Adventures in UPnP with Curl and Netcat

UPnP for port mapping is such a nice, convenient security hole. There have been a few cases where I have needed to forward a port without access to the router's WebUI and 8/10 times, in a residential setting, UPnP saves the day. I normally use miniupnpc, but it's pretty cool seeing this done with curl.

My home fiber connection is unfortunately behind a CGNAT. However, I was surprised the other day that somehow Valheim/Playfab was able to punch a hole through both my NAT and the CGNAT. I'm assuming this is some sort of UPnP trickery, but I haven't been able to determine if it's the application's doing or my gateway sending a request to the CGNAT.

I am almost full IPv6 for what I am using on the net.<p>But... Hacker News, Slashdot... wink! wink! ping6! ping6! PleaAaaaaAase!<p>But the time at which I will FINALLY disable ipv4 is getting really close now.