Properly set remote data mid

include/rtc/description.hpp

@@ -49,6 +49,7 @@ public:
 	bool ended() const;
 
 	void hintType(Type type);
+	void setDataMid(string mid);
 	void setFingerprint(string fingerprint);
 	void setSctpPort(uint16_t port);
 	void setMaxMessageSize(size_t size);

src/description.cpp

@@ -163,6 +163,8 @@ void Description::hintType(Type type) {
 	}
 }
 
+void Description::setDataMid(string mid) { mData.mid = mid; }
+
 void Description::setFingerprint(string fingerprint) {
 	mFingerprint.emplace(std::move(fingerprint));
 }
@@ -216,6 +218,8 @@ string Description::generateSdp(const string &eol) const {
 		sdp << " " << m.first; // mid
 	sdp << " " << mData.mid << eol;
 
+	sdp << "a=msid-semantic: WMS" << eol;
+
 	// Data
 	const string dataDescription = "UDP/DTLS/SCTP webrtc-datachannel";
 	sdp << "m=application" << ' ' << (!mMedia.empty() ? 0 : 9) << ' ' << dataDescription << eol;
@@ -249,11 +253,14 @@ string Description::generateSdp(const string &eol) const {
 	}
 
 	// Common
-	sdp << "a=ice-options:trickle" << eol;
+	if (!mEnded)
+		sdp << "a=ice-options:trickle" << eol;
+
 	sdp << "a=ice-ufrag:" << mIceUfrag << eol;
 	sdp << "a=ice-pwd:" << mIcePwd << eol;
 	sdp << "a=setup:" << roleToString(mRole) << eol;
 	sdp << "a=tls-id:1" << eol;
+
 	if (mFingerprint)
 		sdp << "a=fingerprint:sha-256 " << *mFingerprint << eol;
 

src/peerconnection.cpp

@@ -594,14 +594,20 @@ void PeerConnection::remoteCloseDataChannels() {
 
 void PeerConnection::processLocalDescription(Description description) {
 	std::optional<uint16_t> remoteSctpPort;
-	if (auto remote = remoteDescription())
-		remoteSctpPort = remote->sctpPort();
+	std::optional<string> remoteDataMid;
+	if (auto remote = remoteDescription()) {
+		remoteDataMid = remote->dataMid();
+	    remoteSctpPort = remote->sctpPort();
+	}
 
 	auto certificate = mCertificate.get(); // wait for certificate if not ready
 
 	{
 		std::lock_guard lock(mLocalDescriptionMutex);
 		mLocalDescription.emplace(std::move(description));
+		if (remoteDataMid)
+			mLocalDescription->setDataMid(*remoteDataMid);
+
 		mLocalDescription->setFingerprint(certificate->fingerprint());
 		mLocalDescription->setSctpPort(remoteSctpPort.value_or(DEFAULT_SCTP_PORT));
 		mLocalDescription->setMaxMessageSize(LOCAL_MAX_MESSAGE_SIZE);