Log an error in RtpDemuxer::FindSsrcAssociations() if kMaxProcessedSsrcs exceeded

webrtc/call/rtp_demuxer.cc

 /*
  *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
 #include "webrtc/call/rtp_demuxer.h"
 #include "webrtc/call/rtp_packet_sink_interface.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_packet_received.h"
 
 namespace webrtc {
 
 namespace {
 
 constexpr size_t kMaxProcessedSsrcs = 1000;  // Prevent memory overuse.
@@ skipping 57 matching lines @@
                                              RtpPacketSinkInterface* sink) {
   RTC_DCHECK(sink);
   // The association might already have been set by a different
   // configuration source.
   if (!MultimapAssociationExists(sinks_, ssrc, sink)) {
     sinks_.emplace(ssrc, sink);
   }
 }
 
 bool RtpDemuxer::OnRtpPacket(const RtpPacketReceived& packet) {
   FindSsrcAssociations(packet);

[nisse-webrtc, 2017/06/13 13:09:26]

Unrelated to this cl, but I wonder if it's really necessary to do this first?

I would have imagined that we could first lookup the ssrc in the |sinks_|
multimap, and only if the returned |it_range| is empty, attempt to process the
rsid. If we can get away with that, we don't need the |processed_ssrcs| mapping
at all.

Is there any valid use case where it's possible that |it_range| is non-empty but
the ssrc isn't present in the |processed_ssrcs_| map?

[eladalon, 2017/06/13 13:19:12]

Yes. It could be that sink A is associated with SSRC 1, and sink B is associated
with with RSID "ELAD". If we now get an RTP message that has (SSRC=1,
RSID=ELAD), we don't want to avoid finding out sink B's association.

   auto it_range = sinks_.equal_range(packet.Ssrc());
   for (auto it = it_range.first; it != it_range.second; ++it) {
     it->second->OnRtpPacket(packet);
   }
   return it_range.first != it_range.second;
 }
 
 void RtpDemuxer::FindSsrcAssociations(const RtpPacketReceived& packet) {
   // Avoid expensive string comparisons for RSID by looking the sinks up only
   // by SSRC whenever possible.
@@ skipping 11 matching lines @@
       RecordSsrcToSinkAssociation(packet.Ssrc(), it->second);
     }
 
     // To prevent memory-overuse attacks, forget this RSID. Future packets
     // with this RSID, but a different SSRC, will not spawn new associations.
     rsid_sinks_.erase(it_range.first, it_range.second);
   }
 
   if (processed_ssrcs_.size() < kMaxProcessedSsrcs) {  // Prevent memory overuse
     processed_ssrcs_.insert(packet.Ssrc());  // Avoid re-examining in-depth.
+  } else {
+    LOG(LS_WARNING) << "More than kMaxProcessedSsrcs different SSRCs seen.";

[danilchap, 2017/06/13 12:59:01]

if you have to log it, then likely you want to log it only once.
consider adding a variable to ensure you do not spam log file.

[danilchap, 2017/06/13 13:00:08]

log value of the kMaxProcessedSsrcs: 
"More than " << kMaxProcessedSsrcs << " different"

   }
 }
 
 }  // namespace webrtc