Add systemd socket support; incomplete but works

llama-swap.go

@@ -5,10 +5,12 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"os/signal"
 	"path/filepath"
+	"strconv"
 	"syscall"
 	"time"
 
@@ -64,16 +66,45 @@ func main() {
 		fmt.Println("Error: Both --tls-cert-file and --tls-key-file must be provided for TLS.")
 		os.Exit(1)
 	}
-
-	// Set default ports.
-	if *listenStr == "" {
-		defaultPort := ":8080"
-		if useTLS {
-			defaultPort = ":8443"
+	// Check for systemd socket activation
+	var listener net.Listener
+    	listenFdsStr := os.Getenv("LISTEN_FDS")
+    	if listenFdsStr != "" {
+		listenFds, err := strconv.Atoi(listenFdsStr)
+		if err != nil {
+	    		log.Fatal("Failed to parse LISTEN_FDS:", err)
 		}
-		listenStr = &defaultPort
-	}
+		if listenFds > 0 {
+	    		// The first socket is on FD 3
+	    		fd := 3
+	    		f := os.NewFile(uintptr(fd), "systemd socket")
+	    		if f == nil {
+				log.Fatal("Failed to get file descriptor")
+	    		}
+	    		listener, err = net.FileListener(f)
+	    		if err != nil {
+				log.Fatal("Failed to create listener:", err)
+	    		}
+	    		// The listener now owns the file, so we don't close it here.
+		} else {
+	    		log.Fatal("LISTEN_FDS is set but no sockets are passed")
+		}
+    	} else {
+	
 
+		// Set default ports.
+		if *listenStr == "" {
+			defaultPort := ":8080"
+			if useTLS {
+				defaultPort = ":8443"
+			}
+			listenStr = &defaultPort
+			listener, err = net.Listen("tcp", *listenStr)
+        		if err != nil {
+            			log.Fatal("Failed to listen:", err)
+        		}
+		}
+	}
 	// Setup channels for server management
 	exitChan := make(chan struct{})
 	sigChan := make(chan os.Signal, 1)
@@ -81,7 +112,7 @@ func main() {
 
 	// Create server with initial handler
 	srv := &http.Server{
-		Addr: *listenStr,
+		//Addr: *listenStr,
 	}
 
 	// Support for watching config and reloading when it changes
@@ -194,10 +225,10 @@ func main() {
 		var err error
 		if useTLS {
 			fmt.Printf("llama-swap listening with TLS on https://%s\n", *listenStr)
-			err = srv.ListenAndServeTLS(*certFile, *keyFile)
+			err = srv.ServeTLS(listener, *certFile, *keyFile)
 		} else {
 			fmt.Printf("llama-swap listening on http://%s\n", *listenStr)
-			err = srv.ListenAndServe()
+			err = srv.Serve(listener)
 		}
 		if err != nil && err != http.ErrServerClosed {
 			log.Fatalf("Fatal server error: %v\n", err)