Calm down and relax dns query check

firewall/tunnel.go

@@ -34,7 +34,7 @@ func checkTunneling(ctx context.Context, conn *network.Connection, pkt packet.Pa
 	case conn.Process().Pid == ownPID:
 		// Bypass tunneling for certain own connections.
 		switch {
-		case captain.ClientBootstrapping():
+		case !captain.ClientReady():
 			return
 		case captain.IsExcepted(conn.Entity.IP):
 			return

netenv/online-status.go

@@ -37,13 +37,12 @@ var (
 	PortalTestIP  = net.IPv4(192, 0, 2, 1)
 	PortalTestURL = fmt.Sprintf("http://%s/", PortalTestIP)
 
-	DNSTestDomain     = "one.one.one.one."
-	DNSTestExpectedIP = net.IPv4(1, 1, 1, 1)
-
-	DNSFallbackTestDomain     = "dns-check.safing.io."
-	DNSFallbackTestExpectedIP = net.IPv4(0, 65, 67, 75) // Ascii: \0ACK
+	DNSTestDomain     = "online-check.safing.io."
+	DNSTestExpectedIP = net.IPv4(0, 65, 67, 75) // Ascii: \0ACK
+	DNSTestQueryFunc  func(ctx context.Context, fdqn string) (ips []net.IP, ok bool, err error)
 
 	ConnectedToSPN = abool.New()
+	ConnectedToDNS = abool.New()
 
 	// SpecialCaptivePortalDomain is the domain name used to point to the detected captive portal IP
 	// or the captive portal test IP. The default value should be overridden by the resolver package,
@@ -53,8 +52,6 @@ var (
 	// ConnectivityDomains holds all connectivity domains. This slice must not be modified.
 	ConnectivityDomains = []string{
 		SpecialCaptivePortalDomain,
-		DNSTestDomain,         // Internal DNS Check
-		DNSFallbackTestDomain, // Internal DNS Check
 
 		// Windows
 		"dns.msftncsi.com.", // DNS Check
@@ -380,20 +377,20 @@ func monitorOnlineStatus(ctx context.Context) error {
 func getDynamicStatusTrigger() <-chan time.Time {
 	switch GetOnlineStatus() {
 	case StatusOffline:
-		// Will be triggered by network change anyway.
-		return time.After(20 * time.Second)
+		// Will also be triggered by network change.
+		return time.After(10 * time.Second)
 	case StatusLimited, StatusPortal:
 		// Change will not be detected otherwise, but impact is minor.
 		return time.After(5 * time.Second)
 	case StatusSemiOnline:
 		// Very small impact.
-		return time.After(20 * time.Second)
+		return time.After(60 * time.Second)
 	case StatusOnline:
 		// Don't check until resolver reports problems.
 		return nil
 	case StatusUnknown:
-		return time.After(5 * time.Second)
-	default: // other unknown status
+		fallthrough
+	default:
 		return time.After(5 * time.Minute)
 	}
 }
@@ -407,13 +404,18 @@ func checkOnlineStatus(ctx context.Context) {
 		return StatusUnknown
 	}*/
 
-	// 0) check if connected to SPN
+	// 0) check if connected to SPN and/or DNS.
 
 	if ConnectedToSPN.IsSet() {
 		updateOnlineStatus(StatusOnline, nil, "connected to SPN")
 		return
 	}
 
+	if ConnectedToDNS.IsSet() {
+		updateOnlineStatus(StatusOnline, nil, "connected to DNS")
+		return
+	}
+
 	// 1) check for addresses
 
 	ipv4, ipv6, err := GetAssignedAddresses()
@@ -508,34 +510,28 @@ func checkOnlineStatus(ctx context.Context) {
 
 	// 3) resolve a query
 
-	// Check with primary dns check domain.
-	ips, err := net.LookupIP(DNSTestDomain)
-	if err != nil {
-		log.Warningf("netenv: dns check query failed: %s", err)
-	} else {
-		// check for expected response
-		for _, ip := range ips {
-			if ip.Equal(DNSTestExpectedIP) {
-				updateOnlineStatus(StatusOnline, nil, "all checks passed")
-				return
-			}
-		}
-	}
-
-	// If that did not work, check with fallback dns check domain.
-	ips, err = net.LookupIP(DNSFallbackTestDomain)
-	if err != nil {
-		log.Warningf("netenv: dns fallback check query failed: %s", err)
-		updateOnlineStatus(StatusLimited, nil, "dns fallback check query failed")
+	// Check if we can resolve the dns check domain.
+	if DNSTestQueryFunc == nil {
+		updateOnlineStatus(StatusOnline, nil, "all checks passed, dns query check disabled")
 		return
 	}
-	// check for expected response
-	for _, ip := range ips {
-		if ip.Equal(DNSFallbackTestExpectedIP) {
-			updateOnlineStatus(StatusOnline, nil, "all checks passed")
-			return
-		}
+	ips, ok, err := DNSTestQueryFunc(ctx, DNSTestDomain)
+	switch {
+	case ok && err != nil:
+		updateOnlineStatus(StatusOnline, nil, fmt.Sprintf(
+			"all checks passed, acceptable result for dns query check: %s",
+			err,
+		))
+	case ok && len(ips) >= 1 && ips[0].Equal(DNSTestExpectedIP):
+		updateOnlineStatus(StatusOnline, nil, "all checks passed")
+	case ok && len(ips) >= 1:
+		log.Warningf("netenv: dns query check response mismatched: got %s", ips[0])
+		updateOnlineStatus(StatusOnline, nil, "all checks passed, dns query check response mismatched")
+	case ok:
+		log.Warningf("netenv: dns query check response mismatched: empty response")
+		updateOnlineStatus(StatusOnline, nil, "all checks passed, dns query check response was empty")
+	default:
+		log.Warningf("netenv: dns query check failed: %s", err)
+		updateOnlineStatus(StatusOffline, nil, "dns query check failed")
 	}
-	// unexpected response
-	updateOnlineStatus(StatusSemiOnline, nil, "dns check query response mismatched")
 }

resolver/resolve.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net"
 	"sync"
 	"time"
 
@@ -318,8 +319,8 @@ func resolveAndCache(ctx context.Context, q *Query, oldCache *RRCache) (rrCache
 	}
 
 	// check if we are online
-	if primarySource != ServerSourceEnv && netenv.GetOnlineStatus() == netenv.StatusOffline {
-		if !netenv.IsConnectivityDomain(q.FQDN) {
+	if netenv.GetOnlineStatus() == netenv.StatusOffline && primarySource != ServerSourceEnv {
+		if q.FQDN != netenv.DNSTestDomain && !netenv.IsConnectivityDomain(q.FQDN) {
 			// we are offline and this is not an online check query
 			return oldCache, ErrOffline
 		}
@@ -358,6 +359,7 @@ resolveLoop:
 					// some resolvers might also block
 					return nil, err
 				case netenv.GetOnlineStatus() == netenv.StatusOffline &&
+					q.FQDN != netenv.DNSTestDomain &&
 					!netenv.IsConnectivityDomain(q.FQDN):
 					// we are offline and this is not an online check query
 					return oldCache, ErrOffline
@@ -478,3 +480,45 @@ func shouldResetCache(q *Query) (reset bool) {
 
 	return false
 }
+
+func init() {
+	netenv.DNSTestQueryFunc = testConnectivity
+}
+
+// testConnectivity test if resolving a query succeeds and returns whether the
+// query itself succeeded, separate from interpreting the result.
+func testConnectivity(ctx context.Context, fdqn string) (ips []net.IP, ok bool, err error) {
+	q := &Query{
+		FQDN:      fdqn,
+		QType:     dns.Type(dns.TypeA),
+		NoCaching: true,
+	}
+	if !q.check() {
+		return nil, false, ErrInvalid
+	}
+
+	rrCache, err := resolveAndCache(ctx, q, nil)
+	switch {
+	case err == nil:
+		switch rrCache.RCode {
+		case dns.RcodeNameError:
+			return nil, true, ErrNotFound
+		case dns.RcodeRefused:
+			return nil, true, errors.New("refused")
+		default:
+			ips := rrCache.ExportAllARecords()
+			if len(ips) > 0 {
+				return ips, true, nil
+			}
+			return nil, true, ErrNotFound
+		}
+	case errors.Is(err, ErrNotFound):
+		return nil, true, err
+	case errors.Is(err, ErrBlocked):
+		return nil, true, err
+	case errors.Is(err, ErrNoCompliance):
+		return nil, true, err
+	default:
+		return nil, false, err
+	}
+}

resolver/resolver.go

@@ -206,8 +206,8 @@ func (brc *BasicResolverConn) init() {
 
 // ReportFailure reports that an error occurred with this resolver.
 func (brc *BasicResolverConn) ReportFailure() {
+	// Don't mark resolver as failed if we are offline.
 	if !netenv.Online() {
-		// don't mark failed if we are offline
 		return
 	}
 
@@ -224,6 +224,11 @@ func (brc *BasicResolverConn) ReportFailure() {
 		// the fail.
 		brc.networkChangedFlag.Refresh()
 	}
+
+	// Report to netenv that a configured server failed.
+	if brc.resolver.Info.Source == ServerSourceConfigured {
+		netenv.ConnectedToDNS.UnSet()
+	}
 }
 
 // IsFailing returns if this resolver is currently failing.
@@ -255,4 +260,9 @@ func (brc *BasicResolverConn) ResetFailure() {
 		defer brc.failLock.Unlock()
 		brc.fails = 0
 	}
+
+	// Report to netenv that a configured server succeeded.
+	if brc.resolver.Info.Source == ServerSourceConfigured {
+		netenv.ConnectedToDNS.Set()
+	}
 }