Add NATSymmetricUDPFirewall to punchable NATs #5931
NATSymmetricUDPFirewall actually is not NAT at all, but means the machine has a global IP address and an UDP firewall in front (RFC calls it Symmetric UDP Firewall). This is punchable fine, both theoretically and also practically in testing.
See https://forum.syncthing.net/t/issues-with-quic-transport/13590/6 , this allows to use QUIC also for hosts which are behind an UDP firewall with a global IP address.
I tested with a host behind a
If this is a user visible change (including API and protocol changes), add a link here
Your name and email will be added automatically to the AUTHORS file