Add INCLUDE_LOOPBACK_CANDIDATE

Allow users to enable listening for WebRTC traffic on loopback

README.md

@@ -208,6 +208,7 @@ The backend can be configured with the following environment variables.
 - `INTERFACE_FILTER` - Only use a certain interface for UDP traffic
 - `NAT_ICE_CANDIDATE_TYPE` - By default setting a NAT_1_TO_1_IP overrides. Set this to `srflx` to instead append IPs
 - `STUN_SERVERS` - List of STUN servers delineated by '|'. Useful if Broadcast Box is running behind a NAT
+- `INCLUDE_LOOPBACK_CANDIDATE` - Also listen for WebRTC traffic on loopback, disabled by default
 
 - `UDP_MUX_PORT_WHEP` - Like `UDP_MUX_PORT` but only for WHEP traffic
 - `UDP_MUX_PORT_WHIP` - Like `UDP_MUX_PORT` but only for WHIP traffic

internal/webrtc/webrtc.go

@@ -273,6 +273,7 @@ func createSettingEngine(isWHIP bool, udpMuxCache map[int]*ice.MultiUDPMuxDefaul
 	settingEngine.SetNetworkTypes(networkTypes)
 	settingEngine.DisableSRTCPReplayProtection(true)
 	settingEngine.DisableSRTPReplayProtection(true)
+	settingEngine.SetIncludeLoopbackCandidate(os.Getenv("INCLUDE_LOOPBACK_CANDIDATE") != "")
 
 	return
 }