docker: move host-gateway-ip config to systemd (#904)

* docker: move host-gateway-ip config to systemd

* chore: remove redundant code

environment/container/docker/daemon.go

@@ -7,6 +7,7 @@ import (
 )
 
 const daemonFile = "/etc/docker/daemon.json"
+const hostGatewayIPKey = "host-gateway-ip"
 
 func (d dockerRuntime) createDaemonFile(conf map[string]any, env map[string]string) error {
 	if conf == nil {
@@ -24,20 +25,9 @@ func (d dockerRuntime) createDaemonFile(conf map[string]any, env map[string]stri
 	} else if opts, ok := conf["exec-opts"].([]string); ok {
 		conf["exec-opts"] = append(opts, "native.cgroupdriver=cgroupfs")
 	}
-
-	// get host-gateway ip from the guest
-	ip, err := d.guest.RunOutput("sh", "-c", "grep 'host.lima.internal' /etc/hosts | awk -F' ' '{print $1}'")
-	if err != nil {
-		return fmt.Errorf("error retrieving host gateway IP address: %w", err)
-	}
-	if net.ParseIP(ip) == nil {
-		return fmt.Errorf("invalid host gateway IP address: '%s'", ip)
-	}
-
-	// set host-gateway ip to loopback interface (if not set by user)
-	if _, ok := conf["host-gateway"]; !ok {
-		conf["host-gateway-ip"] = ip
-	}
+	// remove host-gateway-ip if set by the user
+	// to avoid clash with systemd configuration
+	delete(conf, hostGatewayIPKey)
 
 	// add proxy vars if set
 	// according to https://docs.docker.com/config/daemon/systemd/#httphttps-proxy
@@ -59,3 +49,35 @@ func (d dockerRuntime) createDaemonFile(conf map[string]any, env map[string]stri
 	}
 	return d.guest.Write(daemonFile, b)
 }
+
+func (d dockerRuntime) addHostGateway(conf map[string]any) error {
+	// get host-gateway ip from the guest
+	ip, err := d.guest.RunOutput("sh", "-c", "grep 'host.lima.internal' /etc/hosts | awk -F' ' '{print $1}'")
+	if err != nil {
+		return fmt.Errorf("error retrieving host gateway IP address: %w", err)
+	}
+	// if set by the user, use the user specified value
+	if _, ok := conf[hostGatewayIPKey]; ok {
+		if gip, ok := conf[hostGatewayIPKey].(string); ok {
+			ip = gip
+		}
+	}
+	if net.ParseIP(ip) == nil {
+		return fmt.Errorf("invalid host gateway IP address: '%s'", ip)
+	}
+
+	// set host-gateway ip as systemd service file
+	content := fmt.Sprintf(systemdUnitFileContent, ip)
+	if err := d.guest.Write(systemdUnitFilename, []byte(content)); err != nil {
+		return fmt.Errorf("error creating systemd unit file: %w", err)
+	}
+
+	return nil
+}
+
+const systemdUnitFilename = "/etc/systemd/system/docker.service.d/docker.conf"
+const systemdUnitFileContent string = `
+[Service]
+ExecStart=
+ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock --host-gateway-ip=%s
+`

environment/container/docker/docker.go

@@ -45,10 +45,13 @@ func (d dockerRuntime) Provision(ctx context.Context) error {
 
 	// daemon.json
 	a.Add(func() error {
-		// not a fatal error
+		// these are not fatal errors
 		if err := d.createDaemonFile(conf.Docker, conf.Env); err != nil {
 			log.Warnln(err)
 		}
+		if err := d.addHostGateway(conf.Docker); err != nil {
+			log.Warnln(err)
+		}
 		return nil
 	})