Naive config reload support

go.mod

@@ -10,6 +10,8 @@ require github.com/pires/go-proxyproto v0.7.0
 
 require github.com/pelletier/go-toml/v2 v2.2.2
 
+require github.com/fsnotify/fsnotify v1.7.0
+
 require github.com/julienschmidt/httprouter v1.3.0
 
 require golang.org/x/sys v0.23.0 // indirect

go.sum

@@ -1,6 +1,8 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
 github.com/julienschmidt/httprouter v1.3.0 h1:U0609e9tgbseu3rBINet9P48AI/D3oJs4dN7jwJOQ1U=
 github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=
 github.com/libp2p/go-reuseport v0.4.0 h1:nR5KU7hD0WxXCJbmw7r2rhRYruNRl2koHw8fQscQm2s=

main.go

@@ -3,13 +3,49 @@ package main
 import (
 	"encoding/json"
 	"flag"
+	"fmt"
 	"log"
 	"os"
 	"strings"
 
+	"github.com/fsnotify/fsnotify"
 	"github.com/pelletier/go-toml/v2"
 )
 
+func watchConfigFile(path string) (chan fsnotify.Event, error) {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil, err
+	}
+	err = watcher.Add(path)
+	if err != nil {
+		return nil, err
+	}
+	return watcher.Events, nil
+}
+
+func replaceServer(sshmux *Server, event fsnotify.Event) (*Server, error) {
+	if event.Has(fsnotify.Write) || event.Has(fsnotify.Create) {
+		log.Printf("info: %s has been changed, reloading...\n", event.Name)
+		// Start new server instance
+		newServer, err := sshmuxServer(event.Name)
+		if err != nil {
+			return sshmux, fmt.Errorf("failed to parse %s: %w", event.Name, err)
+		}
+		err = newServer.Start()
+		if err != nil {
+			return sshmux, fmt.Errorf("failed to start sshmux server: %w", err)
+		}
+		// Replace old server
+		go sshmux.Shutdown()
+		return newServer, nil
+	}
+	if event.Has(fsnotify.Remove) || event.Has(fsnotify.Rename) {
+		log.Printf("warn: %s has been deleted\n", event.Name)
+	}
+	return sshmux, nil
+}
+
 func sshmuxServer(configFile string) (*Server, error) {
 	var config Config
 	configFileBytes, err := os.ReadFile(configFile)
@@ -35,7 +71,9 @@ func sshmuxServer(configFile string) (*Server, error) {
 
 func main() {
 	var configFile string
+	var reload bool
 	flag.StringVar(&configFile, "c", "/etc/sshmux/config.toml", "config file")
+	flag.BoolVar(&reload, "r", false, "auto reload")
 	flag.Parse()
 	sshmux, err := sshmuxServer(configFile)
 	if err != nil {
@@ -45,5 +83,18 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	sshmux.Wait()
+	if reload {
+		events, err := watchConfigFile(configFile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		for event := range events {
+			sshmux, err = replaceServer(sshmux, event)
+			if err != nil {
+				log.Print(err)
+			}
+		}
+	} else {
+		sshmux.Wait()
+	}
 }