7 +54,7 @@ TEST_F(CubicHystartTest, CwndLargerThanSSThresh) {
 
 TEST_F(CubicHystartTest, NoDelayIncrease) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
-  updateUdpSendPacketLen(conn, 100);
+  conn.udpSendPacketLen = 100;
   Cubic cubic(conn);
   auto initCwnd = cubic.getWritableBytes();
   // Packet 0 is sent:

quic/congestion_control/test/CubicSteadyTest.cpp

@@ -20,7 +20,7 @@ TEST_F(CubicSteadyTest, CubicReduction) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
   // initCwnd > initSsthresh: an ack will immediately make the state machine
   // transit to Steady state:
-  updateUdpSendPacketLen(conn, 200); // initCwnd = 2000, minCwnd = 400
+  conn.udpSendPacketLen = 200; // initCwnd = 2000, minCwnd = 400
   Cubic cubic(conn, 1000);
 
   // Send one and get acked, this moves the state machine to steady. Cwnd will

quic/congestion_control/test/CubicTest.cpp

@@ -115,7 +115,7 @@ TEST_F(CubicTest, CwndIncreaseAfterReduction) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
   auto qLogger = std::make_shared<FileQLogger>(VantagePoint::Client);
   conn.qLogger = qLogger;
-  updateUdpSendPacketLen(conn, 200);
+  conn.udpSendPacketLen = 200;
   // initCwnd > initSsthresh: an ack will immediately make the state machine
   // transit to Steady state:
   Cubic cubic(conn, 1000);
@@ -178,7 +178,7 @@ TEST_F(CubicTest, AppIdle) {
   QuicConnectionStateBase conn(QuicNodeType::Client);
   auto qLogger = std::make_shared<FileQLogger>(VantagePoint::Client);
   conn.qLogger = qLogger;
-  updateUdpSendPacketLen(conn, 1500);
+  conn.udpSendPacketLen = 1500;
   TestingCubic cubic(conn);
   cubic.setStateForTest(CubicStates::Steady);
 
@@ -244,7 +244,7 @@ TEST_F(CubicTest, PacingGain) {
   conn.pacer = std::move(mockPacer);
   auto qLogger = std::make_shared<FileQLogger>(VantagePoint::Client);
   conn.qLogger = qLogger;
-  updateUdpSendPacketLen(conn, 1500);
+  conn.udpSendPacketLen = 1500;
   Cubic cubic(conn);
 
   conn.lossState.srtt = 3000us;

quic/fizz/client/test/QuicClientTransportTest.cpp

@@ -1811,12 +1811,12 @@ TEST_F(QuicClientTransportTest, AddNewPeerAddressSetsPacketSize) {
   folly::SocketAddress v4Address("0.0.0.0", 0);
   ASSERT_TRUE(v4Address.getFamily() == AF_INET);
   client->addNewPeerAddress(v4Address);
-  EXPECT_EQ(kDefaultV4UDPSendPacketLen, client->getConn().currentPMTU);
+  EXPECT_EQ(kDefaultV4UDPSendPacketLen, client->getConn().udpSendPacketLen);
 
   folly::SocketAddress v6Address("::", 0);
   ASSERT_TRUE(v6Address.getFamily() == AF_INET6);
   client->addNewPeerAddress(v6Address);
-  EXPECT_EQ(kDefaultV6UDPSendPacketLen, client->getConn().currentPMTU);
+  EXPECT_EQ(kDefaultV6UDPSendPacketLen, client->getConn().udpSendPacketLen);
 
   client->closeNow(folly::none);
 }

quic/server/QuicServerTransport.cpp

@@ -61,10 +61,9 @@ void QuicServerTransport::setRoutingCallback(
 void QuicServerTransport::setOriginalPeerAddress(
     const folly::SocketAddress& addr) {
   conn_->originalPeerAddress = addr;
-  updateUdpSendPacketLen(
+  conn_->udpSendPacketLen = addr.getFamily() == AF_INET6
-      *conn_,
+      ? kDefaultV6UDPSendPacketLen
-      addr.getFamily() == AF_INET6 ? kDefaultV6UDPSendPacketLen
+      : kDefaultV4UDPSendPacketLen;
-                                   : kDefaultV4UDPSendPacketLen);
 }
 
 void QuicServerTransport::setServerConnectionIdParams(

quic/server/state/ServerStateMachine.cpp

@@ -181,7 +181,7 @@ void processClientInitialParams(
     if (*packetSize > kDefaultMaxUDPPayload) {
       *packetSize = kDefaultUDPSendPacketLen;
     }
-    updateUdpSendPacketLen(conn, *packetSize);
+    conn.udpSendPacketLen = *packetSize;
   }
 
   conn.peerActiveConnectionIdLimit =

quic/server/test/QuicServerTransportTest.cpp

@@ -3783,11 +3783,11 @@ TEST_F(
 
 TEST_F(QuicUnencryptedServerTransportTest, MaxReceivePacketSizeTooLarge) {
   getFakeHandshakeLayer()->allowZeroRttKeys();
-  auto originalPeerMaxPacketSize = server->getConn().udpSendPacketLen;
+  auto originalUdpSize = server->getConn().udpSendPacketLen;
   fakeHandshake->maxRecvPacketSize = 4096;
   setupClientReadCodec();
   recvClientHello();
-  EXPECT_NE(originalPeerMaxPacketSize, server->getConn().udpSendPacketLen);
+  EXPECT_NE(originalUdpSize, server->getConn().udpSendPacketLen);
   EXPECT_EQ(server->getConn().udpSendPacketLen, kDefaultUDPSendPacketLen);
 }
 

quic/state/QuicStateFunctions.cpp

@@ -208,22 +208,6 @@ void increaseNextPacketNum(
   }
 }
 
-void updatePeerMaxPacketSize(QuicConnectionStateBase& conn, uint64_t size) {
-  conn.peerMaxPacketSize = size;
-  conn.udpSendPacketLen = std::min(conn.peerMaxPacketSize, conn.currentPMTU);
-}
-
-void updateCurrentPMTU(QuicConnectionStateBase& conn, uint64_t size) {
-  conn.currentPMTU = size;
-  conn.udpSendPacketLen = std::min(conn.peerMaxPacketSize, conn.currentPMTU);
-}
-
-void updateUdpSendPacketLen(QuicConnectionStateBase& conn, uint64_t size) {
-  conn.peerMaxPacketSize = size;
-  conn.currentPMTU = size;
-  conn.udpSendPacketLen = size;
-}
-
 std::deque<OutstandingPacket>::iterator getFirstOutstandingPacket(
     QuicConnectionStateBase& conn,
     PacketNumberSpace packetNumberSpace) {

quic/state/QuicStateFunctions.h

@@ -55,24 +55,6 @@ void increaseNextPacketNum(
     QuicConnectionStateBase& conn,
     PacketNumberSpace pnSpace) noexcept;
 
-/**
- * Update peerMaxPacketSize, will re-calculate udpSendPacketLen
- */
-void updatePeerMaxPacketSize(QuicConnectionStateBase& conn, uint64_t size);
-
-/**
- * Update currPMTU, will re-calculate udpSendPacketLen
- */
-void updateCurrentPMTU(QuicConnectionStateBase& conn, uint64_t size);
-
-/**
- * Update the actual maximum udp packet length, this will set both
- * peerMaxPacketSize and PMTU to the same value.
- * This is useful for initialization when setting peer socket address and
- * testing.
- */
-void updateUdpSendPacketLen(QuicConnectionStateBase& conn, uint64_t size);
-
 /**
  * Update largestReceivedPacketNum in ackState with packetNum. Return if the
  * current packetNum is received out of order.

quic/state/StateData.h

@@ -728,15 +728,8 @@ struct QuicConnectionStateBase : public folly::DelayedDestruction {
   // until the handshake sets the timeout.
   std::chrono::milliseconds peerIdleTimeout{kMaxIdleTimeout};
 
-  // The max_packet_size Transport Parameters
+  // The max UDP packet size we will be sending, limited by both the received
-  uint64_t peerMaxPacketSize{kDefaultUDPSendPacketLen};
+  // max_packet_size in Transport Parameters and PMTU
-
-  // Current PMTU, which may change as d6d discovers new PMTU on the path
-  uint64_t currentPMTU{kDefaultUDPSendPacketLen};
-
-  // The effective max UDP packet size we will be sending, limited by both the
-  // received max_packet_size in Transport Parameters and PMTU. Should not be
-  // set directly, use setUDPSendPacketLen()
   uint64_t udpSendPacketLen{kDefaultUDPSendPacketLen};
 
   struct PacketSchedulingState {

quic/state/test/StateDataTest.cpp

@@ -87,7 +87,7 @@ TEST_F(PendingPathRateLimiterTest, TestSetInitialCredit) {
   EXPECT_EQ(
       limiter_.currentCredit(now, std::chrono::microseconds{kRtt}),
       maxWindowBytes);
-  updateUdpSendPacketLen(conn_, 2000);
+  conn_.udpSendPacketLen = 2000;
   PendingPathRateLimiter limiter2{conn_.udpSendPacketLen};
   EXPECT_EQ(
       limiter2.currentCredit(now, std::chrono::microseconds{kRtt}),