Test usrsctp with usrsctp_get_timeout()

### Details

- Related task: #1011. Note that usrsctp author never cared about the existing PR so we are on our own.
- So I've forked usrctp, added the `usrsctp_get_timeout()` feature and released version 0.9.6.0: versatica/usrsctp#1
- And I've made `usrsctp.wrap` point to it.

### Notes

- It would be great to have a way to pass `sctp_debug=true` when building usrsctp Meson subproject so it defines `SCTP_DEBUG` (needed in `DepUsrSCTP.cpp` to show SCTP debug). An manual alternative is to edit `meson.build` of usrsctp and add it unconditionally.
- I'm calling `HandleUsrSctpTimers()` everytime the timer fires (of course), also in `onSendSctpData` callback and also when SCTP data is received (in `SctpAssociation::ProcessSctpData()`. Not sure if correct.

worker/include/DepUsrSCTP.hpp

@@ -18,6 +18,7 @@ class DepUsrSCTP
 	public:
 		void Start();
 		void Stop();
+		void HandleUsrSctpTimers();
 
 		/* Pure virtual methods inherited from TimerHandle::Listener. */
 	public:
@@ -37,6 +38,7 @@ class DepUsrSCTP
 	static void RegisterSctpAssociation(RTC::SctpAssociation* sctpAssociation);
 	static void DeregisterSctpAssociation(RTC::SctpAssociation* sctpAssociation);
 	static RTC::SctpAssociation* RetrieveSctpAssociation(uintptr_t id);
+	static void HandleUsrSctpTimers();
 
 private:
 	thread_local static Checker* checker;

worker/src/DepUsrSCTP.cpp

@@ -13,33 +13,42 @@
 
 /* Static. */
 
-static constexpr size_t CheckerInterval{ 10u }; // In ms.
 static std::mutex GlobalSyncMutex;
 static size_t GlobalInstances{ 0u };
 
 /* Static methods for usrsctp global callbacks. */
 
-inline static int onSendSctpData(void* addr, void* data, size_t len, uint8_t /*tos*/, uint8_t /*setDf*/)
+static int onSendSctpData(void* addr, void* data, size_t len, uint8_t /*tos*/, uint8_t /*setDf*/)
 {
+	MS_TRACE();
+
 	auto* sctpAssociation = DepUsrSCTP::RetrieveSctpAssociation(reinterpret_cast<uintptr_t>(addr));
 
 	if (!sctpAssociation)
 	{
 		MS_WARN_TAG(sctp, "no SctpAssociation found");
 
+		DepUsrSCTP::HandleUsrSctpTimers();
+
+		// TODO: Why are we returning -1 here? What does it tell usrsctp?
+		// If the SctpAssociation doesn't exist anymore we don't want that usrscp
+		// insists.
 		return -1;
 	}
 
 	sctpAssociation->OnUsrSctpSendSctpData(data, len);
 
 	// NOTE: Must not free data, usrsctp lib does it.
 
+	DepUsrSCTP::HandleUsrSctpTimers();
+
 	return 0;
 }
 
 // Static method for printing usrsctp debug.
-inline static void sctpDebug(const char* format, ...)
+static void sctpDebug(const char* format, ...)
 {
+	MS_TRACE();
 	char buffer[10000];
 	va_list ap;
 
@@ -207,6 +216,13 @@ RTC::SctpAssociation* DepUsrSCTP::RetrieveSctpAssociation(uintptr_t id)
 	return it->second;
 }
 
+void DepUsrSCTP::HandleUsrSctpTimers()
+{
+	MS_TRACE();
+
+	DepUsrSCTP::checker->HandleUsrSctpTimers();
+}
+
 /* DepUsrSCTP::Checker instance methods. */
 
 DepUsrSCTP::Checker::Checker() : timer(new TimerHandle(this))
@@ -229,7 +245,7 @@ void DepUsrSCTP::Checker::Start()
 
 	this->lastCalledAtMs = 0u;
 
-	this->timer->Start(CheckerInterval, CheckerInterval);
+	HandleUsrSctpTimers();
 }
 
 void DepUsrSCTP::Checker::Stop()
@@ -243,10 +259,23 @@ void DepUsrSCTP::Checker::Stop()
 	this->timer->Stop();
 }
 
+void DepUsrSCTP::Checker::HandleUsrSctpTimers()
+{
+	MS_TRACE();
+
+	auto timeout = static_cast<uint64_t>(usrsctp_get_timeout());
+
+	MS_DUMP("------ starting timer with usrsctp timeout: %" PRIu64 " ms", timeout);
+
+	this->timer->Start(timeout);
+}
+
 void DepUsrSCTP::Checker::OnTimer(TimerHandle* /*timer*/)
 {
 	MS_TRACE();
 
+	MS_DUMP("------ onTimer!");
+
 	auto nowMs          = DepLibUV::GetTimeMs();
 	const int elapsedMs = this->lastCalledAtMs ? static_cast<int>(nowMs - this->lastCalledAtMs) : 0;
 
@@ -267,4 +296,6 @@ void DepUsrSCTP::Checker::OnTimer(TimerHandle* /*timer*/)
 #endif
 
 	this->lastCalledAtMs = nowMs;
+
+	HandleUsrSctpTimers();
 }

worker/src/RTC/SctpAssociation.cpp

@@ -390,6 +390,10 @@ namespace RTC
 #endif
 
 		usrsctp_conninput(reinterpret_cast<void*>(this->id), data, len, 0);
+
+		// TODO: IMHO it makes sense that we handle/refresh usrsctp timers when
+		// SCTP data is received.
+		DepUsrSCTP::HandleUsrSctpTimers();
 	}
 
 	void SctpAssociation::SendSctpMessage(

worker/subprojects/usrsctp.wrap

@@ -1,8 +1,8 @@
 [wrap-file]
-directory = usrsctp-ebb18adac6501bad4501b1f6dccb67a1c85cc299
-source_url = https://github.com/sctplab/usrsctp/archive/ebb18adac6501bad4501b1f6dccb67a1c85cc299.zip
-source_filename = ebb18adac6501bad4501b1f6dccb67a1c85cc299.zip
-source_hash = e77a855ce395b877e9f2aa7ebe070dfaf5cb11cfecdeb424cc876fc0d98e5d11
+directory = usrsctp-0.9.6.0
+source_url = https://github.com/versatica/usrsctp/archive/refs/tags/0.9.6.0.zip
+source_filename = usrsctp-0.9.6.0.zip
+source_hash = 13518f1912631c796da167ba3c3e4fd7f80886de4afa75abc6fcf843160b65f8
 
 [provide]
 usrsctp = usrsctp_dep