fix(main): sanitize remoteConfigURL to prevent 400 Bad Request on bandwidth reports (#82)

[Adityakk9031]

Summary

Fixes #82.

After updating to Gerbil v1.4, bandwidth reporting failed every 10 seconds with:

Failed to report peer bandwidth: API returned non-OK status: 400 Bad Request

Root Cause

Gerbil v1.4 changed bandwidth reporting to construct the reporting endpoint dynamically from remoteConfigURL:

remoteConfigURL + "/gerbil/receive-bandwidth"

The existing sanitization logic in main.go:

remoteConfigURL = strings.TrimSuffix(remoteConfigURL, "/gerbil/get-config")
remoteConfigURL = strings.TrimSuffix(remoteConfigURL, "/")

failed when REMOTE_CONFIG ended with a trailing slash, for example:

http://pangolin:3001/api/v1/gerbil/get-config/

In this case:

1. TrimSuffix(..., "/gerbil/get-config") failed because of the trailing /.
2. TrimSuffix(..., "/") only removed the final slash.
3. The URL remained:

http://pangolin:3001/api/v1/gerbil/get-config

Gerbil then constructed an invalid endpoint:

http://pangolin:3001/api/v1/gerbil/get-config/gerbil/receive-bandwidth

This targeted a non-existent route, causing the server to return 400 Bad Request every 10 seconds.

Fix

Updated remoteConfigURL sanitization to remove trailing slashes before and after stripping legacy endpoint suffixes.

// Clean up the remote config URL for backwards compatibility.
remoteConfigURL = strings.TrimRight(remoteConfigURL, "/")
remoteConfigURL = strings.TrimSuffix(remoteConfigURL, "/gerbil/get-config")
remoteConfigURL = strings.TrimSuffix(remoteConfigURL, "/gerbil/receive-bandwidth")
remoteConfigURL = strings.TrimSuffix(remoteConfigURL, "/gerbil")
remoteConfigURL = strings.TrimRight(remoteConfigURL, "/")

The normalization now correctly handles all supported formats, including:

http://pangolin:3001/api/v1
http://pangolin:3001/api/v1/
http://pangolin:3001/api/v1/gerbil/get-config
http://pangolin:3001/api/v1/gerbil/get-config/
http://pangolin:3001/api/v1/gerbil/receive-bandwidth/

All of these normalize to:

http://pangolin:3001/api/v1

which results in the correct bandwidth reporting endpoint:

http://pangolin:3001/api/v1/gerbil/receive-bandwidth

Testing

• ✅ Tested REMOTE_CONFIG values with and without trailing slashes.
• ✅ Tested legacy /gerbil/get-config and /gerbil/receive-bandwidth URLs.
• ✅ Verified all configurations normalize to the expected base URL.
• ✅ Confirmed bandwidth reporting succeeds without returning 400 Bad Request.

[Adityakk9031]

@oschwartz10612 and @miloschwartz have a look