Fix the logic for computing the number of truncated QUIC ACK frames sent.

net/quic/quic_connection_logger.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_connection_logger.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 374 matching lines @@
 
 void QuicConnectionLogger::OnFrameAddedToPacket(const QuicFrame& frame) {
   switch (frame.type) {
     case PADDING_FRAME:
       break;
     case STREAM_FRAME:
       net_log_.AddEvent(
           NetLog::TYPE_QUIC_SESSION_STREAM_FRAME_SENT,
           base::Bind(&NetLogQuicStreamFrameCallback, frame.stream_frame));
       break;
-    case ACK_FRAME:
+    case ACK_FRAME: {
       net_log_.AddEvent(
           NetLog::TYPE_QUIC_SESSION_ACK_FRAME_SENT,
           base::Bind(&NetLogQuicAckFrameCallback, frame.ack_frame));
-      if (frame.ack_frame->is_truncated)
-        ++num_truncated_acks_sent_;
+      const SequenceNumberSet& missing_packets =
+          frame.ack_frame->missing_packets;
+      const uint8 max_ranges = std::numeric_limits<uint8>::max();
+      // Compute an upper bound on the number of NACK ranges. If the bound
+      // is below the max, then it clearly isn't truncated.
+      if (missing_packets.size() < max_ranges ||
+          (*missing_packets.rbegin() - *missing_packets.begin() -
+           missing_packets.size() + 1) < max_ranges) {
+        break;
+      }
+      size_t num_ranges = 0;
+      QuicPacketSequenceNumber last_missing = 0;
+      for (SequenceNumberSet::const_iterator it = missing_packets.begin();
+           it != missing_packets.end(); ++it) {
+        if (*it != last_missing + 1 && ++num_ranges >= max_ranges) {
+          ++num_truncated_acks_sent_;
+          break;
+        }
+        last_missing = *it;
+      }
       break;
+    }
     case CONGESTION_FEEDBACK_FRAME:
       net_log_.AddEvent(
           NetLog::TYPE_QUIC_SESSION_CONGESTION_FEEDBACK_FRAME_SENT,
           base::Bind(&NetLogQuicCongestionFeedbackFrameCallback,
                      frame.congestion_feedback_frame));
       break;
     case RST_STREAM_FRAME:
       UMA_HISTOGRAM_SPARSE_SLOWLY("Net.QuicSession.RstStreamErrorCodeClient",
                                   frame.rst_stream_frame->error_code);
       net_log_.AddEvent(
@@ skipping 465 matching lines @@
       continue;
     }
     // Record some overlapping patterns, to get a better picture, since this is
     // not very expensive.
     if (i % 3 == 0)
       six_packet_histogram->Add(recent_6_mask);
   }
 }
 
 }  // namespace net