From b296fa224653c1ae0003709708039a08f40842eb Mon Sep 17 00:00:00 2001
From: Eugene Burkov <e.burkov@adguard.com>
Date: Mon, 18 Oct 2021 15:29:29 +0300
Subject: [PATCH 1/3] Pull request: 3744 DNS server DHCP option

Merge in DNS/adguard-home from 3744-options-priority to master

Updates #3744.

Squashed commit of the following:

commit 30f1d483bebd92348250573d2edd708247081b45
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 18 15:22:49 2021 +0300

    dhcpd: imp tests more

commit 9a8194e2f259ac7a88b23a1480c74decfef587b3
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 18 15:09:20 2021 +0300

    dhcpd: imp tests

commit d915e0b407adcfd24df6e28be22f095909749aa3
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 18 14:46:20 2021 +0300

    dhcpd: fix options priority
---
 CHANGELOG.md              |   2 +
 internal/dhcpd/v4.go      |   7 +-
 internal/dhcpd/v4_test.go | 145 ++++++++++++++++++++++++++++----------
 3 files changed, 113 insertions(+), 41 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b017cf0..d4de38dd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -114,6 +114,7 @@ In this release, the schema version has changed from 10 to 12.
 
 ### Fixed
 
+- Incorrect assignment of explicitly configured DHCP options ([#3744]).
 - Occasional panic during shutdown ([#3655]).
 - Addition of IPs into only one as opposed to all matching ipsets on Linux
   ([#3638]).
@@ -204,6 +205,7 @@ In this release, the schema version has changed from 10 to 12.
 [#3607]: https://github.com/AdguardTeam/AdGuardHome/issues/3607
 [#3638]: https://github.com/AdguardTeam/AdGuardHome/issues/3638
 [#3655]: https://github.com/AdguardTeam/AdGuardHome/issues/3655
+[#3744]: https://github.com/AdguardTeam/AdGuardHome/issues/3744
 
 
 
diff --git a/internal/dhcpd/v4.go b/internal/dhcpd/v4.go
index d7e4dfae..8ddfe98b 100644
--- a/internal/dhcpd/v4.go
+++ b/internal/dhcpd/v4.go
@@ -900,9 +900,10 @@ func (s *v4Server) process(req, resp *dhcpv4.DHCPv4) int {
 			resp.UpdateOption(dhcpv4.OptGeneric(code, configured.Get(code)))
 		}
 	}
-	// Update the value of Domain Name Server option separately from others
-	// since its value is set after server's creating.
-	if requested.Has(dhcpv4.OptionDomainNameServer) {
+	// Update the value of Domain Name Server option separately from others if
+	// not assigned yet since its value is set after server's creating.
+	if requested.Has(dhcpv4.OptionDomainNameServer) &&
+		!resp.Options.Has(dhcpv4.OptionDomainNameServer) {
 		resp.UpdateOption(dhcpv4.OptDNS(s.conf.dnsIPAddrs...))
 	}
 
diff --git a/internal/dhcpd/v4_test.go b/internal/dhcpd/v4_test.go
index d20e715c..9bed3c60 100644
--- a/internal/dhcpd/v4_test.go
+++ b/internal/dhcpd/v4_test.go
@@ -5,8 +5,10 @@ package dhcpd
 
 import (
 	"net"
+	"strings"
 	"testing"
 
+	"github.com/AdguardTeam/golibs/stringutil"
 	"github.com/insomniacslk/dhcp/dhcpv4"
 	"github.com/mdlayher/raw"
 	"github.com/stretchr/testify/assert"
@@ -16,17 +18,34 @@ import (
 func notify4(flags uint32) {
 }
 
-func TestV4_AddRemove_static(t *testing.T) {
-	s, err := v4Create(V4ServerConf{
+// defaultV4ServerConf returns the default configuration for *v4Server to use in
+// tests.
+func defaultV4ServerConf() (conf V4ServerConf) {
+	return V4ServerConf{
 		Enabled:    true,
 		RangeStart: net.IP{192, 168, 10, 100},
 		RangeEnd:   net.IP{192, 168, 10, 200},
 		GatewayIP:  net.IP{192, 168, 10, 1},
 		SubnetMask: net.IP{255, 255, 255, 0},
 		notify:     notify4,
-	})
+	}
+}
+
+// defaultSrv prepares the default DHCPServer to use in tests.  The underlying
+// type of s is *v4Server.
+func defaultSrv(t *testing.T) (s DHCPServer) {
+	t.Helper()
+
+	var err error
+	s, err = v4Create(defaultV4ServerConf())
 	require.NoError(t, err)
 
+	return s
+}
+
+func TestV4_AddRemove_static(t *testing.T) {
+	s := defaultSrv(t)
+
 	ls := s.GetLeases(LeasesStatic)
 	assert.Empty(t, ls)
 
@@ -37,7 +56,7 @@ func TestV4_AddRemove_static(t *testing.T) {
 		IP:       net.IP{192, 168, 10, 150},
 	}
 
-	err = s.AddStaticLease(l)
+	err := s.AddStaticLease(l)
 	require.NoError(t, err)
 
 	err = s.AddStaticLease(l)
@@ -65,15 +84,7 @@ func TestV4_AddRemove_static(t *testing.T) {
 }
 
 func TestV4_AddReplace(t *testing.T) {
-	sIface, err := v4Create(V4ServerConf{
-		Enabled:    true,
-		RangeStart: net.IP{192, 168, 10, 100},
-		RangeEnd:   net.IP{192, 168, 10, 200},
-		GatewayIP:  net.IP{192, 168, 10, 1},
-		SubnetMask: net.IP{255, 255, 255, 0},
-		notify:     notify4,
-	})
-	require.NoError(t, err)
+	sIface := defaultSrv(t)
 
 	s, ok := sIface.(*v4Server)
 	require.True(t, ok)
@@ -89,7 +100,7 @@ func TestV4_AddReplace(t *testing.T) {
 	}}
 
 	for i := range dynLeases {
-		err = s.addLease(&dynLeases[i])
+		err := s.addLease(&dynLeases[i])
 		require.NoError(t, err)
 	}
 
@@ -104,7 +115,7 @@ func TestV4_AddReplace(t *testing.T) {
 	}}
 
 	for _, l := range stLeases {
-		err = s.AddStaticLease(l)
+		err := s.AddStaticLease(l)
 		require.NoError(t, err)
 	}
 
@@ -118,17 +129,80 @@ func TestV4_AddReplace(t *testing.T) {
 	}
 }
 
-func TestV4StaticLease_Get(t *testing.T) {
-	var err error
-	sIface, err := v4Create(V4ServerConf{
-		Enabled:    true,
-		RangeStart: net.IP{192, 168, 10, 100},
-		RangeEnd:   net.IP{192, 168, 10, 200},
-		GatewayIP:  net.IP{192, 168, 10, 1},
-		SubnetMask: net.IP{255, 255, 255, 0},
-		notify:     notify4,
+func TestV4Server_Process_optionsPriority(t *testing.T) {
+	defaultIP := net.IP{192, 168, 1, 1}
+	knownIP := net.IP{1, 2, 3, 4}
+
+	// prepareSrv creates a *v4Server and sets the opt6IPs in the initial
+	// configuration of the server as the value for DHCP option 6.
+	prepareSrv := func(t *testing.T, opt6IPs []net.IP) (s *v4Server) {
+		t.Helper()
+
+		conf := defaultV4ServerConf()
+		if len(opt6IPs) > 0 {
+			b := &strings.Builder{}
+			stringutil.WriteToBuilder(b, "6 ips ", opt6IPs[0].String())
+			for _, ip := range opt6IPs[1:] {
+				stringutil.WriteToBuilder(b, ",", ip.String())
+			}
+			conf.Options = []string{b.String()}
+		}
+
+		ss, err := v4Create(conf)
+		require.NoError(t, err)
+
+		var ok bool
+		s, ok = ss.(*v4Server)
+		require.True(t, ok)
+
+		s.conf.dnsIPAddrs = []net.IP{defaultIP}
+
+		return s
+	}
+
+	// checkResp creates a discovery message with DHCP option 6 requested amd
+	// asserts the response to contain wantIPs in this option.
+	checkResp := func(t *testing.T, s *v4Server, wantIPs []net.IP) {
+		t.Helper()
+
+		mac := net.HardwareAddr{0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA}
+		req, err := dhcpv4.NewDiscovery(mac, dhcpv4.WithRequestedOptions(
+			dhcpv4.OptionDomainNameServer,
+		))
+		require.NoError(t, err)
+
+		var resp *dhcpv4.DHCPv4
+		resp, err = dhcpv4.NewReplyFromRequest(req)
+		require.NoError(t, err)
+
+		res := s.process(req, resp)
+		require.Equal(t, 1, res)
+
+		o := resp.GetOneOption(dhcpv4.OptionDomainNameServer)
+		require.NotEmpty(t, o)
+
+		wantData := []byte{}
+		for _, ip := range wantIPs {
+			wantData = append(wantData, ip...)
+		}
+		assert.Equal(t, o, wantData)
+	}
+
+	t.Run("default", func(t *testing.T) {
+		s := prepareSrv(t, nil)
+
+		checkResp(t, s, []net.IP{defaultIP})
 	})
-	require.NoError(t, err)
+
+	t.Run("explicitly_configured", func(t *testing.T) {
+		s := prepareSrv(t, []net.IP{knownIP, knownIP})
+
+		checkResp(t, s, []net.IP{knownIP, knownIP})
+	})
+}
+
+func TestV4StaticLease_Get(t *testing.T) {
+	sIface := defaultSrv(t)
 
 	s, ok := sIface.(*v4Server)
 	require.True(t, ok)
@@ -140,7 +214,7 @@ func TestV4StaticLease_Get(t *testing.T) {
 		HWAddr:   net.HardwareAddr{0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA},
 		IP:       net.IP{192, 168, 10, 150},
 	}
-	err = s.AddStaticLease(l)
+	err := s.AddStaticLease(l)
 	require.NoError(t, err)
 
 	var req, resp *dhcpv4.DHCPv4
@@ -208,19 +282,14 @@ func TestV4StaticLease_Get(t *testing.T) {
 }
 
 func TestV4DynamicLease_Get(t *testing.T) {
+	conf := defaultV4ServerConf()
+	conf.Options = []string{
+		"81 hex 303132",
+		"82 ip 1.2.3.4",
+	}
+
 	var err error
-	sIface, err := v4Create(V4ServerConf{
-		Enabled:    true,
-		RangeStart: net.IP{192, 168, 10, 100},
-		RangeEnd:   net.IP{192, 168, 10, 200},
-		GatewayIP:  net.IP{192, 168, 10, 1},
-		SubnetMask: net.IP{255, 255, 255, 0},
-		notify:     notify4,
-		Options: []string{
-			"81 hex 303132",
-			"82 ip 1.2.3.4",
-		},
-	})
+	sIface, err := v4Create(conf)
 	require.NoError(t, err)
 
 	s, ok := sIface.(*v4Server)

From d7aafa7dc6e89d71b613c28689a1ea5f31e09238 Mon Sep 17 00:00:00 2001
From: Dmitry Seregin <d.seregin@adguard.com>
Date: Tue, 19 Oct 2021 19:28:18 +0300
Subject: [PATCH 2/3] Pull request #1329: 3529 validate dhcpv4

Merge in DNS/adguard-home from 3529-validate-dhcpv4 to master

Squashed commit of the following:

commit 2f2455aa13a41398cd2846f31be96da9d34ba95d
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Tue Oct 19 19:18:12 2021 +0300

    dhcpv4: better test && fix changelog

commit ec4ff9180e8390fb739b3be0fc76fd2c715fe691
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 19:08:44 2021 +0300

    dhcpv4: better tests

commit e0e2f27b7a063ed84af170b16c3f87636cb738d2
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 18:55:47 2021 +0300

    dhcpv4: better tests

commit 73e1d08e1265e336ee6339d5021f90883fe3e395
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 18:47:21 2021 +0300

    dhcpv4: better tests

commit f636fc316123f26b6e2930afb4b22c18024ec93d
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 18:47:07 2021 +0300

    all: updated golibs

commit 86dd107a1d483ac24bd8c26422324eb8b9c3d086
Merge: 51aaf6d9 b296fa22
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 17:18:17 2021 +0300

    Merge branch 'master' into 3529-validate-dhcpv4

commit 51aaf6d9eb5fbe2b4304254dc6782305a19c53fa
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 17:18:02 2021 +0300

    dhcpv4: better changelog

commit 720b896bb595c57fab6d376f88c8a4b1d131db40
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 17:14:25 2021 +0300

    dhcpv4: better tests

commit 1098beffca8d5feb2ec104d26419210962c9a97d
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 12:08:26 2021 +0300

    dhcp: changelog

commit d1f6c89d68657431fb261658133c67e9e3135c1c
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 12:03:06 2021 +0300

    dhcpv4: fixed tests

commit 8b6713468fc04321c5238300df90bbb2d67ee679
Merge: 9991e9cb 3fa38fb4
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 11:57:57 2021 +0300

    Merge branch 'master' into 3529-validate-dhcpv4

commit 9991e9cbee7dc87d8fa1d7e86e6cc7e09ab6938c
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 11:55:40 2021 +0300

    dhcpv4: added tests

commit 5798a80de6c060365c1c647326d46cc13ccf28cb
Author: Dmitriy Seregin <d.seregin@adguard.com>
Date:   Mon Oct 18 11:46:03 2021 +0300

    dhcpv4: validate subnet mask and ip range
---
 CHANGELOG.md                                  |   3 +
 client/src/__locales/en.json                  |  12 +-
 .../components/Settings/Dhcp/FormDHCPv4.js    |  28 ++++-
 .../Settings/Dhcp/StaticLeases/Form.js        |   8 +-
 .../Settings/Dhcp/StaticLeases/Modal.js       |   8 ++
 .../Settings/Dhcp/StaticLeases/index.js       |   6 +
 client/src/components/Settings/Dhcp/index.js  |   2 +
 client/src/helpers/helpers.js                 |  14 +++
 client/src/helpers/validators.js              | 113 +++++++++++++++++-
 go.mod                                        |   2 +-
 go.sum                                        |   4 +-
 internal/dhcpd/dhcpd_test.go                  |  44 +++++++
 internal/dhcpd/v4.go                          |  25 ++++
 13 files changed, 258 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4de38dd..99821349 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,8 @@ and this project adheres to
 
 ### Changed
 
+- DHCP gateway address, subnet mask, IP address range, and leases validations
+  ([#3529]).
 - The `systemd` service script will now create the `/var/log` directory when it
   doesn't exist ([#3579]).
 - Items in allowed clients, disallowed clients, and blocked hosts lists are now
@@ -196,6 +198,7 @@ In this release, the schema version has changed from 10 to 12.
 [#3450]: https://github.com/AdguardTeam/AdGuardHome/issues/3450
 [#3457]: https://github.com/AdguardTeam/AdGuardHome/issues/3457
 [#3506]: https://github.com/AdguardTeam/AdGuardHome/issues/3506
+[#3529]: https://github.com/AdguardTeam/AdGuardHome/issues/3529
 [#3538]: https://github.com/AdguardTeam/AdGuardHome/issues/3538
 [#3551]: https://github.com/AdguardTeam/AdGuardHome/issues/3551
 [#3564]: https://github.com/AdguardTeam/AdGuardHome/issues/3564
diff --git a/client/src/__locales/en.json b/client/src/__locales/en.json
index f3d8abcd..6db195fe 100644
--- a/client/src/__locales/en.json
+++ b/client/src/__locales/en.json
@@ -37,6 +37,9 @@
     "dhcp_ipv6_settings": "DHCP IPv6 Settings",
     "form_error_required": "Required field",
     "form_error_ip4_format": "Invalid IPv4 format",
+    "form_error_ip4_range_start_format": "Invalid range start IPv4 format",
+    "form_error_ip4_range_end_format": "Invalid range end IPv4 format",
+    "form_error_ip4_gateway_format": "Invalid gateway IPv4 format",
     "form_error_ip6_format": "Invalid IPv6 format",
     "form_error_ip_format": "Invalid IP format",
     "form_error_mac_format": "Invalid MAC format",
@@ -45,7 +48,14 @@
     "form_error_subnet": "Subnet \"{{cidr}}\" does not contain the IP address \"{{ip}}\"",
     "form_error_positive": "Must be greater than 0",
     "form_error_negative": "Must be equal to 0 or greater",
-    "range_end_error": "Must be greater than range start",
+    "out_of_range_error": "Must be out of range \"{{start}}\"-\"{{end}}\"",
+    "in_range_error": "Must be in range \"{{start}}\"-\"{{end}}\"",
+    "lower_range_start_error": "Must be lower than range start",
+    "lower_range_end_error": "Must be lower than range end",
+    "greater_range_start_error": "Must be greater than range start",
+    "greater_range_end_error": "Must be greater than range end",
+    "subnet_error": "Addresses must be in one subnet",
+    "gateway_or_subnet_invalid": "Subnet mask invalid",
     "dhcp_form_gateway_input": "Gateway IP",
     "dhcp_form_subnet_input": "Subnet mask",
     "dhcp_form_range_title": "Range of IP addresses",
diff --git a/client/src/components/Settings/Dhcp/FormDHCPv4.js b/client/src/components/Settings/Dhcp/FormDHCPv4.js
index 873e7696..cb371f9f 100644
--- a/client/src/components/Settings/Dhcp/FormDHCPv4.js
+++ b/client/src/components/Settings/Dhcp/FormDHCPv4.js
@@ -13,6 +13,9 @@ import {
     validateIpv4,
     validateRequiredValue,
     validateIpv4RangeEnd,
+    validateGatewaySubnetMask,
+    validateIpForGatewaySubnetMask,
+    validateNotInRange,
 } from '../../../helpers/validators';
 
 const FormDHCPv4 = ({
@@ -54,7 +57,11 @@ const FormDHCPv4 = ({
                         type="text"
                         className="form-control"
                         placeholder={t(ipv4placeholders.gateway_ip)}
-                        validate={[validateIpv4, validateRequired]}
+                        validate={[
+                            validateIpv4,
+                            validateRequired,
+                            validateNotInRange,
+                        ]}
                         disabled={!isInterfaceIncludesIpv4}
                     />
                 </div>
@@ -66,7 +73,11 @@ const FormDHCPv4 = ({
                         type="text"
                         className="form-control"
                         placeholder={t(ipv4placeholders.subnet_mask)}
-                        validate={[validateIpv4, validateRequired]}
+                        validate={[
+                            validateIpv4,
+                            validateRequired,
+                            validateGatewaySubnetMask,
+                        ]}
                         disabled={!isInterfaceIncludesIpv4}
                     />
                 </div>
@@ -84,7 +95,11 @@ const FormDHCPv4 = ({
                                 type="text"
                                 className="form-control"
                                 placeholder={t(ipv4placeholders.range_start)}
-                                validate={[validateIpv4]}
+                                validate={[
+                                    validateIpv4,
+                                    validateGatewaySubnetMask,
+                                    validateIpForGatewaySubnetMask,
+                                ]}
                                 disabled={!isInterfaceIncludesIpv4}
                             />
                         </div>
@@ -95,7 +110,12 @@ const FormDHCPv4 = ({
                                 type="text"
                                 className="form-control"
                                 placeholder={t(ipv4placeholders.range_end)}
-                                validate={[validateIpv4, validateIpv4RangeEnd]}
+                                validate={[
+                                    validateIpv4,
+                                    validateIpv4RangeEnd,
+                                    validateGatewaySubnetMask,
+                                    validateIpForGatewaySubnetMask,
+                                ]}
                                 disabled={!isInterfaceIncludesIpv4}
                             />
                         </div>
diff --git a/client/src/components/Settings/Dhcp/StaticLeases/Form.js b/client/src/components/Settings/Dhcp/StaticLeases/Form.js
index e857144d..7e9c641b 100644
--- a/client/src/components/Settings/Dhcp/StaticLeases/Form.js
+++ b/client/src/components/Settings/Dhcp/StaticLeases/Form.js
@@ -10,6 +10,7 @@ import {
     validateMac,
     validateRequiredValue,
     validateIpv4InCidr,
+    validateInRange,
 } from '../../../../helpers/validators';
 import { FORM_NAME } from '../../../../helpers/constants';
 import { toggleLeaseModal } from '../../../../actions';
@@ -53,7 +54,12 @@ const Form = ({
                         type="text"
                         className="form-control"
                         placeholder={t('form_enter_subnet_ip', { cidr })}
-                        validate={[validateRequiredValue, validateIpv4, validateIpv4InCidr]}
+                        validate={[
+                            validateRequiredValue,
+                            validateIpv4,
+                            validateIpv4InCidr,
+                            validateInRange,
+                        ]}
                     />
                 </div>
                 <div className="form__group">
diff --git a/client/src/components/Settings/Dhcp/StaticLeases/Modal.js b/client/src/components/Settings/Dhcp/StaticLeases/Modal.js
index b65c298e..8ad0f009 100644
--- a/client/src/components/Settings/Dhcp/StaticLeases/Modal.js
+++ b/client/src/components/Settings/Dhcp/StaticLeases/Modal.js
@@ -11,6 +11,8 @@ const Modal = ({
     handleSubmit,
     processingAdding,
     cidr,
+    rangeStart,
+    rangeEnd,
 }) => {
     const dispatch = useDispatch();
 
@@ -38,10 +40,14 @@ const Modal = ({
                         ip: '',
                         hostname: '',
                         cidr,
+                        rangeStart,
+                        rangeEnd,
                     }}
                     onSubmit={handleSubmit}
                     processingAdding={processingAdding}
                     cidr={cidr}
+                    rangeStart={rangeStart}
+                    rangeEnd={rangeEnd}
                 />
             </div>
         </ReactModal>
@@ -53,6 +59,8 @@ Modal.propTypes = {
     handleSubmit: PropTypes.func.isRequired,
     processingAdding: PropTypes.bool.isRequired,
     cidr: PropTypes.string.isRequired,
+    rangeStart: PropTypes.string,
+    rangeEnd: PropTypes.string,
 };
 
 export default withTranslation()(Modal);
diff --git a/client/src/components/Settings/Dhcp/StaticLeases/index.js b/client/src/components/Settings/Dhcp/StaticLeases/index.js
index 6e12f30e..bdd7cec5 100644
--- a/client/src/components/Settings/Dhcp/StaticLeases/index.js
+++ b/client/src/components/Settings/Dhcp/StaticLeases/index.js
@@ -22,6 +22,8 @@ const StaticLeases = ({
     processingDeleting,
     staticLeases,
     cidr,
+    rangeStart,
+    rangeEnd,
 }) => {
     const [t] = useTranslation();
     const dispatch = useDispatch();
@@ -100,6 +102,8 @@ const StaticLeases = ({
                 handleSubmit={handleSubmit}
                 processingAdding={processingAdding}
                 cidr={cidr}
+                rangeStart={rangeStart}
+                rangeEnd={rangeEnd}
             />
         </>
     );
@@ -111,6 +115,8 @@ StaticLeases.propTypes = {
     processingAdding: PropTypes.bool.isRequired,
     processingDeleting: PropTypes.bool.isRequired,
     cidr: PropTypes.string.isRequired,
+    rangeStart: PropTypes.string,
+    rangeEnd: PropTypes.string,
 };
 
 cellWrap.propTypes = {
diff --git a/client/src/components/Settings/Dhcp/index.js b/client/src/components/Settings/Dhcp/index.js
index 844e662e..6208d4a6 100644
--- a/client/src/components/Settings/Dhcp/index.js
+++ b/client/src/components/Settings/Dhcp/index.js
@@ -275,6 +275,8 @@ const Dhcp = () => {
                             processingAdding={processingAdding}
                             processingDeleting={processingDeleting}
                             cidr={cidr}
+                            rangeStart={dhcp?.values?.v4?.range_start}
+                            rangeEnd={dhcp?.values?.v4?.range_end}
                         />
                         <div className="btn-list mt-2">
                             <button
diff --git a/client/src/helpers/helpers.js b/client/src/helpers/helpers.js
index 19ed0b70..d6eaa061 100644
--- a/client/src/helpers/helpers.js
+++ b/client/src/helpers/helpers.js
@@ -552,6 +552,20 @@ export const isIpInCidr = (ip, cidr) => {
     }
 };
 
+/**
+ *
+ * @param {string} subnetMask
+ * @returns {IPv4 | null}
+ */
+export const parseSubnetMask = (subnetMask) => {
+    try {
+        return ipaddr.parse(subnetMask).prefixLengthFromSubnetMask();
+    } catch (e) {
+        console.error(e);
+        return null;
+    }
+};
+
 /**
  *
  * @param {string} subnetMask
diff --git a/client/src/helpers/validators.js b/client/src/helpers/validators.js
index 7075ca47..4a4125d2 100644
--- a/client/src/helpers/validators.js
+++ b/client/src/helpers/validators.js
@@ -1,4 +1,5 @@
 import i18next from 'i18next';
+
 import {
     MAX_PORT,
     R_CIDR,
@@ -14,7 +15,7 @@ import {
     R_DOMAIN,
 } from './constants';
 import { ip4ToInt, isValidAbsolutePath } from './form';
-import { isIpInCidr } from './helpers';
+import { isIpInCidr, parseSubnetMask } from './helpers';
 
 // Validation functions
 // https://redux-form.com/8.3.0/examples/fieldlevelvalidation/
@@ -44,7 +45,7 @@ export const validateIpv4RangeEnd = (_, allValues) => {
     const { range_end, range_start } = allValues.v4;
 
     if (ip4ToInt(range_end) <= ip4ToInt(range_start)) {
-        return 'range_end_error';
+        return 'greater_range_start_error';
     }
 
     return undefined;
@@ -61,6 +62,114 @@ export const validateIpv4 = (value) => {
     return undefined;
 };
 
+/**
+ * @returns {undefined|string}
+ * @param _
+ * @param allValues
+ */
+export const validateNotInRange = (value, allValues) => {
+    const { range_start, range_end } = allValues.v4;
+
+    if (range_start && validateIpv4(range_start)) {
+        return 'form_error_ip4_range_start_format';
+    }
+
+    if (range_end && validateIpv4(range_end)) {
+        return 'form_error_ip4_range_end_format';
+    }
+
+    const isAboveMin = range_start && ip4ToInt(value) >= ip4ToInt(range_start);
+    const isBelowMax = range_end && ip4ToInt(value) <= ip4ToInt(range_end);
+
+    if (isAboveMin && isBelowMax) {
+        return i18next.t('out_of_range_error', {
+            start: range_start,
+            end: range_end,
+        });
+    }
+
+    if (!range_end && isAboveMin) {
+        return 'lower_range_start_error';
+    }
+
+    if (!range_start && isBelowMax) {
+        return 'greater_range_end_error';
+    }
+
+    return undefined;
+};
+
+/**
+ * @returns {undefined|string}
+ * @param _
+ * @param allValues
+ */
+export const validateInRange = (value, allValues) => {
+    const { rangeStart, rangeEnd } = allValues;
+
+    if (rangeStart && validateIpv4(rangeStart)) {
+        return 'form_error_ip4_range_start_format';
+    }
+
+    if (rangeEnd && validateIpv4(rangeEnd)) {
+        return 'form_error_ip4_range_end_format';
+    }
+
+    const isBelowMin = rangeStart && ip4ToInt(value) < ip4ToInt(rangeStart);
+    const isAboveMax = rangeEnd && ip4ToInt(value) > ip4ToInt(rangeEnd);
+
+    if (isAboveMax || isBelowMin) {
+        return i18next.t('in_range_error', {
+            start: rangeStart,
+            end: rangeEnd,
+        });
+    }
+
+    return undefined;
+};
+
+/**
+ * @returns {undefined|string}
+ * @param _
+ * @param allValues
+ */
+export const validateGatewaySubnetMask = (_, allValues) => {
+    if (!allValues || !allValues.v4 || !allValues.v4.subnet_mask || !allValues.v4.gateway_ip) {
+        return 'gateway_or_subnet_invalid';
+    }
+
+    const { subnet_mask, gateway_ip } = allValues.v4;
+
+    if (validateIpv4(gateway_ip)) {
+        return 'form_error_ip4_gateway_format';
+    }
+
+    return parseSubnetMask(subnet_mask) ? undefined : 'gateway_or_subnet_invalid';
+};
+
+/**
+ * @returns {undefined|string}
+ * @param value
+ * @param allValues
+ */
+export const validateIpForGatewaySubnetMask = (value, allValues) => {
+    if (!allValues || !allValues.v4 || !value) {
+        return undefined;
+    }
+
+    const {
+        gateway_ip, subnet_mask,
+    } = allValues.v4;
+
+    const subnetPrefix = parseSubnetMask(subnet_mask);
+
+    if (!isIpInCidr(value, `${gateway_ip}/${subnetPrefix}`)) {
+        return 'subnet_error';
+    }
+
+    return undefined;
+};
+
 /**
  * @param value {string}
  * @returns {undefined|string}
diff --git a/go.mod b/go.mod
index 728a0d7f..85738a6e 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,7 @@ go 1.16
 
 require (
 	github.com/AdguardTeam/dnsproxy v0.39.8
-	github.com/AdguardTeam/golibs v0.10.0
+	github.com/AdguardTeam/golibs v0.10.2
 	github.com/AdguardTeam/urlfilter v0.14.6
 	github.com/NYTimes/gziphandler v1.1.1
 	github.com/ameshkov/dnscrypt/v2 v2.2.2
diff --git a/go.sum b/go.sum
index 6ec3396e..86c53f10 100644
--- a/go.sum
+++ b/go.sum
@@ -14,8 +14,8 @@ github.com/AdguardTeam/dnsproxy v0.39.8/go.mod h1:eDpJKAdkHORRwAedjuERv+7SWlcz4c
 github.com/AdguardTeam/golibs v0.4.0/go.mod h1:skKsDKIBB7kkFflLJBpfGX+G8QFTx0WKUzB6TIgtUj4=
 github.com/AdguardTeam/golibs v0.4.2/go.mod h1:skKsDKIBB7kkFflLJBpfGX+G8QFTx0WKUzB6TIgtUj4=
 github.com/AdguardTeam/golibs v0.9.2/go.mod h1:fCAMwPBJ8S7YMYbTWvYS+eeTLblP5E04IDtNAo7y7IY=
-github.com/AdguardTeam/golibs v0.10.0 h1:A7MXRfZ+ItpOyS9tWKtqrLj3vZtE9FJFC+dOVY/LcWs=
-github.com/AdguardTeam/golibs v0.10.0/go.mod h1:rSfQRGHIdgfxriDDNgNJ7HmE5zRoURq8R+VdR81Zuzw=
+github.com/AdguardTeam/golibs v0.10.2 h1:TAwnS4Y49sSUa4UX1yz/MWNGbIlXHqafrWr9MxdIh9A=
+github.com/AdguardTeam/golibs v0.10.2/go.mod h1:rSfQRGHIdgfxriDDNgNJ7HmE5zRoURq8R+VdR81Zuzw=
 github.com/AdguardTeam/gomitmproxy v0.2.0/go.mod h1:Qdv0Mktnzer5zpdpi5rAwixNJzW2FN91LjKJCkVbYGU=
 github.com/AdguardTeam/urlfilter v0.14.6 h1:emqoKZElooHACYehRBYENeKVN1a/rspxiqTIMYLuoIo=
 github.com/AdguardTeam/urlfilter v0.14.6/go.mod h1:klx4JbOfc4EaNb5lWLqOwfg+pVcyRukmoJRvO55lL5U=
diff --git a/internal/dhcpd/dhcpd_test.go b/internal/dhcpd/dhcpd_test.go
index 21f63fd1..8609481b 100644
--- a/internal/dhcpd/dhcpd_test.go
+++ b/internal/dhcpd/dhcpd_test.go
@@ -11,6 +11,7 @@ import (
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
 	"github.com/AdguardTeam/golibs/netutil"
+	"github.com/AdguardTeam/golibs/testutil"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -138,6 +139,49 @@ func TestNormalizeLeases(t *testing.T) {
 	assert.Equal(t, leases[2].HWAddr, dynLeases[1].HWAddr)
 }
 
+func TestV4Server_badRange(t *testing.T) {
+	testCases := []struct {
+		name       string
+		gatewayIP  net.IP
+		subnetMask net.IP
+		wantErrMsg string
+	}{{
+		name:       "gateway_in_range",
+		gatewayIP:  net.IP{192, 168, 10, 120},
+		subnetMask: net.IP{255, 255, 255, 0},
+		wantErrMsg: "dhcpv4: gateway ip 192.168.10.120 in the ip range: " +
+			"192.168.10.20-192.168.10.200",
+	}, {
+		name:       "outside_range_start",
+		gatewayIP:  net.IP{192, 168, 10, 1},
+		subnetMask: net.IP{255, 255, 255, 240},
+		wantErrMsg: "dhcpv4: range start 192.168.10.20 is outside network " +
+			"192.168.10.1/28",
+	}, {
+		name:       "outside_range_end",
+		gatewayIP:  net.IP{192, 168, 10, 1},
+		subnetMask: net.IP{255, 255, 255, 224},
+		wantErrMsg: "dhcpv4: range end 192.168.10.200 is outside network " +
+			"192.168.10.1/27",
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			conf := V4ServerConf{
+				Enabled:    true,
+				RangeStart: net.IP{192, 168, 10, 20},
+				RangeEnd:   net.IP{192, 168, 10, 200},
+				GatewayIP:  tc.gatewayIP,
+				SubnetMask: tc.subnetMask,
+				notify:     testNotify,
+			}
+
+			_, err := v4Create(conf)
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
+		})
+	}
+}
+
 // cloneUDPAddr returns a deep copy of a.
 func cloneUDPAddr(a *net.UDPAddr) (clone *net.UDPAddr) {
 	return &net.UDPAddr{
diff --git a/internal/dhcpd/v4.go b/internal/dhcpd/v4.go
index 8ddfe98b..0107eddf 100644
--- a/internal/dhcpd/v4.go
+++ b/internal/dhcpd/v4.go
@@ -293,6 +293,8 @@ func (s *v4Server) addLease(l *Lease) (err error) {
 	offset, inOffset := r.offset(l.IP)
 
 	if l.IsStatic() {
+		// TODO(a.garipov, d.seregin): Subnet can be nil when dhcp server is
+		// disabled.
 		if sn := s.conf.subnet; !sn.Contains(l.IP) {
 			return fmt.Errorf("subnet %s does not contain the ip %q", sn, l.IP)
 		}
@@ -1125,6 +1127,29 @@ func v4Create(conf V4ServerConf) (srv DHCPServer, err error) {
 		return s, fmt.Errorf("dhcpv4: %w", err)
 	}
 
+	if s.conf.ipRange.contains(routerIP) {
+		return s, fmt.Errorf("dhcpv4: gateway ip %v in the ip range: %v-%v",
+			routerIP,
+			conf.RangeStart,
+			conf.RangeEnd,
+		)
+	}
+
+	if !s.conf.subnet.Contains(conf.RangeStart) {
+		return s, fmt.Errorf("dhcpv4: range start %v is outside network %v",
+			conf.RangeStart,
+			s.conf.subnet,
+		)
+	}
+
+	if !s.conf.subnet.Contains(conf.RangeEnd) {
+		return s, fmt.Errorf("dhcpv4: range end %v is outside network %v",
+			conf.RangeEnd,
+			s.conf.subnet,
+		)
+	}
+
+	// TODO(a.garipov, d.seregin): Check that every lease is inside the IPRange.
 	s.leasedOffsets = newBitSet()
 
 	if conf.LeaseDuration == 0 {

From b8c4651decc0193f9c2089f5ab1ce0921bcddc2d Mon Sep 17 00:00:00 2001
From: Eugene Burkov <e.burkov@adguard.com>
Date: Wed, 20 Oct 2021 19:52:13 +0300
Subject: [PATCH 3/3] Pull request: 1558 enable dnsrewrites on disabled
 protection

Merge in DNS/adguard-home from 1558-always-rewrite to master

Squashed commit of the following:

commit b8508b3b5fb688cad273a9259c09ccfc07948b2f
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Oct 20 19:17:22 2021 +0300

    all: imp log of changes

commit 97e3649b670786a2936e368a9505faf52f8e8804
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 18 13:18:15 2021 +0300

    all: enable dnsrewrites on disabled protection
---
 CHANGELOG.md                            |   3 +
 internal/dnsforward/dns.go              |  70 ++++++++--------
 internal/dnsforward/dnsforward_test.go  | 104 ++++++++++++++----------
 internal/dnsforward/filter.go           |  55 +++++++------
 internal/filtering/filtering.go         |  33 +++++---
 internal/filtering/filtering_test.go    |  16 ++--
 internal/filtering/safebrowsing.go      |   4 +-
 internal/filtering/safebrowsing_test.go |  22 ++---
 internal/filtering/safesearch.go        |   2 +-
 internal/home/controlfiltering.go       |   1 +
 10 files changed, 178 insertions(+), 132 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 99821349..aeb1ed2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,8 @@ and this project adheres to
 
 ### Changed
 
+- `$dnsrewrite` rules and other DNS rewrites will now be applied even when the
+  protection is disabled ([#1558]).
 - DHCP gateway address, subnet mask, IP address range, and leases validations
   ([#3529]).
 - The `systemd` service script will now create the `/var/log` directory when it
@@ -155,6 +157,7 @@ In this release, the schema version has changed from 10 to 12.
 - Go 1.15 support.
 
 [#1381]: https://github.com/AdguardTeam/AdGuardHome/issues/1381
+[#1558]: https://github.com/AdguardTeam/AdGuardHome/issues/1558
 [#1691]: https://github.com/AdguardTeam/AdGuardHome/issues/1691
 [#1898]: https://github.com/AdguardTeam/AdGuardHome/issues/1898
 [#1992]: https://github.com/AdguardTeam/AdGuardHome/issues/1992
diff --git a/internal/dnsforward/dns.go b/internal/dnsforward/dns.go
index 4f1b8d3a..a0aa4cb1 100644
--- a/internal/dnsforward/dns.go
+++ b/internal/dnsforward/dns.go
@@ -90,7 +90,7 @@ func (s *Server) handleDNSRequest(_ *proxy.Proxy, d *proxy.DNSContext) error {
 		s.processRestrictLocal,
 		s.processInternalIPAddrs,
 		s.processClientID,
-		processFilteringBeforeRequest,
+		s.processFilteringBeforeRequest,
 		s.processLocalPTR,
 		s.processUpstream,
 		processDNSSECAfterResponse,
@@ -468,19 +468,18 @@ func (s *Server) processLocalPTR(ctx *dnsContext) (rc resultCode) {
 }
 
 // Apply filtering logic
-func processFilteringBeforeRequest(ctx *dnsContext) (rc resultCode) {
-	s := ctx.srv
-	d := ctx.proxyCtx
-
-	if d.Res != nil {
-		return resultCodeSuccess // response is already set - nothing to do
+func (s *Server) processFilteringBeforeRequest(ctx *dnsContext) (rc resultCode) {
+	if ctx.proxyCtx.Res != nil {
+		// Go on since the response is already set.
+		return resultCodeSuccess
 	}
 
 	s.serverLock.RLock()
 	defer s.serverLock.RUnlock()
 
-	ctx.protectionEnabled = s.conf.ProtectionEnabled && s.dnsFilter != nil
-	if !ctx.protectionEnabled {
+	ctx.protectionEnabled = s.conf.ProtectionEnabled
+
+	if s.dnsFilter == nil {
 		return resultCodeSuccess
 	}
 
@@ -489,8 +488,7 @@ func processFilteringBeforeRequest(ctx *dnsContext) (rc resultCode) {
 	}
 
 	var err error
-	ctx.result, err = s.filterDNSRequest(ctx)
-	if err != nil {
+	if ctx.result, err = s.filterDNSRequest(ctx); err != nil {
 		ctx.err = err
 
 		return resultCodeError
@@ -608,48 +606,50 @@ func processDNSSECAfterResponse(ctx *dnsContext) (rc resultCode) {
 func processFilteringAfterResponse(ctx *dnsContext) (rc resultCode) {
 	s := ctx.srv
 	d := ctx.proxyCtx
-	res := ctx.result
-	var err error
 
-	switch res.Reason {
-	case filtering.Rewritten,
+	switch res := ctx.result; res.Reason {
+	case filtering.NotFilteredAllowList:
+		// Go on.
+	case
+		filtering.Rewritten,
 		filtering.RewrittenRule:
 
 		if len(ctx.origQuestion.Name) == 0 {
-			// origQuestion is set in case we get only CNAME without IP from rewrites table
+			// origQuestion is set in case we get only CNAME without IP from
+			// rewrites table.
 			break
 		}
 
-		d.Req.Question[0] = ctx.origQuestion
-		d.Res.Question[0] = ctx.origQuestion
-
-		if len(d.Res.Answer) != 0 {
-			answer := []dns.RR{}
-			answer = append(answer, s.genAnswerCNAME(d.Req, res.CanonName))
-			answer = append(answer, d.Res.Answer...)
+		d.Req.Question[0], d.Res.Question[0] = ctx.origQuestion, ctx.origQuestion
+		if len(d.Res.Answer) > 0 {
+			answer := append([]dns.RR{s.genAnswerCNAME(d.Req, res.CanonName)}, d.Res.Answer...)
 			d.Res.Answer = answer
 		}
-
-	case filtering.NotFilteredAllowList:
-		// nothing
-
 	default:
-		if !ctx.protectionEnabled || // filters are disabled: there's nothing to check for
-			!ctx.responseFromUpstream { // only check response if it's from an upstream server
+		// Check the response only if the it's from an upstream.  Don't check
+		// the response if the protection is disabled since dnsrewrite rules
+		// aren't applied to it anyway.
+		if !ctx.protectionEnabled || !ctx.responseFromUpstream || s.dnsFilter == nil {
 			break
 		}
-		origResp2 := d.Res
-		ctx.result, err = s.filterDNSResponse(ctx)
+
+		origResp := d.Res
+		result, err := s.filterDNSResponse(ctx)
 		if err != nil {
 			ctx.err = err
+
 			return resultCodeError
 		}
-		if ctx.result != nil {
-			ctx.origResp = origResp2 // matched by response
-		} else {
-			ctx.result = &filtering.Result{}
+
+		if result != nil {
+			ctx.result = result
+			ctx.origResp = origResp
 		}
 	}
 
+	if ctx.result == nil {
+		ctx.result = &filtering.Result{}
+	}
+
 	return resultCodeSuccess
 }
diff --git a/internal/dnsforward/dnsforward_test.go b/internal/dnsforward/dnsforward_test.go
index 3ab76a40..a3aa68c6 100644
--- a/internal/dnsforward/dnsforward_test.go
+++ b/internal/dnsforward/dnsforward_test.go
@@ -909,6 +909,7 @@ func TestRewrite(t *testing.T) {
 		}},
 	}
 	f := filtering.New(c, nil)
+	f.SetEnabled(true)
 
 	snd, err := aghnet.NewSubnetDetector()
 	require.NoError(t, err)
@@ -945,45 +946,56 @@ func TestRewrite(t *testing.T) {
 
 	addr := s.dnsProxy.Addr(proxy.ProtoUDP)
 
-	req := createTestMessageWithType("test.com.", dns.TypeA)
-	reply, err := dns.Exchange(req, addr.String())
-	require.NoError(t, err)
+	subTestFunc := func(t *testing.T) {
+		req := createTestMessageWithType("test.com.", dns.TypeA)
+		reply, eerr := dns.Exchange(req, addr.String())
+		require.NoError(t, eerr)
 
-	require.Len(t, reply.Answer, 1)
+		require.Len(t, reply.Answer, 1)
 
-	a, ok := reply.Answer[0].(*dns.A)
-	require.True(t, ok)
+		a, ok := reply.Answer[0].(*dns.A)
+		require.True(t, ok)
 
-	assert.True(t, net.IP{1, 2, 3, 4}.Equal(a.A))
+		assert.True(t, net.IP{1, 2, 3, 4}.Equal(a.A))
 
-	req = createTestMessageWithType("test.com.", dns.TypeAAAA)
-	reply, err = dns.Exchange(req, addr.String())
-	require.NoError(t, err)
+		req = createTestMessageWithType("test.com.", dns.TypeAAAA)
+		reply, eerr = dns.Exchange(req, addr.String())
+		require.NoError(t, eerr)
 
-	assert.Empty(t, reply.Answer)
+		assert.Empty(t, reply.Answer)
 
-	req = createTestMessageWithType("alias.test.com.", dns.TypeA)
-	reply, err = dns.Exchange(req, addr.String())
-	require.NoError(t, err)
+		req = createTestMessageWithType("alias.test.com.", dns.TypeA)
+		reply, eerr = dns.Exchange(req, addr.String())
+		require.NoError(t, eerr)
 
-	require.Len(t, reply.Answer, 2)
+		require.Len(t, reply.Answer, 2)
 
-	assert.Equal(t, "test.com.", reply.Answer[0].(*dns.CNAME).Target)
-	assert.True(t, net.IP{1, 2, 3, 4}.Equal(reply.Answer[1].(*dns.A).A))
+		assert.Equal(t, "test.com.", reply.Answer[0].(*dns.CNAME).Target)
+		assert.True(t, net.IP{1, 2, 3, 4}.Equal(reply.Answer[1].(*dns.A).A))
 
-	req = createTestMessageWithType("my.alias.example.org.", dns.TypeA)
-	reply, err = dns.Exchange(req, addr.String())
-	require.NoError(t, err)
+		req = createTestMessageWithType("my.alias.example.org.", dns.TypeA)
+		reply, eerr = dns.Exchange(req, addr.String())
+		require.NoError(t, eerr)
 
-	// The original question is restored.
-	require.Len(t, reply.Question, 1)
+		// The original question is restored.
+		require.Len(t, reply.Question, 1)
 
-	assert.Equal(t, "my.alias.example.org.", reply.Question[0].Name)
+		assert.Equal(t, "my.alias.example.org.", reply.Question[0].Name)
 
-	require.Len(t, reply.Answer, 2)
+		require.Len(t, reply.Answer, 2)
 
-	assert.Equal(t, "example.org.", reply.Answer[0].(*dns.CNAME).Target)
-	assert.Equal(t, dns.TypeA, reply.Answer[1].Header().Rrtype)
+		assert.Equal(t, "example.org.", reply.Answer[0].(*dns.CNAME).Target)
+		assert.Equal(t, dns.TypeA, reply.Answer[1].Header().Rrtype)
+	}
+
+	for _, protect := range []bool{true, false} {
+		val := protect
+		conf := s.getDNSConfig()
+		conf.ProtectionEnabled = &val
+		s.setConfig(conf)
+
+		t.Run(fmt.Sprintf("protection_is_%t", val), subTestFunc)
+	}
 }
 
 func publicKey(priv interface{}) interface{} {
@@ -1092,9 +1104,10 @@ func TestPTRResponseFromHosts(t *testing.T) {
 		require.ErrorIs(t, hc.Close(), closeCalled)
 	})
 
-	c := filtering.Config{
+	flt := filtering.New(&filtering.Config{
 		EtcHosts: hc,
-	}
+	}, nil)
+	flt.SetEnabled(true)
 
 	var snd *aghnet.SubnetDetector
 	snd, err = aghnet.NewSubnetDetector()
@@ -1104,7 +1117,7 @@ func TestPTRResponseFromHosts(t *testing.T) {
 	var s *Server
 	s, err = NewServer(DNSCreateParams{
 		DHCPServer:     &testDHCP{},
-		DNSFilter:      filtering.New(&c, nil),
+		DNSFilter:      flt,
 		SubnetDetector: snd,
 	})
 	require.NoError(t, err)
@@ -1112,32 +1125,41 @@ func TestPTRResponseFromHosts(t *testing.T) {
 	s.conf.UDPListenAddrs = []*net.UDPAddr{{}}
 	s.conf.TCPListenAddrs = []*net.TCPAddr{{}}
 	s.conf.UpstreamDNS = []string{"127.0.0.1:53"}
-	s.conf.FilteringConfig.ProtectionEnabled = true
 
 	err = s.Prepare(nil)
 	require.NoError(t, err)
 
 	err = s.Start()
 	require.NoError(t, err)
-
 	t.Cleanup(func() {
 		s.Close()
 	})
 
-	addr := s.dnsProxy.Addr(proxy.ProtoUDP)
-	req := createTestMessageWithType("1.0.0.127.in-addr.arpa.", dns.TypePTR)
+	subTestFunc := func(t *testing.T) {
+		addr := s.dnsProxy.Addr(proxy.ProtoUDP)
+		req := createTestMessageWithType("1.0.0.127.in-addr.arpa.", dns.TypePTR)
 
-	resp, err := dns.Exchange(req, addr.String())
-	require.NoError(t, err)
+		resp, eerr := dns.Exchange(req, addr.String())
+		require.NoError(t, eerr)
 
-	require.Lenf(t, resp.Answer, 1, "%#v", resp)
+		require.Len(t, resp.Answer, 1)
 
-	assert.Equal(t, dns.TypePTR, resp.Answer[0].Header().Rrtype)
-	assert.Equal(t, "1.0.0.127.in-addr.arpa.", resp.Answer[0].Header().Name)
+		assert.Equal(t, dns.TypePTR, resp.Answer[0].Header().Rrtype)
+		assert.Equal(t, "1.0.0.127.in-addr.arpa.", resp.Answer[0].Header().Name)
 
-	ptr, ok := resp.Answer[0].(*dns.PTR)
-	require.True(t, ok)
-	assert.Equal(t, "host.", ptr.Ptr)
+		ptr, ok := resp.Answer[0].(*dns.PTR)
+		require.True(t, ok)
+		assert.Equal(t, "host.", ptr.Ptr)
+	}
+
+	for _, protect := range []bool{true, false} {
+		val := protect
+		conf := s.getDNSConfig()
+		conf.ProtectionEnabled = &val
+		s.setConfig(conf)
+
+		t.Run(fmt.Sprintf("protection_is_%t", val), subTestFunc)
+	}
 }
 
 func TestNewServer(t *testing.T) {
diff --git a/internal/dnsforward/filter.go b/internal/dnsforward/filter.go
index 5edca948..7300b43c 100644
--- a/internal/dnsforward/filter.go
+++ b/internal/dnsforward/filter.go
@@ -52,6 +52,7 @@ func (s *Server) beforeRequestHandler(
 // the client's IP address and ID, if any, from ctx.
 func (s *Server) getClientRequestFilteringSettings(ctx *dnsContext) *filtering.Settings {
 	setts := s.dnsFilter.GetConfig()
+	setts.ProtectionEnabled = ctx.protectionEnabled
 	if s.conf.FilterHandler != nil {
 		ip, _ := netutil.IPAndPortFromAddr(ctx.proxyCtx.Addr)
 		s.conf.FilterHandler(ip, ctx.clientID, &setts)
@@ -65,32 +66,31 @@ func (s *Server) getClientRequestFilteringSettings(ctx *dnsContext) *filtering.S
 func (s *Server) filterDNSRequest(ctx *dnsContext) (*filtering.Result, error) {
 	d := ctx.proxyCtx
 	req := d.Req
-	host := strings.TrimSuffix(req.Question[0].Name, ".")
-	res, err := s.dnsFilter.CheckHost(host, req.Question[0].Qtype, ctx.setts)
-	if err != nil {
-		// Return immediately if there's an error
-		return nil, fmt.Errorf("filtering failed to check host %q: %w", host, err)
-	} else if res.IsFiltered {
-		log.Tracef("Host %s is filtered, reason - %q, matched rule: %q", host, res.Reason, res.Rules[0].Text)
+	q := req.Question[0]
+	host := strings.TrimSuffix(q.Name, ".")
+	res, err := s.dnsFilter.CheckHost(host, q.Qtype, ctx.setts)
+	switch {
+	case err != nil:
+		return nil, fmt.Errorf("failed to check host %q: %w", host, err)
+	case res.IsFiltered:
+		log.Tracef("host %q is filtered, reason %q, rule: %q", host, res.Reason, res.Rules[0].Text)
 		d.Res = s.genDNSFilterMessage(d, &res)
-	} else if res.Reason.In(filtering.Rewritten, filtering.RewrittenRule) &&
+	case res.Reason.In(filtering.Rewritten, filtering.RewrittenRule) &&
 		res.CanonName != "" &&
-		len(res.IPList) == 0 {
-		// Resolve the new canonical name, not the original host
-		// name.  The original question is readded in
-		// processFilteringAfterResponse.
-		ctx.origQuestion = req.Question[0]
+		len(res.IPList) == 0:
+		// Resolve the new canonical name, not the original host name.  The
+		// original question is readded in processFilteringAfterResponse.
+		ctx.origQuestion = q
 		req.Question[0].Name = dns.Fqdn(res.CanonName)
-	} else if res.Reason == filtering.RewrittenAutoHosts && len(res.ReverseHosts) != 0 {
+	case res.Reason == filtering.RewrittenAutoHosts && len(res.ReverseHosts) != 0:
 		resp := s.makeResponse(req)
+		hdr := dns.RR_Header{
+			Name:   q.Name,
+			Rrtype: dns.TypePTR,
+			Ttl:    s.conf.BlockedResponseTTL,
+			Class:  dns.ClassINET,
+		}
 		for _, h := range res.ReverseHosts {
-			hdr := dns.RR_Header{
-				Name:   req.Question[0].Name,
-				Rrtype: dns.TypePTR,
-				Ttl:    s.conf.BlockedResponseTTL,
-				Class:  dns.ClassINET,
-			}
-
 			ptr := &dns.PTR{
 				Hdr: hdr,
 				Ptr: h,
@@ -100,7 +100,7 @@ func (s *Server) filterDNSRequest(ctx *dnsContext) (*filtering.Result, error) {
 		}
 
 		d.Res = resp
-	} else if res.Reason.In(filtering.Rewritten, filtering.RewrittenAutoHosts) {
+	case res.Reason.In(filtering.Rewritten, filtering.RewrittenAutoHosts):
 		resp := s.makeResponse(req)
 
 		name := host
@@ -110,11 +110,12 @@ func (s *Server) filterDNSRequest(ctx *dnsContext) (*filtering.Result, error) {
 		}
 
 		for _, ip := range res.IPList {
-			if req.Question[0].Qtype == dns.TypeA {
+			switch q.Qtype {
+			case dns.TypeA:
 				a := s.genAnswerA(req, ip.To4())
 				a.Hdr.Name = dns.Fqdn(name)
 				resp.Answer = append(resp.Answer, a)
-			} else if req.Question[0].Qtype == dns.TypeAAAA {
+			case dns.TypeAAAA:
 				a := s.genAnswerAAAA(req, ip)
 				a.Hdr.Name = dns.Fqdn(name)
 				resp.Answer = append(resp.Answer, a)
@@ -122,9 +123,8 @@ func (s *Server) filterDNSRequest(ctx *dnsContext) (*filtering.Result, error) {
 		}
 
 		d.Res = resp
-	} else if res.Reason == filtering.RewrittenRule {
-		err = s.filterDNSRewrite(req, res, d)
-		if err != nil {
+	case res.Reason == filtering.RewrittenRule:
+		if err = s.filterDNSRewrite(req, res, d); err != nil {
 			return nil, err
 		}
 	}
@@ -179,6 +179,7 @@ func (s *Server) filterDNSResponse(ctx *dnsContext) (*filtering.Result, error) {
 			continue
 		}
 
+		host = strings.TrimSuffix(host, ".")
 		res, err := s.checkHostRules(host, d.Req.Question[0].Qtype, ctx.setts)
 		if err != nil {
 			return nil, err
diff --git a/internal/filtering/filtering.go b/internal/filtering/filtering.go
index f7a8ebe4..87d0da15 100644
--- a/internal/filtering/filtering.go
+++ b/internal/filtering/filtering.go
@@ -38,6 +38,7 @@ type Settings struct {
 
 	ServicesRules []ServiceEntry
 
+	ProtectionEnabled   bool
 	FilteringEnabled    bool
 	SafeSearchEnabled   bool
 	SafeBrowsingEnabled bool
@@ -221,12 +222,13 @@ func (r Reason) String() string {
 }
 
 // In returns true if reasons include r.
-func (r Reason) In(reasons ...Reason) bool {
+func (r Reason) In(reasons ...Reason) (ok bool) {
 	for _, reason := range reasons {
 		if r == reason {
 			return true
 		}
 	}
+
 	return false
 }
 
@@ -245,7 +247,7 @@ func (d *DNSFilter) GetConfig() (s Settings) {
 	defer d.confLock.RUnlock()
 
 	return Settings{
-		FilteringEnabled:    atomic.LoadUint32(&d.Config.enabled) == 1,
+		FilteringEnabled:    atomic.LoadUint32(&d.Config.enabled) != 0,
 		SafeSearchEnabled:   d.Config.SafeSearchEnabled,
 		SafeBrowsingEnabled: d.Config.SafeBrowsingEnabled,
 		ParentalEnabled:     d.Config.ParentalEnabled,
@@ -421,14 +423,16 @@ func (d *DNSFilter) CheckHost(
 	// Sometimes clients try to resolve ".", which is a request to get root
 	// servers.
 	if host == "" {
-		return Result{Reason: NotFilteredNotFound}, nil
+		return Result{}, nil
 	}
 
 	host = strings.ToLower(host)
 
-	res = d.processRewrites(host, qtype)
-	if res.Reason == Rewritten {
-		return res, nil
+	if setts.FilteringEnabled {
+		res = d.processRewrites(host, qtype)
+		if res.Reason == Rewritten {
+			return res, nil
+		}
 	}
 
 	for _, hc := range d.hostCheckers {
@@ -448,7 +452,7 @@ func (d *DNSFilter) CheckHost(
 // matchSysHosts tries to match the host against the operating system's hosts
 // database.
 func (d *DNSFilter) matchSysHosts(host string, qtype uint16, setts *Settings) (res Result, err error) {
-	if d.EtcHosts == nil {
+	if !setts.FilteringEnabled || d.EtcHosts == nil {
 		return Result{}, nil
 	}
 
@@ -468,10 +472,8 @@ func (d *DNSFilter) matchSysHosts(host string, qtype uint16, setts *Settings) (r
 
 	var ips []net.IP
 	var revHosts []string
-
 	for _, nr := range dnsr {
-		dr := nr.DNSRewrite
-		if dr == nil {
+		if nr.DNSRewrite == nil {
 			continue
 		}
 
@@ -553,6 +555,10 @@ func matchBlockedServicesRules(
 	_ uint16,
 	setts *Settings,
 ) (res Result, err error) {
+	if !setts.ProtectionEnabled {
+		return Result{}, nil
+	}
+
 	svcs := setts.ServicesRules
 	if len(svcs) == 0 {
 		return Result{}, nil
@@ -784,7 +790,7 @@ func (d *DNSFilter) matchHost(
 	// TODO(e.burkov):  Inspect if the above is true.
 	defer d.engineLock.RUnlock()
 
-	if d.filteringEngineAllow != nil {
+	if setts.ProtectionEnabled && d.filteringEngineAllow != nil {
 		dnsres, ok := d.filteringEngineAllow.MatchRequest(ureq)
 		if ok {
 			return d.matchHostProcessAllowList(host, dnsres)
@@ -810,6 +816,11 @@ func (d *DNSFilter) matchHost(
 		return Result{}, nil
 	}
 
+	if !setts.ProtectionEnabled {
+		// Don't check non-dnsrewrite filtering results.
+		return Result{}, nil
+	}
+
 	res = d.matchHostProcessDNSResult(qtype, dnsres)
 	for _, r := range res.Rules {
 		log.Debug(
diff --git a/internal/filtering/filtering_test.go b/internal/filtering/filtering_test.go
index 746e9ed0..b389b386 100644
--- a/internal/filtering/filtering_test.go
+++ b/internal/filtering/filtering_test.go
@@ -21,7 +21,9 @@ func TestMain(m *testing.M) {
 	aghtest.DiscardLogOutput(m)
 }
 
-var setts Settings
+var setts = Settings{
+	ProtectionEnabled: true,
+}
 
 // Helpers.
 
@@ -39,9 +41,9 @@ func purgeCaches() {
 
 func newForTest(c *Config, filters []Filter) *DNSFilter {
 	setts = Settings{
-		FilteringEnabled: true,
+		ProtectionEnabled: true,
+		FilteringEnabled:  true,
 	}
-	setts.FilteringEnabled = true
 	if c != nil {
 		c.SafeBrowsingCacheSize = 10000
 		c.ParentalCacheSize = 10000
@@ -797,7 +799,11 @@ func TestClientSettings(t *testing.T) {
 
 	makeTester := func(tc testCase, before bool) func(t *testing.T) {
 		return func(t *testing.T) {
-			r, _ := d.CheckHost(tc.host, dns.TypeA, &setts)
+			t.Helper()
+
+			r, err := d.CheckHost(tc.host, dns.TypeA, &setts)
+			require.NoError(t, err)
+
 			if before {
 				assert.True(t, r.IsFiltered)
 				assert.Equal(t, tc.wantReason, r.Reason)
@@ -808,7 +814,7 @@ func TestClientSettings(t *testing.T) {
 	}
 
 	// Check behaviour without any per-client settings, then apply per-client
-	// settings and check behaviour once again.
+	// settings and check behavior once again.
 	for _, tc := range testCases {
 		t.Run(tc.name, makeTester(tc, tc.before))
 	}
diff --git a/internal/filtering/safebrowsing.go b/internal/filtering/safebrowsing.go
index d535a39d..ec626315 100644
--- a/internal/filtering/safebrowsing.go
+++ b/internal/filtering/safebrowsing.go
@@ -306,7 +306,7 @@ func (d *DNSFilter) checkSafeBrowsing(
 	_ uint16,
 	setts *Settings,
 ) (res Result, err error) {
-	if !setts.SafeBrowsingEnabled {
+	if !setts.ProtectionEnabled || !setts.SafeBrowsingEnabled {
 		return Result{}, nil
 	}
 
@@ -339,7 +339,7 @@ func (d *DNSFilter) checkParental(
 	_ uint16,
 	setts *Settings,
 ) (res Result, err error) {
-	if !setts.ParentalEnabled {
+	if !setts.ProtectionEnabled || !setts.ParentalEnabled {
 		return Result{}, nil
 	}
 
diff --git a/internal/filtering/safebrowsing_test.go b/internal/filtering/safebrowsing_test.go
index d513c0b2..c88576f1 100644
--- a/internal/filtering/safebrowsing_test.go
+++ b/internal/filtering/safebrowsing_test.go
@@ -117,6 +117,7 @@ func TestSBPC_checkErrorUpstream(t *testing.T) {
 	d.SetParentalUpstream(ups)
 
 	setts := &Settings{
+		ProtectionEnabled:   true,
 		SafeBrowsingEnabled: true,
 		ParentalEnabled:     true,
 	}
@@ -135,35 +136,36 @@ func TestSBPC(t *testing.T) {
 	const hostname = "example.org"
 
 	setts := &Settings{
+		ProtectionEnabled:   true,
 		SafeBrowsingEnabled: true,
 		ParentalEnabled:     true,
 	}
 
 	testCases := []struct {
+		testCache cache.Cache
+		testFunc  func(host string, _ uint16, _ *Settings) (res Result, err error)
 		name      string
 		block     bool
-		testFunc  func(host string, _ uint16, _ *Settings) (res Result, err error)
-		testCache cache.Cache
 	}{{
+		testCache: gctx.safebrowsingCache,
+		testFunc:  d.checkSafeBrowsing,
 		name:      "sb_no_block",
 		block:     false,
-		testFunc:  d.checkSafeBrowsing,
-		testCache: gctx.safebrowsingCache,
 	}, {
+		testCache: gctx.safebrowsingCache,
+		testFunc:  d.checkSafeBrowsing,
 		name:      "sb_block",
 		block:     true,
-		testFunc:  d.checkSafeBrowsing,
-		testCache: gctx.safebrowsingCache,
 	}, {
+		testCache: gctx.parentalCache,
+		testFunc:  d.checkParental,
 		name:      "pc_no_block",
 		block:     false,
-		testFunc:  d.checkParental,
-		testCache: gctx.parentalCache,
 	}, {
+		testCache: gctx.parentalCache,
+		testFunc:  d.checkParental,
 		name:      "pc_block",
 		block:     true,
-		testFunc:  d.checkParental,
-		testCache: gctx.parentalCache,
 	}}
 
 	for _, tc := range testCases {
diff --git a/internal/filtering/safesearch.go b/internal/filtering/safesearch.go
index db9e9ee9..ff89b950 100644
--- a/internal/filtering/safesearch.go
+++ b/internal/filtering/safesearch.go
@@ -74,7 +74,7 @@ func (d *DNSFilter) checkSafeSearch(
 	_ uint16,
 	setts *Settings,
 ) (res Result, err error) {
-	if !setts.SafeSearchEnabled {
+	if !setts.ProtectionEnabled || !setts.SafeSearchEnabled {
 		return Result{}, nil
 	}
 
diff --git a/internal/home/controlfiltering.go b/internal/home/controlfiltering.go
index 550b4b87..ee19fd16 100644
--- a/internal/home/controlfiltering.go
+++ b/internal/home/controlfiltering.go
@@ -404,6 +404,7 @@ func (f *Filtering) handleCheckHost(w http.ResponseWriter, r *http.Request) {
 
 	setts := Context.dnsFilter.GetConfig()
 	setts.FilteringEnabled = true
+	setts.ProtectionEnabled = true
 	Context.dnsFilter.ApplyBlockedServices(&setts, nil, true)
 	result, err := Context.dnsFilter.CheckHost(host, dns.TypeA, &setts)
 	if err != nil {