Switch to structured logging

closes #9

.github/workflows/go.yml

@@ -15,7 +15,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v4
       with:
-        go-version: '1.20'
+        go-version: '1.21'
 
     - name: Build
       run: go build -v ./...

client.go

@@ -3,7 +3,7 @@ package dhclient
 import (
 	"errors"
 	"fmt"
-	"log"
+	"log/slog"
 	"math/rand"
 	"net"
 	"sync"
@@ -27,6 +27,7 @@ type Client struct {
 	OnBound     Callback // On renew or rebound
 	OnExpire    Callback // On expiration of a lease
 	DHCPOptions []Option // List of options to send on discovery and requests
+	Logger      *slog.Logger
 
 	conn     *packet.Conn // Raw socket
 	xid      uint32       // Transaction ID
@@ -92,6 +93,9 @@ func (client *Client) AddParamRequest(dhcpOpt layers.DHCPOpt) {
 
 // Start starts the client
 func (client *Client) Start() {
+	if client.Logger == nil {
+		client.Logger = slog.New(&discardHandler{})
+	}
 
 	// Add default DHCP options if none added yet.
 	if client.DHCPOptions == nil {
@@ -102,7 +106,7 @@ func (client *Client) Start() {
 	}
 
 	if client.notify != nil {
-		log.Panicf("client for %s already started", client.Iface.Name)
+		panic(fmt.Sprintf("client for %s already started", client.Iface.Name))
 	}
 	client.notify = make(chan struct{})
 	client.wg.Add(1)
@@ -111,7 +115,7 @@ func (client *Client) Start() {
 
 // Stop stops the client
 func (client *Client) Stop() {
-	log.Printf("[%s] shutting down dhclient", client.Iface.Name)
+	slog.Info("shutting down dhclient")
 	client.shutdown = true
 	close(client.notify)
 
@@ -155,7 +159,7 @@ func (client *Client) runOnce() {
 	}
 
 	if err != nil {
-		log.Printf("[%s] error: %s", client.Iface.Name, err)
+		client.Logger.Error("failed to acquire lease", "error", err)
 		// delay for a second
 		select {
 		case <-client.notify:
@@ -277,7 +281,7 @@ func (client *Client) request(lease *Lease) error {
 
 // sendPacket creates and sends a DHCP packet
 func (client *Client) sendPacket(msgType layers.DHCPMsgType, options []Option) error {
-	log.Printf("[%s] sending %s", client.Iface.Name, msgType)
+	client.Logger.Debug("sending packet", "type", msgType)
 	return client.sendMulticast(client.newPacket(msgType, options))
 }
 
@@ -366,7 +370,7 @@ func (client *Client) waitForResponse(msgTypes ...layers.DHCPMsgType) (layers.DH
 			// do we have the expected message type?
 			for _, t := range msgTypes {
 				if t == msgType {
-					log.Printf("[%s] received %s", client.Iface.Name, msgType)
+					client.Logger.Debug("received packet", "type", msgType)
 					return msgType, &res, nil
 				}
 			}

cmd/dhclient/main.go

@@ -3,7 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
-	"log"
+	"log/slog"
 	"net"
 	"os"
 	"os/signal"
@@ -28,7 +28,6 @@ func init() {
 }
 
 func main() {
-	log.SetFlags(log.Ltime | log.Lshortfile)
 	flag.Parse()
 
 	if flag.NArg() != 1 {
@@ -43,22 +42,26 @@ func main() {
 		os.Exit(1)
 	}
 
+	logHandler := slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelDebug})
+	logger := slog.New(logHandler)
+
 	client := dhclient.Client{
-		Iface: iface,
+		Iface:  iface,
+		Logger: logger,
 		OnBound: func(lease *dhclient.Lease) {
-			log.Printf("Bound: %+v", lease)
+			logger.Info("bound", "lease", lease)
 		},
 	}
 
 	// Add requests for default options
 	for _, param := range dhclient.DefaultParamsRequestList {
-		log.Printf("Requesting default option %d", param)
+		logger.Info("Requesting default option", "param", param)
 		client.AddParamRequest(layers.DHCPOpt(param))
 	}
 
 	// Add requests for custom options
 	for _, param := range requestParams {
-		log.Printf("Requesting custom option %d", param)
+		logger.Info("Requesting custom option", "param", param)
 		client.AddParamRequest(layers.DHCPOpt(param))
 	}
 
@@ -68,26 +71,26 @@ func main() {
 
 	// Add custom options
 	for _, option := range options {
-		log.Printf("Adding option %d=0x%x", option.Type, option.Data)
+		slog.Info("Adding custom option", "type", option.Type, "value", fmt.Sprintf("0x%x", option.Data))
 		client.AddOption(option.Type, option.Data)
 	}
 
 	client.Start()
 	defer client.Stop()
 
-	c := make(chan os.Signal)
+	c := make(chan os.Signal, 1)
 	signal.Notify(c, os.Interrupt, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP, syscall.SIGUSR1)
 	for {
 		sig := <-c
-		log.Println("received", sig)
+		logger.Info("received signal", "type", sig)
 		switch sig {
 		case syscall.SIGINT, syscall.SIGTERM:
 			return
 		case syscall.SIGHUP:
-			log.Println("renew lease")
+			logger.Info("renew lease")
 			client.Renew()
 		case syscall.SIGUSR1:
-			log.Println("acquire new lease")
+			logger.Info("acquire new lease")
 			client.Rebind()
 		}
 	}

go.mod

@@ -17,4 +17,4 @@ require (
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 
-go 1.18
+go 1.21

go.sum

@@ -1,6 +1,7 @@
 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/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/gopacket v1.1.19 h1:ves8RnFZPGiFnTS0uPQStjwru6uO6h+nlr9j6fL7kF8=
 github.com/google/gopacket v1.1.19/go.mod h1:iJ8V8n6KS+z2U1A8pUwu8bW5SyEMkXJB8Yo/Vo+TKTo=
 github.com/josharian/native v1.1.0 h1:uuaP0hAbW7Y4l0ZRQ6C9zfb7Mg1mbFKry/xzDAfmtLA=

logger.go

@@ -0,0 +1,14 @@
+package dhclient
+
+import (
+	"context"
+	"log/slog"
+)
+
+type discardHandler struct {
+	slog.JSONHandler
+}
+
+func (d *discardHandler) Enabled(context.Context, slog.Level) bool {
+	return false
+}