Do not try to rotate peer CIDs if the original CID is zero length

Reviewed By: lnicco

Differential Revision: D61052814

fbshipit-source-id: 1baabc0d5db9b371bb3901a74b51895998c6de54

quic/server/test/QuicServerTransportTest.cpp

@@ -1721,6 +1721,19 @@ TEST_F(QuicServerTransportTest, SwitchServerCidsMultipleCids) {
   EXPECT_EQ(secondCid.connId, *replacedCid);
 }
 
+TEST_F(
+    QuicServerTransportTest,
+    TestRetireAndSwitchPeerConnectionIdsEmptyPeerCid) {
+  auto& conn = server->getNonConstConn();
+
+  conn.clientConnectionId = ConnectionId(std::vector<uint8_t>{});
+  EXPECT_EQ(conn.peerConnectionIds.size(), 1);
+
+  EXPECT_EQ(conn.retireAndSwitchPeerConnectionIds(), true);
+  EXPECT_EQ(conn.pendingEvents.frames.size(), 0);
+  EXPECT_EQ(conn.peerConnectionIds.size(), 1);
+}
+
 TEST_F(QuicServerTransportTest, ShortHeaderPacketWithNoFrames) {
   auto qLogger = std::make_shared<FileQLogger>(VantagePoint::Server);
   server->getNonConstConn().qLogger = qLogger;

quic/state/StateData.cpp

@@ -118,6 +118,11 @@ bool QuicConnectionStateBase::retireAndSwitchPeerConnectionIds() {
         TransportErrorCode::INTERNAL_ERROR);
   }
 
+  if (mainPeerId->size() == 0) {
+    // No need to rotate CIDs if peer's CID is 0 length.
+    return true;
+  }
+
   // Retrieve the sequence number of the current cId, and find an unused
   // ConnectionIdData.
   for (auto it = peerConnectionIds.begin(); it != end; it++) {