Added bootstrap DNS to the config file

DNS healthcheck now uses the upstream package methods

config.go

@@ -70,6 +70,7 @@ type coreDNSConfig struct {
 	Pprof               string          `yaml:"-"`
 	Cache               string          `yaml:"-"`
 	Prometheus          string          `yaml:"-"`
+	BootstrapDNS        string          `yaml:"bootstrap_dns"`
 	UpstreamDNS         []string        `yaml:"upstream_dns"`
 }
 
@@ -100,6 +101,7 @@ var config = configuration{
 		SafeBrowsingEnabled: false,
 		BlockedResponseTTL:  10, // in seconds
 		QueryLogEnabled:     true,
+		BootstrapDNS:        "8.8.8.8:53",
 		UpstreamDNS:         defaultDNS,
 		Cache:               "cache",
 		Prometheus:          "prometheus :9153",
@@ -253,7 +255,7 @@ const coreDNSConfigTemplate = `.:{{.Port}} {
     hosts {
         fallthrough
     }
-    {{if .UpstreamDNS}}upstream {{range .UpstreamDNS}}{{.}} {{end}} { bootstrap 8.8.8.8:53 }{{end}}
+    {{if .UpstreamDNS}}upstream {{range .UpstreamDNS}}{{.}} {{end}} { bootstrap {{.BootstrapDNS}} }{{end}}
     {{.Cache}}
     {{.Prometheus}}
 }

control.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
-	"net"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -15,8 +14,9 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/upstream"
+
 	corednsplugin "github.com/AdguardTeam/AdGuardHome/coredns_plugin"
-	"github.com/miekg/dns"
 	"gopkg.in/asaskevich/govalidator.v4"
 )
 
@@ -81,6 +81,7 @@ func handleStatus(w http.ResponseWriter, r *http.Request) {
 		"protection_enabled": config.CoreDNS.ProtectionEnabled,
 		"querylog_enabled":   config.CoreDNS.QueryLogEnabled,
 		"running":            isRunning(),
+		"bootstrap_dns":      config.CoreDNS.BootstrapDNS,
 		"upstream_dns":       config.CoreDNS.UpstreamDNS,
 		"version":            VersionString,
 	}
@@ -140,11 +141,8 @@ func handleSetUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	// if empty body -- user is asking for default servers
-	hosts, err := sanitiseDNSServers(string(body))
-	if err != nil {
-		httpError(w, http.StatusBadRequest, "Invalid DNS servers were given: %s", err)
-		return
-	}
+	hosts := strings.Fields(string(body))
+
 	if len(hosts) == 0 {
 		config.CoreDNS.UpstreamDNS = defaultDNS
 	} else {
@@ -214,104 +212,26 @@ func handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 }
 
 func checkDNS(input string) error {
-	input, err := sanitizeDNSServer(input)
+
+	u, err := upstream.NewUpstream(input, config.CoreDNS.BootstrapDNS)
+
 	if err != nil {
 		return err
 	}
 
-	req := dns.Msg{}
-	req.Id = dns.Id()
-	req.RecursionDesired = true
-	req.Question = []dns.Question{
-		{Name: "google-public-dns-a.google.com.", Qtype: dns.TypeA, Qclass: dns.ClassINET},
-	}
+	alive, err := upstream.IsAlive(u)
 
-	prefix, host := splitDNSServerPrefixServer(input)
-
-	c := dns.Client{
-		Timeout: time.Minute,
-	}
-	switch prefix {
-	case "tls://":
-		c.Net = "tcp-tls"
-	}
-
-	resp, rtt, err := c.Exchange(&req, host)
 	if err != nil {
 		return fmt.Errorf("couldn't communicate with DNS server %s: %s", input, err)
 	}
-	trace("exchange with %s took %v", input, rtt)
-	if len(resp.Answer) != 1 {
-		return fmt.Errorf("DNS server %s returned wrong answer", input)
-	}
-	if t, ok := resp.Answer[0].(*dns.A); ok {
-		if !net.IPv4(8, 8, 8, 8).Equal(t.A) {
-			return fmt.Errorf("DNS server %s returned wrong answer: %v", input, t.A)
-		}
+
+	if !alive {
+		return fmt.Errorf("DNS server has not passed the healthcheck: %s", input)
 	}
 
 	return nil
 }
 
-func sanitiseDNSServers(input string) ([]string, error) {
-	fields := strings.Fields(input)
-	hosts := make([]string, 0)
-	for _, field := range fields {
-		sanitized, err := sanitizeDNSServer(field)
-		if err != nil {
-			return hosts, err
-		}
-		hosts = append(hosts, sanitized)
-	}
-	return hosts, nil
-}
-
-func getDNSServerPrefix(input string) string {
-	prefix := ""
-	switch {
-	case strings.HasPrefix(input, "dns://"):
-		prefix = "dns://"
-	case strings.HasPrefix(input, "tls://"):
-		prefix = "tls://"
-	}
-	return prefix
-}
-
-func splitDNSServerPrefixServer(input string) (string, string) {
-	prefix := getDNSServerPrefix(input)
-	host := strings.TrimPrefix(input, prefix)
-	return prefix, host
-}
-
-func sanitizeDNSServer(input string) (string, error) {
-	prefix, host := splitDNSServerPrefixServer(input)
-	host = appendPortIfMissing(prefix, host)
-	{
-		h, _, err := net.SplitHostPort(host)
-		if err != nil {
-			return "", err
-		}
-		ip := net.ParseIP(h)
-		if ip == nil {
-			return "", fmt.Errorf("invalid DNS server field: %s", h)
-		}
-	}
-	return prefix + host, nil
-}
-
-func appendPortIfMissing(prefix, input string) string {
-	port := "53"
-	switch prefix {
-	case "tls://":
-		port = "853"
-	}
-	_, _, err := net.SplitHostPort(input)
-	if err == nil {
-		return input
-	}
-	return net.JoinHostPort(input, port)
-}
-
 //noinspection GoUnusedParameter
 func handleGetVersionJSON(w http.ResponseWriter, r *http.Request) {
 	now := time.Now()

openapi.yaml

@@ -41,6 +41,7 @@ paths:
                             protection_enabled: true
                             querylog_enabled: true
                             running: true
+                            bootstrap_dns: 8.8.8.8:53
                             upstream_dns:
                               - 1.1.1.1
                               - 1.0.0.1

upstream/helpers.go

@@ -93,7 +93,7 @@ func IsAlive(u Upstream) (bool, error) {
 	// If we got a header, we're alright, basically only care about I/O errors 'n stuff.
 	if err != nil && resp != nil {
 		// Silly check, something sane came back.
-		if resp.Response || resp.Opcode == dns.OpcodeQuery {
+		if resp.Rcode != dns.RcodeServerFailure {
 			err = nil
 		}
 	}

upstream/persistent.go

@@ -10,6 +10,8 @@ import (
 	"github.com/miekg/dns"
 )
 
+// Persistent connections cache -- almost similar to the same used in the CoreDNS forward plugin
+
 const (
 	defaultExpire       = 10 * time.Second
 	minDialTimeout      = 100 * time.Millisecond