[ios] [CupertinoClient] http connection issue: nw_path_necp_check_for_updates Failed to copy updated result (22)

[delfme]

We are facing http connection issue when using CupertinoClient.

CC: @brianquinlan would you be so kind as to take a quick look at this? Just noticed you might know why this occurs.

To reproduce:

• create a CupertinoClient as per code below
• make http connection to whatever web api
• http client will stall and console will print this error:
  console nw_path_necp_check_for_updates Failed to copy updated result (22)

Note: Issue occurs frequently if device is connected to Internet via a VPN.

It seems this issue occurred also in the past, maybe a regression?
flutter/flutter#111940

Code sample

Code is simple, as per instructions from http package Readme.
Use below ConnectionService.client to call whatever rest api on iOS.
Note: We needed to use CupertinoClient coz connectivity with standard dart client was pretty unstable.

class ConnectionService {
  static const String _debugPrefix = 'ConnectionService:';

  static final config = URLSessionConfiguration.ephemeralSessionConfiguration()
    ..allowsCellularAccess = false
    ..allowsConstrainedNetworkAccess = false
    ..allowsExpensiveNetworkAccess = false;

  // Initialize client. It will be CupertinoClient on iOS and IOClient on android
  static dynamic client = (Platform.isIOS) ? CupertinoClient.fromSessionConfiguration(config)
      : IOClient();

Logs

Error from console is: console nw_path_necp_check_for_updates Failed to copy updated result (22)
Note: We have this issue with both cupertino_http: 1.0.0 and 0.1.2

Flutter doctor

[✓] Flutter (Channel master, 3.12.0-7.0.pre.22, on macOS 12.6.5 21G531 darwin-arm64, locale en-IT)
[!] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
✗ cmdline-tools component is missing
Run path/to/sdkmanager --install "cmdline-tools;latest"
See https://developer.android.com/studio/command-line for more details.
✗ Android license status unknown.
Run flutter doctor --android-licenses to accept the SDK licenses.
See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.
[✓] Xcode - develop for iOS and macOS (Xcode 14.0.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2022.2)
[✓] Connected device (3 available)
[✓] Network resources

[brianquinlan]

Hi @delfme ,

I'm not sure why this happens?

Does this happen while your app is in the foreground, background or both?

Do you have the com.apple.security.network.client entitlement set?

[delfme]

Hi @brianquinlan thx for the kind support!

It surely happens while app is in foreground. Couldn't check what happens with app in background.

I added com.apple.security.network.client to entitlement.
Couldn't find it from capabilities panel (is that a config. issue?), so added it manually to Runner.entitlements files (pic below). Is that the same?

Will test things and revert.

[brianquinlan]

Actually, the entitlement is not relevant for your configuration.

There isn't really much for me to use to diagnose the problem here. Do you see an error if you use IOClient?

[delfme]

Issue with IOClient was slow connection time on iOS and being a bit unstable.
That brought us to turn to CupertinoClient.

[delfme]

It would be great if CupertinoClient could be tested more under VPN and different network condition.
The feeling is that there is a minor bug that is somehow triggered by these conditions.

[brianquinlan]

Since CupertinoClient relies on Apple APIs for network transport, any bugs related to network conditions would most likely be related to those APIs.

Regarding #972 (comment) - I meant have you tested the scenario that demonstrates this bug using IOClient?

[andynewman10]

I am having the same issue. No http request is failing properly speaking, and I also see that keep-alive is working as expected.

Still, I can see there is an important slowdown when running my application, at least in debug mode (USB debugging).

Not sure it is related but - more worrying perhaps - I am sometimes seeing lots (and I say lots) of

[Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection]

errors, as reported in the comments here:

https://stackoverflow.com/questions/76397964/client-called-nw-connection-copy-protocol-metadata-internal-on-unconnected-nw-co

My setup is described in the comments in the link above. I am using http 1.1.0.

I can't recall what triggered this new behavior.

[andynewman10]

Since CupertinoClient relies on Apple APIs for network transport, any bugs related to network conditions would most likely be related to those APIs.

Regarding #972 (comment) - I meant have you tested the scenario that demonstrates this bug using IOClient?

@brianquinlan Yes, there is the bug when simply using IOClient on iOS. I can reproduce the bug on iOS 16.6 with the following setup:

• connecting to a LAN machine through plain http.
• the HTTP server is hosted by a WAMP server on a Windows 11 machine that only has IPv4 enabled
• the iOS device has both an IPv4 and IPv6 address.

To reproduce the problem, issue eg. 100 http requests with, say, a 1-second interval. From times to times, you will see the issue.