Hi, I have been working on the app that implements DNS Proxy Extension for a while now, and after a couple builds to TestFlight I noticed that I got a couple crashes that seem to be triggered by EXC_BREAKPOINT (SIGTRAP)
After some investigation, it was found that crashes are connected to CFNetwork framework. So, I decided to additionally look into memory issues, but I found the app has no obvious memory leaks, no memory regression (within recommended 25%, actual value is at 20% as of right now), but the app still uses 11mb of memory footprint and most of it (6.5 mb is Swift metadata).
At this point, not sure what's triggering those crashes, but I noticed that sometimes app will return message like this to the console (this example is for PostHog api that I use in the app):
Task <0ABDCF4A-9653-4583-9150-EC11D852CA9E>.<1> finished with error [18 446 744 073 709 550 613] Error Domain=NSURLErrorDomain Code=-1003 "A server with the specified hostname could not be found." UserInfo={_kCFStreamErrorCodeKey=8, NSUnderlyingError=0x1072df0f0 {Error Domain=kCFErrorDomainCFNetwork Code=-1003 "(null)" UserInfo={_kCFStreamErrorDomainKey=12, _kCFStreamErrorCodeKey=8, _NSURLErrorNWResolutionReportKey=Resolved 0 endpoints in 2ms using unknown from cache, _NSURLErrorNWPathKey=satisfied (Path is satisfied), interface: en0[802.11], ipv4, dns, uses wifi}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalUploadTask <0ABDCF4A-9653-4583-9150-EC11D852CA9E>.<1>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
"LocalUploadTask <0ABDCF4A-9653-4583-9150-EC11D852CA9E>.<1>"
), NSLocalizedDescription=A server with the specified hostname could not be found., NSErrorFailingURLStringKey=https://us.i.posthog.com/batch, NSErrorFailingURLKey=https://us.i.posthog.com/batch, _kCFStreamErrorDomainKey=12}
If DNS Proxy Provider uses custom DoH server for resolving packets, could the cache policy for URLSession be a reason?
I had a couple other ideas (HTTP3 failure, CFNetwork core issues like described here) but not sure if they are valid
Would be grateful if someone could give me a hint of what I should look at
In my case, Filter Control Provider writes data received from MDM configuration profile, then Filter Data Provider reads this data to use it for flow filtering.
OK. That should be possible by putting the data into an app group. The control provider will have read/write access to that app group; the data provider will only be able to read it.
And, yes, you will need some sort of concurrency control there (-:
But my Filter Data Provider also writes some data about intercepted flow, that is later used for resolving them.
As long as this only needs to be read back by the data provider, you’re all good. Just put the data into the data provider’s container.
You still might need concurrency control though, although it’s only intra-process concurrency control. That is, multiple threads within the data provider might be accessing this data and you have to make sure they don’t stomp on each other.
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