Media Level Fingerprints Configuration Option

This commit adds an option to put DTLS Fingerprint specification
at the media description level rather then the session description
level. This enhances compatibility with some 3rd party webrtc
implementations (notably Kurento).

settingengine.go

@@ -48,6 +48,7 @@ type SettingEngine struct {
 		SRTP  *uint
 		SRTCP *uint
 	}
+	sdpMediaLevelFingerprints                 bool
 	answeringDTLSRole                         DTLSRole
 	disableCertificateFingerprintVerification bool
 	disableSRTPReplayProtection               bool
@@ -236,3 +237,11 @@ func (e *SettingEngine) DisableSRTPReplayProtection(isDisabled bool) {
 func (e *SettingEngine) DisableSRTCPReplayProtection(isDisabled bool) {
 	e.disableSRTCPReplayProtection = isDisabled
 }
+
+// SetSDPMediaLevelFingerprints configures the logic for DTLS Fingerprint insertion
+// If true, fingerprints will be inserted in the sdp at the fingerprint
+// level, instead of the session level. This helps with compatibility with
+// some webrtc implementations.
+func (e *SettingEngine) SetSDPMediaLevelFingerprints(sdpMediaLevelFingerprints bool) {
+	e.sdpMediaLevelFingerprints = sdpMediaLevelFingerprints
+}