Add advantech router app updates

Dockerfile

@@ -29,7 +29,7 @@ COPY entrypoint.sh /
 
 # Marks this as an official Fossorial container image.
 # Auto-update is disabled in official images — update by pulling a new image tag.
-ENV NEWT_OFFICIAL_CONTAINER=true
+ENV NEWT_SYSTEM_SUBSTRATE="CONTAINER"
 
 # Admin/metrics endpoint (Prometheus scrape)
 EXPOSE 2112

updates/advantech.go

@@ -0,0 +1,48 @@
+//go:build !windows
+
+package updates
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/fosrl/newt/logger"
+)
+
+const advantechVersionFile = "/opt/newt/etc/version"
+
+// postUpdateAdvantech performs Advantech Router App-specific post-update steps:
+//   - Writes the new version string to /opt/newt/etc/version so that the
+//     router firmware's package management reflects the installed version.
+//   - Updates the PID file at pidFile (if non-empty) with the current process
+//     PID, in case the re-exec lands with a new PID on platforms where
+//     syscall.Exec behaviour differs.
+func postUpdateAdvantech(newVersion, pidFile string) error {
+	// --- Write version file ---
+	versionDir := filepath.Dir(advantechVersionFile)
+	if err := os.MkdirAll(versionDir, 0755); err != nil {
+		return fmt.Errorf("advantech: failed to create version directory %s: %w", versionDir, err)
+	}
+
+	if err := os.WriteFile(advantechVersionFile, []byte(newVersion+"\n"), 0644); err != nil {
+		return fmt.Errorf("advantech: failed to write version file %s: %w", advantechVersionFile, err)
+	}
+	logger.Debug("postUpdateAdvantech: wrote version %s to %s", newVersion, advantechVersionFile)
+
+	// --- Update PID file ---
+	// syscall.Exec replaces the process image in-place so the PID is preserved.
+	// We update the PID file here anyway so that any race between the old and
+	// new binary is covered (e.g. on platforms that fork before exec).
+	if pidFile != "" {
+		pid := fmt.Sprintf("%d\n", os.Getpid())
+		if err := os.WriteFile(pidFile, []byte(pid), 0644); err != nil {
+			// Non-fatal: log and continue so the update still proceeds.
+			logger.Debug("postUpdateAdvantech: warning: failed to update PID file %s: %v", pidFile, err)
+		} else {
+			logger.Debug("postUpdateAdvantech: updated PID file %s with PID %d", pidFile, os.Getpid())
+		}
+	}
+
+	return nil
+}

updates/selfupdate.go

@@ -52,10 +52,10 @@ type versionResponse struct {
 
 // isOfficialContainer returns true when the process is running inside an
 // official Fossorial-built container image.  The image sets
-// NEWT_OFFICIAL_CONTAINER=true at build time; users running newt in their own
+// NEWT_SYSTEM_SUBSTRATE="CONTAINER" at build time; users running newt in their own
 // containers (or bare-metal) will not have this variable set.
 func isOfficialContainer() bool {
-	return os.Getenv("NEWT_OFFICIAL_CONTAINER") == "true"
+	return os.Getenv("NEWT_SYSTEM_SUBSTRATE") == "CONTAINER"
 }
 
 // platform returns the OS+arch string used in the newt release binary names,
@@ -109,7 +109,7 @@ func verifySHA256(path, expected string) error {
 // the function does not return – the process is replaced by the new binary via
 // syscall.Exec.
 func CheckAndSelfUpdate(cfg SelfUpdateConfig) error {
-	logger.Debug("++++++++++++++++++++++++++++++++++++++++++++checkAndSelfUpdate: starting update check (currentVersion=%s)", cfg.CurrentVersion)
+	logger.Debug("checkAndSelfUpdate: starting update check (currentVersion=%s)", cfg.CurrentVersion)
 
 	if isOfficialContainer() {
 		logger.Debug("checkAndSelfUpdate: running inside official container, skipping auto-update")
@@ -280,6 +280,15 @@ func CheckAndSelfUpdate(cfg SelfUpdateConfig) error {
 		return fmt.Errorf("failed to replace binary (you may need to run as root): %w", err)
 	}
 
+	systemSubstrate := os.Getenv("NEWT_SYSTEM_SUBSTRATE")
+	logger.Debug("checkAndSelfUpdate: system substrate: %s", systemSubstrate)
+	if systemSubstrate == "ADVANTECH_ROUTER_APP" {
+		pidFile := os.Getenv("NEWT_PID_FILE")
+		if err := postUpdateAdvantech(verResp.Data.LatestVersion, pidFile); err != nil {
+			logger.Debug("checkAndSelfUpdate: advantech post-update steps failed: %v", err)
+		}
+	}
+
 	// --- Step 4: Re-exec ---
 	logger.Debug("checkAndSelfUpdate: re-executing new binary")
 	return reexec(exePath)