Summary

Fixes UDPxy stream URL rewriting so multicast streams are detected by parsing the stream URL instead of only matching the udp://@ prefix.

Previously, Threadfin only rewrote URLs beginning with udp://@. That missed valid multicast RTP URLs such as rtp://239.3.1.54:4120, causing /stream/... to redirect clients back to the original multicast URL even when Settings > UDPxy address was configured.

What changed

• Rewrites multicast streams for both udp and rtp schemes.
• Parses the stream host and only rewrites when it is an IP multicast address.
• Leaves hostnames, unicast IPs, and non-UDP/RTP streams unchanged.
• Supports IPv4 multicast and bracketed IPv6 multicast addresses.
• Allows UDPxy address to be either host:port, http://host:port, or https://host:port.
• Keeps the legacy host:port behavior by defaulting it to http://host:port.
• Updates the settings text to document the accepted UDPxy address forms.
• Adds unit tests for UDP/RTP, IPv4/IPv6 multicast, unicast, hostnames, and HTTP/HTTPS UDPxy base URLs.

msd_lite compatibility

This also makes Threadfin work with msd_lite in UDPxy-compatible mode. msd_lite supports UDPxy-style /udp/ and /rtp/ request paths and adds IPv6 multicast support. With this change, Threadfin can generate compatible URLs such as:

rtp://239.3.1.54:4120
-> http://<udpxy>/rtp/239.3.1.54:4120/

rtp://[ff15::1]:4120
-> http://<udpxy>/rtp/[ff15::1]:4120/

If the configured UDPxy/msd_lite endpoint uses HTTPS, Threadfin now preserves that scheme:

https://<msd_lite>/rtp/[ff15::1]:4120/

Verification

env GOCACHE=/private/tmp/threadfin-go-build GOMODCACHE=/private/tmp/threadfin-go-mod go test -mod=readonly ./...