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/artifacts/server.go

@@ -262,7 +262,7 @@ func downloads(router *httprouter.Router, fsys fs.FS) {
 	})
 }
 
-func Serve(ctx context.Context, artifactPath string, port string) context.CancelFunc {
+func Serve(ctx context.Context, artifactPath string, addr string, port string) context.CancelFunc {
 	serverContext, cancel := context.WithCancel(ctx)
 	logger := common.Logger(serverContext)
 
@@ -276,17 +276,16 @@ func Serve(ctx context.Context, artifactPath string, port string) context.Cancel
 	fs := os.DirFS(artifactPath)
 	uploads(router, MkdirFsImpl{artifactPath, fs})
 	downloads(router, fs)
-	ip := common.GetOutboundIP().String()
 
 	server := &http.Server{
-		Addr:              fmt.Sprintf("%s:%s", ip, port),
+		Addr:              fmt.Sprintf("%s:%s", addr, port),
 		ReadHeaderTimeout: 2 * time.Second,
 		Handler:           router,
 	}
 
 	// run server
 	go func() {
-		logger.Infof("Start server on http://%s:%s", ip, port)
+		logger.Infof("Start server on http://%s:%s", addr, port)
 		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
 			logger.Fatal(err)
 		}

pkg/artifacts/server_test.go

@@ -240,7 +240,8 @@ type TestJobFileInfo struct {
 	containerArchitecture string
 }
 
-var aritfactsPath = path.Join(os.TempDir(), "test-artifacts")
+var artifactsPath = path.Join(os.TempDir(), "test-artifacts")
+var artifactsAddr = "127.0.0.1"
 var artifactsPort = "12345"
 
 func TestArtifactFlow(t *testing.T) {
@@ -250,7 +251,7 @@ func TestArtifactFlow(t *testing.T) {
 
 	ctx := context.Background()
 
-	cancel := Serve(ctx, aritfactsPath, artifactsPort)
+	cancel := Serve(ctx, artifactsPath, artifactsAddr, artifactsPort)
 	defer cancel()
 
 	platforms := map[string]string{
@@ -271,7 +272,7 @@ func runTestJobFile(ctx context.Context, t *testing.T, tjfi TestJobFileInfo) {
 	t.Run(tjfi.workflowPath, func(t *testing.T) {
 		fmt.Printf("::group::%s\n", tjfi.workflowPath)
 
-		if err := os.RemoveAll(aritfactsPath); err != nil {
+		if err := os.RemoveAll(artifactsPath); err != nil {
 			panic(err)
 		}
 
@@ -286,7 +287,8 @@ func runTestJobFile(ctx context.Context, t *testing.T, tjfi TestJobFileInfo) {
 			ReuseContainers:       false,
 			ContainerArchitecture: tjfi.containerArchitecture,
 			GitHubInstance:        "github.com",
-			ArtifactServerPath:    aritfactsPath,
+			ArtifactServerPath:    artifactsPath,
+			ArtifactServerAddr:    artifactsAddr,
 			ArtifactServerPort:    artifactsPort,
 		}
 

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