dynamically populate localIPAddresses without requiring a reboot

cmd/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"log"
-	"time"
 
 	"github.com/doubleunion/accesscontrol/router"
 	rpio "github.com/stianeikeland/go-rpio/v4"
@@ -15,18 +14,5 @@ func main() {
 	}
 	defer rpio.Close()
 
-	// Run updateIPAndRestart every minute in a separate thread
-	go func() {
-		ticker := time.NewTicker(1 * time.Minute)
-		defer ticker.Stop()
-
-		for range ticker.C {
-			err := router.UpdateIPAndRestart()
-			if err != nil {
-				log.Printf("Error in updateIPAndRestart: %v", err)
-			}
-		}
-	}()
-
 	router.RunRouter()
 }

door/door.go

@@ -4,10 +4,11 @@ import (
 	"bytes"
 	cryptoRand "crypto/rand"
 	"fmt"
-	rpio "github.com/stianeikeland/go-rpio/v4"
 	"log"
 	"sync"
 	"time"
+
+	rpio "github.com/stianeikeland/go-rpio/v4"
 )
 
 type Door struct {

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/labstack/echo-jwt/v4 v4.2.0
 	github.com/labstack/echo/v4 v4.11.3
 	github.com/stianeikeland/go-rpio/v4 v4.6.0
+	golang.org/x/crypto v0.14.0
 )
 
 require (
@@ -16,7 +17,6 @@ require (
 	github.com/mattn/go-isatty v0.0.19 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	github.com/valyala/fasttemplate v1.2.2 // indirect
-	golang.org/x/crypto v0.14.0 // indirect
 	golang.org/x/net v0.17.0 // indirect
 	golang.org/x/sys v0.13.0 // indirect
 	golang.org/x/text v0.13.0 // indirect

router/local_ip.go

@@ -0,0 +1,76 @@
+package router
+
+import (
+	"log"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+	"slices"
+
+	"github.com/labstack/echo/v4"
+)
+
+var (
+	localInternetAddresses      []string
+	localInternetAddressesMutex sync.RWMutex
+)
+
+func beginLocalIPMonitoring() {
+	updateLocalIPAddresses()
+
+	go func() {
+		ticker := time.NewTicker(30 * time.Second)
+		defer ticker.Stop()
+
+		for range ticker.C {
+			updateLocalIPAddresses()
+		}
+	}()
+}
+
+func updateLocalIPAddresses() {
+	ips, err := net.LookupIP("doorcontrol.doubleunion.org")
+	if err != nil {
+		log.Printf("Error in updateLocalIPAddresses: %v", err)
+	}
+
+	var ipStrings []string
+	for _, ip := range ips {
+		ipStrings = append(ipStrings, ip.String())
+	}
+
+	localInternetAddressesMutex.Lock()
+	defer localInternetAddressesMutex.Unlock()
+	hasChanged := !slices.Equal(ipStrings, localInternetAddresses)
+	localInternetAddresses = ipStrings
+
+	if hasChanged {
+		log.Printf("Updated local IP addresses to: %v", ipStrings)
+	}
+}
+
+func requireLocalNetworkMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
+	return func(c echo.Context) error {
+		// Get the remote address from the request
+		remoteAddr := c.Request().RemoteAddr
+
+		// Parse the IP address
+		ip, _, err := net.SplitHostPort(remoteAddr)
+		if err != nil {
+			return echo.NewHTTPError(http.StatusInternalServerError, "failed to parse IP address")
+		}
+
+		localInternetAddressesMutex.RLock()
+		defer localInternetAddressesMutex.RUnlock()
+		for _, allowedIP := range localInternetAddresses {
+			if ip == allowedIP {
+				// Continue to the next middleware or route handler
+				return next(c)
+			}
+		}
+
+		// Fail the request, there was no matching IP
+		return jsonResponse(c, http.StatusForbidden, "requests not allowed from remote hosts")
+	}
+}

router/router.go

@@ -5,11 +5,8 @@ import (
 	"fmt"
 	"io"
 	"log"
-	"net"
 	"net/http"
 	"os"
-	"os/exec"
-	"strings"
 	"time"
 
 	"github.com/doubleunion/accesscontrol/door"
@@ -21,20 +18,13 @@ import (
 	"golang.org/x/crypto/acme/autocert"
 )
 
-const serviceFilePath = "/etc/systemd/system/accesscontrol.service"
-const ipQueryURL = "https://wtfismyip.com/text"
-
-var localInternetAddress = os.Getenv("LOCAL_INTERNET_ADDRESS")
-
 func RunRouter() {
 	signingKey := os.Getenv("ACCESS_CONTROL_SIGNING_KEY")
 	if signingKey == "" {
 		log.Fatal("signing key is missing")
 	}
 
-	if localInternetAddress == "" {
-		log.Fatal("local internet address is missing")
-	}
+	beginLocalIPMonitoring()
 
 	door := door.New()
 
@@ -96,88 +86,3 @@ func RunRouter() {
 func jsonResponse(c echo.Context, code int, message string) error {
 	return c.JSON(code, map[string]string{"message": message})
 }
-
-func requireLocalNetworkMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
-	return func(c echo.Context) error {
-		// Get the remote address from the request
-		remoteAddr := c.Request().RemoteAddr
-
-		// Parse the IP address
-		ip, _, err := net.SplitHostPort(remoteAddr)
-		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, "failed to parse IP address")
-		}
-
-		if ip != localInternetAddress {
-			return jsonResponse(c, http.StatusForbidden, "requests not allowed from remote hosts")
-		}
-
-		// Continue to the next middleware or route handler
-		return next(c)
-	}
-}
-
-func UpdateIPAndRestart() error {
-	// Step 1: Query current IP address
-	resp, err := http.Get(ipQueryURL)
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
-
-	ipBytes, err := io.ReadAll(resp.Body)
-	if err != nil {
-		return err
-	}
-	currentIP := strings.TrimSpace(string(ipBytes))
-
-	// Step 2: Read the service file
-	content, err := os.ReadFile(serviceFilePath)
-	if err != nil {
-		return err
-	}
-
-	// Step 3: Check if the IP matches
-	lines := strings.Split(string(content), "\n")
-	var updatedContent []string
-	ipUpdated := false
-	for _, line := range lines {
-		if strings.HasPrefix(line, "Environment=LOCAL_INTERNET_ADDRESS=") {
-			fileIP := strings.TrimPrefix(line, "Environment=LOCAL_INTERNET_ADDRESS=")
-			if fileIP != currentIP {
-				line = "Environment=LOCAL_INTERNET_ADDRESS=" + currentIP
-				ipUpdated = true
-			}
-		}
-		updatedContent = append(updatedContent, line)
-	}
-
-	// Step 4: Update the file if necessary
-	if ipUpdated {
-		// first we have to output the new contents to a temporary file
-		// because we don't have access to the service file directly
-		tempFilePath := "/tmp/accesscontrol.service"
-		err = os.WriteFile(tempFilePath, []byte(strings.Join(updatedContent, "\n")), 0644)
-		if err != nil {
-			return err
-		}
-
-		// then we copy the temporary file to the service file path
-		// the path is owned by the process user so this is allowed by the OS without sudo
-		cmd := exec.Command("cp", tempFilePath, serviceFilePath)
-		err = cmd.Run()
-		if err != nil {
-			return err
-		}
-
-		// Step 5: Restart the Raspberry Pi
-		cmd = exec.Command("sudo", "shutdown", "-r", "now")
-		//log.Printf("Error in updateIPAndRestart: %v", err)
-		err = cmd.Run()
-		if err != nil {
-			return err
-		}
-	}
-
-	return nil
-}