The GitHub Runner Charm itself requires access to the
- GitHub API (e.g. to register and remove runners).
- GitHub website (e.g. to download the runner binary or other applications like yq)
- Ubuntu package repositories (e.g. to install packages)
- Snap store (e.g. to install LXD or aproxy)
- Ubuntu Cloud Images (for the image used by a runner)
- npm registry (e.g. to download and install specific packages)
In addition, access is required depending on the requirements of the workloads that the runners will be running (as they will be running on the same machine as the charm).
More details on network configuration can be found in the charm architecture documentation.