action.yml

name: Setup DNS spoofing to azure.archive.ubuntu.com
description: 'Redirects DNS requests from archive.ubuntu.com to azure.archive.ubuntu.com'

runs:
  using: 'composite'
  steps:
    - name: Add dnsmasq config
      id: dnsmasq-config
      shell: bash
      run: |
        set -euxo pipefail

        # Address dnsmasq will listen on
        LISTEN_IP="$(hostname -I | awk '{ print $1 }')"
        echo "DNSMASQ_IP=${LISTEN_IP}" >> "${GITHUB_OUTPUT}"

        # Lookup a v4 A record for azure's mirror
        # We'll use this as the reply to archive.ubuntu.com requests
        AZURE_MIRROR_IP="$(getent ahostsv4 azure.archive.ubuntu.com | awk '{print $1}' | head -1)"

        sudo mkdir -p /etc/dnsmasq.d
        cat <<EOF | sudo tee /etc/dnsmasq.d/apt-mirror.conf
        listen-address=${LISTEN_IP}
        bind-interfaces
        address=/archive.ubuntu.com/${AZURE_MIRROR_IP}
        address=/security.ubuntu.com/${AZURE_MIRROR_IP}
        server=127.0.0.53
        log-queries
        EOF

    - name: Install dnsmasq
      shell: bash
      run: |
        set -ex -o pipefail
        sudo apt update && sudo apt install -y dnsmasq
    - name: Finalize dnsmasq config
      shell: bash
      run: |
        echo 'conf-dir=/etc/dnsmasq.d/,*.conf' | sudo tee /etc/dnsmasq.conf
        sudo systemctl restart dnsmasq
    - name: Configure Docker DNS
      shell: bash
      run: |
        tmp="$(mktemp)"
        if ! sudo cp /etc/docker/daemon.json "${tmp}" 2>/dev/null; then
          echo '{}' > "${tmp}"
        fi

        sudo mkdir -p /etc/docker
        jq --arg dns "${DNSMASQ_IP}" '.dns = [$dns]' "${tmp}" | sudo tee /etc/docker/daemon.json

        sudo systemctl stop docker
        if ! sudo systemctl start docker; then
          sudo systemctl reset-failed docker
          if ! sudo systemctl start docker; then
            echo "::error::error restarting dockerd with custom DNS"
            journalctl -u docker
            exit 1
          fi
        fi
      env:
        DNSMASQ_IP: ${{ steps.dnsmasq-config.outputs.DNSMASQ_IP }}