From 46b9fb69f49898acf690cec6ced7325709b1e045 Mon Sep 17 00:00:00 2001
From: Yang Chi <yangchi@fb.com>
Date: Fri, 8 May 2020 11:38:17 -0700
Subject: [PATCH] Skip a packet number for Quic probe packets

Summary: to elicit acks

Reviewed By: mjoras

Differential Revision: D21309835

fbshipit-source-id: fd56de66c806d5e03292298c79eab49014291b75
---
 quic/api/QuicTransportFunctions.cpp          | 2 ++
 quic/api/test/QuicTransportFunctionsTest.cpp | 9 +++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/quic/api/QuicTransportFunctions.cpp b/quic/api/QuicTransportFunctions.cpp
index 1efc2dc1a..a78cf2a70 100644
--- a/quic/api/QuicTransportFunctions.cpp
+++ b/quic/api/QuicTransportFunctions.cpp
@@ -1084,6 +1084,8 @@ uint64_t writeProbingDataToSocket(
     const Aead& aead,
     const PacketNumberCipher& headerCipher,
     QuicVersion version) {
+  // Skip a packet number for probing packets to elicit acks
+  increaseNextPacketNum(connection, pnSpace);
   CloningScheduler cloningScheduler(
       scheduler, connection, "CloningScheduler", aead.getCipherOverhead());
   auto written = writeConnectionDataToSocket(
diff --git a/quic/api/test/QuicTransportFunctionsTest.cpp b/quic/api/test/QuicTransportFunctionsTest.cpp
index f616528bc..429ec38a3 100644
--- a/quic/api/test/QuicTransportFunctionsTest.cpp
+++ b/quic/api/test/QuicTransportFunctionsTest.cpp
@@ -1384,6 +1384,9 @@ TEST_F(QuicTransportFunctionsTest, WriteProbingNewData) {
       *rawSocket, *conn, 1, *aead, *headerCipher, getVersion(*conn));
   EXPECT_LT(currentPacketSeqNum, conn->ackStates.appDataAckState.nextPacketNum);
   EXPECT_FALSE(conn->outstandingPackets.empty());
+  EXPECT_EQ(
+      conn->outstandingPackets.back().packet.header.getPacketSequenceNum(),
+      currentPacketSeqNum + 1);
   EXPECT_TRUE(conn->pendingEvents.setLossDetectionAlarm);
   EXPECT_GT(stream1->currentWriteOffset, currentStreamWriteOffset);
   EXPECT_FALSE(stream1->retransmissionBuffer.empty());
@@ -1505,7 +1508,8 @@ TEST_F(QuicTransportFunctionsTest, WriteProbesNoNewDataNoCryptoDataNoOldData) {
           *headerCipher,
           getVersion(*conn)));
   EXPECT_EQ(1, probesToSend);
-  EXPECT_EQ(currentPacketSeqNum, conn->ackStates.appDataAckState.nextPacketNum);
+  EXPECT_EQ(
+      currentPacketSeqNum + 1, conn->ackStates.appDataAckState.nextPacketNum);
   EXPECT_TRUE(conn->outstandingPackets.empty());
   EXPECT_FALSE(conn->pendingEvents.setLossDetectionAlarm);
   EXPECT_EQ(stream1->currentWriteOffset, currentStreamWriteOffset);
@@ -1546,7 +1550,8 @@ TEST_F(QuicTransportFunctionsTest, ProbingNotWriteOtherFrames) {
           *headerCipher,
           getVersion(*conn)));
   EXPECT_EQ(1, probesToSend);
-  EXPECT_EQ(currentPacketSeqNum, conn->ackStates.appDataAckState.nextPacketNum);
+  EXPECT_EQ(
+      currentPacketSeqNum + 1, conn->ackStates.appDataAckState.nextPacketNum);
   EXPECT_TRUE(conn->outstandingPackets.empty());
   EXPECT_FALSE(conn->pendingEvents.setLossDetectionAlarm);
   EXPECT_EQ(stream1->currentWriteOffset, currentStreamWriteOffset);