Include appropriate user-agent header when making map requests

[pnorman]

I'm one of the admins of tile.openstreetmap.org. Currently flutter_map uses the default dart:io HTTP User-Agent (e.g. Dart/2.17 (dart:io)). This means that when looking at traffic, flutter traffic gets lumped in with other Dart traffic, and if any Dart users are causing usage problems, all Dart users including flutter could end up blocked. This happened recently, and because it was a generic user-agent, I was unable to figure out who the traffic was coming from.

The tile usage policy requires a Valid HTTP User-Agent identifying application. For flutter, this could be something like flutter_map/1.2.3, where 1.2.3 is a version.

A better option for your users would be to automatically generate a user-agent from the name of their app, if possible. Frequently the name of the app is something like com.example.app, so a user-agent could be com.example.app/456 flutter_map/1.2.3. If an app-specific default is not set, then the instructions should be clear about the need to set an appropriate user-agent

[ibrierley]

Quick thoughts, as not about much the next few days....Here's a possible starting point for a workaround I just pasted...

NetworkImage allows headers, but NetworkImageWIthRetry doesn't afaics (there is an issue raised there though flutter/flutter#19532 so sounds like maybe that's coming, altho maybe what I did later actually works...)

If we need a quick hack (without hacking flutter_map itself...this _may_ work...
import 'package:flutter_map/src/layer/tile_layer/coords.dart';

class NetworkTileProvider extends TileProvider {
  Map<String,String> headers = const {};
  NetworkTileProvider({this.headers = const {}});

  @override
  ImageProvider getImage(Coords<num> coords, TileLayerOptions options) {
    return NetworkImage(getTileUrl(coords, options), headers: headers);
  }
}


in FlutterMap widget

TileLayerOptions(
  tileProvider: NetworkTileProvider(headers: { 'User-Agent' : 'flutter_map/1.1.1)' }),
  urlTemplate: 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
    subdomains: ['a', 'b', 'c'],
  ),
)

For FlutterMap itself, could we do something like (untested)...

class NetworkTileProvider extends TileProvider {
  @override
  ImageProvider getImage(Coords<num> coords, TileLayerOptions options) {
    return NetworkImageWithRetry(getTileUrl(coords, options), headers: const { 'User-Agent' : 'flutter_map/1.1.1)' });
  }
}

class NonCachingNetworkTileProvider extends TileProvider {
  const NonCachingNetworkTileProvider();

  @override
  ImageProvider getImage(Coords<num> coords, TileLayerOptions options) {
    return NetworkImage(getTileUrl(coords, options), headers: const { 'User-Agent' : 'flutter_map/1.1.1)' });
  }
}

in tile_provider/network_image_with_retry.dart

Not quite sure if this affects browser user_agents...or if I was doing something wrong, so above may be a load of rubbish!

[ibrierley]

(we should probably let users set any header they want actually if we can, at the same time)

[ibrierley]

Out of interest, are there any notification emails or anything for OpenStreetMaps, or work more closely with them somehow. Naturally it feels like it's in everyones interests to be more aware of changes, potential issues etc

[ibrierley]

Note, browser says "Refused to set unsafe header "User-Agent" when I try some previous suggestions, so for security I'm wondering if that's not possible in web mode...

[namanshergill]

Note, browser says "Refused to set unsafe header "User-Agent" when I try some previous suggestions, so for security I'm wondering if that's not possible in web mode...

Is this on a debug build? Because sometimes developer modes of browsers fail CORS checks by default for localhost, so it’s not necessary the issue would replicate in release builds if that’s the case

[JaffaKetchup]

@pnorman Would it be possible to have an agent like:
"flutter_map/1.2.3 (com.example.app)"?

If so, I like the version given above. We can provide a default in case they don't change it: we can use package_info_plus to get the application/package name.

[JaffaKetchup]

If so, I'll make a PR ASAP to fix it.

[pnorman]

Yes that would work