feat: add MIDDLEWARE_LOCALDNS_RESOLVERS

Dockerfile

@@ -81,6 +81,7 @@ ENV \
     MIDDLEWARE_LOG_DIRECTORY=/var/log/dns/ \
     MIDDLEWARE_LOG_REQUESTS=on \
     MIDDLEWARE_LOG_RESPONSES=off \
+    MIDDLEWARE_LOCALDNS_RESOLVERS= \
     CACHE_TYPE=lru \
     CACHE_LRU_MAX_ENTRIES=10000 \
     BLOCK_MALICIOUS=on \

README.md

@@ -141,6 +141,7 @@ If you're running Kubernetes, there is a separate article on [how to set up K8s]
 | `METRICS_TYPE` | `noop` | `noop` or `prometheus` |
 | `METRICS_PROMETHEUS_ADDRESS` | `:9090` | HTTP Prometheus server listening address |
 | `METRICS_PROMETHEUS_SUBSYSTEM` | `dns` | Prometheus metrics prefix/subsystem |
+| `MIDDLEWARE_LOCALDNS_RESOLVERS` | | Comma separated list of local DNS resolvers to use for local names DNS requests |
 | `CHECK_DNS` | `on` | `on` or `off`. Check resolving github.com using `127.0.0.1:53` at start |
 | `UPDATE_PERIOD` | `24h` | Period to update block lists and restart Unbound. Set to `0` to disable. |
 

internal/config/localdns.go

@@ -0,0 +1,60 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"net/netip"
+
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gotree"
+)
+
+type LocalDNS struct {
+	Resolvers []netip.AddrPort
+}
+
+var (
+	ErrLocalResolverAddressNotValid = errors.New("local resolver address is not valid")
+	ErrLocalResolverPortIsZero      = errors.New("local resolver port is zero")
+)
+
+func (l *LocalDNS) validate() (err error) {
+	for _, resolver := range l.Resolvers {
+		switch {
+		case !resolver.IsValid():
+			return fmt.Errorf("%w: %s",
+				ErrLocalResolverAddressNotValid, resolver)
+		case resolver.Port() == 0:
+			return fmt.Errorf("%w: %s",
+				ErrLocalResolverPortIsZero, resolver)
+		}
+	}
+
+	return nil
+}
+
+func (l *LocalDNS) String() string {
+	return l.ToLinesNode().String()
+}
+
+func (l *LocalDNS) ToLinesNode() (node *gotree.Node) {
+	if len(l.Resolvers) == 0 {
+		return gotree.New("Local DNS middleware: disabled")
+	}
+
+	node = gotree.New("Local DNS middleware:")
+	resolversNode := gotree.New("Local resolvers:")
+	for _, resolver := range l.Resolvers {
+		resolversNode.Appendf("%s", resolver)
+	}
+	node.AppendNode(resolversNode)
+	return node
+}
+
+func (l *LocalDNS) read(reader *reader.Reader) (err error) {
+	l.Resolvers, err = reader.CSVNetipAddrPorts("MIDDLEWARE_LOCALDNS_RESOLVERS")
+	if err != nil {
+		return err
+	}
+	return nil
+}

internal/config/settings.go

@@ -31,6 +31,7 @@ type Settings struct {
 	Log              Log
 	MiddlewareLog    MiddlewareLog
 	Metrics          Metrics
+	LocalDNS         LocalDNS
 	CheckDNS         *bool
 	UpdatePeriod     *time.Duration
 }
@@ -74,6 +75,7 @@ func (s *Settings) Validate() (err error) {
 		"log":            s.Log.validate,
 		"middleware log": s.MiddlewareLog.validate,
 		"metrics":        s.Metrics.validate,
+		"local DNS":      s.LocalDNS.validate,
 	}
 	for name, validate := range nameToValidate {
 		err = validate()
@@ -115,6 +117,7 @@ func (s *Settings) ToLinesNode() (node *gotree.Node) {
 	node.AppendNode(s.Log.ToLinesNode())
 	node.AppendNode(s.MiddlewareLog.ToLinesNode())
 	node.AppendNode(s.Metrics.ToLinesNode())
+	node.AppendNode(s.LocalDNS.ToLinesNode())
 	node.Appendf("Check DNS: %s", gosettings.BoolToYesNo(s.CheckDNS))
 
 	if *s.UpdatePeriod == 0 {
@@ -164,6 +167,11 @@ func (s *Settings) Read(reader *reader.Reader, warner Warner) (err error) {
 
 	s.Metrics.read(reader)
 
+	err = s.LocalDNS.read(reader)
+	if err != nil {
+		return fmt.Errorf("local DNS settings: %w", err)
+	}
+
 	s.CheckDNS, err = reader.BoolPtr("CHECK_DNS")
 	if err != nil {
 		return err

internal/setup/dns.go

@@ -7,6 +7,7 @@ import (
 	"github.com/qdm12/dns/v2/pkg/metrics/prometheus"
 	cachemiddleware "github.com/qdm12/dns/v2/pkg/middlewares/cache"
 	filtermiddleware "github.com/qdm12/dns/v2/pkg/middlewares/filter"
+	"github.com/qdm12/dns/v2/pkg/middlewares/localdns"
 )
 
 type Service interface {
@@ -18,14 +19,61 @@ type Service interface {
 func DNS(userSettings config.Settings, ipv6Support bool, //nolint:ireturn
 	cache Cache, filter Filter, logger Logger, promRegistry PrometheusRegistry) (
 	server Service, err error) {
-	var middlewares []Middleware
+	commonPrometheus := prometheus.Settings{
+		Prefix:   *userSettings.Metrics.Prometheus.Subsystem,
+		Registry: promRegistry,
+	}
+
+	middlewares, err := setupMiddlewares(userSettings, cache,
+		filter, logger, commonPrometheus)
+	if err != nil {
+		return nil, fmt.Errorf("setting up middlewares: %w", err)
+	}
+
+	switch userSettings.Upstream {
+	case "dot":
+		dotMetrics, err := dotMetrics(userSettings.Metrics.Type, commonPrometheus)
+		if err != nil {
+			return nil, fmt.Errorf("DoT metrics: %w", err)
+		}
+
+		return dotServer(userSettings, ipv6Support, middlewares,
+			logger, dotMetrics)
+	case "doh":
+		dohMetrics, err := dohMetrics(userSettings.Metrics.Type, commonPrometheus)
+		if err != nil {
+			return nil, fmt.Errorf("DoH metrics: %w", err)
+		}
+
+		return dohServer(userSettings, ipv6Support, middlewares,
+			logger, dohMetrics)
+	default:
+		panic(fmt.Sprintf("unknown upstream: %s", userSettings.Upstream))
+	}
+}
 
+func setupMiddlewares(userSettings config.Settings, cache Cache,
+	filter Filter, logger Logger, commonPrometheus prometheus.Settings) (
+	middlewares []Middleware, err error) {
 	cacheMiddleware, err := cachemiddleware.New(cachemiddleware.Settings{Cache: cache})
 	if err != nil {
 		return nil, fmt.Errorf("creating cache middleware: %w", err)
 	}
 	middlewares = append(middlewares, cacheMiddleware)
 
+	if len(userSettings.LocalDNS.Resolvers) > 0 {
+		localDNSMiddleware, err := localdns.New(localdns.Settings{
+			Resolvers: userSettings.LocalDNS.Resolvers,
+			Logger:    logger,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("creating local DNS middleware: %w", err)
+		}
+		// Place after cache middleware, since we want to avoid caching for local
+		// hostnames that may change regularly.
+		middlewares = append(middlewares, localDNSMiddleware)
+	}
+
 	filterMiddleware, err := filtermiddleware.New(filtermiddleware.Settings{Filter: filter})
 	if err != nil {
 		return nil, fmt.Errorf("creating filter middleware: %w", err)
@@ -34,14 +82,7 @@ func DNS(userSettings config.Settings, ipv6Support bool, //nolint:ireturn
 	// to catch filtered responses found from the cache.
 	middlewares = append(middlewares, filterMiddleware)
 
-	commonPrometheus := prometheus.Settings{
-		Prefix:   *userSettings.Metrics.Prometheus.Subsystem,
-		Registry: promRegistry,
-	}
-
-	metricsType := userSettings.Metrics.Type
-
-	metricsMiddleware, err := middlewareMetrics(metricsType,
+	metricsMiddleware, err := middlewareMetrics(userSettings.Metrics.Type,
 		commonPrometheus)
 	if err != nil {
 		return nil, fmt.Errorf("middleware metrics: %w", err)
@@ -58,24 +99,5 @@ func DNS(userSettings config.Settings, ipv6Support bool, //nolint:ireturn
 	}
 	middlewares = append(middlewares, logMiddleware)
 
-	switch userSettings.Upstream {
-	case "dot":
-		dotMetrics, err := dotMetrics(metricsType, commonPrometheus)
-		if err != nil {
-			return nil, fmt.Errorf("DoT metrics: %w", err)
-		}
-
-		return dotServer(userSettings, ipv6Support, middlewares,
-			logger, dotMetrics)
-	case "doh":
-		dohMetrics, err := dohMetrics(metricsType, commonPrometheus)
-		if err != nil {
-			return nil, fmt.Errorf("DoH metrics: %w", err)
-		}
-
-		return dohServer(userSettings, ipv6Support, middlewares,
-			logger, dohMetrics)
-	default:
-		panic(fmt.Sprintf("unknown upstream: %s", userSettings.Upstream))
-	}
+	return middlewares, nil
 }