Mitigate libsrtp wraparound with loss decryption failure

Fixes #1437

### Details

- Read the issue, please.
- So solution is that `SeqManager` now includes a second constructor with `initialOutput` and we use it in all `XxxxConsumer` classes.

worker/include/RTC/SeqManager.hpp

@@ -36,6 +36,7 @@ namespace RTC
 
 	public:
 		SeqManager() = default;
+		SeqManager(T initialOutput);
 
 	public:
 		void Sync(T input);
@@ -50,6 +51,7 @@ namespace RTC
 	private:
 		// Whether at least a sequence number has been inserted.
 		bool started{ false };
+		T initialOutput{ 0 };
 		T base{ 0 };
 		T maxOutput{ 0 };
 		T maxInput{ 0 };

worker/include/RTC/SimpleConsumer.hpp

@@ -87,7 +87,7 @@ namespace RTC
 		RTC::RtpStreamRecv* producerRtpStream{ nullptr };
 		bool keyFrameSupported{ false };
 		bool syncRequired{ false };
-		RTC::SeqManager<uint16_t> rtpSeqManager;
+		std::unique_ptr<RTC::SeqManager<uint16_t>> rtpSeqManager;
 		bool managingBitrate{ false };
 		std::unique_ptr<RTC::Codecs::EncodingContext> encodingContext;
 	};

worker/src/RTC/SeqManager.cpp

@@ -39,9 +39,17 @@ namespace RTC
 		return isSeqHigherThan(lhs, rhs);
 	}
 
+	template<typename T, uint8_t N>
+	SeqManager<T, N>::SeqManager(T initialOutput) : initialOutput(initialOutput)
+	{
+		MS_TRACE();
+	}
+
 	template<typename T, uint8_t N>
 	void SeqManager<T, N>::Sync(T input)
 	{
+		MS_TRACE();
+
 		// Update base.
 		this->base = (this->maxOutput - input) & MaxValue;
 
@@ -55,6 +63,8 @@ namespace RTC
 	template<typename T, uint8_t N>
 	void SeqManager<T, N>::Drop(T input)
 	{
+		MS_TRACE();
+
 		// Mark as dropped if 'input' is higher than anyone already processed.
 		if (SeqManager<T, N>::IsSeqHigherThan(input, this->maxInput))
 		{
@@ -71,6 +81,8 @@ namespace RTC
 	template<typename T, uint8_t N>
 	bool SeqManager<T, N>::Input(T input, T& output)
 	{
+		MS_TRACE();
+
 		auto base = this->base;
 
 		// No dropped inputs to consider.
@@ -140,6 +152,8 @@ namespace RTC
 			}
 		}
 
+		output = (output + this->initialOutput) & MaxValue;
+
 		return true;
 	}
 
@@ -162,6 +176,8 @@ namespace RTC
 	template<typename T, uint8_t N>
 	void SeqManager<T, N>::ClearDropped()
 	{
+		MS_TRACE();
+
 		// Cleanup dropped values.
 		if (this->dropped.empty())
 		{

worker/src/RTC/SimpleConsumer.cpp

@@ -5,6 +5,7 @@
 #include "DepLibUV.hpp"
 #include "Logger.hpp"
 #include "MediaSoupErrors.hpp"
+#include "Utils.hpp"
 #include "RTC/Codecs/Tools.hpp"
 #include "RTC/SimpleConsumer.hpp"
 
@@ -36,6 +37,14 @@ namespace RTC
 		// Create RtpStreamSend instance for sending a single stream to the remote.
 		CreateRtpStream();
 
+		// Let's chosee an initial output seq number between 1000 and 32768 to avoid
+		// libsrtp bug:
+		// https://github.com/versatica/mediasoup/issues/1437
+		const uint16_t initialOutputSeq =
+		  Utils::Crypto::GetRandomUInt(1000u, std::numeric_limits<uint16_t>::max() / 2);
+
+		this->rtpSeqManager.reset(new RTC::SeqManager<uint16_t>(initialOutputSeq));
+
 		// Create the encoding context for Opus.
 		if (
 		  mediaCodec->mimeType.type == RTC::RtpCodecMimeType::Type::AUDIO &&
@@ -340,7 +349,7 @@ namespace RTC
 			  packet->GetSequenceNumber(),
 			  packet->GetTimestamp());
 
-			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
+			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
 
 #ifdef MS_RTC_LOGGER_RTP
 			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::DROPPED_BY_CODEC);
@@ -363,7 +372,7 @@ namespace RTC
 		// Packets with only padding are not forwarded.
 		if (packet->GetPayloadLength() == 0)
 		{
-			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
+			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
 
 #ifdef MS_RTC_LOGGER_RTP
 			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
@@ -383,15 +392,15 @@ namespace RTC
 				MS_DEBUG_TAG(rtp, "sync key frame received");
 			}
 
-			this->rtpSeqManager.Sync(packet->GetSequenceNumber() - 1);
+			this->rtpSeqManager->Sync(packet->GetSequenceNumber() - 1);
 
 			this->syncRequired = false;
 		}
 
 		// Update RTP seq number and timestamp.
 		uint16_t seq;
 
-		this->rtpSeqManager.Input(packet->GetSequenceNumber(), seq);
+		this->rtpSeqManager->Input(packet->GetSequenceNumber(), seq);
 
 		// Save original packet fields.
 		auto origSsrc = packet->GetSsrc();