@DTS Engineer I found another Intel based Mac to test on and it also did not work so for now let's say that the Intel vs Apple Silicon is a red herring and continue to look at this as a 15.1.1 issue alone. Scott

@DTS Engineer So there is nothing else? The fact that our software worked just fine on 15.0 when it first came out and the ONLY thing that changed is upgrading to 15.1.1 points specifically to an issue on the macOS side. I have tested this on various machines, even a brand new out of the box Macbook Air, and get the same results. The fact that no packets are even making it to the TUN interface (via wireshark) points to something in the OS and not our client, correct? Especially when it worked on 15.0. I want to submit a Code Level support ticket but extracting out the code into a focused Xcode project is going to be time consuming.

@DTS Engineer One last question (I guess) do you see anything in how the PTP is configured above that would cause an issue?

@DTS Engineer Thank you for all your help on this. I am going to close this as answered. In debugging I found that a thread in the extension was actually throwing a BAD_INSTRUCTION error in the OpenSSL lib we were using. After upgrading to a new version of OpenSSL that fixed the BAD_INSTRUCTION everything now works. Of course the mystery is why does the same client work just fine on 14.x but 15.x it did not? No matter it seems to be working now and that is all that matters. :-) Again thank you.

@DTS Engineer Completely agree and why I was doing a very intensive code inspection, prior to finding the assert, to make sure things under our control were being alloc'd correctly and that there were no memory stomps. Unfortunately when you have Customers yelling at you, you have to take the win and hope you don't have a ticking time bomb and then move forward with this in the back of your mind. It's the way of the SW world. :-)