fix: allow override of artifact server bind address (#1560)

* Prior to this change, the artifact server always binds to the detected
  "outbound IP", breaks functionality when that IP is unroutable.
  For example, Zscaler assigns the host a local CGNAT address,
  100.64.0.1, which is unreachable from Docker Desktop.
* Add the `--artifact-server-addr` flag to allow override of the address
  to which the artifact server binds, defaulting to the existing
  behaviour.

Fixes: #1559

pkg/runner/run_context.go

@@ -751,7 +751,7 @@ func (rc *RunContext) withGithubEnv(ctx context.Context, github *model.GithubCon
 func setActionRuntimeVars(rc *RunContext, env map[string]string) {
 	actionsRuntimeURL := os.Getenv("ACTIONS_RUNTIME_URL")
 	if actionsRuntimeURL == "" {
-		actionsRuntimeURL = fmt.Sprintf("http://%s:%s/", common.GetOutboundIP().String(), rc.Config.ArtifactServerPort)
+		actionsRuntimeURL = fmt.Sprintf("http://%s:%s/", rc.Config.ArtifactServerAddr, rc.Config.ArtifactServerPort)
 	}
 	env["ACTIONS_RUNTIME_URL"] = actionsRuntimeURL
 

pkg/runner/runner.go

@@ -48,6 +48,7 @@ type Config struct {
 	ContainerCapDrop                   []string          // list of kernel capabilities to remove from the containers
 	AutoRemove                         bool              // controls if the container is automatically removed upon workflow completion
 	ArtifactServerPath                 string            // the path where the artifact server stores uploads
+	ArtifactServerAddr                 string            // the address the artifact server binds to
 	ArtifactServerPort                 string            // the port the artifact server binds to
 	NoSkipCheckout                     bool              // do not skip actions/checkout
 	RemoteName                         string            // remote name in local git repo config