feat: pass custom ICE ufrag and pwd as local description init

Adds an optional second argument to `rtc::PeerConnection::setLocalDescription`
that can contain an ICE ufrag and pwd that if passed will be used in place
of the randomly generated versions.

Refs: paullouisageneau#1166
Refs: paullouisageneau#1201 (comment)

include/rtc/peerconnection.hpp

@@ -35,6 +35,12 @@ struct RTC_CPP_EXPORT DataChannelInit {
 	string protocol = "";
 };
 
+struct RTC_CPP_EXPORT LocalDescriptionInit {
+    Description::Type type = Description::Type::Unspec;
+    optional<string> iceUfrag;
+    optional<string> icePwd;
+};
+
 class RTC_CPP_EXPORT PeerConnection final : CheshireCat<impl::PeerConnection> {
 public:
 	enum class State : int {
@@ -90,7 +96,7 @@ class RTC_CPP_EXPORT PeerConnection final : CheshireCat<impl::PeerConnection> {
 	uint16_t maxDataChannelId() const;
 	bool getSelectedCandidatePair(Candidate *local, Candidate *remote);
 
-	void setLocalDescription(Description::Type type = Description::Type::Unspec);
+	void setLocalDescription(Description::Type type = Description::Type::Unspec, LocalDescriptionInit init = {});
 	void setRemoteDescription(Description description);
 	void addRemoteCandidate(Candidate candidate);
 	void gatherLocalCandidates(std::vector<IceServer> additionalIceServers = {});

src/impl/icetransport.cpp

@@ -140,6 +140,10 @@ IceTransport::IceTransport(const Configuration &config, candidate_callback candi
 			addIceServer(server);
 }
 
+void IceTransport::setUfragAndPwd(string uFrag, string pwd) {
+	juice_set_local_ice_attributes(mAgent.get(), uFrag.c_str(), pwd.c_str());
+}
+
 void IceTransport::addIceServer(IceServer server) {
 	if (server.hostname.empty())
 		return;

src/impl/icetransport.hpp

@@ -51,6 +51,7 @@ class IceTransport : public Transport {
 	void setRemoteDescription(const Description &description);
 	bool addRemoteCandidate(const Candidate &candidate);
 	void gatherLocalCandidates(string mid, std::vector<IceServer> additionalIceServers = {});
+	void setUfragAndPwd(string uFrag, string pwd);
 
 	optional<string> getLocalAddress() const;
 	optional<string> getRemoteAddress() const;

src/peerconnection.cpp

@@ -76,7 +76,7 @@ bool PeerConnection::hasMedia() const {
 	return local && local->hasAudioOrVideo();
 }
 
-void PeerConnection::setLocalDescription(Description::Type type) {
+void PeerConnection::setLocalDescription(Description::Type type, LocalDescriptionInit init) {
 	std::unique_lock signalingLock(impl()->signalingMutex);
 	PLOG_VERBOSE << "Setting local description, type=" << Description::typeToString(type);
 
@@ -140,6 +140,11 @@ void PeerConnection::setLocalDescription(Description::Type type) {
 	if (!iceTransport)
 		return; // closed
 
+	if (init.iceUfrag && init.icePwd) {
+		PLOG_DEBUG << "Using custom ufrag/pwd";
+		iceTransport->setUfragAndPwd(init.iceUfrag.value(), init.iceUfrag.value());
+	}
+
 	Description local = iceTransport->getLocalDescription(type);
 	impl()->processLocalDescription(std::move(local));