Android `fetch` hangs indefinitely with IPv6 hosts on some devices (Happy Eyeballs)

[andreialecu]

Description

This is a very bizarre issue that has been previously reported a bunch of times, and this is basically a continuation of:

#29608

I initially started running into this on RN 0.66 with AWS Cognito. Bumping to 0.66.3 didn't help.

I'm also pretty sure this used to work before and I'm not sure when it broke. It's on an app that has been shelved for a while.

The problem is very strange because the network request does not seem to be issued, but simply hitting CMD+S to save any file so that a hot-reload is issued will immediately dispatch the network request.

I discovered the promise hanging issue by adding some logs to the fetch calls the cognito library was doing:

Notice how the .then is not executed.

While troubleshooting I came across a mention here of a workaround: #29608 (comment) (courtesy of @danmaas) which seems to completely resolve the issue.

Here's the same .then correctly being executed after applying that patch:

Version

0.66.3

Output of react-native info

System:
    OS: macOS 12.0.1
    CPU: (8) arm64 Apple M1
    Memory: 142.27 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.13.0 - /private/var/folders/9p/k1yqxx0d7rn1nlztg_wm7sbw0000gn/T/xfs-2dcae145/node
    Yarn: 2.4.0-git.20210330.hash-ebcd71d5 - /private/var/folders/9p/k1yqxx0d7rn1nlztg_wm7sbw0000gn/T/xfs-2dcae145/yarn
    npm: 7.20.1 - ~/.nvm/versions/node/v16.13.0/bin/npm
    Watchman: 2021.11.01.00 - /opt/homebrew/bin/watchman
  Managers:
    CocoaPods: 1.11.0 - /Users/andreialecu/.rbenv/shims/pod
  SDKs:
    iOS SDK:
      Platforms: DriverKit 21.0.1, iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0
    Android SDK: Not Found
  IDEs:
    Android Studio: 4.2 AI-202.7660.26.42.7351085
    Xcode: 13.1/13A1030d - /usr/bin/xcodebuild
  Languages:
    Java: 11.0.8 - /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/javac
  npmPackages:
    @react-native-community/cli: Not Found
    react: 17.0.2 => 17.0.2 
    react-native: 0.66.3 => 0.66.3 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps to reproduce

I'm able to reproduce it with this:

  React.useEffect(() => {
    console.log('confirm start', new Date());
    fetch('https://cognito-idp.eu-west-1.amazonaws.com/', {
      method: 'POST',
      mode: 'cors',
    })
      .then(() => console.log('then', new Date()))
      .catch(() => console.log('catch', new Date()));
    setTimeout(() => {
      console.log('5 seconds passed');
    }, 5000);
  }, []);

Output:

After applying #29608 (comment):

Snack, code example, screenshot, or link to a repository

No response

Skip to this comment for the actual cause: #32730 (comment)

[andreialecu]

Note that this doesn't repro on the emulator, this is the output on the emulator:

 LOG  confirm x 2021-12-09T18:44:08.229Z
 LOG  then x 2021-12-09T18:44:08.607Z
 LOG  5 seconds passed

❗ The device where this is happening, and where I initially noticed it on is an Oppo A72 (CPH2067) running Android 11

[andreialecu]

I'm also not able to reproduce it on a Samsung Galaxy Tab A (SM-T290) device.

[danmaas]

In my case, this issue also affected only some devices. I think it has something to do with the network stack or driver on the device. Or how they interact with IPv6 devices out on the network.

[andreialecu]

Interesting. I left it running for a while and it actually seems to time out on the connection:

 LOG  confirm x 2021-12-09T19:00:10.557Z
 LOG  5 seconds passed
 LOG  then x 2021-12-09T19:04:23.177Z

It took 4 minutes to time out.

I just noticed that the device does not have IPv6 connectivity at all based on https://test-ipv6.com/

Might be a router problem on my end, usually I have IPv6. However, I'm not sure why it would even attempt to use an IPv6 address considering it does not have IPv6 connectivity at all.

[andreialecu]

Very interesting, I rebooted the router and now I have IPv6 again.

❗ The Oppo now no longer has the error. It works perfectly:

 LOG  confirm x 2021-12-09T19:28:07.714Z
 LOG  then x 2021-12-09T19:28:09.217Z
 LOG  5 seconds passed

I'm not sure what to make of this. 🤔

[vamper424]

Yo mismo me encargo de resolver lo de sus vidas, ni hay ni habrá problema alguno, temor alguno o alguien que me agreda saludo sigan igual y cada vez mejoren más, ok. Si se puede. Atte: Jesus Francisco Urias García.

[vamper424]

Y nuevamente tu gol, esta vez artificial.

[vamper424]

Jajaja mediocres ellos, sobre ellos.