Getting connection reset on 53/tcp

Still testing my DNS service and UDP query responses have been 100% for the past week which is great.

However, I’ve just tested DNS TCP and unfortunately it no longer seems to work. E.g.,:

$ dig @213.188.193.79 wombatsoftware.com +tcp
;; communications error to 213.188.193.79#53: connection reset

My DNS server is running both 53/udp and 53/tcp and they’re both configured in my fly.toml. App name is slickdns.

Weirdly the 53/tcp port is configured as the health check and all instances are showing healthy…

@jbarham Sorry about this. Looks like a change we made had unforeseen consequences for port 53. We reverted the commit after much debugging and it appears to be working properly again.

Fix confirmed. Thanks!

This is mostly my fault, for what it’s worth; we built an off-network infrastructure for monitoring UDP DNS a few weeks ago, and I should have done TCP at the same time (UDP is routed differently than TCP in our network and so I had a lot of specific UDP things I wanted to monitor, and it got away from me.)

We should end the weekend with monitoring that pages me out of bed if 53/tcp starts getting routed weirdly.