all: github action for potential dups and improved issue forms

Merge in DNS/adguard-home from upd-proxy to master

Updates #5872.

Squashed commit of the following:

commit fac8d1cdeb53cb5cfe867c7a3521bb5ca76331ef
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Jun 9 19:18:35 2023 +0300

    all: fix chlog

commit 10f64ba5683422ecc3cb5d0bd6c679ed4e80e0cc
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Jun 9 19:14:07 2023 +0300

    all: log changes

commit 14410c4997c674a4f8a4adf8b77c1cf692131d24
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Jun 9 18:48:09 2023 +0300

    all: upd proxy

.github/ISSUE_TEMPLATE/bug.yml

@@ -1,109 +1,142 @@
 'body':
   - 'attributes':
-        'description': >
-            Please make sure that the issue is not a duplicate or a question.
-            If it's a duplicate, please react to the original issue with a
-            thumbs up.  If it's a question, please post it to the GitHub
-            Discussions page.
-        'label': 'Prerequisites'
-        'options':
-          - 'label': >
-                I have checked the
-                [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and
-                [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions)
-                and found no answer
-            'required': true
-          - 'label': >
-                I have searched other issues and found no duplicates
-            'required': true
-          - 'label': >
-                I want to report a bug and not ask a question
-            'required': true
+      'description': >
+        Please make sure that the issue is not a duplicate or a question.
+        If it's a duplicate, please react to the original issue with a
+        thumbs up.  If it's a question, please post it to the GitHub
+        Discussions page.
+      'label': 'Prerequisites'
+      'options':
+        - 'label': >
+            I have checked the
+            [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and
+            [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions)
+            and found no answer
+          'required': true
+        - 'label': >
+            I have searched other issues and found no duplicates
+          'required': true
+        - 'label': >
+            I want to report a bug and not ask a question
+          'required': true
     'id': 'prerequisites'
     'type': 'checkboxes'
   - 'attributes':
-        'description': 'On which operating system type does the issue occur?'
-        'label': 'Operating system type'
-        'options':
-          - 'FreeBSD'
-          - 'Linux, OpenWrt'
-          - 'Linux, Other (please mention the version in the description)'
-          - 'macOS (aka Darwin)'
-          - 'OpenBSD'
-          - 'Windows'
-          - 'Other (please mention in the description)'
+      'description': 'On which operating system type does the issue occur?'
+      'label': 'Operating system type'
+      'options':
+        - 'FreeBSD'
+        - 'Linux, OpenWrt'
+        - 'Linux, Other (please mention the version in the description)'
+        - 'macOS (aka Darwin)'
+        - 'OpenBSD'
+        - 'Windows'
+        - 'Other (please mention in the description)'
     'id': 'os'
     'type': 'dropdown'
     'validations':
-        'required': true
+      'required': true
   - 'attributes':
-        'description': 'On which CPU architecture does the issue occur?'
-        'label': 'CPU architecture'
-        'options':
-          - 'AMD64'
-          - 'x86'
-          - '64-bit ARM'
-          - 'ARMv5'
-          - 'ARMv6'
-          - 'ARMv7'
-          - '64-bit MIPS'
-          - '64-bit MIPS LE'
-          - '32-bit MIPS'
-          - '32-bit MIPS LE'
-          - '64-bit PowerPC LE'
-          - 'Other (please mention in the description)'
+      'description': 'On which CPU architecture does the issue occur?'
+      'label': 'CPU architecture'
+      'options':
+        - 'AMD64'
+        - 'x86'
+        - '64-bit ARM'
+        - 'ARMv5'
+        - 'ARMv6'
+        - 'ARMv7'
+        - '64-bit MIPS'
+        - '64-bit MIPS LE'
+        - '32-bit MIPS'
+        - '32-bit MIPS LE'
+        - '64-bit PowerPC LE'
+        - 'Other (please mention in the description)'
     'id': 'arch'
     'type': 'dropdown'
     'validations':
-        'required': true
+      'required': true
   - 'attributes':
-        'description': 'How did you install AdGuard Home?'
-        'label': 'Installation'
-        'options':
-          - 'GitHub releases or script from README'
-          - 'Docker'
-          - 'Snapcraft'
-          - 'Custom port'
-          - 'Other (please mention in the description)'
+      'description': 'How did you install AdGuard Home?'
+      'label': 'Installation'
+      'options':
+        - 'GitHub releases or script from README'
+        - 'Docker'
+        - 'Snapcraft'
+        - 'Custom port'
+        - 'Other (please mention in the description)'
     'id': 'install'
     'type': 'dropdown'
     'validations':
-        'required': true
+      'required': true
   - 'attributes':
-        'description': 'How did you setup AdGuard Home?'
-        'label': 'Setup'
-        'options':
-          - 'On one machine'
-          - 'On a router, DHCP is handled by the router'
-          - 'On a router, DHCP is handled by AdGuard Home'
-          - 'Other (please mention in the description)'
+      'description': 'How did you setup AdGuard Home?'
+      'label': 'Setup'
+      'options':
+        - 'On one machine'
+        - 'On a router, DHCP is handled by the router'
+        - 'On a router, DHCP is handled by AdGuard Home'
+        - 'Other (please mention in the description)'
     'id': 'setup'
     'type': 'dropdown'
     'validations':
-        'required': true
+      'required': true
   - 'attributes':
-        'description': 'What version of AdGuard Home are you using?'
-        'label': 'AdGuard Home version'
+      'description': 'What version of AdGuard Home are you using?'
+      'label': 'AdGuard Home version'
     'id': 'version'
     'type': 'input'
     'validations':
-        'required': true
+      'required': true
   - 'attributes':
-        'description': 'Please describe the bug'
-        'label': 'Description'
-        'value': |
-            #### What did you do?
-
-            #### Expected result
-
-            #### Actual result
-
-            #### Screenshots (if applicable)
-
-            #### Additional information
-    'id': 'description'
+      'description': 'Please provide a set of steps to reproduce the issue'
+      'label': 'Issue Details'
+      'placeholder':
+      'value': |
+        Steps to reproduce:
+        1.
+        2.
+        3.
+    'id': 'what-happened'
     'type': 'textarea'
     'validations':
-        'required': true
-'description': 'File a bug report'
-'name': 'Bug'
+      'required': true
+  - 'attributes':
+      'label': 'Expected Behavior'
+      'description': 'Describe the expected behavior'
+      'placeholder': |
+        A clear and concise description of what you expected to happen.
+    'id': 'expected-behavior'
+    'type': 'textarea'
+    'validations':
+      'required': false
+  - 'attributes':
+      'label': 'Actual Behavior'
+      'description': 'Describe the actual behavior'
+      'placeholder': 'A clear description of what happened instead.'
+    'id': 'actual-behavior'
+    'type': 'textarea'
+    'validations':
+      'required': true
+  - 'attributes':
+      'label': 'Screenshots'
+      'description': |
+        If applicable add screenshots explaining your problem.
+        You can drag and drop images or paste them from clipboard.
+        Use `<details> </details>` tag to hide screenshots under the spoiler.
+      'placeholder': 'If applicable add screenshots explaining your problem.'
+      'value': |
+        <details><summary>Screenshot 1:</summary>
+        
+        <!-- paste screenshot here -->
+        
+        </details>
+    'id': 'screenshots'
+    'type': 'textarea'
+    'validations':
+      'required': false
+'description': >
+  Open a bug report. Please do not open bug reports for questions. If you
+  want to ask a question, ask in in the Discussions section.
+'name': 'Bug report'
+'labels': [ 'bug' ]

.github/ISSUE_TEMPLATE/feature.yml

@@ -1,41 +1,54 @@
 'body':
   - 'attributes':
-        'description': >
-            Please make sure that the issue is not a duplicate or a question.
-            If it's a duplicate, please react to the original issue with a
-            thumbs up.  If it's a question, please post it to the GitHub
-            Discussions page.
-        'label': 'Prerequisites'
-        'options':
-          - 'label': >
-                I have checked the
-                [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and
-                [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions)
-                and found no answer
-            'required': true
-          - 'label': >
-                I have searched other issues and found no duplicates
-            'required': true
-          - 'label': >
-                I want to request a feature or enhancement and not ask a
-                question
-            'required': true
+      'description': >
+        Please make sure that the issue is not a duplicate or a question.
+        If it's a duplicate, please react to the original issue with a
+        thumbs up.  If it's a question, please post it to the GitHub
+        Discussions page.
+      'label': 'Prerequisites'
+      'options':
+        - 'label': >
+            I have checked the
+            [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and
+            [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions)
+            and found no answer
+          'required': true
+        - 'label': >
+            I have searched other issues and found no duplicates
+          'required': true
+        - 'label': >
+            I want to request a feature or enhancement and not ask a
+            question
+          'required': true
     'id': 'prerequisites'
     'type': 'checkboxes'
   - 'attributes':
-        'description': 'Please describe the request'
-        'label': 'Description'
-        'value': |
-            #### What problem are you trying to solve?
-
-            #### Proposed solution
-
-            #### Alternatives considered
-
-            #### Additional information
-    'id': 'description'
+      'description': 'What happened?'
+      'placeholder': |
+        Is your feature request related to a problem? Please add a clear and 
+        concise description of what the problem is.
+      'label': 'Issue Details'
+    'id': 'what-happened'
     'type': 'textarea'
     'validations':
-        'required': true
+      'required': true
+  - 'attributes':
+      'description': 'What do you propose to change in AdGuard Home?'
+      'placeholder': |
+        Describe the solution you'd like in a clear and concise manner.
+      'label': 'Proposed solution'
+    'id': 'proposed-solution'
+    'type': 'textarea'
+    'validations':
+      'required': true
+  - 'attributes':
+      'description': 'Are there any other ways to solve the problem?'
+      'placeholder': |
+        A clear and concise description of any alternative solutions or features
+        you've considered.
+      'label': 'Alternative solution'
+    'id': 'alternative-solution'
+    'type': 'textarea'
 'description': 'Suggest a feature or an enhancement for AdGuard Home'
 'name': 'Feature request or enhancement'
+'labels': [ 'feature request' ]

.github/workflows/potential-duplicates.yml

@@ -0,0 +1,34 @@
+'name': 'potential-duplicates'
+'on':
+  'issues':
+    'types': [ 'opened', 'edited' ]
+'jobs':
+  'run':
+    'runs-on': 'ubuntu-latest'
+    'steps':
+      - 'uses': 'wow-actions/potential-duplicates@v1'
+        'with':
+          'GITHUB_TOKEN': ${{ secrets.GITHUB_TOKEN }}
+          # Issue title filter work with https://www.npmjs.com/package/anymatch.
+          # Any matched issue will stop detection immediately.
+          # You can specify multi filters in each line.
+          # 'filter': ''
+          # Exclude keywords in title before detecting.
+          # 'exclude': ''
+          # Label to set, when potential duplicates are detected.
+          'label': 'potential-duplicate'
+          # Get issues with state to compare. Supported state: 'all', 'closed',
+          # 'open'.
+          'state': 'all'
+          # If similarity is higher than this threshold([0,1]), issue will be
+          # marked as duplicate.
+          'threshold': 0.6
+          # Reactions to be add to comment when potential duplicates are
+          # detected. Available reactions: "-1", "+1", "confused", "laugh",
+          # "heart", "hooray", "rocket", "eyes".
+          # 'reactions': 'eyes, confused'
+          # Comment to post when potential duplicates are detected.
+          'comment': >
+            Potential duplicates: {{#issues}}
+              - [#{{ number }}] {{ title }} ({{ accuracy }}%)
+            {{/issues}}

CHANGELOG.md

@@ -28,6 +28,11 @@ NOTE: Add new changes BELOW THIS COMMENT.
 - The ability to edit rewrite rules via `PUT /control/rewrite/update` HTTP API
   ([#1577]).
 
+### Fixed
+
+ - DNSCrypt upstream not resetting the client and resolver information on
+   dialing errors ([#5872]).
+
 [#1577]: https://github.com/AdguardTeam/AdGuardHome/issues/1577
 
 <!--

Makefile

@@ -37,6 +37,8 @@ SIGN = 1
 VERSION = v0.0.0
 YARN = yarn
 
+NEXTAPI = 0
+
 # Macros for the build-release target.  If FRONTEND_PREBUILT is 0, the
 # default, the macro $(BUILD_RELEASE_DEPS_$(FRONTEND_PREBUILT)) expands
 # into BUILD_RELEASE_DEPS_0, and so both frontend and backend
@@ -64,6 +66,7 @@ ENV = env\
 	PATH="$${PWD}/bin:$$( "$(GO.MACRO)" env GOPATH )/bin:$${PATH}"\
 	RACE='$(RACE)'\
 	SIGN='$(SIGN)'\
+	NEXTAPI='$(NEXTAPI)'\
 	VERBOSE="$(VERBOSE.MACRO)"\
 	VERSION='$(VERSION)'\
 

go.mod

@@ -3,12 +3,13 @@ module github.com/AdguardTeam/AdGuardHome
 go 1.19
 
 require (
-	github.com/AdguardTeam/dnsproxy v0.50.1
+	github.com/AdguardTeam/dnsproxy v0.50.2
 	github.com/AdguardTeam/golibs v0.13.2
 	github.com/AdguardTeam/urlfilter v0.16.1
 	github.com/NYTimes/gziphandler v1.1.1
 	github.com/ameshkov/dnscrypt/v2 v2.2.7
 	github.com/digineo/go-ipset/v2 v2.2.1
+	github.com/dimfeld/httptreemux/v5 v5.5.0
 	github.com/fsnotify/fsnotify v1.6.0
 	github.com/go-ping/ping v1.1.0
 	github.com/google/go-cmp v0.5.9

go.sum

@@ -1,5 +1,5 @@
-github.com/AdguardTeam/dnsproxy v0.50.1 h1:A0HmAxb2izkOcuD50pRmR7ZnBL3/qF2DR2SlI6fN+6E=
-github.com/AdguardTeam/dnsproxy v0.50.1/go.mod h1:CQhZTkqC8X0ID6glrtyaxgqRRdiYfn1gJulC1cZ5Dn8=
+github.com/AdguardTeam/dnsproxy v0.50.2 h1:p1471SsMZ6SMo7T51Olw4aNluahvMwSLMorwxYV18ts=
+github.com/AdguardTeam/dnsproxy v0.50.2/go.mod h1:CQhZTkqC8X0ID6glrtyaxgqRRdiYfn1gJulC1cZ5Dn8=
 github.com/AdguardTeam/golibs v0.4.0/go.mod h1:skKsDKIBB7kkFflLJBpfGX+G8QFTx0WKUzB6TIgtUj4=
 github.com/AdguardTeam/golibs v0.10.4/go.mod h1:rSfQRGHIdgfxriDDNgNJ7HmE5zRoURq8R+VdR81Zuzw=
 github.com/AdguardTeam/golibs v0.13.2 h1:BPASsyQKmb+b8VnvsNOHp7bKfcZl9Z+Z2UhPjOiupSc=
@@ -29,6 +29,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/digineo/go-ipset/v2 v2.2.1 h1:k6skY+0fMqeUjjeWO/m5OuWPSZUAn7AucHMnQ1MX77g=
 github.com/digineo/go-ipset/v2 v2.2.1/go.mod h1:wBsNzJlZlABHUITkesrggFnZQtgW5wkqw1uo8Qxe0VU=
+github.com/dimfeld/httptreemux/v5 v5.5.0 h1:p8jkiMrCuZ0CmhwYLcbNbl7DDo21fozhKHQ2PccwOFQ=
+github.com/dimfeld/httptreemux/v5 v5.5.0/go.mod h1:QeEylH57C0v3VO0tkKraVz9oD3Uu93CKPnTLbsidvSw=
 github.com/fsnotify/fsnotify v1.6.0 h1:n+5WquG0fcWoWp6xPWfHdbskMCQaFnG6PfBrh1Ky4HY=
 github.com/fsnotify/fsnotify v1.6.0/go.mod h1:sl3t1tCWJFWoRz9R8WJCbQihKKwmorjAbSClcnxKAGw=
 github.com/go-logr/logr v1.2.4 h1:g01GSCwiDw2xSZfjJ2/T9M+S6pFdcNtFYsp+Y43HYDQ=

internal/aghtest/interface.go

@@ -1,10 +1,12 @@
 package aghtest
 
 import (
+	"context"
 	"io/fs"
 	"net"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
 	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/miekg/dns"
 )
@@ -116,6 +118,36 @@ func (w *FSWatcher) Close() (err error) {
 	return w.OnClose()
 }
 
+// Package agh
+
+// type check
+var _ agh.ServiceWithConfig[struct{}] = (*ServiceWithConfig[struct{}])(nil)
+
+// ServiceWithConfig is a mock [agh.ServiceWithConfig] implementation for tests.
+type ServiceWithConfig[ConfigType any] struct {
+	OnStart    func() (err error)
+	OnShutdown func(ctx context.Context) (err error)
+	OnConfig   func() (c ConfigType)
+}
+
+// Start implements the [agh.ServiceWithConfig] interface for
+// *ServiceWithConfig.
+func (s *ServiceWithConfig[_]) Start() (err error) {
+	return s.OnStart()
+}
+
+// Shutdown implements the [agh.ServiceWithConfig] interface for
+// *ServiceWithConfig.
+func (s *ServiceWithConfig[_]) Shutdown(ctx context.Context) (err error) {
+	return s.OnShutdown(ctx)
+}
+
+// Config implements the [agh.ServiceWithConfig] interface for
+// *ServiceWithConfig.
+func (s *ServiceWithConfig[ConfigType]) Config() (c ConfigType) {
+	return s.OnConfig()
+}
+
 // Module dnsproxy
 
 // Package upstream

internal/filtering/http.go

@@ -555,6 +555,7 @@ func (d *DNSFilter) RegisterFilteringHandlers() {
 
 	registerHTTP(http.MethodGet, "/control/rewrite/list", d.handleRewriteList)
 	registerHTTP(http.MethodPost, "/control/rewrite/add", d.handleRewriteAdd)
+	registerHTTP(http.MethodPut, "/control/rewrite/update", d.handleRewriteUpdate)
 	registerHTTP(http.MethodPost, "/control/rewrite/delete", d.handleRewriteDelete)
 
 	registerHTTP(http.MethodGet, "/control/blocked_services/services", d.handleBlockedServicesIDs)

internal/filtering/rewritehttp.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
+	"golang.org/x/exp/slices"
 )
 
 // TODO(d.kolyshev): Use [rewrite.Item] instead.
@@ -91,3 +92,62 @@ func (d *DNSFilter) handleRewriteDelete(w http.ResponseWriter, r *http.Request)
 
 	d.Config.ConfigModified()
 }
+
+// rewriteUpdateJSON is a struct for JSON object with rewrite rule update info.
+type rewriteUpdateJSON struct {
+	Target rewriteEntryJSON `json:"target"`
+	Update rewriteEntryJSON `json:"update"`
+}
+
+// handleRewriteUpdate is the handler for the PUT /control/rewrite/update HTTP
+// API.
+func (d *DNSFilter) handleRewriteUpdate(w http.ResponseWriter, r *http.Request) {
+	updateJSON := rewriteUpdateJSON{}
+	err := json.NewDecoder(r.Body).Decode(&updateJSON)
+	if err != nil {
+		aghhttp.Error(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+
+		return
+	}
+
+	rwDel := &LegacyRewrite{
+		Domain: updateJSON.Target.Domain,
+		Answer: updateJSON.Target.Answer,
+	}
+
+	rwAdd := &LegacyRewrite{
+		Domain: updateJSON.Update.Domain,
+		Answer: updateJSON.Update.Answer,
+	}
+
+	err = rwAdd.normalize()
+	if err != nil {
+		// Shouldn't happen currently, since normalize only returns a non-nil
+		// error when a rewrite is nil, but be change-proof.
+		aghhttp.Error(r, w, http.StatusBadRequest, "normalizing: %s", err)
+
+		return
+	}
+
+	index := -1
+	defer func() {
+		if index >= 0 {
+			d.Config.ConfigModified()
+		}
+	}()
+
+	d.confLock.Lock()
+	defer d.confLock.Unlock()
+
+	index = slices.IndexFunc(d.Config.Rewrites, rwDel.equal)
+	if index == -1 {
+		aghhttp.Error(r, w, http.StatusBadRequest, "target rule not found")
+
+		return
+	}
+
+	d.Config.Rewrites = slices.Replace(d.Config.Rewrites, index, index+1, rwAdd)
+
+	log.Debug("rewrite: removed element: %s -> %s", rwDel.Domain, rwDel.Answer)
+	log.Debug("rewrite: added element: %s -> %s", rwAdd.Domain, rwAdd.Answer)
+}

internal/filtering/rewritehttp_test.go

@@ -0,0 +1,237 @@
+package filtering_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/filtering"
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TODO(d.kolyshev): Use [rewrite.Item] instead.
+type rewriteJSON struct {
+	Domain string `json:"domain"`
+	Answer string `json:"answer"`
+}
+
+type rewriteUpdateJSON struct {
+	Target rewriteJSON `json:"target"`
+	Update rewriteJSON `json:"update"`
+}
+
+const (
+	// testTimeout is the common timeout for tests.
+	testTimeout = 100 * time.Millisecond
+
+	listURL   = "/control/rewrite/list"
+	addURL    = "/control/rewrite/add"
+	deleteURL = "/control/rewrite/delete"
+	updateURL = "/control/rewrite/update"
+
+	decodeErrorMsg = "json.Decode: json: cannot unmarshal string into Go value of type" +
+		" filtering.rewriteEntryJSON\n"
+)
+
+func TestDNSFilter_handleRewriteHTTP(t *testing.T) {
+	confModCh := make(chan struct{})
+	reqCh := make(chan struct{})
+	testRewrites := []*rewriteJSON{
+		{Domain: "example.local", Answer: "example.rewrite"},
+		{Domain: "one.local", Answer: "one.rewrite"},
+	}
+
+	testRewritesJSON, mErr := json.Marshal(testRewrites)
+	require.NoError(t, mErr)
+
+	testCases := []struct {
+		reqData     any
+		name        string
+		url         string
+		method      string
+		wantList    []*rewriteJSON
+		wantBody    string
+		wantConfMod bool
+		wantStatus  int
+	}{{
+		name:        "list",
+		url:         listURL,
+		method:      http.MethodGet,
+		reqData:     nil,
+		wantConfMod: false,
+		wantStatus:  http.StatusOK,
+		wantBody:    string(testRewritesJSON) + "\n",
+		wantList:    testRewrites,
+	}, {
+		name:        "add",
+		url:         addURL,
+		method:      http.MethodPost,
+		reqData:     rewriteJSON{Domain: "add.local", Answer: "add.rewrite"},
+		wantConfMod: true,
+		wantStatus:  http.StatusOK,
+		wantBody:    "",
+		wantList: append(
+			testRewrites,
+			&rewriteJSON{Domain: "add.local", Answer: "add.rewrite"},
+		),
+	}, {
+		name:        "add_error",
+		url:         addURL,
+		method:      http.MethodPost,
+		reqData:     "invalid_json",
+		wantConfMod: false,
+		wantStatus:  http.StatusBadRequest,
+		wantBody:    decodeErrorMsg,
+		wantList:    testRewrites,
+	}, {
+		name:        "delete",
+		url:         deleteURL,
+		method:      http.MethodPost,
+		reqData:     rewriteJSON{Domain: "one.local", Answer: "one.rewrite"},
+		wantConfMod: true,
+		wantStatus:  http.StatusOK,
+		wantBody:    "",
+		wantList:    []*rewriteJSON{{Domain: "example.local", Answer: "example.rewrite"}},
+	}, {
+		name:        "delete_error",
+		url:         deleteURL,
+		method:      http.MethodPost,
+		reqData:     "invalid_json",
+		wantConfMod: false,
+		wantStatus:  http.StatusBadRequest,
+		wantBody:    decodeErrorMsg,
+		wantList:    testRewrites,
+	}, {
+		name:   "update",
+		url:    updateURL,
+		method: http.MethodPut,
+		reqData: rewriteUpdateJSON{
+			Target: rewriteJSON{Domain: "one.local", Answer: "one.rewrite"},
+			Update: rewriteJSON{Domain: "upd.local", Answer: "upd.rewrite"},
+		},
+		wantConfMod: true,
+		wantStatus:  http.StatusOK,
+		wantBody:    "",
+		wantList: []*rewriteJSON{
+			{Domain: "example.local", Answer: "example.rewrite"},
+			{Domain: "upd.local", Answer: "upd.rewrite"},
+		},
+	}, {
+		name:        "update_error",
+		url:         updateURL,
+		method:      http.MethodPut,
+		reqData:     "invalid_json",
+		wantConfMod: false,
+		wantStatus:  http.StatusBadRequest,
+		wantBody: "json.Decode: json: cannot unmarshal string into Go value of type" +
+			" filtering.rewriteUpdateJSON\n",
+		wantList: testRewrites,
+	}, {
+		name:   "update_error_target",
+		url:    updateURL,
+		method: http.MethodPut,
+		reqData: rewriteUpdateJSON{
+			Target: rewriteJSON{Domain: "inv.local", Answer: "inv.rewrite"},
+			Update: rewriteJSON{Domain: "upd.local", Answer: "upd.rewrite"},
+		},
+		wantConfMod: false,
+		wantStatus:  http.StatusBadRequest,
+		wantBody:    "target rule not found\n",
+		wantList:    testRewrites,
+	}}
+
+	for _, tc := range testCases {
+		onConfModified := func() {
+			if !tc.wantConfMod {
+				panic("config modified has been fired")
+			}
+
+			testutil.RequireSend(testutil.PanicT{}, confModCh, struct{}{}, testTimeout)
+		}
+
+		t.Run(tc.name, func(t *testing.T) {
+			handlers := make(map[string]http.Handler)
+
+			d, err := filtering.New(&filtering.Config{
+				ConfigModified: onConfModified,
+				HTTPRegister: func(_, url string, handler http.HandlerFunc) {
+					handlers[url] = handler
+				},
+				Rewrites: rewriteEntriesToLegacyRewrites(testRewrites),
+			}, nil)
+			require.NoError(t, err)
+			t.Cleanup(d.Close)
+
+			d.RegisterFilteringHandlers()
+			require.NotEmpty(t, handlers)
+			require.Contains(t, handlers, listURL)
+			require.Contains(t, handlers, tc.url)
+
+			var body io.Reader
+			if tc.reqData != nil {
+				data, rErr := json.Marshal(tc.reqData)
+				require.NoError(t, rErr)
+
+				body = bytes.NewReader(data)
+			}
+
+			r := httptest.NewRequest(tc.method, tc.url, body)
+			w := httptest.NewRecorder()
+
+			go func() {
+				handlers[tc.url].ServeHTTP(w, r)
+
+				testutil.RequireSend(testutil.PanicT{}, reqCh, struct{}{}, testTimeout)
+			}()
+
+			if tc.wantConfMod {
+				testutil.RequireReceive(t, confModCh, testTimeout)
+			}
+
+			testutil.RequireReceive(t, reqCh, testTimeout)
+			assert.Equal(t, tc.wantStatus, w.Code)
+
+			respBody, err := io.ReadAll(w.Body)
+			require.NoError(t, err)
+			assert.Equal(t, []byte(tc.wantBody), respBody)
+
+			assertRewritesList(t, handlers[listURL], tc.wantList)
+		})
+	}
+}
+
+// assertRewritesList checks if rewrites list equals the list received from the
+// handler by listURL.
+func assertRewritesList(t *testing.T, handler http.Handler, wantList []*rewriteJSON) {
+	t.Helper()
+
+	r := httptest.NewRequest(http.MethodGet, listURL, nil)
+	w := httptest.NewRecorder()
+
+	handler.ServeHTTP(w, r)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	var actual []*rewriteJSON
+	err := json.NewDecoder(w.Body).Decode(&actual)
+	require.NoError(t, err)
+
+	assert.Equal(t, wantList, actual)
+}
+
+// rewriteEntriesToLegacyRewrites gets legacy rewrites from json entries.
+func rewriteEntriesToLegacyRewrites(entries []*rewriteJSON) (rw []*filtering.LegacyRewrite) {
+	for _, entry := range entries {
+		rw = append(rw, &filtering.LegacyRewrite{
+			Domain: entry.Domain,
+			Answer: entry.Answer,
+		})
+	}
+
+	return rw
+}

internal/next/agh/agh.go

@@ -0,0 +1,63 @@
+// Package agh contains common entities and interfaces of AdGuard Home.
+package agh
+
+import "context"
+
+// Service is the interface for API servers.
+//
+// TODO(a.garipov): Consider adding a context to Start.
+//
+// TODO(a.garipov): Consider adding a Wait method or making an extension
+// interface for that.
+type Service interface {
+	// Start starts the service.  It does not block.
+	Start() (err error)
+
+	// Shutdown gracefully stops the service.  ctx is used to determine
+	// a timeout before trying to stop the service less gracefully.
+	Shutdown(ctx context.Context) (err error)
+}
+
+// type check
+var _ Service = EmptyService{}
+
+// EmptyService is a [Service] that does nothing.
+//
+// TODO(a.garipov): Remove if unnecessary.
+type EmptyService struct{}
+
+// Start implements the [Service] interface for EmptyService.
+func (EmptyService) Start() (err error) { return nil }
+
+// Shutdown implements the [Service] interface for EmptyService.
+func (EmptyService) Shutdown(_ context.Context) (err error) { return nil }
+
+// ServiceWithConfig is an extension of the [Service] interface for services
+// that can return their configuration.
+//
+// TODO(a.garipov): Consider removing this generic interface if we figure out
+// how to make it testable in a better way.
+type ServiceWithConfig[ConfigType any] interface {
+	Service
+
+	Config() (c ConfigType)
+}
+
+// type check
+var _ ServiceWithConfig[struct{}] = (*EmptyServiceWithConfig[struct{}])(nil)
+
+// EmptyServiceWithConfig is a ServiceWithConfig that does nothing.  Its Config
+// method returns Conf.
+//
+// TODO(a.garipov): Remove if unnecessary.
+type EmptyServiceWithConfig[ConfigType any] struct {
+	EmptyService
+
+	Conf ConfigType
+}
+
+// Config implements the [ServiceWithConfig] interface for
+// *EmptyServiceWithConfig.
+func (s *EmptyServiceWithConfig[ConfigType]) Config() (conf ConfigType) {
+	return s.Conf
+}

internal/next/cmd/cmd.go

@@ -0,0 +1,77 @@
+// Package cmd is the AdGuard Home entry point.  It contains the on-disk
+// configuration file utilities, signal processing logic, and so on.
+//
+// TODO(a.garipov): Move to the upper-level internal/.
+package cmd
+
+import (
+	"context"
+	"io/fs"
+	"math/rand"
+	"os"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/configmgr"
+	"github.com/AdguardTeam/AdGuardHome/internal/version"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// Main is the entry point of application.
+func Main(clientBuildFS fs.FS) {
+	// Initial Configuration
+
+	start := time.Now()
+	rand.Seed(start.UnixNano())
+
+	// TODO(a.garipov): Set up logging.
+
+	log.Info("starting adguard home, version %s, pid %d", version.Version(), os.Getpid())
+
+	// Web Service
+
+	// TODO(a.garipov): Use in the Web service.
+	_ = clientBuildFS
+
+	// TODO(a.garipov): Set up configuration file name.
+	const confFile = "AdGuardHome.1.yaml"
+
+	confMgr, err := configmgr.New(confFile, start)
+	fatalOnError(err)
+
+	web := confMgr.Web()
+	err = web.Start()
+	fatalOnError(err)
+
+	dns := confMgr.DNS()
+	err = dns.Start()
+	fatalOnError(err)
+
+	sigHdlr := newSignalHandler(
+		confFile,
+		start,
+		web,
+		dns,
+	)
+
+	go sigHdlr.handle()
+
+	select {}
+}
+
+// defaultTimeout is the timeout used for some operations where another timeout
+// hasn't been defined yet.
+const defaultTimeout = 15 * time.Second
+
+// ctxWithDefaultTimeout is a helper function that returns a context with
+// timeout set to defaultTimeout.
+func ctxWithDefaultTimeout() (ctx context.Context, cancel context.CancelFunc) {
+	return context.WithTimeout(context.Background(), defaultTimeout)
+}
+
+// fatalOnError is a helper that exits the program with an error code if err is
+// not nil.  It must only be used within Main.
+func fatalOnError(err error) {
+	if err != nil {
+		log.Fatal(err)
+	}
+}

internal/next/cmd/signal.go

@@ -0,0 +1,118 @@
+package cmd
+
+import (
+	"os"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/configmgr"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// signalHandler processes incoming signals and shuts services down.
+type signalHandler struct {
+	// signal is the channel to which OS signals are sent.
+	signal chan os.Signal
+
+	// confFile is the path to the configuration file.
+	confFile string
+
+	// start is the time at which AdGuard Home has been started.
+	start time.Time
+
+	// services are the services that are shut down before application exiting.
+	services []agh.Service
+}
+
+// handle processes OS signals.
+func (h *signalHandler) handle() {
+	defer log.OnPanic("signalHandler.handle")
+
+	for sig := range h.signal {
+		log.Info("sighdlr: received signal %q", sig)
+
+		if aghos.IsReconfigureSignal(sig) {
+			h.reconfigure()
+		} else if aghos.IsShutdownSignal(sig) {
+			status := h.shutdown()
+			log.Info("sighdlr: exiting with status %d", status)
+
+			os.Exit(status)
+		}
+	}
+}
+
+// reconfigure rereads the configuration file and updates and restarts services.
+func (h *signalHandler) reconfigure() {
+	log.Info("sighdlr: reconfiguring adguard home")
+
+	status := h.shutdown()
+	if status != statusSuccess {
+		log.Info("sighdlr: reconfiruging: exiting with status %d", status)
+
+		os.Exit(status)
+	}
+
+	// TODO(a.garipov): This is a very rough way to do it.  Some services can be
+	// reconfigured without the full shutdown, and the error handling is
+	// currently not the best.
+
+	confMgr, err := configmgr.New(h.confFile, h.start)
+	fatalOnError(err)
+
+	web := confMgr.Web()
+	err = web.Start()
+	fatalOnError(err)
+
+	dns := confMgr.DNS()
+	err = dns.Start()
+	fatalOnError(err)
+
+	h.services = []agh.Service{
+		dns,
+		web,
+	}
+
+	log.Info("sighdlr: successfully reconfigured adguard home")
+}
+
+// Exit status constants.
+const (
+	statusSuccess = 0
+	statusError   = 1
+)
+
+// shutdown gracefully shuts down all services.
+func (h *signalHandler) shutdown() (status int) {
+	ctx, cancel := ctxWithDefaultTimeout()
+	defer cancel()
+
+	status = statusSuccess
+
+	log.Info("sighdlr: shutting down services")
+	for i, service := range h.services {
+		err := service.Shutdown(ctx)
+		if err != nil {
+			log.Error("sighdlr: shutting down service at index %d: %s", i, err)
+			status = statusError
+		}
+	}
+
+	return status
+}
+
+// newSignalHandler returns a new signalHandler that shuts down svcs.
+func newSignalHandler(confFile string, start time.Time, svcs ...agh.Service) (h *signalHandler) {
+	h = &signalHandler{
+		signal:   make(chan os.Signal, 1),
+		confFile: confFile,
+		start:    start,
+		services: svcs,
+	}
+
+	aghos.NotifyShutdownSignal(h.signal)
+	aghos.NotifyReconfigureSignal(h.signal)
+
+	return h
+}

internal/next/configmgr/config.go

@@ -0,0 +1,40 @@
+package configmgr
+
+import (
+	"net/netip"
+
+	"github.com/AdguardTeam/golibs/timeutil"
+)
+
+// Configuration Structures
+
+// config is the top-level on-disk configuration structure.
+type config struct {
+	DNS  *dnsConfig  `yaml:"dns"`
+	HTTP *httpConfig `yaml:"http"`
+	// TODO(a.garipov): Use.
+	SchemaVersion int `yaml:"schema_version"`
+	// TODO(a.garipov): Use.
+	DebugPprof bool `yaml:"debug_pprof"`
+	Verbose    bool `yaml:"verbose"`
+}
+
+// dnsConfig is the on-disk DNS configuration.
+//
+// TODO(a.garipov): Validate.
+type dnsConfig struct {
+	Addresses       []netip.AddrPort  `yaml:"addresses"`
+	BootstrapDNS    []string          `yaml:"bootstrap_dns"`
+	UpstreamDNS     []string          `yaml:"upstream_dns"`
+	UpstreamTimeout timeutil.Duration `yaml:"upstream_timeout"`
+}
+
+// httpConfig is the on-disk web API configuration.
+//
+// TODO(a.garipov): Validate.
+type httpConfig struct {
+	Addresses       []netip.AddrPort  `yaml:"addresses"`
+	SecureAddresses []netip.AddrPort  `yaml:"secure_addresses"`
+	Timeout         timeutil.Duration `yaml:"timeout"`
+	ForceHTTPS      bool              `yaml:"force_https"`
+}

internal/next/configmgr/configmgr.go

@@ -0,0 +1,205 @@
+// Package configmgr defines the AdGuard Home on-disk configuration entities and
+// configuration manager.
+package configmgr
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/log"
+	"gopkg.in/yaml.v3"
+)
+
+// Configuration Manager
+
+// Manager handles full and partial changes in the configuration, persisting
+// them to disk if necessary.
+type Manager struct {
+	// updMu makes sure that at most one reconfiguration is performed at a time.
+	// updMu protects all fields below.
+	updMu *sync.RWMutex
+
+	// dns is the DNS service.
+	dns *dnssvc.Service
+
+	// Web is the Web API service.
+	web *websvc.Service
+
+	// current is the current configuration.
+	current *config
+
+	// fileName is the name of the configuration file.
+	fileName string
+}
+
+// New creates a new *Manager that persists changes to the file pointed to by
+// fileName.  It reads the configuration file and populates the service fields.
+// start is the startup time of AdGuard Home.
+func New(fileName string, start time.Time) (m *Manager, err error) {
+	defer func() { err = errors.Annotate(err, "reading config") }()
+
+	conf := &config{}
+	f, err := os.Open(fileName)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return nil, err
+	}
+	defer func() { err = errors.WithDeferred(err, f.Close()) }()
+
+	err = yaml.NewDecoder(f).Decode(conf)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return nil, err
+	}
+
+	// TODO(a.garipov): Move into a separate function and add other logging
+	// settings.
+	if conf.Verbose {
+		log.SetLevel(log.DEBUG)
+	}
+
+	// TODO(a.garipov): Validate the configuration structure.  Return an error
+	// if it's incorrect.
+
+	m = &Manager{
+		updMu:    &sync.RWMutex{},
+		current:  conf,
+		fileName: fileName,
+	}
+
+	// TODO(a.garipov): Get the context with the timeout from the arguments?
+	const assemblyTimeout = 5 * time.Second
+	ctx, cancel := context.WithTimeout(context.Background(), assemblyTimeout)
+	defer cancel()
+
+	err = m.assemble(ctx, conf, start)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return nil, err
+	}
+
+	return m, nil
+}
+
+// assemble creates all services and puts them into the corresponding fields.
+// The fields of conf must not be modified after calling assemble.
+func (m *Manager) assemble(ctx context.Context, conf *config, start time.Time) (err error) {
+	dnsConf := &dnssvc.Config{
+		Addresses:        conf.DNS.Addresses,
+		BootstrapServers: conf.DNS.BootstrapDNS,
+		UpstreamServers:  conf.DNS.UpstreamDNS,
+		UpstreamTimeout:  conf.DNS.UpstreamTimeout.Duration,
+	}
+	err = m.updateDNS(ctx, dnsConf)
+	if err != nil {
+		return fmt.Errorf("assembling dnssvc: %w", err)
+	}
+
+	webSvcConf := &websvc.Config{
+		ConfigManager: m,
+		// TODO(a.garipov): Fill from config file.
+		TLS:             nil,
+		Start:           start,
+		Addresses:       conf.HTTP.Addresses,
+		SecureAddresses: conf.HTTP.SecureAddresses,
+		Timeout:         conf.HTTP.Timeout.Duration,
+		ForceHTTPS:      conf.HTTP.ForceHTTPS,
+	}
+
+	err = m.updateWeb(ctx, webSvcConf)
+	if err != nil {
+		return fmt.Errorf("assembling websvc: %w", err)
+	}
+
+	return nil
+}
+
+// DNS returns the current DNS service.  It is safe for concurrent use.
+func (m *Manager) DNS() (dns agh.ServiceWithConfig[*dnssvc.Config]) {
+	m.updMu.RLock()
+	defer m.updMu.RUnlock()
+
+	return m.dns
+}
+
+// UpdateDNS implements the [websvc.ConfigManager] interface for *Manager.  The
+// fields of c must not be modified after calling UpdateDNS.
+func (m *Manager) UpdateDNS(ctx context.Context, c *dnssvc.Config) (err error) {
+	m.updMu.Lock()
+	defer m.updMu.Unlock()
+
+	// TODO(a.garipov): Update and write the configuration file.  Return an
+	// error if something went wrong.
+
+	err = m.updateDNS(ctx, c)
+	if err != nil {
+		return fmt.Errorf("reassembling dnssvc: %w", err)
+	}
+
+	return nil
+}
+
+// updateDNS recreates the DNS service.  m.updMu is expected to be locked.
+func (m *Manager) updateDNS(ctx context.Context, c *dnssvc.Config) (err error) {
+	if prev := m.dns; prev != nil {
+		err = prev.Shutdown(ctx)
+		if err != nil {
+			return fmt.Errorf("shutting down dns svc: %w", err)
+		}
+	}
+
+	svc, err := dnssvc.New(c)
+	if err != nil {
+		return fmt.Errorf("creating dns svc: %w", err)
+	}
+
+	m.dns = svc
+
+	return nil
+}
+
+// Web returns the current web service.  It is safe for concurrent use.
+func (m *Manager) Web() (web agh.ServiceWithConfig[*websvc.Config]) {
+	m.updMu.RLock()
+	defer m.updMu.RUnlock()
+
+	return m.web
+}
+
+// UpdateWeb implements the [websvc.ConfigManager] interface for *Manager.  The
+// fields of c must not be modified after calling UpdateWeb.
+func (m *Manager) UpdateWeb(ctx context.Context, c *websvc.Config) (err error) {
+	m.updMu.Lock()
+	defer m.updMu.Unlock()
+
+	// TODO(a.garipov): Update and write the configuration file.  Return an
+	// error if something went wrong.
+
+	err = m.updateWeb(ctx, c)
+	if err != nil {
+		return fmt.Errorf("reassembling websvc: %w", err)
+	}
+
+	return nil
+}
+
+// updateWeb recreates the web service.  m.upd is expected to be locked.
+func (m *Manager) updateWeb(ctx context.Context, c *websvc.Config) (err error) {
+	if prev := m.web; prev != nil {
+		err = prev.Shutdown(ctx)
+		if err != nil {
+			return fmt.Errorf("shutting down web svc: %w", err)
+		}
+	}
+
+	m.web = websvc.New(c)
+
+	return nil
+}

internal/next/dnssvc/dnssvc.go

@@ -0,0 +1,216 @@
+// Package dnssvc contains the AdGuard Home DNS service.
+//
+// TODO(a.garipov): Define, if all methods of a *Service should work with a nil
+// receiver.
+package dnssvc
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/netip"
+	"sync/atomic"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	// TODO(a.garipov): Add a “dnsproxy proxy” package to shield us from changes
+	// and replacement of module dnsproxy.
+	"github.com/AdguardTeam/dnsproxy/proxy"
+	"github.com/AdguardTeam/dnsproxy/upstream"
+)
+
+// Config is the AdGuard Home DNS service configuration structure.
+//
+// TODO(a.garipov): Add timeout for incoming requests.
+type Config struct {
+	// Addresses are the addresses on which to serve plain DNS queries.
+	Addresses []netip.AddrPort
+
+	// Upstreams are the DNS upstreams to use.  If not set, upstreams are
+	// created using data from BootstrapServers, UpstreamServers, and
+	// UpstreamTimeout.
+	//
+	// TODO(a.garipov): Think of a better scheme.  Those other three parameters
+	// are here only to make Config work properly.
+	Upstreams []upstream.Upstream
+
+	// BootstrapServers are the addresses for bootstrapping the upstream DNS
+	// server addresses.
+	BootstrapServers []string
+
+	// UpstreamServers are the upstream DNS server addresses to use.
+	UpstreamServers []string
+
+	// UpstreamTimeout is the timeout for upstream requests.
+	UpstreamTimeout time.Duration
+}
+
+// Service is the AdGuard Home DNS service.  A nil *Service is a valid
+// [agh.Service] that does nothing.
+type Service struct {
+	proxy      *proxy.Proxy
+	bootstraps []string
+	upstreams  []string
+	upsTimeout time.Duration
+	running    atomic.Bool
+}
+
+// New returns a new properly initialized *Service.  If c is nil, svc is a nil
+// *Service that does nothing.  The fields of c must not be modified after
+// calling New.
+func New(c *Config) (svc *Service, err error) {
+	if c == nil {
+		return nil, nil
+	}
+
+	svc = &Service{
+		bootstraps: c.BootstrapServers,
+		upstreams:  c.UpstreamServers,
+		upsTimeout: c.UpstreamTimeout,
+	}
+
+	var upstreams []upstream.Upstream
+	if len(c.Upstreams) > 0 {
+		upstreams = c.Upstreams
+	} else {
+		upstreams, err = addressesToUpstreams(
+			c.UpstreamServers,
+			c.BootstrapServers,
+			c.UpstreamTimeout,
+		)
+		if err != nil {
+			return nil, fmt.Errorf("converting upstreams: %w", err)
+		}
+	}
+
+	svc.proxy = &proxy.Proxy{
+		Config: proxy.Config{
+			UDPListenAddr: udpAddrs(c.Addresses),
+			TCPListenAddr: tcpAddrs(c.Addresses),
+			UpstreamConfig: &proxy.UpstreamConfig{
+				Upstreams: upstreams,
+			},
+		},
+	}
+
+	err = svc.proxy.Init()
+	if err != nil {
+		return nil, fmt.Errorf("proxy: %w", err)
+	}
+
+	return svc, nil
+}
+
+// addressesToUpstreams is a wrapper around [upstream.AddressToUpstream].  It
+// accepts a slice of addresses and other upstream parameters, and returns a
+// slice of upstreams.
+func addressesToUpstreams(
+	upsStrs []string,
+	bootstraps []string,
+	timeout time.Duration,
+) (upstreams []upstream.Upstream, err error) {
+	upstreams = make([]upstream.Upstream, len(upsStrs))
+	for i, upsStr := range upsStrs {
+		upstreams[i], err = upstream.AddressToUpstream(upsStr, &upstream.Options{
+			Bootstrap: bootstraps,
+			Timeout:   timeout,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("upstream at index %d: %w", i, err)
+		}
+	}
+
+	return upstreams, nil
+}
+
+// tcpAddrs converts []netip.AddrPort into []*net.TCPAddr.
+func tcpAddrs(addrPorts []netip.AddrPort) (tcpAddrs []*net.TCPAddr) {
+	if addrPorts == nil {
+		return nil
+	}
+
+	tcpAddrs = make([]*net.TCPAddr, len(addrPorts))
+	for i, a := range addrPorts {
+		tcpAddrs[i] = net.TCPAddrFromAddrPort(a)
+	}
+
+	return tcpAddrs
+}
+
+// udpAddrs converts []netip.AddrPort into []*net.UDPAddr.
+func udpAddrs(addrPorts []netip.AddrPort) (udpAddrs []*net.UDPAddr) {
+	if addrPorts == nil {
+		return nil
+	}
+
+	udpAddrs = make([]*net.UDPAddr, len(addrPorts))
+	for i, a := range addrPorts {
+		udpAddrs[i] = net.UDPAddrFromAddrPort(a)
+	}
+
+	return udpAddrs
+}
+
+// type check
+var _ agh.Service = (*Service)(nil)
+
+// Start implements the [agh.Service] interface for *Service.  svc may be nil.
+// After Start exits, all DNS servers have tried to start, but there is no
+// guarantee that they did.  Errors from the servers are written to the log.
+func (svc *Service) Start() (err error) {
+	if svc == nil {
+		return nil
+	}
+
+	defer func() {
+		// TODO(a.garipov): [proxy.Proxy.Start] doesn't actually have any way to
+		// tell when all servers are actually up, so at best this is merely an
+		// assumption.
+		svc.running.Store(err == nil)
+	}()
+
+	return svc.proxy.Start()
+}
+
+// Shutdown implements the [agh.Service] interface for *Service.  svc may be
+// nil.
+func (svc *Service) Shutdown(ctx context.Context) (err error) {
+	if svc == nil {
+		return nil
+	}
+
+	return svc.proxy.Stop()
+}
+
+// Config returns the current configuration of the web service.  Config must not
+// be called simultaneously with Start.  If svc was initialized with ":0"
+// addresses, addrs will not return the actual bound ports until Start is
+// finished.
+func (svc *Service) Config() (c *Config) {
+	// TODO(a.garipov): Do we need to get the TCP addresses separately?
+
+	var addrs []netip.AddrPort
+	if svc.running.Load() {
+		udpAddrs := svc.proxy.Addrs(proxy.ProtoUDP)
+		addrs = make([]netip.AddrPort, len(udpAddrs))
+		for i, a := range udpAddrs {
+			addrs[i] = a.(*net.UDPAddr).AddrPort()
+		}
+	} else {
+		conf := svc.proxy.Config
+		udpAddrs := conf.UDPListenAddr
+		addrs = make([]netip.AddrPort, len(udpAddrs))
+		for i, a := range udpAddrs {
+			addrs[i] = a.AddrPort()
+		}
+	}
+
+	c = &Config{
+		Addresses:        addrs,
+		BootstrapServers: svc.bootstraps,
+		UpstreamServers:  svc.upstreams,
+		UpstreamTimeout:  svc.upsTimeout,
+	}
+
+	return c
+}

internal/next/dnssvc/dnssvc_test.go

@@ -0,0 +1,96 @@
+package dnssvc_test
+
+import (
+	"context"
+	"net/netip"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/dnsproxy/upstream"
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMain(m *testing.M) {
+	testutil.DiscardLogOutput(m)
+}
+
+// testTimeout is the common timeout for tests.
+const testTimeout = 100 * time.Millisecond
+
+func TestService(t *testing.T) {
+	const (
+		bootstrapAddr = "bootstrap.example"
+		upstreamAddr  = "upstream.example"
+
+		closeErr errors.Error = "closing failed"
+	)
+
+	ups := &aghtest.UpstreamMock{
+		OnAddress: func() (addr string) {
+			return upstreamAddr
+		},
+		OnExchange: func(req *dns.Msg) (resp *dns.Msg, err error) {
+			resp = (&dns.Msg{}).SetReply(req)
+
+			return resp, nil
+		},
+		OnClose: func() (err error) {
+			return closeErr
+		},
+	}
+
+	c := &dnssvc.Config{
+		Addresses:        []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:0")},
+		Upstreams:        []upstream.Upstream{ups},
+		BootstrapServers: []string{bootstrapAddr},
+		UpstreamServers:  []string{upstreamAddr},
+		UpstreamTimeout:  testTimeout,
+	}
+
+	svc, err := dnssvc.New(c)
+	require.NoError(t, err)
+
+	err = svc.Start()
+	require.NoError(t, err)
+
+	gotConf := svc.Config()
+	require.NotNil(t, gotConf)
+	require.Len(t, gotConf.Addresses, 1)
+
+	addr := gotConf.Addresses[0]
+
+	t.Run("dns", func(t *testing.T) {
+		req := &dns.Msg{
+			MsgHdr: dns.MsgHdr{
+				Id:               dns.Id(),
+				RecursionDesired: true,
+			},
+			Question: []dns.Question{{
+				Name:   "example.com.",
+				Qtype:  dns.TypeA,
+				Qclass: dns.ClassINET,
+			}},
+		}
+
+		ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
+		defer cancel()
+
+		cli := &dns.Client{}
+		resp, _, excErr := cli.ExchangeContext(ctx, req, addr.String())
+		require.NoError(t, excErr)
+
+		assert.NotNil(t, resp)
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
+	defer cancel()
+
+	err = svc.Shutdown(ctx)
+	require.ErrorIs(t, err, closeErr)
+}

internal/next/websvc/dns.go

@@ -0,0 +1,84 @@
+package websvc
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/netip"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+)
+
+// DNS Settings Handlers
+
+// ReqPatchSettingsDNS describes the request to the PATCH /api/v1/settings/dns
+// HTTP API.
+type ReqPatchSettingsDNS struct {
+	// TODO(a.garipov): Add more as we go.
+
+	Addresses        []netip.AddrPort `json:"addresses"`
+	BootstrapServers []string         `json:"bootstrap_servers"`
+	UpstreamServers  []string         `json:"upstream_servers"`
+	UpstreamTimeout  JSONDuration     `json:"upstream_timeout"`
+}
+
+// HTTPAPIDNSSettings are the DNS settings as used by the HTTP API.  See the
+// DnsSettings object in the OpenAPI specification.
+type HTTPAPIDNSSettings struct {
+	// TODO(a.garipov): Add more as we go.
+
+	Addresses        []netip.AddrPort `json:"addresses"`
+	BootstrapServers []string         `json:"bootstrap_servers"`
+	UpstreamServers  []string         `json:"upstream_servers"`
+	UpstreamTimeout  JSONDuration     `json:"upstream_timeout"`
+}
+
+// handlePatchSettingsDNS is the handler for the PATCH /api/v1/settings/dns HTTP
+// API.
+func (svc *Service) handlePatchSettingsDNS(w http.ResponseWriter, r *http.Request) {
+	req := &ReqPatchSettingsDNS{
+		Addresses:        []netip.AddrPort{},
+		BootstrapServers: []string{},
+		UpstreamServers:  []string{},
+	}
+
+	// TODO(a.garipov): Validate nulls and proper JSON patch.
+
+	err := json.NewDecoder(r.Body).Decode(&req)
+	if err != nil {
+		writeJSONErrorResponse(w, r, fmt.Errorf("decoding: %w", err))
+
+		return
+	}
+
+	newConf := &dnssvc.Config{
+		Addresses:        req.Addresses,
+		BootstrapServers: req.BootstrapServers,
+		UpstreamServers:  req.UpstreamServers,
+		UpstreamTimeout:  time.Duration(req.UpstreamTimeout),
+	}
+
+	ctx := r.Context()
+	err = svc.confMgr.UpdateDNS(ctx, newConf)
+	if err != nil {
+		writeJSONErrorResponse(w, r, fmt.Errorf("updating: %w", err))
+
+		return
+	}
+
+	newSvc := svc.confMgr.DNS()
+	err = newSvc.Start()
+	if err != nil {
+		writeJSONErrorResponse(w, r, fmt.Errorf("starting new service: %w", err))
+
+		return
+	}
+
+	writeJSONOKResponse(w, r, &HTTPAPIDNSSettings{
+		Addresses:        newConf.Addresses,
+		BootstrapServers: newConf.BootstrapServers,
+		UpstreamServers:  newConf.UpstreamServers,
+		UpstreamTimeout:  JSONDuration(newConf.UpstreamTimeout),
+	})
+}

internal/next/websvc/dns_test.go

@@ -0,0 +1,68 @@
+package websvc_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestService_HandlePatchSettingsDNS(t *testing.T) {
+	wantDNS := &websvc.HTTPAPIDNSSettings{
+		Addresses:        []netip.AddrPort{netip.MustParseAddrPort("127.0.1.1:53")},
+		BootstrapServers: []string{"1.0.0.1"},
+		UpstreamServers:  []string{"1.1.1.1"},
+		UpstreamTimeout:  websvc.JSONDuration(2 * time.Second),
+	}
+
+	var started atomic.Bool
+	confMgr := newConfigManager()
+	confMgr.onDNS = func() (s agh.ServiceWithConfig[*dnssvc.Config]) {
+		return &aghtest.ServiceWithConfig[*dnssvc.Config]{
+			OnStart: func() (err error) {
+				started.Store(true)
+
+				return nil
+			},
+			OnShutdown: func(_ context.Context) (err error) { panic("not implemented") },
+			OnConfig:   func() (c *dnssvc.Config) { panic("not implemented") },
+		}
+	}
+	confMgr.onUpdateDNS = func(ctx context.Context, c *dnssvc.Config) (err error) {
+		return nil
+	}
+
+	_, addr := newTestServer(t, confMgr)
+	u := &url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   websvc.PathV1SettingsDNS,
+	}
+
+	req := jobj{
+		"addresses":         wantDNS.Addresses,
+		"bootstrap_servers": wantDNS.BootstrapServers,
+		"upstream_servers":  wantDNS.UpstreamServers,
+		"upstream_timeout":  wantDNS.UpstreamTimeout,
+	}
+
+	respBody := httpPatch(t, u, req, http.StatusOK)
+	resp := &websvc.HTTPAPIDNSSettings{}
+	err := json.Unmarshal(respBody, resp)
+	require.NoError(t, err)
+
+	assert.True(t, started.Load())
+	assert.Equal(t, wantDNS, resp)
+	assert.Equal(t, wantDNS, resp)
+}

internal/next/websvc/http.go

@@ -0,0 +1,110 @@
+package websvc
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/netip"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// HTTP Settings Handlers
+
+// ReqPatchSettingsHTTP describes the request to the PATCH /api/v1/settings/http
+// HTTP API.
+type ReqPatchSettingsHTTP struct {
+	// TODO(a.garipov): Add more as we go.
+	//
+	// TODO(a.garipov): Add wait time.
+
+	Addresses       []netip.AddrPort `json:"addresses"`
+	SecureAddresses []netip.AddrPort `json:"secure_addresses"`
+	Timeout         JSONDuration     `json:"timeout"`
+}
+
+// HTTPAPIHTTPSettings are the HTTP settings as used by the HTTP API.  See the
+// HttpSettings object in the OpenAPI specification.
+type HTTPAPIHTTPSettings struct {
+	// TODO(a.garipov): Add more as we go.
+
+	Addresses       []netip.AddrPort `json:"addresses"`
+	SecureAddresses []netip.AddrPort `json:"secure_addresses"`
+	Timeout         JSONDuration     `json:"timeout"`
+	ForceHTTPS      bool             `json:"force_https"`
+}
+
+// handlePatchSettingsHTTP is the handler for the PATCH /api/v1/settings/http
+// HTTP API.
+func (svc *Service) handlePatchSettingsHTTP(w http.ResponseWriter, r *http.Request) {
+	req := &ReqPatchSettingsHTTP{}
+
+	// TODO(a.garipov): Validate nulls and proper JSON patch.
+
+	err := json.NewDecoder(r.Body).Decode(&req)
+	if err != nil {
+		writeJSONErrorResponse(w, r, fmt.Errorf("decoding: %w", err))
+
+		return
+	}
+
+	newConf := &Config{
+		ConfigManager:   svc.confMgr,
+		TLS:             svc.tls,
+		Addresses:       req.Addresses,
+		SecureAddresses: req.SecureAddresses,
+		Timeout:         time.Duration(req.Timeout),
+		ForceHTTPS:      svc.forceHTTPS,
+	}
+
+	writeJSONOKResponse(w, r, &HTTPAPIHTTPSettings{
+		Addresses:       newConf.Addresses,
+		SecureAddresses: newConf.SecureAddresses,
+		Timeout:         JSONDuration(newConf.Timeout),
+		ForceHTTPS:      newConf.ForceHTTPS,
+	})
+
+	cancelUpd := func() {}
+	updCtx := context.Background()
+
+	ctx := r.Context()
+	if deadline, ok := ctx.Deadline(); ok {
+		updCtx, cancelUpd = context.WithDeadline(updCtx, deadline)
+	}
+
+	// Launch the new HTTP service in a separate goroutine to let this handler
+	// finish and thus, this server to shutdown.
+	go func() {
+		defer cancelUpd()
+
+		updErr := svc.confMgr.UpdateWeb(updCtx, newConf)
+		if updErr != nil {
+			writeJSONErrorResponse(w, r, fmt.Errorf("updating: %w", updErr))
+
+			return
+		}
+
+		// TODO(a.garipov): Consider better ways to do this.
+		const maxUpdDur = 10 * time.Second
+		updStart := time.Now()
+		var newSvc agh.ServiceWithConfig[*Config]
+		for newSvc = svc.confMgr.Web(); newSvc == svc; {
+			if time.Since(updStart) >= maxUpdDur {
+				log.Error("websvc: failed to update svc after %s", maxUpdDur)
+
+				return
+			}
+
+			log.Debug("websvc: waiting for new websvc to be configured")
+			time.Sleep(1 * time.Second)
+		}
+
+		updErr = newSvc.Start()
+		if updErr != nil {
+			log.Error("websvc: new svc failed to start with error: %s", updErr)
+		}
+	}()
+}

internal/next/websvc/http_test.go

@@ -0,0 +1,63 @@
+package websvc_test
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/json"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestService_HandlePatchSettingsHTTP(t *testing.T) {
+	wantWeb := &websvc.HTTPAPIHTTPSettings{
+		Addresses:       []netip.AddrPort{netip.MustParseAddrPort("127.0.1.1:80")},
+		SecureAddresses: []netip.AddrPort{netip.MustParseAddrPort("127.0.1.1:443")},
+		Timeout:         websvc.JSONDuration(10 * time.Second),
+		ForceHTTPS:      false,
+	}
+
+	confMgr := newConfigManager()
+	confMgr.onWeb = func() (s agh.ServiceWithConfig[*websvc.Config]) {
+		return websvc.New(&websvc.Config{
+			TLS: &tls.Config{
+				Certificates: []tls.Certificate{{}},
+			},
+			Addresses:       []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:80")},
+			SecureAddresses: []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:443")},
+			Timeout:         5 * time.Second,
+			ForceHTTPS:      true,
+		})
+	}
+	confMgr.onUpdateWeb = func(ctx context.Context, c *websvc.Config) (err error) {
+		return nil
+	}
+
+	_, addr := newTestServer(t, confMgr)
+	u := &url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   websvc.PathV1SettingsHTTP,
+	}
+
+	req := jobj{
+		"addresses":        wantWeb.Addresses,
+		"secure_addresses": wantWeb.SecureAddresses,
+		"timeout":          wantWeb.Timeout,
+		"force_https":      wantWeb.ForceHTTPS,
+	}
+
+	respBody := httpPatch(t, u, req, http.StatusOK)
+	resp := &websvc.HTTPAPIHTTPSettings{}
+	err := json.Unmarshal(respBody, resp)
+	require.NoError(t, err)
+
+	assert.Equal(t, wantWeb, resp)
+}

internal/next/websvc/json.go

@@ -0,0 +1,144 @@
+package websvc
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
+	"github.com/AdguardTeam/golibs/httphdr"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// JSON Utilities
+
+// nsecPerMsec is the number of nanoseconds in a millisecond.
+const nsecPerMsec = float64(time.Millisecond / time.Nanosecond)
+
+// JSONDuration is a time.Duration that can be decoded from JSON and encoded
+// into JSON according to our API conventions.
+type JSONDuration time.Duration
+
+// type check
+var _ json.Marshaler = JSONDuration(0)
+
+// MarshalJSON implements the json.Marshaler interface for JSONDuration.  err is
+// always nil.
+func (d JSONDuration) MarshalJSON() (b []byte, err error) {
+	msec := float64(time.Duration(d)) / nsecPerMsec
+	b = strconv.AppendFloat(nil, msec, 'f', -1, 64)
+
+	return b, nil
+}
+
+// type check
+var _ json.Unmarshaler = (*JSONDuration)(nil)
+
+// UnmarshalJSON implements the json.Marshaler interface for *JSONDuration.
+func (d *JSONDuration) UnmarshalJSON(b []byte) (err error) {
+	if d == nil {
+		return fmt.Errorf("json duration is nil")
+	}
+
+	msec, err := strconv.ParseFloat(string(b), 64)
+	if err != nil {
+		return fmt.Errorf("parsing json time: %w", err)
+	}
+
+	*d = JSONDuration(int64(msec * nsecPerMsec))
+
+	return nil
+}
+
+// JSONTime is a time.Time that can be decoded from JSON and encoded into JSON
+// according to our API conventions.
+type JSONTime time.Time
+
+// type check
+var _ json.Marshaler = JSONTime{}
+
+// MarshalJSON implements the json.Marshaler interface for JSONTime.  err is
+// always nil.
+func (t JSONTime) MarshalJSON() (b []byte, err error) {
+	msec := float64(time.Time(t).UnixNano()) / nsecPerMsec
+	b = strconv.AppendFloat(nil, msec, 'f', -1, 64)
+
+	return b, nil
+}
+
+// type check
+var _ json.Unmarshaler = (*JSONTime)(nil)
+
+// UnmarshalJSON implements the json.Marshaler interface for *JSONTime.
+func (t *JSONTime) UnmarshalJSON(b []byte) (err error) {
+	if t == nil {
+		return fmt.Errorf("json time is nil")
+	}
+
+	msec, err := strconv.ParseFloat(string(b), 64)
+	if err != nil {
+		return fmt.Errorf("parsing json time: %w", err)
+	}
+
+	*t = JSONTime(time.Unix(0, int64(msec*nsecPerMsec)).UTC())
+
+	return nil
+}
+
+// writeJSONOKResponse writes headers with the code 200 OK, encodes v into w,
+// and logs any errors it encounters.  r is used to get additional information
+// from the request.
+func writeJSONOKResponse(w http.ResponseWriter, r *http.Request, v any) {
+	writeJSONResponse(w, r, v, http.StatusOK)
+}
+
+// writeJSONResponse writes headers with code, encodes v into w, and logs any
+// errors it encounters.  r is used to get additional information from the
+// request.
+func writeJSONResponse(w http.ResponseWriter, r *http.Request, v any, code int) {
+	// TODO(a.garipov): Put some of these to a middleware.
+	h := w.Header()
+	h.Set(httphdr.ContentType, aghhttp.HdrValApplicationJSON)
+	h.Set(httphdr.Server, aghhttp.UserAgent())
+
+	w.WriteHeader(code)
+
+	err := json.NewEncoder(w).Encode(v)
+	if err != nil {
+		log.Error("websvc: writing resp to %s %s: %s", r.Method, r.URL.Path, err)
+	}
+}
+
+// ErrorCode is the error code as used by the HTTP API.  See the ErrorCode
+// definition in the OpenAPI specification.
+type ErrorCode string
+
+// ErrorCode constants.
+//
+// TODO(a.garipov): Expand and document codes.
+const (
+	// ErrorCodeTMP000 is the temporary error code used for all errors.
+	ErrorCodeTMP000 = ""
+)
+
+// HTTPAPIErrorResp is the error response as used by the HTTP API.  See the
+// BadRequestResp, InternalServerErrorResp, and similar objects in the OpenAPI
+// specification.
+type HTTPAPIErrorResp struct {
+	Code ErrorCode `json:"code"`
+	Msg  string    `json:"msg"`
+}
+
+// writeJSONErrorResponse encodes err as a JSON error into w, and logs any
+// errors it encounters.  r is used to get additional information from the
+// request.
+func writeJSONErrorResponse(w http.ResponseWriter, r *http.Request, err error) {
+	log.Error("websvc: %s %s: %s", r.Method, r.URL.Path, err)
+
+	writeJSONResponse(w, r, &HTTPAPIErrorResp{
+		Code: ErrorCodeTMP000,
+		Msg:  err.Error(),
+	}, http.StatusUnprocessableEntity)
+}

internal/next/websvc/json_test.go

@@ -0,0 +1,114 @@
+package websvc_test
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// testJSONTime is the JSON time for tests.
+var testJSONTime = websvc.JSONTime(time.Unix(1_234_567_890, 123_456_000).UTC())
+
+// testJSONTimeStr is the string with the JSON encoding of testJSONTime.
+const testJSONTimeStr = "1234567890123.456"
+
+func TestJSONTime_MarshalJSON(t *testing.T) {
+	testCases := []struct {
+		name       string
+		wantErrMsg string
+		in         websvc.JSONTime
+		want       []byte
+	}{{
+		name:       "unix_zero",
+		wantErrMsg: "",
+		in:         websvc.JSONTime(time.Unix(0, 0)),
+		want:       []byte("0"),
+	}, {
+		name:       "empty",
+		wantErrMsg: "",
+		in:         websvc.JSONTime{},
+		want:       []byte("-6795364578871.345"),
+	}, {
+		name:       "time",
+		wantErrMsg: "",
+		in:         testJSONTime,
+		want:       []byte(testJSONTimeStr),
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := tc.in.MarshalJSON()
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
+
+			assert.Equal(t, tc.want, got)
+		})
+	}
+
+	t.Run("json", func(t *testing.T) {
+		in := &struct {
+			A websvc.JSONTime
+		}{
+			A: testJSONTime,
+		}
+
+		got, err := json.Marshal(in)
+		require.NoError(t, err)
+
+		assert.Equal(t, []byte(`{"A":`+testJSONTimeStr+`}`), got)
+	})
+}
+
+func TestJSONTime_UnmarshalJSON(t *testing.T) {
+	testCases := []struct {
+		name       string
+		wantErrMsg string
+		want       websvc.JSONTime
+		data       []byte
+	}{{
+		name:       "time",
+		wantErrMsg: "",
+		want:       testJSONTime,
+		data:       []byte(testJSONTimeStr),
+	}, {
+		name: "bad",
+		wantErrMsg: `parsing json time: strconv.ParseFloat: parsing "{}": ` +
+			`invalid syntax`,
+		want: websvc.JSONTime{},
+		data: []byte(`{}`),
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var got websvc.JSONTime
+			err := got.UnmarshalJSON(tc.data)
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
+
+			assert.Equal(t, tc.want, got)
+		})
+	}
+
+	t.Run("nil", func(t *testing.T) {
+		err := (*websvc.JSONTime)(nil).UnmarshalJSON([]byte("0"))
+		require.Error(t, err)
+
+		msg := err.Error()
+		assert.Equal(t, "json time is nil", msg)
+	})
+
+	t.Run("json", func(t *testing.T) {
+		want := testJSONTime
+		var got struct {
+			A websvc.JSONTime
+		}
+
+		err := json.Unmarshal([]byte(`{"A":`+testJSONTimeStr+`}`), &got)
+		require.NoError(t, err)
+
+		assert.Equal(t, want, got.A)
+	})
+}

internal/next/websvc/middleware.go

@@ -0,0 +1,21 @@
+package websvc
+
+import (
+	"net/http"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
+	"github.com/AdguardTeam/golibs/httphdr"
+)
+
+// Middlewares
+
+// jsonMw sets the content type of the response to application/json.
+func jsonMw(h http.Handler) (wrapped http.HandlerFunc) {
+	f := func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set(httphdr.ContentType, aghhttp.HdrValApplicationJSON)
+
+		h.ServeHTTP(w, r)
+	}
+
+	return http.HandlerFunc(f)
+}

internal/next/websvc/path.go

@@ -0,0 +1,11 @@
+package websvc
+
+// Path constants
+const (
+	PathHealthCheck = "/health-check"
+
+	PathV1SettingsAll  = "/api/v1/settings/all"
+	PathV1SettingsDNS  = "/api/v1/settings/dns"
+	PathV1SettingsHTTP = "/api/v1/settings/http"
+	PathV1SystemInfo   = "/api/v1/system/info"
+)

internal/next/websvc/settings.go

@@ -0,0 +1,42 @@
+package websvc
+
+import (
+	"net/http"
+)
+
+// All Settings Handlers
+
+// RespGetV1SettingsAll describes the response of the GET /api/v1/settings/all
+// HTTP API.
+type RespGetV1SettingsAll struct {
+	// TODO(a.garipov): Add more as we go.
+
+	DNS  *HTTPAPIDNSSettings  `json:"dns"`
+	HTTP *HTTPAPIHTTPSettings `json:"http"`
+}
+
+// handleGetSettingsAll is the handler for the GET /api/v1/settings/all HTTP
+// API.
+func (svc *Service) handleGetSettingsAll(w http.ResponseWriter, r *http.Request) {
+	dnsSvc := svc.confMgr.DNS()
+	dnsConf := dnsSvc.Config()
+
+	webSvc := svc.confMgr.Web()
+	httpConf := webSvc.Config()
+
+	// TODO(a.garipov): Add all currently supported parameters.
+	writeJSONOKResponse(w, r, &RespGetV1SettingsAll{
+		DNS: &HTTPAPIDNSSettings{
+			Addresses:        dnsConf.Addresses,
+			BootstrapServers: dnsConf.BootstrapServers,
+			UpstreamServers:  dnsConf.UpstreamServers,
+			UpstreamTimeout:  JSONDuration(dnsConf.UpstreamTimeout),
+		},
+		HTTP: &HTTPAPIHTTPSettings{
+			Addresses:       httpConf.Addresses,
+			SecureAddresses: httpConf.SecureAddresses,
+			Timeout:         JSONDuration(httpConf.Timeout),
+			ForceHTTPS:      httpConf.ForceHTTPS,
+		},
+	})
+}

internal/next/websvc/settings_test.go

@@ -0,0 +1,75 @@
+package websvc_test
+
+import (
+	"crypto/tls"
+	"encoding/json"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestService_HandleGetSettingsAll(t *testing.T) {
+	// TODO(a.garipov): Add all currently supported parameters.
+
+	wantDNS := &websvc.HTTPAPIDNSSettings{
+		Addresses:        []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:53")},
+		BootstrapServers: []string{"94.140.14.140", "94.140.14.141"},
+		UpstreamServers:  []string{"94.140.14.14", "1.1.1.1"},
+		UpstreamTimeout:  websvc.JSONDuration(1 * time.Second),
+	}
+
+	wantWeb := &websvc.HTTPAPIHTTPSettings{
+		Addresses:       []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:80")},
+		SecureAddresses: []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:443")},
+		Timeout:         websvc.JSONDuration(5 * time.Second),
+		ForceHTTPS:      true,
+	}
+
+	confMgr := newConfigManager()
+	confMgr.onDNS = func() (s agh.ServiceWithConfig[*dnssvc.Config]) {
+		c, err := dnssvc.New(&dnssvc.Config{
+			Addresses:        wantDNS.Addresses,
+			UpstreamServers:  wantDNS.UpstreamServers,
+			BootstrapServers: wantDNS.BootstrapServers,
+			UpstreamTimeout:  time.Duration(wantDNS.UpstreamTimeout),
+		})
+		require.NoError(t, err)
+
+		return c
+	}
+
+	confMgr.onWeb = func() (s agh.ServiceWithConfig[*websvc.Config]) {
+		return websvc.New(&websvc.Config{
+			TLS: &tls.Config{
+				Certificates: []tls.Certificate{{}},
+			},
+			Addresses:       wantWeb.Addresses,
+			SecureAddresses: wantWeb.SecureAddresses,
+			Timeout:         time.Duration(wantWeb.Timeout),
+			ForceHTTPS:      true,
+		})
+	}
+
+	_, addr := newTestServer(t, confMgr)
+	u := &url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   websvc.PathV1SettingsAll,
+	}
+
+	body := httpGet(t, u, http.StatusOK)
+	resp := &websvc.RespGetV1SettingsAll{}
+	err := json.Unmarshal(body, resp)
+	require.NoError(t, err)
+
+	assert.Equal(t, wantDNS, resp.DNS)
+	assert.Equal(t, wantWeb, resp.HTTP)
+}

internal/next/websvc/system.go

@@ -0,0 +1,35 @@
+package websvc
+
+import (
+	"net/http"
+	"runtime"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/version"
+)
+
+// System Handlers
+
+// RespGetV1SystemInfo describes the response of the GET /api/v1/system/info
+// HTTP API.
+type RespGetV1SystemInfo struct {
+	Arch       string   `json:"arch"`
+	Channel    string   `json:"channel"`
+	OS         string   `json:"os"`
+	NewVersion string   `json:"new_version,omitempty"`
+	Start      JSONTime `json:"start"`
+	Version    string   `json:"version"`
+}
+
+// handleGetV1SystemInfo is the handler for the GET /api/v1/system/info HTTP
+// API.
+func (svc *Service) handleGetV1SystemInfo(w http.ResponseWriter, r *http.Request) {
+	writeJSONOKResponse(w, r, &RespGetV1SystemInfo{
+		Arch:    runtime.GOARCH,
+		Channel: version.Channel(),
+		OS:      runtime.GOOS,
+		// TODO(a.garipov): Fill this when we have an updater.
+		NewVersion: "",
+		Start:      JSONTime(svc.start),
+		Version:    version.Version(),
+	})
+}

internal/next/websvc/system_test.go

@@ -0,0 +1,37 @@
+package websvc_test
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/url"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestService_handleGetV1SystemInfo(t *testing.T) {
+	confMgr := newConfigManager()
+	_, addr := newTestServer(t, confMgr)
+	u := &url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   websvc.PathV1SystemInfo,
+	}
+
+	body := httpGet(t, u, http.StatusOK)
+	resp := &websvc.RespGetV1SystemInfo{}
+	err := json.Unmarshal(body, resp)
+	require.NoError(t, err)
+
+	// TODO(a.garipov): Consider making version.Channel and version.Version
+	// testable and test these better.
+	assert.NotEmpty(t, resp.Channel)
+
+	assert.Equal(t, resp.Arch, runtime.GOARCH)
+	assert.Equal(t, resp.OS, runtime.GOOS)
+	assert.Equal(t, testStart, time.Time(resp.Start))
+}

internal/next/websvc/waitlistener.go

@@ -0,0 +1,31 @@
+package websvc
+
+import (
+	"net"
+	"sync"
+)
+
+// Wait Listener
+
+// waitListener is a wrapper around a listener that also calls wg.Done() on the
+// first call to Accept.  It is useful in situations where it is important to
+// catch the precise moment of the first call to Accept, for example when
+// starting an HTTP server.
+//
+// TODO(a.garipov): Move to aghnet?
+type waitListener struct {
+	net.Listener
+
+	firstAcceptWG   *sync.WaitGroup
+	firstAcceptOnce sync.Once
+}
+
+// type check
+var _ net.Listener = (*waitListener)(nil)
+
+// Accept implements the [net.Listener] interface for *waitListener.
+func (l *waitListener) Accept() (conn net.Conn, err error) {
+	l.firstAcceptOnce.Do(l.firstAcceptWG.Done)
+
+	return l.Listener.Accept()
+}

internal/next/websvc/waitlistener_internal_test.go

@@ -0,0 +1,45 @@
+package websvc
+
+import (
+	"net"
+	"sync"
+	"sync/atomic"
+	"testing"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghchan"
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWaitListener_Accept(t *testing.T) {
+	var accepted atomic.Bool
+	var l net.Listener = &aghtest.Listener{
+		OnAccept: func() (conn net.Conn, err error) {
+			accepted.Store(true)
+
+			return nil, nil
+		},
+		OnAddr:  func() (addr net.Addr) { panic("not implemented") },
+		OnClose: func() (err error) { panic("not implemented") },
+	}
+
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	done := make(chan struct{})
+	go aghchan.MustReceive(done, testTimeout)
+
+	go func() {
+		var wrapper net.Listener = &waitListener{
+			Listener:      l,
+			firstAcceptWG: wg,
+		}
+
+		_, _ = wrapper.Accept()
+	}()
+
+	wg.Wait()
+	close(done)
+
+	assert.True(t, accepted.Load())
+}

internal/next/websvc/websvc.go

@@ -0,0 +1,305 @@
+// Package websvc contains the AdGuard Home HTTP API service.
+//
+// NOTE: Packages other than cmd must not import this package, as it imports
+// most other packages.
+//
+// TODO(a.garipov): Add tests.
+package websvc
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/netip"
+	"sync"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/log"
+	httptreemux "github.com/dimfeld/httptreemux/v5"
+)
+
+// ConfigManager is the configuration manager interface.
+type ConfigManager interface {
+	DNS() (svc agh.ServiceWithConfig[*dnssvc.Config])
+	Web() (svc agh.ServiceWithConfig[*Config])
+
+	UpdateDNS(ctx context.Context, c *dnssvc.Config) (err error)
+	UpdateWeb(ctx context.Context, c *Config) (err error)
+}
+
+// Config is the AdGuard Home web service configuration structure.
+type Config struct {
+	// ConfigManager is used to show information about services as well as
+	// dynamically reconfigure them.
+	ConfigManager ConfigManager
+
+	// TLS is the optional TLS configuration.  If TLS is not nil,
+	// SecureAddresses must not be empty.
+	TLS *tls.Config
+
+	// Start is the time of start of AdGuard Home.
+	Start time.Time
+
+	// Addresses are the addresses on which to serve the plain HTTP API.
+	Addresses []netip.AddrPort
+
+	// SecureAddresses are the addresses on which to serve the HTTPS API.  If
+	// SecureAddresses is not empty, TLS must not be nil.
+	SecureAddresses []netip.AddrPort
+
+	// Timeout is the timeout for all server operations.
+	Timeout time.Duration
+
+	// ForceHTTPS tells if all requests to Addresses should be redirected to a
+	// secure address instead.
+	//
+	// TODO(a.garipov): Use; define rules, which address to redirect to.
+	ForceHTTPS bool
+}
+
+// Service is the AdGuard Home web service.  A nil *Service is a valid
+// [agh.Service] that does nothing.
+type Service struct {
+	confMgr    ConfigManager
+	tls        *tls.Config
+	start      time.Time
+	servers    []*http.Server
+	timeout    time.Duration
+	forceHTTPS bool
+}
+
+// New returns a new properly initialized *Service.  If c is nil, svc is a nil
+// *Service that does nothing.  The fields of c must not be modified after
+// calling New.
+func New(c *Config) (svc *Service) {
+	if c == nil {
+		return nil
+	}
+
+	svc = &Service{
+		confMgr:    c.ConfigManager,
+		tls:        c.TLS,
+		start:      c.Start,
+		timeout:    c.Timeout,
+		forceHTTPS: c.ForceHTTPS,
+	}
+
+	mux := newMux(svc)
+
+	for _, a := range c.Addresses {
+		addr := a.String()
+		errLog := log.StdLog("websvc: plain http: "+addr, log.ERROR)
+		svc.servers = append(svc.servers, &http.Server{
+			Addr:              addr,
+			Handler:           mux,
+			ErrorLog:          errLog,
+			ReadTimeout:       c.Timeout,
+			WriteTimeout:      c.Timeout,
+			IdleTimeout:       c.Timeout,
+			ReadHeaderTimeout: c.Timeout,
+		})
+	}
+
+	for _, a := range c.SecureAddresses {
+		addr := a.String()
+		errLog := log.StdLog("websvc: https: "+addr, log.ERROR)
+		svc.servers = append(svc.servers, &http.Server{
+			Addr:              addr,
+			Handler:           mux,
+			TLSConfig:         c.TLS,
+			ErrorLog:          errLog,
+			ReadTimeout:       c.Timeout,
+			WriteTimeout:      c.Timeout,
+			IdleTimeout:       c.Timeout,
+			ReadHeaderTimeout: c.Timeout,
+		})
+	}
+
+	return svc
+}
+
+// newMux returns a new HTTP request multiplexor for the AdGuard Home web
+// service.
+func newMux(svc *Service) (mux *httptreemux.ContextMux) {
+	mux = httptreemux.NewContextMux()
+
+	routes := []struct {
+		handler http.HandlerFunc
+		method  string
+		path    string
+		isJSON  bool
+	}{{
+		handler: svc.handleGetHealthCheck,
+		method:  http.MethodGet,
+		path:    PathHealthCheck,
+		isJSON:  false,
+	}, {
+		handler: svc.handleGetSettingsAll,
+		method:  http.MethodGet,
+		path:    PathV1SettingsAll,
+		isJSON:  true,
+	}, {
+		handler: svc.handlePatchSettingsDNS,
+		method:  http.MethodPatch,
+		path:    PathV1SettingsDNS,
+		isJSON:  true,
+	}, {
+		handler: svc.handlePatchSettingsHTTP,
+		method:  http.MethodPatch,
+		path:    PathV1SettingsHTTP,
+		isJSON:  true,
+	}, {
+		handler: svc.handleGetV1SystemInfo,
+		method:  http.MethodGet,
+		path:    PathV1SystemInfo,
+		isJSON:  true,
+	}}
+
+	for _, r := range routes {
+		if r.isJSON {
+			mux.Handle(r.method, r.path, jsonMw(r.handler))
+		} else {
+			mux.Handle(r.method, r.path, r.handler)
+		}
+	}
+
+	return mux
+}
+
+// addrs returns all addresses on which this server serves the HTTP API.  addrs
+// must not be called simultaneously with Start.  If svc was initialized with
+// ":0" addresses, addrs will not return the actual bound ports until Start is
+// finished.
+func (svc *Service) addrs() (addrs, secureAddrs []netip.AddrPort) {
+	for _, srv := range svc.servers {
+		addrPort, err := netip.ParseAddrPort(srv.Addr)
+		if err != nil {
+			// Technically shouldn't happen, since all servers must have a valid
+			// address.
+			panic(fmt.Errorf("websvc: server %q: bad address: %w", srv.Addr, err))
+		}
+
+		// srv.Serve will set TLSConfig to an almost empty value, so, instead of
+		// relying only on the nilness of TLSConfig, check the length of the
+		// certificates field as well.
+		if srv.TLSConfig == nil || len(srv.TLSConfig.Certificates) == 0 {
+			addrs = append(addrs, addrPort)
+		} else {
+			secureAddrs = append(secureAddrs, addrPort)
+		}
+
+	}
+
+	return addrs, secureAddrs
+}
+
+// handleGetHealthCheck is the handler for the GET /health-check HTTP API.
+func (svc *Service) handleGetHealthCheck(w http.ResponseWriter, _ *http.Request) {
+	_, _ = io.WriteString(w, "OK")
+}
+
+// type check
+var _ agh.Service = (*Service)(nil)
+
+// Start implements the [agh.Service] interface for *Service.  svc may be nil.
+// After Start exits, all HTTP servers have tried to start, possibly failing and
+// writing error messages to the log.
+func (svc *Service) Start() (err error) {
+	if svc == nil {
+		return nil
+	}
+
+	wg := &sync.WaitGroup{}
+	wg.Add(len(svc.servers))
+	for _, srv := range svc.servers {
+		go serve(srv, wg)
+	}
+
+	wg.Wait()
+
+	return nil
+}
+
+// serve starts and runs srv and writes all errors into its log.
+func serve(srv *http.Server, wg *sync.WaitGroup) {
+	addr := srv.Addr
+	defer log.OnPanic(addr)
+
+	var proto string
+	var l net.Listener
+	var err error
+	if srv.TLSConfig == nil {
+		proto = "http"
+		l, err = net.Listen("tcp", addr)
+	} else {
+		proto = "https"
+		l, err = tls.Listen("tcp", addr, srv.TLSConfig)
+	}
+	if err != nil {
+		srv.ErrorLog.Printf("starting srv %s: binding: %s", addr, err)
+	}
+
+	// Update the server's address in case the address had the port zero, which
+	// would mean that a random available port was automatically chosen.
+	srv.Addr = l.Addr().String()
+
+	log.Info("websvc: starting srv %s://%s", proto, srv.Addr)
+
+	l = &waitListener{
+		Listener:      l,
+		firstAcceptWG: wg,
+	}
+
+	err = srv.Serve(l)
+	if err != nil && !errors.Is(err, http.ErrServerClosed) {
+		srv.ErrorLog.Printf("starting srv %s: %s", addr, err)
+	}
+}
+
+// Shutdown implements the [agh.Service] interface for *Service.  svc may be
+// nil.
+func (svc *Service) Shutdown(ctx context.Context) (err error) {
+	if svc == nil {
+		return nil
+	}
+
+	var errs []error
+	for _, srv := range svc.servers {
+		serr := srv.Shutdown(ctx)
+		if serr != nil {
+			errs = append(errs, fmt.Errorf("shutting down srv %s: %w", srv.Addr, serr))
+		}
+	}
+
+	if len(errs) > 0 {
+		return errors.List("shutting down", errs...)
+	}
+
+	return nil
+}
+
+// Config returns the current configuration of the web service.  Config must not
+// be called simultaneously with Start.  If svc was initialized with ":0"
+// addresses, addrs will not return the actual bound ports until Start is
+// finished.
+func (svc *Service) Config() (c *Config) {
+	c = &Config{
+		ConfigManager: svc.confMgr,
+		TLS:           svc.tls,
+		// Leave Addresses and SecureAddresses empty and get the actual
+		// addresses that include the :0 ones later.
+		Start:      svc.start,
+		Timeout:    svc.timeout,
+		ForceHTTPS: svc.forceHTTPS,
+	}
+
+	c.Addresses, c.SecureAddresses = svc.addrs()
+
+	return c
+}

internal/next/websvc/websvc_internal_test.go

@@ -0,0 +1,6 @@
+package websvc
+
+import "time"
+
+// testTimeout is the common timeout for tests.
+const testTimeout = 1 * time.Second

internal/next/websvc/websvc_test.go

@@ -0,0 +1,187 @@
+package websvc_test
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMain(m *testing.M) {
+	testutil.DiscardLogOutput(m)
+}
+
+// testTimeout is the common timeout for tests.
+const testTimeout = 1 * time.Second
+
+// testStart is the server start value for tests.
+var testStart = time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+
+// type check
+var _ websvc.ConfigManager = (*configManager)(nil)
+
+// configManager is a [websvc.ConfigManager] for tests.
+type configManager struct {
+	onDNS func() (svc agh.ServiceWithConfig[*dnssvc.Config])
+	onWeb func() (svc agh.ServiceWithConfig[*websvc.Config])
+
+	onUpdateDNS func(ctx context.Context, c *dnssvc.Config) (err error)
+	onUpdateWeb func(ctx context.Context, c *websvc.Config) (err error)
+}
+
+// DNS implements the [websvc.ConfigManager] interface for *configManager.
+func (m *configManager) DNS() (svc agh.ServiceWithConfig[*dnssvc.Config]) {
+	return m.onDNS()
+}
+
+// Web implements the [websvc.ConfigManager] interface for *configManager.
+func (m *configManager) Web() (svc agh.ServiceWithConfig[*websvc.Config]) {
+	return m.onWeb()
+}
+
+// UpdateDNS implements the [websvc.ConfigManager] interface for *configManager.
+func (m *configManager) UpdateDNS(ctx context.Context, c *dnssvc.Config) (err error) {
+	return m.onUpdateDNS(ctx, c)
+}
+
+// UpdateWeb implements the [websvc.ConfigManager] interface for *configManager.
+func (m *configManager) UpdateWeb(ctx context.Context, c *websvc.Config) (err error) {
+	return m.onUpdateWeb(ctx, c)
+}
+
+// newConfigManager returns a *configManager all methods of which panic.
+func newConfigManager() (m *configManager) {
+	return &configManager{
+		onDNS: func() (svc agh.ServiceWithConfig[*dnssvc.Config]) { panic("not implemented") },
+		onWeb: func() (svc agh.ServiceWithConfig[*websvc.Config]) { panic("not implemented") },
+		onUpdateDNS: func(_ context.Context, _ *dnssvc.Config) (err error) {
+			panic("not implemented")
+		},
+		onUpdateWeb: func(_ context.Context, _ *websvc.Config) (err error) {
+			panic("not implemented")
+		},
+	}
+}
+
+// newTestServer creates and starts a new web service instance as well as its
+// sole address.  It also registers a cleanup procedure, which shuts the
+// instance down.
+//
+// TODO(a.garipov): Use svc or remove it.
+func newTestServer(
+	t testing.TB,
+	confMgr websvc.ConfigManager,
+) (svc *websvc.Service, addr netip.AddrPort) {
+	t.Helper()
+
+	c := &websvc.Config{
+		ConfigManager:   confMgr,
+		TLS:             nil,
+		Addresses:       []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:0")},
+		SecureAddresses: nil,
+		Timeout:         testTimeout,
+		Start:           testStart,
+		ForceHTTPS:      false,
+	}
+
+	svc = websvc.New(c)
+
+	err := svc.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
+		t.Cleanup(cancel)
+
+		err = svc.Shutdown(ctx)
+		require.NoError(t, err)
+	})
+
+	c = svc.Config()
+	require.NotNil(t, c)
+	require.Len(t, c.Addresses, 1)
+
+	return svc, c.Addresses[0]
+}
+
+// jobj is a utility alias for JSON objects.
+type jobj map[string]any
+
+// httpGet is a helper that performs an HTTP GET request and returns the body of
+// the response as well as checks that the status code is correct.
+//
+// TODO(a.garipov): Add helpers for other methods.
+func httpGet(t testing.TB, u *url.URL, wantCode int) (body []byte) {
+	t.Helper()
+
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
+	require.NoErrorf(t, err, "creating req")
+
+	httpCli := &http.Client{
+		Timeout: testTimeout,
+	}
+	resp, err := httpCli.Do(req)
+	require.NoErrorf(t, err, "performing req")
+	require.Equal(t, wantCode, resp.StatusCode)
+
+	testutil.CleanupAndRequireSuccess(t, resp.Body.Close)
+
+	body, err = io.ReadAll(resp.Body)
+	require.NoErrorf(t, err, "reading body")
+
+	return body
+}
+
+// httpPatch is a helper that performs an HTTP PATCH request with JSON-encoded
+// reqBody as the request body and returns the body of the response as well as
+// checks that the status code is correct.
+//
+// TODO(a.garipov): Add helpers for other methods.
+func httpPatch(t testing.TB, u *url.URL, reqBody any, wantCode int) (body []byte) {
+	t.Helper()
+
+	b, err := json.Marshal(reqBody)
+	require.NoErrorf(t, err, "marshaling reqBody")
+
+	req, err := http.NewRequest(http.MethodPatch, u.String(), bytes.NewReader(b))
+	require.NoErrorf(t, err, "creating req")
+
+	httpCli := &http.Client{
+		Timeout: testTimeout,
+	}
+	resp, err := httpCli.Do(req)
+	require.NoErrorf(t, err, "performing req")
+	require.Equal(t, wantCode, resp.StatusCode)
+
+	testutil.CleanupAndRequireSuccess(t, resp.Body.Close)
+
+	body, err = io.ReadAll(resp.Body)
+	require.NoErrorf(t, err, "reading body")
+
+	return body
+}
+
+func TestService_Start_getHealthCheck(t *testing.T) {
+	confMgr := newConfigManager()
+	_, addr := newTestServer(t, confMgr)
+	u := &url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   websvc.PathHealthCheck,
+	}
+
+	body := httpGet(t, u, http.StatusOK)
+
+	assert.Equal(t, []byte("OK"), body)
+}

main.go

@@ -1,3 +1,5 @@
+//go:build !next
+
 package main
 
 import (

main_next.go

@@ -0,0 +1,20 @@
+//go:build next
+
+package main
+
+import (
+	"embed"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/cmd"
+)
+
+// Embed the prebuilt client here since we strive to keep .go files inside the
+// internal directory and the embed package is unable to embed files located
+// outside of the same or underlying directory.
+
+//go:embed build
+var clientBuildFS embed.FS
+
+func main() {
+	cmd.Main(clientBuildFS)
+}

openapi/openapi.yaml

@@ -1061,6 +1061,17 @@
       'responses':
         '200':
           'description': 'OK.'
+  '/rewrite/update':
+    'put':
+      'tags':
+        - 'rewrite'
+      'operationId': 'rewriteUpdate'
+      'summary': 'Update a Rewrite rule'
+      'requestBody':
+        '$ref': '#/components/requestBodies/RewriteUpdate'
+      'responses':
+        '200':
+          'description': 'OK.'
   '/i18n/change_language':
     'post':
       'deprecated': true
@@ -1311,6 +1322,12 @@
           'schema':
             '$ref': '#/components/schemas/RewriteEntry'
       'required': true
+    'RewriteUpdate':
+      'content':
+        'application/json':
+          'schema':
+            '$ref': '#/components/schemas/RewriteUpdate'
+      'required': true
   'schemas':
     'ServerStatus':
       'type': 'object'
@@ -2702,6 +2719,14 @@
       'items':
         '$ref': '#/components/schemas/RewriteEntry'
       'description': 'Rewrite rules array'
+    'RewriteUpdate':
+      'type': 'object'
+      'description': 'Rewrite rule update object'
+      'properties':
+        'target':
+          '$ref': '#/components/schemas/RewriteEntry'
+        'update':
+          '$ref': '#/components/schemas/RewriteEntry'
     'RewriteEntry':
       'type': 'object'
       'description': 'Rewrite rule'

scripts/make/go-build.sh

@@ -128,7 +128,13 @@ export CGO_ENABLED
 GO111MODULE='on'
 export GO111MODULE
 
-tags_flags='--tags='
+# Build the new binary if requested.
+if [ "${NEXTAPI:-0}" -eq '0' ]
+then
+	tags_flags='--tags='
+else
+	tags_flags='--tags=next'
+fi
 readonly tags_flags
 
 if [ "$verbose" -gt '0' ]

scripts/make/go-lint.sh

@@ -122,6 +122,7 @@ underscores() {
 			-e '_freebsd.go'\
 			-e '_linux.go'\
 			-e '_little.go'\
+			-e '_next.go'\
 			-e '_openbsd.go'\
 			-e '_others.go'\
 			-e '_test.go'\