all: mv v1 to next; imp tests, docs

internal/next/agh/agh.go

@@ -0,0 +1,33 @@
+// Package agh contains common entities and interfaces of AdGuard Home.
+//
+// TODO(a.garipov): Move to the upper-level internal/.
+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.
+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 }

internal/next/cmd/cmd.go

@@ -0,0 +1,70 @@
+// 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"
+	"net/netip"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"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.
+
+	// Web Service
+
+	// TODO(a.garipov): Use in the Web service.
+	_ = clientBuildFS
+
+	// TODO(a.garipov): Make configurable.
+	web := websvc.New(&websvc.Config{
+		// TODO(a.garipov): Use an actual implementation.
+		ConfigManager: nil,
+		Addresses:     []netip.AddrPort{netip.MustParseAddrPort("127.0.0.1:3001")},
+		Start:         start,
+		Timeout:       60 * time.Second,
+		ForceHTTPS:    false,
+	})
+
+	err := web.Start()
+	fatalOnError(err)
+
+	sigHdlr := newSignalHandler(
+		web,
+	)
+
+	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 +1,70 @@
+package cmd
+
+import (
+	"os"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// signalHandler processes incoming signals and shuts services down.
+type signalHandler struct {
+	signal chan os.Signal
+
+	// 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.IsShutdownSignal(sig) {
+			h.shutdown()
+		}
+	}
+}
+
+// Exit status constants.
+const (
+	statusSuccess = 0
+	statusError   = 1
+)
+
+// shutdown gracefully shuts down all services.
+func (h *signalHandler) shutdown() {
+	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
+		}
+	}
+
+	log.Info("sighdlr: shutting down adguard home")
+
+	os.Exit(status)
+}
+
+// newSignalHandler returns a new signalHandler that shuts down svcs.
+func newSignalHandler(svcs ...agh.Service) (h *signalHandler) {
+	h = &signalHandler{
+		signal:   make(chan os.Signal, 1),
+		services: svcs,
+	}
+
+	aghos.NotifyShutdownSignal(h.signal)
+
+	return h
+}

internal/next/dnssvc/dnssvc.go

@@ -0,0 +1,223 @@
+// 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 {
+	// running is an atomic boolean value.  Keep it the first value in the
+	// struct to ensure atomic alignment.  0 means that the service is not
+	// running, 1 means that it is running.
+	//
+	// TODO(a.garipov): Use [atomic.Bool] in Go 1.19 or get rid of it
+	// completely.
+	running uint64
+
+	proxy      *proxy.Proxy
+	bootstraps []string
+	upstreams  []string
+	upsTimeout time.Duration
+}
+
+// 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.
+		atomic.StoreUint64(&svc.running, 1)
+	}()
+
+	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 atomic.LoadUint64(&svc.running) == 1 {
+		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 +1,89 @@
+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/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMain(m *testing.M) {
+	aghtest.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"
+	)
+
+	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
+		},
+	}
+
+	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.NoError(t, err)
+}

internal/next/websvc/dns.go

@@ -0,0 +1,86 @@
+package websvc
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/netip"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
+	"github.com/AdguardTeam/golibs/timeutil"
+)
+
+// DNS Settings Handlers
+
+// TODO(a.garipov): !! Write tests!
+
+// 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  timeutil.Duration `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  timeutil.Duration `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 {
+		writeHTTPError(w, r, fmt.Errorf("decoding: %w", err))
+
+		return
+	}
+
+	newConf := &dnssvc.Config{
+		Addresses:        req.Addresses,
+		BootstrapServers: req.BootstrapServers,
+		UpstreamServers:  req.UpstreamServers,
+		UpstreamTimeout:  req.UpstreamTimeout.Duration,
+	}
+
+	ctx := r.Context()
+	err = svc.confMgr.UpdateDNS(ctx, newConf)
+	if err != nil {
+		writeHTTPError(w, r, fmt.Errorf("updating: %w", err))
+
+		return
+	}
+
+	newSvc := svc.confMgr.DNS()
+	err = newSvc.Start()
+	if err != nil {
+		writeHTTPError(w, r, fmt.Errorf("starting new service: %w", err))
+
+		return
+	}
+
+	writeJSONResponse(w, r, &HTTPAPIDNSSettings{
+		Addresses:        newConf.Addresses,
+		BootstrapServers: newConf.BootstrapServers,
+		UpstreamServers:  newConf.UpstreamServers,
+		UpstreamTimeout:  timeutil.Duration{Duration: newConf.UpstreamTimeout},
+	})
+}

internal/next/websvc/http.go

@@ -0,0 +1,104 @@
+package websvc
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/netip"
+	"time"
+
+	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/timeutil"
+)
+
+// HTTP Settings Handlers
+
+// TODO(a.garipov): !! Write tests!
+
+// 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         timeutil.Duration `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         timeutil.Duration `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 {
+		writeHTTPError(w, r, fmt.Errorf("decoding: %w", err))
+
+		return
+	}
+
+	newConf := &Config{
+		ConfigManager:   svc.confMgr,
+		TLS:             svc.tls,
+		Addresses:       req.Addresses,
+		SecureAddresses: req.SecureAddresses,
+		Timeout:         req.Timeout.Duration,
+		ForceHTTPS:      svc.forceHTTPS,
+	}
+
+	writeJSONResponse(w, r, &HTTPAPIHTTPSettings{
+		Addresses:       newConf.Addresses,
+		SecureAddresses: newConf.SecureAddresses,
+		Timeout:         timeutil.Duration{Duration: 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 {
+			writeHTTPError(w, r, fmt.Errorf("updating: %w", updErr))
+
+			return
+		}
+
+		// TODO(a.garipov): !! Add some kind of timeout?  Context?
+		var newSvc *Service
+		for newSvc = svc.confMgr.Web(); newSvc == svc; {
+			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: %s", updErr)
+		}
+	}()
+}

internal/next/websvc/json.go

@@ -0,0 +1,74 @@
+package websvc
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// JSON Utilities
+
+// 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{}
+
+// nsecPerMsec is the number of nanoseconds in a millisecond.
+const nsecPerMsec = float64(time.Millisecond / time.Nanosecond)
+
+// 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
+}
+
+// writeJSONResponse encodes v into w and logs any errors it encounters.  r is
+// used to get additional information from the request.
+func writeJSONResponse(w io.Writer, r *http.Request, v any) {
+	err := json.NewEncoder(w).Encode(v)
+	if err != nil {
+		log.Error("websvc: writing resp to %s %s: %s", r.Method, r.URL.Path, err)
+	}
+}
+
+// writeHTTPError is a helper for logging and writing HTTP errors.
+//
+// TODO(a.garipov): Improve codes, and add JSON error codes.
+func writeHTTPError(w http.ResponseWriter, r *http.Request, err error) {
+	log.Error("websvc: %s %s: %s", r.Method, r.URL.Path, err)
+
+	w.WriteHeader(http.StatusUnprocessableEntity)
+	_, werr := io.WriteString(w, err.Error())
+	if werr != nil {
+		log.Debug("websvc: writing error resp to %s %s: %s", r.Method, r.URL.Path, werr)
+	}
+}

internal/next/websvc/json_internal_test.go

@@ -0,0 +1,113 @@
+package websvc
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// testJSONTime is the JSON time for tests.
+var testJSONTime = 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         jsonTime
+		want       []byte
+	}{{
+		name:       "unix_zero",
+		wantErrMsg: "",
+		in:         jsonTime(time.Unix(0, 0)),
+		want:       []byte("0"),
+	}, {
+		name:       "empty",
+		wantErrMsg: "",
+		in:         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 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       jsonTime
+		data       []byte
+	}{{
+		name:       "time",
+		wantErrMsg: "",
+		want:       testJSONTime,
+		data:       []byte(testJSONTimeStr),
+	}, {
+		name: "bad",
+		wantErrMsg: `parsing json time: strconv.ParseFloat: parsing "{}": ` +
+			`invalid syntax`,
+		want: jsonTime{},
+		data: []byte(`{}`),
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var got 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 := (*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 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 +1,16 @@
+package websvc
+
+import "net/http"
+
+// 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("Content-Type", "application/json")
+
+		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 +1,44 @@
+package websvc
+
+import (
+	"net/http"
+
+	"github.com/AdguardTeam/golibs/timeutil"
+)
+
+// 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.
+	writeJSONResponse(w, r, &RespGetV1SettingsAll{
+		DNS: &HTTPAPIDNSSettings{
+			Addresses:        dnsConf.Addresses,
+			BootstrapServers: dnsConf.BootstrapServers,
+			UpstreamServers:  dnsConf.UpstreamServers,
+			UpstreamTimeout:  timeutil.Duration{Duration: dnsConf.UpstreamTimeout},
+		},
+		HTTP: &HTTPAPIHTTPSettings{
+			Addresses:       httpConf.Addresses,
+			SecureAddresses: httpConf.SecureAddresses,
+			Timeout:         timeutil.Duration{Duration: 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/dnssvc"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
+	"github.com/AdguardTeam/golibs/timeutil"
+	"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:  timeutil.Duration{Duration: 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:         timeutil.Duration{Duration: 5 * time.Second},
+		ForceHTTPS:      true,
+	}
+
+	confMgr := newConfigManager()
+	confMgr.onDNS = func() (c *dnssvc.Service) {
+		c, err := dnssvc.New(&dnssvc.Config{
+			Addresses:        wantDNS.Addresses,
+			UpstreamServers:  wantDNS.UpstreamServers,
+			BootstrapServers: wantDNS.BootstrapServers,
+			UpstreamTimeout:  wantDNS.UpstreamTimeout.Duration,
+		})
+		require.NoError(t, err)
+
+		return c
+	}
+
+	confMgr.onWeb = func() (c *websvc.Service) {
+		return websvc.New(&websvc.Config{
+			TLS: &tls.Config{
+				Certificates: []tls.Certificate{{}},
+			},
+			Addresses:       wantWeb.Addresses,
+			SecureAddresses: wantWeb.SecureAddresses,
+			Timeout:         wantWeb.Timeout.Duration,
+			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) {
+	writeJSONResponse(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 +1,50 @@
+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) {
+	// TODO(a.garipov): use atomic.Bool in Go 1.19.
+	var numAcceptCalls uint32
+	var l net.Listener = &aghtest.Listener{
+		OnAccept: func() (conn net.Conn, err error) {
+			atomic.AddUint32(&numAcceptCalls, 1)
+
+			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.Equal(t, uint32(1), atomic.LoadUint32(&numAcceptCalls))
+}

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 *dnssvc.Service)
+	Web() (svc *Service)
+
+	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 +1,153 @@
+package websvc_test
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"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) {
+	aghtest.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 *dnssvc.Service)
+	onWeb func() (svc *websvc.Service)
+
+	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 *dnssvc.Service) {
+	return m.onDNS()
+}
+
+// Web implements the [websvc.ConfigManager] interface for *configManager.
+func (m *configManager) Web() (svc *websvc.Service) {
+	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 *dnssvc.Service) { panic("not implemented") },
+		onWeb: func() (svc *websvc.Service) { 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]
+}
+
+// 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
+}
+
+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)
+}