all: imp code

internal/cmd/config.go

@@ -49,14 +49,17 @@ func createProxyConfig(
 	l *slog.Logger,
 	options *Options,
 ) (conf *proxy.Config, err error) {
-	reqHdlr := handler.NewDefault(ctx, &handler.DefaultConfig{
+	reqHdlr, err := handler.NewDefault(ctx, &handler.DefaultConfig{
 		Logger: l.With(slogutil.KeyPrefix, "default_handler"),
 		// TODO(e.burkov):  Use the configured message constructor.
 		MessageConstructor: dnsmsg.DefaultMessageConstructor{},
 		HaltIPv6:           options.IPv6Disabled,
 		HostsFiles:         options.hostsFiles(ctx, l),
 		FileSystem:         osutil.RootDirFS(),
 	})
+	if err != nil {
+		return nil, fmt.Errorf("creating default handler: %w", err)
+	}
 
 	conf = &proxy.Config{
 		Logger: l.With(slogutil.KeyPrefix, proxy.LogPrefix),

internal/handler/constructor.go

@@ -17,8 +17,8 @@ type messageConstructor interface {
 	NewCompressedResponse(req *dns.Msg, code int) (resp *dns.Msg)
 
 	// NewPTRAnswer creates a new resource record for PTR response with the
-	// given name and PTR domain.
-	NewPTRAnswer(name, ptrDomain string) (ans *dns.PTR)
+	// given FQDN and PTR domain.
+	NewPTRAnswer(fqdn, ptrDomain string) (ans *dns.PTR)
 
 	// NewIPResponse creates a new A/AAAA response message for req with the
 	// given IP addresses.  All IP addresses must be of the same family.
@@ -48,9 +48,9 @@ func (defaultConstructor) NewCompressedResponse(req *dns.Msg, code int) (resp *d
 
 // NewPTRAnwer implements the [messageConstructor] interface for
 // [defaultConstructor].
-func (defaultConstructor) NewPTRAnswer(name, ptrDomain string) (ans *dns.PTR) {
+func (defaultConstructor) NewPTRAnswer(fqdn, ptrDomain string) (ans *dns.PTR) {
 	return &dns.PTR{
-		Hdr: hdr(name, dns.TypePTR),
+		Hdr: hdr(fqdn, dns.TypePTR),
 		Ptr: ptrDomain,
 	}
 }

internal/handler/default.go

@@ -43,12 +43,10 @@ type Default struct {
 }
 
 // NewDefault creates a new [Default] handler.
-func NewDefault(ctx context.Context, conf *DefaultConfig) (d *Default) {
-	l := conf.Logger
-
+func NewDefault(ctx context.Context, conf *DefaultConfig) (d *Default, err error) {
 	hosts, err := readHosts(conf.FileSystem, conf.HostsFiles)
 	if err != nil {
-		l.DebugContext(ctx, "creating hosts container", "err", err)
+		return nil, err
 	}
 
 	mc, ok := conf.MessageConstructor.(messageConstructor)
@@ -63,7 +61,7 @@ func NewDefault(ctx context.Context, conf *DefaultConfig) (d *Default) {
 		isIPv6Halted: conf.HaltIPv6,
 		messages:     mc,
 		hosts:        hosts,
-	}
+	}, nil
 }
 
 // HandleRequest resolves the DNS request within proxyCtx.  It only calls

internal/handler/default_internal_test.go

@@ -53,12 +53,13 @@ func TestDefault_haltAAAA(t *testing.T) {
 		t.Parallel()
 
 		ctx := testutil.ContextWithTimeout(t, defaultTimeout)
-		hdlr := NewDefault(ctx, &DefaultConfig{
+		hdlr, err := NewDefault(ctx, &DefaultConfig{
 			Logger:             slogutil.NewDiscardLogger(),
 			MessageConstructor: messages,
 			HaltIPv6:           false,
 			FileSystem:         testdata,
 		})
+		require.NoError(t, err)
 
 		ctx = testutil.ContextWithTimeout(t, defaultTimeout)
 
@@ -70,12 +71,13 @@ func TestDefault_haltAAAA(t *testing.T) {
 		t.Parallel()
 
 		ctx := testutil.ContextWithTimeout(t, defaultTimeout)
-		hdlr := NewDefault(ctx, &DefaultConfig{
+		hdlr, err := NewDefault(ctx, &DefaultConfig{
 			Logger:             slogutil.NewDiscardLogger(),
 			MessageConstructor: messages,
 			HaltIPv6:           true,
 			FileSystem:         testdata,
 		})
+		require.NoError(t, err)
 
 		ctx = testutil.ContextWithTimeout(t, defaultTimeout)
 
@@ -91,13 +93,14 @@ func TestDefault_resolveFromHosts(t *testing.T) {
 	messages := dnsmsg.DefaultMessageConstructor{}
 
 	ctx := testutil.ContextWithTimeout(t, defaultTimeout)
-	hdlr := NewDefault(ctx, &DefaultConfig{
+	hdlr, err := NewDefault(ctx, &DefaultConfig{
 		MessageConstructor: messages,
 		FileSystem:         testdata,
 		Logger:             slogutil.NewDiscardLogger(),
 		HostsFiles:         []string{path.Join(t.Name(), "hosts")},
 		HaltIPv6:           true,
 	})
+	require.NoError(t, err)
 
 	const (
 		domainV4 = "ipv4.domain.example"

internal/handler/hosts.go

@@ -101,10 +101,10 @@ func (h *Default) resolveFromHosts(ctx context.Context, req *dns.Msg) (resp *dns
 		return nil
 	}
 
-	switch addrsNum, namesNum := len(addrs), len(ptrs); {
-	case addrsNum != 0:
+	switch {
+	case len(addrs) > 0:
 		resp = h.messages.NewIPResponse(req, addrs)
-	case namesNum != 0:
+	case len(ptrs) > 0:
 		resp = h.messages.NewCompressedResponse(req, dns.RcodeSuccess)
 		name = req.Question[0].Name
 		for _, ptr := range ptrs {