From ea1b189330d1ed4749f4044bc646681beb91720f Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Fri, 20 May 2022 16:35:46 +0200
Subject: [PATCH 1/8] Reset system self-check after network change

---
 compat/module.go | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/compat/module.go b/compat/module.go
index d1a27628..77478f7e 100644
--- a/compat/module.go
+++ b/compat/module.go
@@ -26,6 +26,10 @@ var (
 	// selfcheckFails counts how often the self check failed successively.
 	// selfcheckFails is not locked as it is only accessed by the self-check task.
 	selfcheckFails int
+
+	// selfcheckNetworkChangedFlag is used to track changed to the network for
+	// the self-check.
+	selfcheckNetworkChangedFlag = netenv.GetNetworkChangedFlag()
 )
 
 // selfcheckFailThreshold holds the threshold of how many times the selfcheck
@@ -49,6 +53,7 @@ func prep() error {
 func start() error {
 	startNotify()
 
+	selfcheckNetworkChangedFlag.Refresh()
 	selfcheckTask = module.NewTask("compatibility self-check", selfcheckTaskFunc).
 		Repeat(5 * time.Minute).
 		MaxDelay(selfcheckTaskRetryAfter).
@@ -83,19 +88,23 @@ func selfcheckTaskFunc(ctx context.Context, task *modules.Task) error {
 
 	// Run selfcheck and return if successful.
 	issue, err := selfcheck(ctx)
-	if err == nil {
-		selfCheckIsFailing.UnSet()
-		selfcheckFails = 0
-		resetSystemIssue()
+	switch {
+	case err == nil:
+		// Successful.
 		tracer.Debugf("compat: self-check successful")
-		return nil
-	}
+	case issue == nil:
+		// Internal error.
+		tracer.Warningf("compat: %s", err)
+	case selfcheckNetworkChangedFlag.IsSet():
+		// The network changed, ignore the issue.
+	default:
+		// The self-check failed.
 
-	// Log result.
-	if issue != nil {
+		// Set state and increase counter.
 		selfCheckIsFailing.Set()
 		selfcheckFails++
 
+		// Log and notify.
 		tracer.Errorf("compat: %s", err)
 		if selfcheckFails >= selfcheckFailThreshold {
 			issue.notify(err)
@@ -103,14 +112,16 @@ func selfcheckTaskFunc(ctx context.Context, task *modules.Task) error {
 
 		// Retry quicker when failed.
 		task.Schedule(time.Now().Add(selfcheckTaskRetryAfter))
-	} else {
-		selfCheckIsFailing.UnSet()
-		selfcheckFails = 0
 
-		// Only log internal errors, but don't notify.
-		tracer.Warningf("compat: %s", err)
+		return nil
 	}
 
+	// Reset self-check state.
+	selfcheckNetworkChangedFlag.Refresh()
+	selfCheckIsFailing.UnSet()
+	selfcheckFails = 0
+	resetSystemIssue()
+
 	return nil
 }
 

From e178b732bca2a3daa0f5ab67e8e01a0500ccd4e6 Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Fri, 20 May 2022 16:37:19 +0200
Subject: [PATCH 2/8] Calm down and relax dns query check

---
 firewall/tunnel.go      |  2 +-
 netenv/online-status.go | 76 +++++++++++++++++++----------------------
 resolver/resolve.go     | 48 ++++++++++++++++++++++++--
 resolver/resolver.go    | 12 ++++++-
 4 files changed, 94 insertions(+), 44 deletions(-)

diff --git a/firewall/tunnel.go b/firewall/tunnel.go
index 32d60de1..08adff33 100644
--- a/firewall/tunnel.go
+++ b/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
diff --git a/netenv/online-status.go b/netenv/online-status.go
index a7589a13..0ef612fd 100644
--- a/netenv/online-status.go
+++ b/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")
 }
diff --git a/resolver/resolve.go b/resolver/resolve.go
index 8663a32e..1b0b429e 100644
--- a/resolver/resolve.go
+++ b/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
+	}
+}
diff --git a/resolver/resolver.go b/resolver/resolver.go
index 56d4b6cc..1f12c8f2 100644
--- a/resolver/resolver.go
+++ b/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()
+	}
 }

From 49e79fe3fdd3b5f3a03a3a36e398d8604b9922bc Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Tue, 24 May 2022 11:18:23 +0200
Subject: [PATCH 3/8] Detect responses to multi/broadcast queries

---
 firewall/master.go     | 43 ++++++++++++++++++++++++++++++++++++++++++
 firewall/tunnel.go     |  4 ++--
 netenv/addresses.go    | 14 ++++++--------
 network/multicast.go   | 43 ++++++++++++++++++++++++++++++++++++++++++
 network/netutils/ip.go | 31 ++++++++++++++++++++++++++++++
 process/process.go     | 26 +++++++++++++++++++++++++
 6 files changed, 151 insertions(+), 10 deletions(-)
 create mode 100644 network/multicast.go

diff --git a/firewall/master.go b/firewall/master.go
index 16dc2b5f..4be457aa 100644
--- a/firewall/master.go
+++ b/firewall/master.go
@@ -3,7 +3,9 @@ package firewall
 import (
 	"context"
 	"fmt"
+	"net"
 	"path/filepath"
+	"strconv"
 	"strings"
 
 	"github.com/agext/levenshtein"
@@ -41,6 +43,7 @@ type deciderFn func(context.Context, *network.Connection, *profile.LayeredProfil
 var defaultDeciders = []deciderFn{
 	checkPortmasterConnection,
 	checkSelfCommunication,
+	checkIfBroadcastReply,
 	checkConnectionType,
 	checkConnectionScope,
 	checkEndpointLists,
@@ -182,6 +185,46 @@ func checkSelfCommunication(ctx context.Context, conn *network.Connection, _ *pr
 	return false
 }
 
+func checkIfBroadcastReply(ctx context.Context, conn *network.Connection, _ *profile.LayeredProfile, _ packet.Packet) bool {
+	// Only check inbound connections.
+	if !conn.Inbound {
+		return false
+	}
+	// Only check if the process has been identified.
+	if !conn.Process().IsIdentified() {
+		return false
+	}
+
+	// Check if the remote IP is part of a local network.
+	localNet, err := netenv.GetLocalNetwork(conn.Entity.IP)
+	if err != nil {
+		log.Tracer(ctx).Warningf("filter: failed to get local network: %s", err)
+		return false
+	}
+	if localNet == nil {
+		return false
+	}
+
+	// Search for a matching requesting connection.
+	requestingConn := network.GetMulticastRequestConn(conn, localNet)
+	if requestingConn == nil {
+		return false
+	}
+
+	conn.Accept(
+		fmt.Sprintf(
+			"response to multi/broadcast query to %s/%s",
+			packet.IPProtocol(requestingConn.Entity.Protocol),
+			net.JoinHostPort(
+				requestingConn.Entity.IP.String(),
+				strconv.Itoa(int(requestingConn.Entity.Port)),
+			),
+		),
+		"",
+	)
+	return true
+}
+
 func checkEndpointLists(ctx context.Context, conn *network.Connection, p *profile.LayeredProfile, _ packet.Packet) bool {
 	// DNS request from the system resolver require a special decision process,
 	// because the original requesting process is not known. Here, we only check
diff --git a/firewall/tunnel.go b/firewall/tunnel.go
index 08adff33..28f0e37d 100644
--- a/firewall/tunnel.go
+++ b/firewall/tunnel.go
@@ -42,10 +42,10 @@ func checkTunneling(ctx context.Context, conn *network.Connection, pkt packet.Pa
 	}
 
 	// Check more extensively for Local/LAN connections.
-	myNet, err := netenv.IsMyNet(conn.Entity.IP)
+	localNet, err := netenv.GetLocalNetwork(conn.Entity.IP)
 	if err != nil {
 		log.Warningf("firewall: failed to check if %s is in my net: %s", conn.Entity.IP, err)
-	} else if myNet {
+	} else if localNet != nil {
 		// With IPv6, just checking the IP scope is not enough, as the host very
 		// likely has a public IPv6 address.
 		// Don't tunnel LAN connections.
diff --git a/netenv/addresses.go b/netenv/addresses.go
index 14762c78..67c4c999 100644
--- a/netenv/addresses.go
+++ b/netenv/addresses.go
@@ -152,11 +152,9 @@ func IsMyIP(ip net.IP) (yes bool, err error) {
 	return false, nil
 }
 
-// IsMyNet returns whether the given IP is currently in the host's broadcast
-// domain - ie. the networks that the host is directly attached to.
-// Function is optimized with the assumption that is unlikely that the IP is
-// in the broadcast domain.
-func IsMyNet(ip net.IP) (yes bool, err error) {
+// GetLocalNetwork uses the given IP to search for a network configured on the
+// device and returns it.
+func GetLocalNetwork(ip net.IP) (myNet *net.IPNet, err error) {
 	myNetworksLock.Lock()
 	defer myNetworksLock.Unlock()
 
@@ -164,16 +162,16 @@ func IsMyNet(ip net.IP) (yes bool, err error) {
 	if myNetworksNetworkChangedFlag.IsSet() {
 		err := refreshMyNetworks()
 		if err != nil {
-			return false, err
+			return nil, err
 		}
 	}
 
 	// Check if the IP address is in my networks.
 	for _, myNet := range myNetworks {
 		if myNet.Contains(ip) {
-			return true, nil
+			return myNet, nil
 		}
 	}
 
-	return false, nil
+	return nil, nil
 }
diff --git a/network/multicast.go b/network/multicast.go
new file mode 100644
index 00000000..82cb2173
--- /dev/null
+++ b/network/multicast.go
@@ -0,0 +1,43 @@
+package network
+
+import (
+	"net"
+
+	"github.com/safing/portmaster/network/netutils"
+)
+
+// GetMulticastRequestConn searches for and returns the requesting connnection
+// of a possible multicast/broadcast response.
+func GetMulticastRequestConn(responseConn *Connection, responseFromNet *net.IPNet) *Connection {
+	// Calculate the broadcast address the query would have gone to.
+	responseNetBroadcastIP := netutils.GetBroadcastAddress(responseFromNet.IP, responseFromNet.Mask)
+
+	// Find requesting multicast/broadcast connection.
+	for _, conn := range conns.clone() {
+		switch {
+		case conn.Inbound:
+			// Ignore incoming connections.
+		//case conn.Ended != 0:
+		// Ignore ended connections.
+		case conn.Entity.Protocol != responseConn.Entity.Protocol:
+			// Ignore on protocol mismatch.
+		case conn.LocalPort != responseConn.LocalPort:
+			// Ignore on local port mismatch.
+		case !conn.LocalIP.Equal(responseConn.LocalIP):
+			// Ignore on local IP mismatch.
+		case !conn.Process().Equal(responseConn.Process()):
+			// Ignore if processes mismatch.
+		case conn.Entity.IPScope == netutils.LocalMulticast &&
+			(responseConn.Entity.IPScope == netutils.LinkLocal ||
+				responseConn.Entity.IPScope == netutils.SiteLocal):
+			// We found a (possibly routed) multicast request that matches the response!
+			return conn
+		case conn.Entity.IP.Equal(responseNetBroadcastIP) &&
+			responseFromNet.Contains(conn.LocalIP):
+			// We found a (link local) broadcast request that matches the response!
+			return conn
+		}
+	}
+
+	return nil
+}
diff --git a/network/netutils/ip.go b/network/netutils/ip.go
index f6a34003..76bb0230 100644
--- a/network/netutils/ip.go
+++ b/network/netutils/ip.go
@@ -28,6 +28,9 @@ func GetIPScope(ip net.IP) IPScope { //nolint:gocognit
 	if ip4 := ip.To4(); ip4 != nil {
 		// IPv4
 		switch {
+		case ip4[0] == 0:
+			// 0.0.0.0/8
+			return Invalid
 		case ip4[0] == 127:
 			// 127.0.0.0/8 (RFC1918)
 			return HostLocal
@@ -79,6 +82,8 @@ func GetIPScope(ip net.IP) IPScope { //nolint:gocognit
 	} else if len(ip) == net.IPv6len {
 		// IPv6
 		switch {
+		case ip.Equal(net.IPv6zero):
+			return Invalid
 		case ip.Equal(net.IPv6loopback):
 			return HostLocal
 		case ip[0]&0xfe == 0xfc:
@@ -124,3 +129,29 @@ func (scope IPScope) IsGlobal() bool {
 		return false
 	}
 }
+
+// GetBroadcastAddress returns the broadcast address of the given IP and network mask.
+// If a mixed IPv4/IPv6 input is given, it returns nil.
+func GetBroadcastAddress(ip net.IP, netMask net.IPMask) net.IP {
+	// Convert to standard v4.
+	if ip4 := ip.To4(); ip4 != nil {
+		ip = ip4
+	}
+	mask := net.IP(netMask)
+	if ip4Mask := mask.To4(); ip4Mask != nil {
+		mask = ip4Mask
+	}
+
+	// Check for mixed v4/v6 input.
+	if len(ip) != len(mask) {
+		return nil
+	}
+
+	// Merge to broadcast address
+	n := len(ip)
+	broadcastAddress := make(net.IP, n)
+	for i := 0; i < n; i++ {
+		broadcastAddress[i] = ip[i] | ^mask[i]
+	}
+	return broadcastAddress
+}
diff --git a/process/process.go b/process/process.go
index 8bae2772..ff04896e 100644
--- a/process/process.go
+++ b/process/process.go
@@ -67,6 +67,32 @@ func (p *Process) Profile() *profile.LayeredProfile {
 	return p.profile
 }
 
+// IsIdentified returns whether the process has been identified or if it
+// represents some kind of unidentified process.
+func (p *Process) IsIdentified() bool {
+	// Check if process exists.
+	if p == nil {
+		return false
+	}
+
+	// Check for special PIDs.
+	switch p.Pid {
+	case UndefinedProcessID:
+		return false
+	case UnidentifiedProcessID:
+		return false
+	case UnsolicitedProcessID:
+		return false
+	default:
+		return true
+	}
+}
+
+// Equal returns if the two processes are both identified and have the same PID.
+func (p *Process) Equal(other *Process) bool {
+	return p.IsIdentified() && other.IsIdentified() && p.Pid == other.Pid
+}
+
 // IsSystemResolver is a shortcut to check if the process is or belongs to the
 // system resolver and needs special handling.
 func (p *Process) IsSystemResolver() bool {

From 9a89f65027d923a0e44ff6ec2fcff0df514b9f75 Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Tue, 24 May 2022 11:21:11 +0200
Subject: [PATCH 4/8] Improve support for DNS-SD and fall back to cached data
 for non-ICANN queries

---
 firewall/master.go        |  5 +--
 nameserver/nameserver.go  | 73 +++++++++++++++++++++++++++++++++++----
 network/netutils/dns.go   | 52 +++++++++++++++++++---------
 resolver/resolve.go       | 42 ++++++++++++++++++++++
 resolver/resolver-env.go  | 11 +++++-
 resolver/resolver_test.go | 56 ++++++++++++++++++++++++++++++
 6 files changed, 211 insertions(+), 28 deletions(-)

diff --git a/firewall/master.go b/firewall/master.go
index 4be457aa..e50617d0 100644
--- a/firewall/master.go
+++ b/firewall/master.go
@@ -482,10 +482,7 @@ func checkDomainHeuristics(ctx context.Context, conn *network.Connection, p *pro
 	trimmedDomain := strings.TrimRight(conn.Entity.Domain, ".")
 	etld1, err := publicsuffix.EffectiveTLDPlusOne(trimmedDomain)
 	if err != nil {
-		// we don't apply any checks here and let the request through
-		// because a malformed domain-name will likely be dropped by
-		// checks better suited for that.
-		log.Tracer(ctx).Warningf("filter: failed to get eTLD+1: %s", err)
+		// Don't run the check if the domain is a TLD.
 		return false
 	}
 
diff --git a/nameserver/nameserver.go b/nameserver/nameserver.go
index a92ca8ad..afdae60b 100644
--- a/nameserver/nameserver.go
+++ b/nameserver/nameserver.go
@@ -106,6 +106,9 @@ func handleRequest(ctx context.Context, w dns.ResponseWriter, request *dns.Msg)
 		return reply(nsutil.Refused("invalid domain"))
 	}
 
+	// Get public suffix after validation.
+	q.InitPublicSuffixData()
+
 	// Check if query is failing.
 	// Some software retries failing queries excessively. This might not be a
 	// problem normally, but handling a request is pretty expensive for the
@@ -252,10 +255,13 @@ func handleRequest(ctx context.Context, w dns.ResponseWriter, request *dns.Msg)
 	if err != nil {
 		switch {
 		case errors.Is(err, resolver.ErrNotFound):
-			tracer.Tracef("nameserver: %s", err)
-			conn.Failed("domain does not exist", "")
-			return reply(nsutil.NxDomain("nxdomain: " + err.Error()))
-
+			// Try alternatives domain names for unofficial domain spaces.
+			rrCache = checkAlternativeCaches(ctx, q)
+			if rrCache == nil {
+				tracer.Tracef("nameserver: %s", err)
+				conn.Failed("domain does not exist", "")
+				return reply(nsutil.NxDomain("nxdomain: " + err.Error()))
+			}
 		case errors.Is(err, resolver.ErrBlocked):
 			tracer.Tracef("nameserver: %s", err)
 			conn.Block(err.Error(), "")
@@ -268,7 +274,7 @@ func handleRequest(ctx context.Context, w dns.ResponseWriter, request *dns.Msg)
 
 		case errors.Is(err, resolver.ErrOffline):
 			if rrCache == nil {
-				log.Tracer(ctx).Debugf("nameserver: not resolving %s, device is offline", q.ID())
+				tracer.Debugf("nameserver: not resolving %s, device is offline", q.ID())
 				conn.Failed("not resolving, device is offline", "")
 				return reply(nsutil.ServerFailure(err.Error()))
 			}
@@ -290,8 +296,12 @@ func handleRequest(ctx context.Context, w dns.ResponseWriter, request *dns.Msg)
 		addFailingQuery(q, errors.New("emptry reply from resolver"))
 		return reply(nsutil.ServerFailure("internal error: empty reply"))
 	case rrCache.RCode == dns.RcodeNameError:
-		// Return now if NXDomain.
-		return reply(nsutil.NxDomain("no answer found (NXDomain)"))
+		// Try alternatives domain names for unofficial domain spaces.
+		rrCache = checkAlternativeCaches(ctx, q)
+		if rrCache == nil {
+			// Return now if NXDomain.
+			return reply(nsutil.NxDomain("no answer found (NXDomain)"))
+		}
 	}
 
 	// Check with firewall again after resolving.
@@ -336,3 +346,52 @@ func handleRequest(ctx context.Context, w dns.ResponseWriter, request *dns.Msg)
 	)
 	return reply(rrCache, conn, rrCache)
 }
+
+func checkAlternativeCaches(ctx context.Context, q *resolver.Query) *resolver.RRCache {
+	// Do not try alternatives when the query is in a public suffix.
+	// This also includes arpa. and local.
+	if q.ICANNSpace {
+		return nil
+	}
+
+	// Check if the env resolver has something.
+	pmEnvQ := &resolver.Query{
+		FQDN:  q.FQDN + "local." + resolver.InternalSpecialUseDomain,
+		QType: q.QType,
+	}
+	rrCache, err := resolver.QueryPortmasterEnv(ctx, pmEnvQ)
+	if err == nil && rrCache != nil && rrCache.RCode == dns.RcodeSuccess {
+		makeAlternativeRecord(ctx, q, rrCache, pmEnvQ.FQDN)
+		return rrCache
+	}
+
+	// Check if we have anything in cache
+	localFQDN := q.FQDN + "local."
+	rrCache, err = resolver.GetRRCache(localFQDN, q.QType)
+	if err == nil && rrCache != nil && rrCache.RCode == dns.RcodeSuccess {
+		makeAlternativeRecord(ctx, q, rrCache, localFQDN)
+		return rrCache
+	}
+
+	return nil
+}
+
+func makeAlternativeRecord(ctx context.Context, q *resolver.Query, rrCache *resolver.RRCache, altName string) {
+	log.Tracer(ctx).Debugf("using %s to answer query", altName)
+
+	// Duplicate answers so they match the query.
+	copied := make([]dns.RR, 0, len(rrCache.Answer))
+	for _, answer := range rrCache.Answer {
+		if strings.ToLower(answer.Header().Name) == altName {
+			copiedAnswer := dns.Copy(answer)
+			copiedAnswer.Header().Name = q.FQDN
+			copied = append(copied, copiedAnswer)
+		}
+	}
+	if len(copied) > 0 {
+		rrCache.Answer = append(rrCache.Answer, copied...)
+	}
+
+	// Update the question.
+	rrCache.Domain = q.FQDN
+}
diff --git a/network/netutils/dns.go b/network/netutils/dns.go
index 7a7bd6e5..252dca47 100644
--- a/network/netutils/dns.go
+++ b/network/netutils/dns.go
@@ -4,21 +4,38 @@ import (
 	"fmt"
 	"net"
 	"regexp"
+	"strings"
 
 	"github.com/miekg/dns"
 )
 
-var cleanDomainRegex = regexp.MustCompile(
-	`^` + // match beginning
-		`(` + // start subdomain group
-		`(xn--)?` + // idn prefix
-		`[a-z0-9_-]{1,63}` + // main chunk
-		`\.` + // ending with a dot
-		`)*` + // end subdomain group, allow any number of subdomains
-		`(xn--)?` + // TLD idn prefix
-		`[a-z0-9_-]{2,63}` + // TLD main chunk with at least two characters
-		`\.` + // ending with a dot
-		`$`, // match end
+var (
+	cleanDomainRegex = regexp.MustCompile(
+		`^` + // match beginning
+			`(` + // start subdomain group
+			`(xn--)?` + // idn prefix
+			`[a-z0-9_-]{1,63}` + // main chunk
+			`\.` + // ending with a dot
+			`)*` + // end subdomain group, allow any number of subdomains
+			`(xn--)?` + // TLD idn prefix
+			`[a-z0-9_-]{2,63}` + // TLD main chunk with at least two characters
+			`\.` + // ending with a dot
+			`$`, // match end
+	)
+
+	// dnsSDDomainRegex is a lot more lax to better suit the allowed characters in DNS-SD.
+	// Not all characters have been allowed - some special characters were
+	// removed to reduce the general attack surface.
+	dnsSDDomainRegex = regexp.MustCompile(
+		// Start of charset selection.
+		`^[` +
+			// Printable ASCII (character code 32-127), excluding some special characters.
+			` !#$%&()*+,\-\./0-9:;=?@A-Z[\\\]^_\a-z{|}~` +
+			// Only latin characters from extended ASCII (character code 128-255).
+			`ŠŒŽšœžŸ¡¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõöøùúûüýþÿ` +
+			// End of charset selection.
+			`]*$`,
+	)
 )
 
 // IsValidFqdn returns whether the given string is a valid fqdn.
@@ -33,15 +50,18 @@ func IsValidFqdn(fqdn string) bool {
 		return false
 	}
 
-	// check with regex
-	if !cleanDomainRegex.MatchString(fqdn) {
+	// IsFqdn checks if a domain name is fully qualified.
+	if !dns.IsFqdn(fqdn) {
 		return false
 	}
 
-	// check with miegk/dns
+	// Use special check for .local domains to support DNS-SD.
+	if strings.HasSuffix(fqdn, ".local.") {
+		return dnsSDDomainRegex.MatchString(fqdn)
+	}
 
-	// IsFqdn checks if a domain name is fully qualified.
-	if !dns.IsFqdn(fqdn) {
+	// check with regex
+	if !cleanDomainRegex.MatchString(fqdn) {
 		return false
 	}
 
diff --git a/resolver/resolve.go b/resolver/resolve.go
index 1b0b429e..9f7fad66 100644
--- a/resolver/resolve.go
+++ b/resolver/resolve.go
@@ -5,10 +5,12 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"strings"
 	"sync"
 	"time"
 
 	"github.com/miekg/dns"
+	"golang.org/x/net/publicsuffix"
 
 	"github.com/safing/portbase/database"
 	"github.com/safing/portbase/log"
@@ -90,6 +92,11 @@ type Query struct {
 	IgnoreFailing      bool
 	LocalResolversOnly bool
 
+	// ICANNSpace signifies if the domain is within ICANN managed domain space.
+	ICANNSpace bool
+	// Domain root is the effective TLD +1.
+	DomainRoot string
+
 	// internal
 	dotPrefixedFQDN string
 }
@@ -99,6 +106,41 @@ func (q *Query) ID() string {
 	return q.FQDN + q.QType.String()
 }
 
+// InitPublicSuffixData initializes the public suffix data.
+func (q *Query) InitPublicSuffixData() {
+	// Get public suffix and derive if domain is in ICANN space.
+	suffix, icann := publicsuffix.PublicSuffix(strings.TrimSuffix(q.FQDN, "."))
+	if icann || strings.Contains(suffix, ".") {
+		q.ICANNSpace = true
+	}
+	// Override some cases.
+	switch suffix {
+	case "example":
+		q.ICANNSpace = true // Defined by ICANN.
+	case "invalid":
+		q.ICANNSpace = true // Defined by ICANN.
+	case "local":
+		q.ICANNSpace = true // Defined by ICANN.
+	case "localhost":
+		q.ICANNSpace = true // Defined by ICANN.
+	case "onion":
+		q.ICANNSpace = false // Defined by ICANN, but special.
+	case "test":
+		q.ICANNSpace = true // Defined by ICANN.
+	}
+	// Add suffix to adhere to FQDN format.
+	suffix += "."
+
+	switch {
+	case len(q.FQDN) == len(suffix):
+		// We are at or below the domain root, reset.
+		q.DomainRoot = ""
+	case len(q.FQDN) > len(suffix):
+		domainRootStart := strings.LastIndex(q.FQDN[:len(q.FQDN)-len(suffix)-1], ".") + 1
+		q.DomainRoot = q.FQDN[domainRootStart:]
+	}
+}
+
 // check runs sanity checks and does some initialization. Returns whether the query passed the basic checks.
 func (q *Query) check() (ok bool) {
 	if q.FQDN == "" {
diff --git a/resolver/resolver-env.go b/resolver/resolver-env.go
index 18acfba4..b8710ff3 100644
--- a/resolver/resolver-env.go
+++ b/resolver/resolver-env.go
@@ -128,7 +128,7 @@ func (er *envResolverConn) makeRRCache(q *Query, answers []dns.RR) *RRCache {
 	// Disable caching, as the env always has the raw data available.
 	q.NoCaching = true
 
-	return &RRCache{
+	rrCache := &RRCache{
 		Domain:   q.FQDN,
 		Question: q.QType,
 		RCode:    dns.RcodeSuccess,
@@ -136,6 +136,10 @@ func (er *envResolverConn) makeRRCache(q *Query, answers []dns.RR) *RRCache {
 		Extra:    []dns.RR{internalSpecialUseComment}, // Always add comment about this TLD.
 		Resolver: envResolver.Info.Copy(),
 	}
+	if len(rrCache.Answer) == 0 {
+		rrCache.RCode = dns.RcodeNameError
+	}
+	return rrCache
 }
 
 func (er *envResolverConn) ReportFailure() {}
@@ -145,3 +149,8 @@ func (er *envResolverConn) IsFailing() bool {
 }
 
 func (er *envResolverConn) ResetFailure() {}
+
+// QueryPortmasterEnv queries the environment resolver directly.
+func QueryPortmasterEnv(ctx context.Context, q *Query) (*RRCache, error) {
+	return envResolver.Conn.Query(ctx, q)
+}
diff --git a/resolver/resolver_test.go b/resolver/resolver_test.go
index f385e52e..61e05376 100644
--- a/resolver/resolver_test.go
+++ b/resolver/resolver_test.go
@@ -7,6 +7,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/miekg/dns"
 
 	"github.com/safing/portbase/log"
@@ -103,3 +105,57 @@ func TestBulkResolving(t *testing.T) {
 
 	t.Logf("total time taken: %s", time.Since(started))
 }
+
+func TestPublicSuffix(t *testing.T) {
+	t.Parallel()
+
+	testSuffix(t, "co.uk.", "", true)
+	testSuffix(t, "amazon.co.uk.", "amazon.co.uk.", true)
+	testSuffix(t, "books.amazon.co.uk.", "amazon.co.uk.", true)
+	testSuffix(t, "www.books.amazon.co.uk.", "amazon.co.uk.", true)
+	testSuffix(t, "com.", "", true)
+	testSuffix(t, "amazon.com.", "amazon.com.", true)
+	testSuffix(t, "example0.debian.net.", "example0.debian.net.", true)
+	testSuffix(t, "example1.debian.org.", "debian.org.", true)
+	testSuffix(t, "golang.dev.", "golang.dev.", true)
+	testSuffix(t, "golang.net.", "golang.net.", true)
+	testSuffix(t, "play.golang.org.", "golang.org.", true)
+	testSuffix(t, "gophers.in.space.museum.", "in.space.museum.", true)
+	testSuffix(t, "0emm.com.", "0emm.com.", true)
+	testSuffix(t, "a.0emm.com.", "", true)
+	testSuffix(t, "b.c.d.0emm.com.", "c.d.0emm.com.", true)
+	testSuffix(t, "org.", "", true)
+	testSuffix(t, "foo.org.", "foo.org.", true)
+	testSuffix(t, "foo.co.uk.", "foo.co.uk.", true)
+	testSuffix(t, "foo.dyndns.org.", "foo.dyndns.org.", true)
+	testSuffix(t, "foo.blogspot.co.uk.", "foo.blogspot.co.uk.", true)
+	testSuffix(t, "there.is.no.such-tld.", "no.such-tld.", false)
+	testSuffix(t, "www.some.bit.", "some.bit.", false)
+	testSuffix(t, "cromulent.", "", false)
+	testSuffix(t, "arpa.", "", true)
+	testSuffix(t, "in-addr.arpa.", "", true)
+	testSuffix(t, "1.in-addr.arpa.", "1.in-addr.arpa.", true)
+	testSuffix(t, "ip6.arpa.", "", true)
+	testSuffix(t, "1.ip6.arpa.", "1.ip6.arpa.", true)
+	testSuffix(t, "www.some.arpa.", "some.arpa.", true)
+	testSuffix(t, "www.some.home.arpa.", "home.arpa.", true)
+	testSuffix(t, ".", "", false)
+	testSuffix(t, "", "", false)
+
+	// Test edge case domains.
+	testSuffix(t, "www.some.example.", "some.example.", true)
+	testSuffix(t, "www.some.invalid.", "some.invalid.", true)
+	testSuffix(t, "www.some.local.", "some.local.", true)
+	testSuffix(t, "www.some.localhost.", "some.localhost.", true)
+	testSuffix(t, "www.some.onion.", "some.onion.", false)
+	testSuffix(t, "www.some.test.", "some.test.", true)
+}
+
+func testSuffix(t *testing.T, fqdn, domainRoot string, icannSpace bool) {
+	t.Helper()
+
+	q := &Query{FQDN: fqdn}
+	q.InitPublicSuffixData()
+	assert.Equal(t, domainRoot, q.DomainRoot)
+	assert.Equal(t, icannSpace, q.ICANNSpace)
+}

From 65f646aad02a081330242a9491c1af25cc8ec92e Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Tue, 24 May 2022 11:27:44 +0200
Subject: [PATCH 5/8] Improve wording on setting dns/noInsecureProtocols

---
 resolver/config.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/resolver/config.go b/resolver/config.go
index b274ee23..ff17cb99 100644
--- a/resolver/config.go
+++ b/resolver/config.go
@@ -224,9 +224,9 @@ The format is: "protocol://ip:port?parameter=value&parameter=value"
 	noMulticastDNS = status.SecurityLevelOption(CfgOptionNoMulticastDNSKey)
 
 	err = config.Register(&config.Option{
-		Name:           "Enforce Secure DNS",
+		Name:           "Use Secure Protocols Only",
 		Key:            CfgOptionNoInsecureProtocolsKey,
-		Description:    "Never resolve using insecure protocols, ie. plain DNS.",
+		Description:    "Never resolve using insecure protocols, ie. plain DNS. This may break certain local DNS services, which always use plain DNS.",
 		OptType:        config.OptTypeInt,
 		ExpertiseLevel: config.ExpertiseLevelExpert,
 		ReleaseLevel:   config.ReleaseLevelStable,

From 515f4686f7eb28db095f6fe676e3d110bd7d00d4 Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Wed, 25 May 2022 13:57:31 +0200
Subject: [PATCH 6/8] Send notification instead of killing conflicting DNS
 service

---
 nameserver/conflict.go |  75 +++++++++++++++++++
 nameserver/module.go   |  85 +++++++++++++++++++--
 nameserver/takeover.go | 164 -----------------------------------------
 3 files changed, 154 insertions(+), 170 deletions(-)
 create mode 100644 nameserver/conflict.go
 delete mode 100644 nameserver/takeover.go

diff --git a/nameserver/conflict.go b/nameserver/conflict.go
new file mode 100644
index 00000000..e02e1fd5
--- /dev/null
+++ b/nameserver/conflict.go
@@ -0,0 +1,75 @@
+package nameserver
+
+import (
+	"net"
+	"os"
+
+	processInfo "github.com/shirou/gopsutil/process"
+
+	"github.com/safing/portbase/log"
+	"github.com/safing/portmaster/network/packet"
+	"github.com/safing/portmaster/network/state"
+)
+
+var commonResolverIPs = []net.IP{
+	net.IPv4zero,
+	net.IPv4(127, 0, 0, 1),  // default
+	net.IPv4(127, 0, 0, 53), // some resolvers on Linux
+	net.IPv6zero,
+	net.IPv6loopback,
+}
+
+func findConflictingProcess(ip net.IP, port uint16) (conflictingProcess *processInfo.Process) {
+	// Evaluate which IPs to check.
+	var ipsToCheck []net.IP
+	if ip.Equal(net.IPv4zero) || ip.Equal(net.IPv6zero) {
+		ipsToCheck = commonResolverIPs
+	} else {
+		ipsToCheck = []net.IP{ip}
+	}
+
+	// Find the conflicting process.
+	var err error
+	for _, resolverIP := range ipsToCheck {
+		conflictingProcess, err = getListeningProcess(resolverIP, port)
+		switch {
+		case err != nil:
+			// Log the error and let the worker try again.
+			log.Warningf("nameserver: failed to find conflicting service: %s", err)
+		case conflictingProcess != nil:
+			// Conflicting service found.
+			return conflictingProcess
+		}
+	}
+
+	return nil
+}
+
+func getListeningProcess(resolverIP net.IP, resolverPort uint16) (*processInfo.Process, error) {
+	pid, _, err := state.Lookup(&packet.Info{
+		Inbound:  true,
+		Version:  0, // auto-detect
+		Protocol: packet.UDP,
+		Src:      nil, // do not record direction
+		SrcPort:  0,   // do not record direction
+		Dst:      resolverIP,
+		DstPort:  resolverPort,
+	}, true)
+	if err != nil {
+		// there may be nothing listening on :53
+		return nil, nil //nolint:nilerr // Treat lookup error as "not found".
+	}
+
+	// Ignore if it's us for some reason.
+	if pid == os.Getpid() {
+		return nil, nil
+	}
+
+	proc, err := processInfo.NewProcess(int32(pid))
+	if err != nil {
+		// Process may have disappeared already.
+		return nil, err
+	}
+
+	return proc, nil
+}
diff --git a/nameserver/module.go b/nameserver/module.go
index 1c1dc871..f5165585 100644
--- a/nameserver/module.go
+++ b/nameserver/module.go
@@ -13,6 +13,7 @@ import (
 	"github.com/safing/portbase/log"
 	"github.com/safing/portbase/modules"
 	"github.com/safing/portbase/modules/subsystems"
+	"github.com/safing/portbase/notifications"
 	"github.com/safing/portmaster/compat"
 	"github.com/safing/portmaster/firewall"
 	"github.com/safing/portmaster/netenv"
@@ -25,6 +26,9 @@ var (
 	stopListener1     func() error
 	stopListener2     func() error
 	stopListenersLock sync.Mutex
+
+	eventIDConflictingService = "nameserver:conflicting-service"
+	eventIDListenerFailed     = "nameserver:listener-failed"
 )
 
 func init() {
@@ -133,24 +137,93 @@ func startListener(ip net.IP, port uint16, first bool) {
 			return nil
 		}
 
+		// Resolve generic listener error, if primary listener.
+		if first {
+			module.Resolve(eventIDListenerFailed)
+		}
+
 		// Start listening.
 		log.Infof("nameserver: starting to listen on %s", dnsServer.Addr)
 		err := dnsServer.ListenAndServe()
 		if err != nil {
-			// check if we are shutting down
+			// Stop worker without error if we are shutting down.
 			if module.IsStopping() {
 				return nil
 			}
-			// is something blocking our port?
-			checkErr := checkForConflictingService(ip, port)
-			if checkErr != nil {
-				return checkErr
-			}
+			log.Warningf("nameserver: failed to listen on %s: %s", dnsServer.Addr, err)
+			handleListenError(err, ip, port, first)
 		}
 		return err
 	})
 }
 
+func handleListenError(err error, ip net.IP, port uint16, primaryListener bool) {
+	var n *notifications.Notification
+
+	// Create suffix for secondary listener
+	var secondaryEventIDSuffix string
+	if !primaryListener {
+		secondaryEventIDSuffix = "-secondary"
+	}
+
+	// Find a conflicting service.
+	cfProcess := findConflictingProcess(ip, port)
+	if cfProcess != nil {
+		// Report the conflicting process.
+
+		// Build conflicting process description.
+		var cfDescription string
+		cfName, err := cfProcess.Name()
+		if err == nil && cfName != "" {
+			cfDescription = cfName
+		}
+		cfExe, err := cfProcess.Exe()
+		if err == nil && cfDescription != "" {
+			if cfDescription != "" {
+				cfDescription += " (" + cfExe + ")"
+			} else {
+				cfDescription = cfName
+			}
+		}
+
+		// Notify user about conflicting service.
+		n = notifications.Notify(&notifications.Notification{
+			EventID: eventIDConflictingService + secondaryEventIDSuffix,
+			Type:    notifications.Error,
+			Title:   "Conflicting DNS Software",
+			Message: fmt.Sprintf(
+				"Restart Portmaster after you have deactivated or properly configured the conflicting software: %s",
+				cfDescription,
+			),
+			ShowOnSystem: true,
+			AvailableActions: []*notifications.Action{
+				{
+					Text:    "Open Docs",
+					Type:    notifications.ActionTypeOpenURL,
+					Payload: "https://docs.safing.io/portmaster/install/status/software-compatibility",
+				},
+			},
+		})
+	} else {
+		// If no conflict is found, report the error directly.
+		n = notifications.Notify(&notifications.Notification{
+			EventID: eventIDListenerFailed + secondaryEventIDSuffix,
+			Type:    notifications.Error,
+			Title:   "Secure DNS Error",
+			Message: fmt.Sprintf(
+				"The internal DNS server failed. Restart Portmaster to try again. Error: %s",
+				err,
+			),
+			ShowOnSystem: true,
+		})
+	}
+
+	// Attach error to module, if primary listener.
+	if primaryListener {
+		n.AttachToModule(module)
+	}
+}
+
 func stop() error {
 	stopListenersLock.Lock()
 	defer stopListenersLock.Unlock()
diff --git a/nameserver/takeover.go b/nameserver/takeover.go
deleted file mode 100644
index fa1b65af..00000000
--- a/nameserver/takeover.go
+++ /dev/null
@@ -1,164 +0,0 @@
-package nameserver
-
-import (
-	"fmt"
-	"net"
-	"os"
-	"strconv"
-	"time"
-
-	"github.com/safing/portbase/log"
-	"github.com/safing/portbase/modules"
-	"github.com/safing/portbase/notifications"
-	"github.com/safing/portmaster/network/packet"
-	"github.com/safing/portmaster/network/state"
-)
-
-var (
-	commonResolverIPs = []net.IP{
-		net.IPv4zero,
-		net.IPv4(127, 0, 0, 1),  // default
-		net.IPv4(127, 0, 0, 53), // some resolvers on Linux
-		net.IPv6zero,
-		net.IPv6loopback,
-	}
-
-	// lastKilledPID holds the PID of the last killed conflicting service.
-	// It is only accessed by checkForConflictingService, which is only called by
-	// the nameserver worker.
-	lastKilledPID int
-)
-
-func checkForConflictingService(ip net.IP, port uint16) error {
-	// Evaluate which IPs to check.
-	var ipsToCheck []net.IP
-	if ip.Equal(net.IPv4zero) || ip.Equal(net.IPv6zero) {
-		ipsToCheck = commonResolverIPs
-	} else {
-		ipsToCheck = []net.IP{ip}
-	}
-
-	// Check if there is another resolver when need to take over.
-	var killed int
-	var killingFailed bool
-ipsToCheckLoop:
-	for _, resolverIP := range ipsToCheck {
-		pid, err := takeover(resolverIP, port)
-		switch {
-		case err != nil:
-			// Log the error and let the worker try again.
-			log.Infof("nameserver: failed to stop conflicting service: %s", err)
-			killingFailed = true
-			break ipsToCheckLoop
-		case pid != 0:
-			// Conflicting service identified and killed!
-			killed = pid
-			break ipsToCheckLoop
-		}
-	}
-
-	// Notify user of failed killing or repeated kill.
-	if killingFailed || (killed != 0 && killed == lastKilledPID) {
-		// Notify the user that we failed to kill something.
-		notifications.Notify(&notifications.Notification{
-			EventID:      "namserver:failed-to-kill-conflicting-service",
-			Type:         notifications.Error,
-			Title:        "Failed to Stop Conflicting DNS Client",
-			Message:      "The Portmaster failed to stop a conflicting DNS client to gain required system integration. If there is another DNS Client (Nameserver; Resolver) on this device, please disable it.",
-			ShowOnSystem: true,
-			AvailableActions: []*notifications.Action{
-				{
-					ID:   "ack",
-					Text: "OK",
-				},
-				{
-					Text:    "Open Docs",
-					Type:    notifications.ActionTypeOpenURL,
-					Payload: "https://docs.safing.io/portmaster/install/status/software-compatibility",
-				},
-			},
-		})
-		return nil
-	}
-
-	// Check if something was killed.
-	if killed == 0 {
-		return nil
-	}
-	lastKilledPID = killed
-
-	// Notify the user that we killed something.
-	notifications.Notify(&notifications.Notification{
-		EventID: "namserver:stopped-conflicting-service",
-		Type:    notifications.Info,
-		Title:   "Stopped Conflicting DNS Client",
-		Message: fmt.Sprintf(
-			"The Portmaster stopped a conflicting DNS client (pid %d) to gain required system integration. If you are running another DNS client on this device on purpose, you can the check the documentation if it is compatible with the Portmaster.",
-			killed,
-		),
-		ShowOnSystem: true,
-		AvailableActions: []*notifications.Action{
-			{
-				ID:   "ack",
-				Text: "OK",
-			},
-			{
-				Text:    "Open Docs",
-				Type:    notifications.ActionTypeOpenURL,
-				Payload: "https://docs.safing.io/portmaster/install/status/software-compatibility",
-			},
-		},
-	})
-
-	// Restart nameserver via service-worker logic.
-	// Wait shortly so that the other process can shut down.
-	time.Sleep(10 * time.Millisecond)
-	return fmt.Errorf("%w: stopped conflicting name service with pid %d", modules.ErrRestartNow, killed)
-}
-
-func takeover(resolverIP net.IP, resolverPort uint16) (int, error) {
-	pid, _, err := state.Lookup(&packet.Info{
-		Inbound:  true,
-		Version:  0, // auto-detect
-		Protocol: packet.UDP,
-		Src:      nil, // do not record direction
-		SrcPort:  0,   // do not record direction
-		Dst:      resolverIP,
-		DstPort:  resolverPort,
-	}, true)
-	if err != nil {
-		// there may be nothing listening on :53
-		return 0, nil //nolint:nilerr // Treat lookup error as "not found".
-	}
-
-	// Just don't, uh, kill ourselves...
-	if pid == os.Getpid() {
-		return 0, nil
-	}
-
-	proc, err := os.FindProcess(pid)
-	if err != nil {
-		// huh. gone already? I guess we'll wait then...
-		return 0, err
-	}
-
-	err = proc.Signal(os.Interrupt)
-	if err != nil {
-		err = proc.Kill()
-		if err != nil {
-			log.Errorf("nameserver: failed to stop conflicting service (pid %d): %s", pid, err)
-			return 0, err
-		}
-	}
-
-	log.Warningf(
-		"nameserver: killed conflicting service with PID %d over %s",
-		pid,
-		net.JoinHostPort(
-			resolverIP.String(),
-			strconv.Itoa(int(resolverPort)),
-		),
-	)
-
-	return pid, nil
-}

From 787f9e7dec106e79f36196caa8f1047ee7e7c8cc Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Wed, 1 Jun 2022 13:28:10 +0200
Subject: [PATCH 7/8] Add support for upcoming UNBREAK filter list

---
 firewall/filter.go | 18 +++++++++++++++++-
 firewall/master.go | 10 ++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/firewall/filter.go b/firewall/filter.go
index 58a24737..390ef3f3 100644
--- a/firewall/filter.go
+++ b/firewall/filter.go
@@ -2,9 +2,11 @@ package firewall
 
 import (
 	"github.com/safing/portbase/config"
+	"github.com/safing/portbase/log"
 	"github.com/safing/portbase/modules"
 	"github.com/safing/portbase/modules/subsystems"
 	_ "github.com/safing/portmaster/core"
+	"github.com/safing/portmaster/intel/filterlists"
 	"github.com/safing/spn/captain"
 )
 
@@ -12,10 +14,13 @@ var (
 	filterModule  *modules.Module
 	filterEnabled config.BoolOption
 	tunnelEnabled config.BoolOption
+
+	unbreakFilterListIDs         = []string{"UNBREAK"}
+	resolvedUnbreakFilterListIDs []string
 )
 
 func init() {
-	filterModule = modules.Register("filter", filterPrep, nil, nil, "core", "intel")
+	filterModule = modules.Register("filter", filterPrep, filterStart, nil, "core", "intel")
 	subsystems.Register(
 		"filter",
 		"Privacy Filter",
@@ -47,3 +52,14 @@ func filterPrep() (err error) {
 	tunnelEnabled = config.Concurrent.GetAsBool(captain.CfgOptionEnableSPNKey, false)
 	return nil
 }
+
+func filterStart() error {
+	// TODO: Re-resolve IDs when filterlist index changes.
+	resolvedIDs, err := filterlists.ResolveListIDs(unbreakFilterListIDs)
+	if err != nil {
+		log.Warningf("filter: failed to resolve unbreak filter list IDs: %s", err)
+	} else {
+		resolvedUnbreakFilterListIDs = resolvedIDs
+	}
+	return nil
+}
diff --git a/firewall/master.go b/firewall/master.go
index e50617d0..1de7f194 100644
--- a/firewall/master.go
+++ b/firewall/master.go
@@ -432,6 +432,16 @@ func checkFilterLists(ctx context.Context, conn *network.Connection, p *profile.
 	result, reason := p.MatchFilterLists(ctx, conn.Entity)
 	switch result {
 	case endpoints.Denied:
+		// If the connection matches a filter list, check if the "unbreak" list matches too and abort blocking.
+		for _, blockedListID := range conn.Entity.BlockedByLists {
+			for _, unbreakListID := range resolvedUnbreakFilterListIDs {
+				if blockedListID == unbreakListID {
+					log.Tracer(ctx).Debugf("filter: unbreak filter %s matched, ignoring other filter list matches", unbreakListID)
+					return false
+				}
+			}
+		}
+		// Otherwise, continue with blocking.
 		conn.DenyWithContext(reason.String(), profile.CfgOptionFilterListsKey, reason.Context())
 		return true
 	case endpoints.NoMatch:

From 911a80996a6abc208fe078c3461ab40d6bd3a3a3 Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Wed, 1 Jun 2022 13:45:13 +0200
Subject: [PATCH 8/8] Fix multicast detection on ended connections as well as
 some linter errors

---
 core/base/databases.go    | 2 --
 network/multicast.go      | 4 ++--
 profile/module.go         | 2 --
 resolver/resolver_test.go | 3 +--
 4 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/core/base/databases.go b/core/base/databases.go
index d2ba2552..56355125 100644
--- a/core/base/databases.go
+++ b/core/base/databases.go
@@ -2,8 +2,6 @@ package base
 
 import (
 	"github.com/safing/portbase/database"
-
-	// Dependencies.
 	_ "github.com/safing/portbase/database/dbmodule"
 	_ "github.com/safing/portbase/database/storage/bbolt"
 )
diff --git a/network/multicast.go b/network/multicast.go
index 82cb2173..8a32aea7 100644
--- a/network/multicast.go
+++ b/network/multicast.go
@@ -17,8 +17,8 @@ func GetMulticastRequestConn(responseConn *Connection, responseFromNet *net.IPNe
 		switch {
 		case conn.Inbound:
 			// Ignore incoming connections.
-		//case conn.Ended != 0:
-		// Ignore ended connections.
+		case conn.Ended != 0:
+			// Ignore ended connections.
 		case conn.Entity.Protocol != responseConn.Entity.Protocol:
 			// Ignore on protocol mismatch.
 		case conn.LocalPort != responseConn.LocalPort:
diff --git a/profile/module.go b/profile/module.go
index da479663..31b52704 100644
--- a/profile/module.go
+++ b/profile/module.go
@@ -6,8 +6,6 @@ import (
 	"github.com/safing/portbase/database/migration"
 	"github.com/safing/portbase/log"
 	"github.com/safing/portbase/modules"
-
-	// Dependency.
 	_ "github.com/safing/portmaster/core/base"
 	"github.com/safing/portmaster/updates"
 )
diff --git a/resolver/resolver_test.go b/resolver/resolver_test.go
index 61e05376..a03b3eb9 100644
--- a/resolver/resolver_test.go
+++ b/resolver/resolver_test.go
@@ -7,9 +7,8 @@ import (
 	"testing"
 	"time"
 
-	"github.com/stretchr/testify/assert"
-
 	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
 
 	"github.com/safing/portbase/log"
 )