fix: edit Envoy config on startup to support case where IPv6 is disabled

Author: thebengeu

ansible/files/start-envoy.sh

@@ -1,5 +1,12 @@
 #!/usr/bin/env bash
 set -eou pipefail
+
+if [[ $(cat /sys/module/ipv6/parameters/disable) = 1 ]]; then
+  sed -i -e "s/address: '::'/address: '0.0.0.0'/" -e 's/ipv4_compat: true/ipv4_compat: false/' /etc/envoy/lds.yaml
+else
+  sed -i -e "s/address: '0.0.0.0'/address: '::'/" -e 's/ipv4_compat: false/ipv4_compat: true/' /etc/envoy/lds.yaml
+fi
+
 # Workaround using `tee` to get `/dev/stdout` access logging to work, see:
 # https://github.com/envoyproxy/envoy/issues/8297#issuecomment-620659781
-exec /opt/envoy --config-path /etc/envoy/envoy.yaml --restart-epoch "$RESTART_EPOCH" 2>&1 | tee
+exec /opt/envoy --config-path /etc/envoy/envoy.yaml --restart-epoch "${RESTART_EPOCH}" 2>&1 | tee