Make rtcp sender use max transfer unit.

webrtc/modules/rtp_rtcp/source/rtcp_sender.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
index a5fccebad1dd67eb792fcf70ae402fafdcac5700..edca8ff36f4d0adfc656004dedd6da06c655a49d 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
@@ -99,8 +99,10 @@ class PacketContainer : public rtcp::CompoundPacket,
     }
   }
 
-  size_t SendPackets() {
-    rtcp::CompoundPacket::Build(this);
+  size_t SendPackets(size_t max_payload_length) {
+    RTC_DCHECK_LE(max_payload_length, static_cast<size_t>(IP_PACKET_SIZE));
+    uint8_t buffer[IP_PACKET_SIZE];
+    BuildExternalBuffer(buffer, max_payload_length, this);
     return bytes_sent_;
   }
 
@@ -168,7 +170,8 @@ RTCPSender::RTCPSender(
 
       tmmbr_help_(),
       tmmbr_send_(0),
-      packet_oh_send_(0),
+      packet_overhead_(28),
+      max_payload_length_(IP_PACKET_SIZE - packet_overhead_),
 
       app_sub_type_(0),
       app_name_(0),
@@ -277,6 +280,12 @@ void RTCPSender::SetTMMBRStatus(bool enable) {
   }
 }
 
+void RTCPSender::SetMaxPayloadLength(size_t length, uint16_t packet_overhead) {
+  rtc::CritScope lock(&critical_section_rtcp_sender_);
+  max_payload_length_ = length;
+  packet_overhead_ = packet_overhead;
+}
+
 void RTCPSender::SetStartTimestamp(uint32_t start_timestamp) {
   rtc::CritScope lock(&critical_section_rtcp_sender_);
   start_timestamp_ = start_timestamp;
@@ -590,7 +599,7 @@ std::unique_ptr<rtcp::RtcpPacket> RTCPSender::BuildTMMBR(
   if (lengthOfBoundingSet > 0) {
     for (int32_t i = 0; i < lengthOfBoundingSet; i++) {
       if (candidateSet->Tmmbr(i) == tmmbr_send_ &&
-          candidateSet->PacketOH(i) == packet_oh_send_) {
+          candidateSet->PacketOH(i) == packet_overhead_) {
         // Do not send the same tuple.
         return nullptr;
       }
@@ -598,7 +607,7 @@ std::unique_ptr<rtcp::RtcpPacket> RTCPSender::BuildTMMBR(
     if (!tmmbrOwner) {
       // use received bounding set as candidate set
       // add current tuple
-      candidateSet->SetEntry(lengthOfBoundingSet, tmmbr_send_, packet_oh_send_,
+      candidateSet->SetEntry(lengthOfBoundingSet, tmmbr_send_, packet_overhead_,

[åsapersson, 2016/03/30 10:28:36]

Should packet_overhead_ for tmmbr include the RTP header length (i.e. be 40
bytes by default)?

[danilchap, 2016/03/30 12:38:24]

Yes, in fact it should, as well as rtp header extensions.
Which make it more complicated and subject of a different dedicated CL.

                              ssrc_);
       int numCandidates = lengthOfBoundingSet + 1;
 
@@ -622,7 +631,7 @@ std::unique_ptr<rtcp::RtcpPacket> RTCPSender::BuildTMMBR(
   rtcp::TmmbItem request;
   request.set_ssrc(remote_ssrc_);
   request.set_bitrate_bps(tmmbr_send_ * 1000);
-  request.set_packet_overhead(packet_oh_send_);
+  request.set_packet_overhead(packet_overhead_);
   tmmbr->WithTmmbr(request);
 
   return std::unique_ptr<rtcp::RtcpPacket>(tmmbr);
@@ -809,7 +818,7 @@ int32_t RTCPSender::SendCompoundRTCP(
     RTC_DCHECK(AllVolatileFlagsConsumed());
   }
 
-  size_t bytes_sent = container.SendPackets();
+  size_t bytes_sent = container.SendPackets(max_payload_length_);
   return bytes_sent == 0 ? -1 : 0;
 }
 
@@ -1030,8 +1039,9 @@ bool RTCPSender::SendFeedbackPacket(const rtcp::TransportFeedback& packet) {
     // but we can't because of an incorrect warning (C4822) in MVS 2013.
   } sender(transport_, event_log_);
 
+  RTC_DCHECK_LE(max_payload_length_, static_cast<size_t>(IP_PACKET_SIZE));
   uint8_t buffer[IP_PACKET_SIZE];
-  return packet.BuildExternalBuffer(buffer, IP_PACKET_SIZE, &sender) &&
+  return packet.BuildExternalBuffer(buffer, max_payload_length_, &sender) &&
          !sender.send_failure_;
 }