Merge pull request #381 from AkihiroSuda/fix-380

pkg/hostagent/dns: truncate messages

Author: AkihiroSuda

cmd/limactl/debug.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"strconv"
+
+	"github.com/lima-vm/lima/pkg/hostagent/dns"
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+func newDebugCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:    "debug",
+		Short:  "Debug utilities",
+		Long:   "DO NOT USE! THE COMMAND SYNTAX IS SUBJECT TO CHANGE!",
+		Hidden: true,
+	}
+	cmd.AddCommand(newDebugDNSCommand())
+	return cmd
+}
+
+func newDebugDNSCommand() *cobra.Command {
+	var cmd = &cobra.Command{
+		Use:   "dns UDPPORT [TCPPORT]",
+		Short: "Debug built-in DNS",
+		Long:  "DO NOT USE! THE COMMAND SYNTAX IS SUBJECT TO CHANGE!",
+		Args:  cobra.RangeArgs(1, 2),
+		RunE:  debugDNSAction,
+	}
+	return cmd
+}
+
+func debugDNSAction(cmd *cobra.Command, args []string) error {
+	udpLocalPort, err := strconv.Atoi(args[0])
+	if err != nil {
+		return err
+	}
+	tcpLocalPort := 0
+	if len(args) > 2 {
+		tcpLocalPort, err = strconv.Atoi(args[1])
+		if err != nil {
+			return err
+		}
+	}
+	srv, err := dns.Start(udpLocalPort, tcpLocalPort)
+	if err != nil {
+		return err
+	}
+	logrus.Infof("Started srv %+v (UDP %d, TCP %d)", srv, udpLocalPort, tcpLocalPort)
+	for {
+	}
+}

cmd/limactl/main.go

@@ -81,6 +81,7 @@ func newApp() *cobra.Command {
 		newHostagentCommand(),
 		newInfoCommand(),
 		newShowSSHCommand(),
+		newDebugCommand(),
 	)
 	return rootCmd
 }

pkg/hostagent/dns.go renamed to pkg/hostagent/dns/dns.go

@@ -1,6 +1,6 @@
 // This file has been adapted from https://github.com/norouter/norouter/blob/v0.6.4/pkg/agent/dns/dns.go
 
-package hostagent
+package dns
 
 import (
 	"fmt"
@@ -11,6 +11,10 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// Truncate for avoiding "Parse error" from `busybox nslookup`
+// https://github.com/lima-vm/lima/issues/380
+const truncateSize = 512
+
 type Handler struct {
 	clientConfig *dns.ClientConfig
 	clients      []*dns.Client
@@ -174,6 +178,7 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
 		}
 	}
 	if handled {
+		reply.Truncate(truncateSize)
 		_ = w.WriteMsg(&reply)
 		return
 	}
@@ -186,13 +191,15 @@ func (h *Handler) handleDefault(w dns.ResponseWriter, req *dns.Msg) {
 			addr := fmt.Sprintf("%s:%s", srv, h.clientConfig.Port)
 			reply, _, err := client.Exchange(req, addr)
 			if err == nil {
+				reply.Truncate(truncateSize)
 				_ = w.WriteMsg(reply)
 				return
 			}
 		}
 	}
 	var reply dns.Msg
 	reply.SetReply(req)
+	reply.Truncate(truncateSize)
 	_ = w.WriteMsg(&reply)
 }
 
@@ -205,14 +212,14 @@ func (h *Handler) ServeDNS(w dns.ResponseWriter, req *dns.Msg) {
 	}
 }
 
-func (a *HostAgent) StartDNS() (*Server, error) {
+func Start(udpLocalPort, tcpLocalPort int) (*Server, error) {
 	h, err := newHandler()
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 	server := &Server{}
-	if a.udpDNSLocalPort > 0 {
-		addr := fmt.Sprintf("127.0.0.1:%d", a.udpDNSLocalPort)
+	if udpLocalPort > 0 {
+		addr := fmt.Sprintf("127.0.0.1:%d", udpLocalPort)
 		s := &dns.Server{Net: "udp", Addr: addr, Handler: h}
 		server.udp = s
 		go func() {
@@ -221,8 +228,8 @@ func (a *HostAgent) StartDNS() (*Server, error) {
 			}
 		}()
 	}
-	if a.tcpDNSLocalPort > 0 {
-		addr := fmt.Sprintf("127.0.0.1:%d", a.tcpDNSLocalPort)
+	if tcpLocalPort > 0 {
+		addr := fmt.Sprintf("127.0.0.1:%d", tcpLocalPort)
 		s := &dns.Server{Net: "tcp", Addr: addr, Handler: h}
 		server.tcp = s
 		go func() {

pkg/hostagent/hostagent.go

@@ -23,6 +23,7 @@ import (
 	guestagentapi "github.com/lima-vm/lima/pkg/guestagent/api"
 	guestagentclient "github.com/lima-vm/lima/pkg/guestagent/api/client"
 	hostagentapi "github.com/lima-vm/lima/pkg/hostagent/api"
+	"github.com/lima-vm/lima/pkg/hostagent/dns"
 	"github.com/lima-vm/lima/pkg/hostagent/events"
 	"github.com/lima-vm/lima/pkg/limayaml"
 	"github.com/lima-vm/lima/pkg/qemu"
@@ -248,7 +249,7 @@ func (a *HostAgent) Run(ctx context.Context) error {
 	}()
 
 	if *a.y.UseHostResolver {
-		dnsServer, err := a.StartDNS()
+		dnsServer, err := dns.Start(a.udpDNSLocalPort, a.tcpDNSLocalPort)
 		if err != nil {
 			return fmt.Errorf("cannot start DNS server: %w", err)
 		}