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We have a relatively simple app that using Network.Framework, NWConnection, NWEndpoint to setup TCP connections with nearby devices also using the app. It's actually been working great for a while now but we've recently noticed with iOS 17.4/17.4.1 that we're spontaneously getting:
nw_proto_tcp_route_init [C6:3] no mtu received
sometimes the [C6:3] will be [C7:3] or another similar code. We may also occasionally see No route to Host appear in our console logs though this isn't definite. After this point the connection is effectively lost but we don't actually receive any updates on our NWConnection stateUpdateHandler to action on. It's sort of dead in the water so to speak.
We've reproduced this issue with multiple devices on iOS 17.4.x and in multiple network settings (in office, cafe, home networks...etc). Nothing seems to make a difference. Any ideas on how to fix or workaround this?
I saw a similar issue here: https://developer.apple.com/forums/thread/669519 but the original author never followed up and it's around 3 years old. I've captured a sysdiagnose log and can submit an issue if it warrants filing a bug report.