Firebase app seems to bypass proxy

### Description

A client of mine wants to use our iPadOS app behind a proxy. While all normal connections to firebase work, all subscriptions to firestore do not work. The client reported that they can see in the firewall that some connections are bypassing the http proxy (WinGate), and directly use tcp, which is then blocked by the firewall. The connection to the proxy is configured in the iPad settings.

So my question is, whether it is possible to make the subscriptions go through the http proxy or just use http directly, which should already force it to through the proxy. Interestingly, the web version of our app that uses the same firebase backend works without problems. Any pointers are greatly appreciated!

Note: I was in contact with firebase support already as was directed towards GitHub.

## Related issues

- https://github.com/firebase/firebase-ios-sdk/issues/2364
- https://stackoverflow.com/questions/52441316/firestore-grpc-behind-a-corporate-firewall-proxy
- https://stackoverflow.com/questions/58411376/static-ip-to-access-gcp-machine-learning-apis-via-grpc-stream-over-http-2/58536630#58536630

### Reproducing the issue

Unfortunately, I can not reproduce the problem in my local network.

### Firebase SDK Version

10.20.0

### Xcode Version

15.2

### Installation Method

Swift Package Manager

### Firebase Product(s)

Firestore

### Targeted Platforms

iOS

### Relevant Log Output

_No response_

### If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

```json

{
"pins" : [
{
"identity" : "abseil-cpp-binary",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/abseil-cpp-binary.git",
"state" : {
"revision" : "bfc0b6f81adc06ce5121eb23f628473638d67c5c",
"version" : "1.2022062300.0"
}
},
{
"identity" : "alamofire",
"kind" : "remoteSourceControl",
"location" : "https://github.com/Alamofire/Alamofire.git",
"state" : {
"revision" : "78424be314842833c04bc3bef5b72e85fff99204",
"version" : "5.6.4"
}
},
{
"identity" : "app-check",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/app-check.git",
"state" : {
"revision" : "3e464dad87dad2d29bb29a97836789bf0f8f67d2",
"version" : "10.18.1"
}
},
{
"identity" : "cryptoswift",
"kind" : "remoteSourceControl",
"location" : "https://github.com/krzyzanowskim/CryptoSwift.git",
"state" : {
"revision" : "19b3c3ceed117c5cc883517c4e658548315ba70b",
"version" : "1.6.0"
}
},
{
"identity" : "firebase-ios-sdk",
"kind" : "remoteSourceControl",
"location" : "https://github.com/firebase/firebase-ios-sdk.git",
"state" : {
"revision" : "b880ec8ec927a838c51c12862c6222c30d7097d7",
"version" : "10.20.0"
}
},
{
"identity" : "googleappmeasurement",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/GoogleAppMeasurement.git",
"state" : {
"revision" : "ceec9f28dea12b7cf3dabf18b5ed7621c88fd4aa",
"version" : "10.20.0"
}
},
{
"identity" : "googledatatransport",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/GoogleDataTransport.git",
"state" : {
"revision" : "a732a4b47f59e4f725a2ea10f0c77e93a7131117",
"version" : "9.3.0"
}
},
{
"identity" : "googleutilities",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/GoogleUtilities.git",
"state" : {
"revision" : "bc27fad73504f3d4af235de451f02ee22586ebd3",
"version" : "7.12.1"
}
},
{
"identity" : "grpc-binary",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/grpc-binary.git",
"state" : {
"revision" : "a673bc2937fbe886dd1f99c401b01b6d977a9c98",
"version" : "1.49.1"
}
},
{
"identity" : "gtm-session-fetcher",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/gtm-session-fetcher.git",
"state" : {
"revision" : "5ccda3981422a84186387dbb763ba739178b529c",
"version" : "2.3.0"
}
},
{
"identity" : "interop-ios-for-google-sdks",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/interop-ios-for-google-sdks.git",
"state" : {
"revision" : "2d12673670417654f08f5f90fdd62926dc3a2648",
"version" : "100.0.0"
}
},
{
"identity" : "iqkeyboardmanager",
"kind" : "remoteSourceControl",
"location" : "https://github.com/hackiftekhar/IQKeyboardManager.git",
"state" : {
"revision" : "1e442766a41e2948df25559eb03ab752c6d3aad0",
"version" : "6.5.0"
}
},
{
"identity" : "leveldb",
"kind" : "remoteSourceControl",
"location" : "https://github.com/firebase/leveldb.git",
"state" : {
"revision" : "0706abcc6b0bd9cedfbb015ba840e4a780b5159b",
"version" : "1.22.2"
}
},
{
"identity" : "lottie-spm",
"kind" : "remoteSourceControl",
"location" : "https://github.com/airbnb/lottie-spm.git",
"state" : {
"revision" : "26d84192430ed5b104d64b8086872bb4979d65a4",
"version" : "4.4.0"
}
},
{
"identity" : "nanopb",
"kind" : "remoteSourceControl",
"location" : "https://github.com/firebase/nanopb.git",
"state" : {
"revision" : "819d0a2173aff699fb8c364b6fb906f7cdb1a692",
"version" : "2.30909.0"
}
},
{
"identity" : "promises",
"kind" : "remoteSourceControl",
"location" : "https://github.com/google/promises.git",
"state" : {
"revision" : "e70e889c0196c76d22759eb50d6a0270ca9f1d9e",
"version" : "2.3.1"
}
},
{
"identity" : "sdwebimage",
"kind" : "remoteSourceControl",
"location" : "https://github.com/SDWebImage/SDWebImage.git",
"state" : {
"revision" : "c51ba84499268ea3020e6aee9e229c0f56b9d924",
"version" : "5.16.0"
}
},
{
"identity" : "sdwebimageswiftui",
"kind" : "remoteSourceControl",
"location" : "https://github.com/SDWebImage/SDWebImageSwiftUI",
"state" : {
"revision" : "e837c37d45449fbd3b4745c10c5b5274e73edead",
"version" : "2.2.3"
}
},
{
"identity" : "semaphore",
"kind" : "remoteSourceControl",
"location" : "https://github.com/groue/Semaphore",
"state" : {
"revision" : "f1c4a0acabeb591068dea6cffdd39660b86dec28",
"version" : "0.0.8"
}
},
{
"identity" : "starscream",
"kind" : "remoteSourceControl",
"location" : "https://github.com/daltoniam/Starscream.git",
"state" : {
"revision" : "ac6c0fc9da221873e01bd1a0d4818498a71eef33",
"version" : "4.0.6"
}
},
{
"identity" : "swift-power-assert",
"kind" : "remoteSourceControl",
"location" : "https://github.com/kishikawakatsumi/swift-power-assert",
"state" : {
"revision" : "2fa10dcbbff807fad73b4e2469b43300a50e9bbc",
"version" : "0.12.0"
}
},
{
"identity" : "swift-protobuf",
"kind" : "remoteSourceControl",
"location" : "https://github.com/apple/swift-protobuf.git",
"state" : {
"revision" : "ab3a58b7209a17d781c0d1dbb3e1ff3da306bae8",
"version" : "1.20.3"
}
},
{
"identity" : "swift-syntax",
"kind" : "remoteSourceControl",
"location" : "https://github.com/apple/swift-syntax.git",
"state" : {
"revision" : "ffa3cd6fc2aa62adbedd31d3efaf7c0d86a9f029",
"version" : "509.0.1"
}
},
{
"identity" : "viewinspector",
"kind" : "remoteSourceControl",
"location" : "https://github.com/nalexn/ViewInspector",
"state" : {
"branch" : "0.9.8",
"revision" : "c4e73093f926247fd5805e53d3fe4b523e605502"
}
}
],
"version" : 2
}
```

### If using CocoaPods, the project's Podfile.lock

_No response_

No repository file, test, or entry point is named. Start by reviewing the Firestore subscription path and related issue 2364, then reproduce on iPadOS with Firebase SDK 10.20.0 behind the reported WinGate proxy; done means determining whether subscriptions honor the system proxy or documenting the supported limitation.

Written by the indexing model from the issue text.