test: Add functions to check and rewrite local URLs

docker-compose.yml

@@ -8,8 +8,7 @@ services:
     ports:
       - "${CONTRIBUTOOR_METRICS_ADDRESS}:${CONTRIBUTOOR_METRICS_PORT}:${CONTRIBUTOOR_METRICS_PORT}"
     extra_hosts:
-      - "127.0.0.1:host-gateway"
-      - "localhost:host-gateway"
+      - "host.docker.internal:host-gateway"
     volumes:
       - ${CONTRIBUTOOR_CONFIG_PATH}/config.yaml:/config/config.yaml:ro
     restart: always

internal/sidecar/docker.go

@@ -14,6 +14,12 @@ import (
 
 //go:generate mockgen -package mock -destination mock/docker.mock.go github.com/ethpandaops/contributoor-installer/internal/sidecar DockerSidecar
 
+var localHostnames = map[string]bool{
+	"localhost": true,
+	"127.0.0.1": true,
+	"0.0.0.0":   true,
+}
+
 type DockerSidecar interface {
 	SidecarRunner
 }
@@ -124,35 +130,32 @@ func (s *dockerSidecar) Update() error {
 	return nil
 }
 
-func (s *dockerSidecar) getComposeEnv() []string {
-	cfg := s.sidecarCfg.Get()
+// IsLocalURL checks if the given URL is pointing to a local address.
+func IsLocalURL(url string) bool {
+	for hostname := range localHostnames {
+		if strings.Contains(url, hostname) {
+			return true
+		}
+	}
 
-	env := append(
-		os.Environ(),
-		fmt.Sprintf("CONTRIBUTOOR_CONFIG_PATH=%s", filepath.Dir(s.configPath)),
-		fmt.Sprintf("CONTRIBUTOOR_VERSION=%s", cfg.Version),
-	)
+	return false
+}
 
-	// Handle metrics address (always added).
-	metricsHost, metricsPort := cfg.GetMetricsHostPort()
-	env = append(
-		env,
-		fmt.Sprintf("CONTRIBUTOOR_METRICS_ADDRESS=%s", metricsHost),
-		fmt.Sprintf("CONTRIBUTOOR_METRICS_PORT=%s", metricsPort),
-	)
+// RewriteBeaconURL rewrites local URLs to use host.docker.internal.
+func RewriteBeaconURL(url string) string {
+	if !IsLocalURL(url) {
+		return url
+	}
 
-	// Handle pprof address (only added if set).
-	if pprofHost, pprofPort := cfg.GetPprofHostPort(); pprofHost != "" {
-		env = append(
-			env,
-			fmt.Sprintf("CONTRIBUTOOR_PPROF_ADDRESS=%s", pprofHost),
-			fmt.Sprintf("CONTRIBUTOOR_PPROF_PORT=%s", pprofPort),
-		)
+	// Replace all local hostnames with host.docker.internal.
+	for hostname := range localHostnames {
+		url = strings.Replace(url, hostname, "host.docker.internal", 1)
 	}
 
-	return env
+	return url
 }
 
+// findComposeFile finds the docker-compose file based on the OS.
 func findComposeFile() (string, error) {
 	// Get binary directory
 	ex, err := os.Executable()
@@ -162,18 +165,17 @@ func findComposeFile() (string, error) {
 
 	binDir := filepath.Dir(ex)
 
+	cwd, err := os.Getwd()
+	if err != nil {
+		return "", fmt.Errorf("could not get working directory: %w", err)
+	}
+
 	// Check release mode (next to binary)
 	composePath := filepath.Join(binDir, "docker-compose.yml")
 	if _, e := os.Stat(composePath); e == nil {
 		return composePath, nil
 	}
 
-	// Check dev mode paths
-	cwd, err := os.Getwd()
-	if err != nil {
-		return "", fmt.Errorf("could not get working directory: %w", err)
-	}
-
 	// Try current directory
 	if _, err := os.Stat(filepath.Join(cwd, "docker-compose.yml")); err == nil {
 		return filepath.Join(cwd, "docker-compose.yml"), nil
@@ -212,3 +214,41 @@ func validateComposePath(path string) error {
 
 	return nil
 }
+
+func (s *dockerSidecar) getComposeEnv() []string {
+	cfg := s.sidecarCfg.Get()
+
+	// Docker containers can't directly access the host via localhost/127.0.0.1.
+	// We rewrite these to host.docker.internal which resolves differently per platform:
+	// - macOS: Built-in DNS name that points to the Docker Desktop VM's gateway
+	// - Linux: Maps to host-gateway via extra_hosts in docker-compose.yml
+	// This provides a consistent way to access the host machine across platforms.
+	if cfg.BeaconNodeAddress != "" {
+		cfg.BeaconNodeAddress = RewriteBeaconURL(cfg.BeaconNodeAddress)
+	}
+
+	env := append(
+		os.Environ(),
+		fmt.Sprintf("CONTRIBUTOOR_CONFIG_PATH=%s", filepath.Dir(s.configPath)),
+		fmt.Sprintf("CONTRIBUTOOR_VERSION=%s", cfg.Version),
+	)
+
+	// Handle metrics address (always added).
+	metricsHost, metricsPort := cfg.GetMetricsHostPort()
+	env = append(
+		env,
+		fmt.Sprintf("CONTRIBUTOOR_METRICS_ADDRESS=%s", metricsHost),
+		fmt.Sprintf("CONTRIBUTOOR_METRICS_PORT=%s", metricsPort),
+	)
+
+	// Handle pprof address (only added if set).
+	if pprofHost, pprofPort := cfg.GetPprofHostPort(); pprofHost != "" {
+		env = append(
+			env,
+			fmt.Sprintf("CONTRIBUTOOR_PPROF_ADDRESS=%s", pprofHost),
+			fmt.Sprintf("CONTRIBUTOOR_PPROF_PORT=%s", pprofPort),
+		)
+	}
+
+	return env
+}

internal/sidecar/docker_test.go

@@ -152,3 +152,95 @@ func TestDockerService_Integration(t *testing.T) {
 		require.False(t, running)
 	})
 }
+
+func TestIsLocalURL(t *testing.T) {
+	tests := []struct {
+		name string
+		url  string
+		want bool
+	}{
+		{
+			name: "localhost",
+			url:  "http://localhost:5052",
+			want: true,
+		},
+		{
+			name: "127.0.0.1",
+			url:  "http://127.0.0.1:5052",
+			want: true,
+		},
+		{
+			name: "0.0.0.0",
+			url:  "http://0.0.0.0:5052",
+			want: true,
+		},
+		{
+			name: "remote url",
+			url:  "http://example.com:5052",
+			want: false,
+		},
+		{
+			name: "empty url",
+			url:  "",
+			want: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := sidecar.IsLocalURL(tt.url)
+			require.Equal(t, tt.want, got)
+		})
+	}
+}
+
+func TestRewriteBeaconURL(t *testing.T) {
+	tests := []struct {
+		name string
+		url  string
+		want string
+	}{
+		{
+			name: "localhost",
+			url:  "http://localhost:5052",
+			want: "http://host.docker.internal:5052",
+		},
+		{
+			name: "127.0.0.1",
+			url:  "http://127.0.0.1:5052",
+			want: "http://host.docker.internal:5052",
+		},
+		{
+			name: "0.0.0.0",
+			url:  "http://0.0.0.0:5052",
+			want: "http://host.docker.internal:5052",
+		},
+		{
+			name: "remote url",
+			url:  "http://example.com:5052",
+			want: "http://example.com:5052",
+		},
+		{
+			name: "localhost with path",
+			url:  "http://localhost:5052/eth/v1/node/syncing",
+			want: "http://host.docker.internal:5052/eth/v1/node/syncing",
+		},
+		{
+			name: "localhost with protocol and path",
+			url:  "https://localhost:5052/eth/v1/node/syncing",
+			want: "https://host.docker.internal:5052/eth/v1/node/syncing",
+		},
+		{
+			name: "empty url",
+			url:  "",
+			want: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := sidecar.RewriteBeaconURL(tt.url)
+			require.Equal(t, tt.want, got)
+		})
+	}
+}