Pull request: 3835 check ports properly

Merge in DNS/adguard-home from 3835-imp-error-msg to master

Updates #3835.

Squashed commit of the following:

commit ba31cb67833df9f293fe13be96a35c2a823f115b
Merge: 19c7dfc9 4be69d35
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 16 20:07:25 2021 +0300

    Merge branch 'master' into 3835-imp-error-msg

commit 19c7dfc96284a271d30d7111c86c439be3461389
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 16 19:42:10 2021 +0300

    all: imp more

commit 5b9c6a3e357238bf44ef800a6033a7671f27d469
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 16 18:57:02 2021 +0300

    all: introduce aghhttp

commit 29caa17200957aad2b98461573bb33d80931adcf
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 16 14:23:53 2021 +0300

    all: imp more

commit 754c020191d7b9518cb0e789f3f5741ba38c3cf4
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Dec 15 20:53:41 2021 +0300

    all: imp code, log changes

commit ec712dd562f31fcc2fbc27e7035f926c79827444
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Dec 15 18:40:54 2021 +0300

    home: check ports properly

CHANGELOG.md

@@ -49,6 +49,7 @@ and this project adheres to
 
 ### Changed
 
+- Port bindings are now checked for uniqueness ([#3835]).
 - The DNSSEC check now simply checks against the AD flag in the response
   ([#3904]).
 - Client objects in the configuration file are now sorted ([#3933]).
@@ -241,6 +242,7 @@ In this release, the schema version has changed from 10 to 12.
 [#3772]: https://github.com/AdguardTeam/AdGuardHome/issues/3772
 [#3778]: https://github.com/AdguardTeam/AdGuardHome/issues/3778
 [#3815]: https://github.com/AdguardTeam/AdGuardHome/issues/3815
+[#3835]: https://github.com/AdguardTeam/AdGuardHome/issues/3835
 [#3887]: https://github.com/AdguardTeam/AdGuardHome/issues/3887
 [#3890]: https://github.com/AdguardTeam/AdGuardHome/issues/3890
 [#3904]: https://github.com/AdguardTeam/AdGuardHome/issues/3904

internal/aghhttp/aghhttp.go

@@ -0,0 +1,24 @@
+// Package aghhttp provides some common methods to work with HTTP.
+package aghhttp
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// OK responds with word OK.
+func OK(w http.ResponseWriter) {
+	if _, err := io.WriteString(w, "OK\n"); err != nil {
+		log.Error("couldn't write body: %s", err)
+	}
+}
+
+// Error writes formatted message to w and also logs it.
+func Error(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
+	text := fmt.Sprintf(format, args...)
+	log.Error("%s %s: %s", r.Method, r.URL, text)
+	http.Error(w, text, code)
+}

internal/aghnet/hostscontainer.go

@@ -431,7 +431,7 @@ func (hp *hostsParser) writeMainHostRule(host string, ip net.IP) (added, addedPt
 		rwSuccess    = "^$dnsrewrite=NOERROR;"
 		rwSuccessPTR = "^$dnsrewrite=NOERROR;PTR;"
 
-		modLen    = len("||") + len(rwSuccess)
+		modLen    = len("||") + len(rwSuccess) + len(";")
 		modLenPTR = len("||") + len(rwSuccessPTR)
 	)
 

internal/aghnet/interfaces.go

@@ -118,3 +118,11 @@ func IfaceDNSIPAddrs(
 
 	return addrs, nil
 }
+
+// interfaceName is a string containing network interface's name.  The name is
+// used in file walking methods.
+type interfaceName string
+
+// Use interfaceName in the OS-independent code since it's actually only used in
+// several OS-dependent implementations which causes linting issues.
+var _ = interfaceName("")

internal/aghnet/net.go

@@ -4,13 +4,11 @@ package aghnet
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"net"
-	"os"
 	"os/exec"
-	"runtime"
 	"strings"
 	"syscall"
-	"time"
 
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
@@ -189,57 +187,30 @@ func GetSubnet(ifaceName string) *net.IPNet {
 	return nil
 }
 
-// CheckPortAvailable - check if TCP port is available
+// CheckPort checks if the port is available for binding.
-func CheckPortAvailable(host net.IP, port int) error {
+func CheckPort(network string, ip net.IP, port int) (err error) {
-	ln, err := net.Listen("tcp", netutil.JoinHostPort(host.String(), port))
+	var c io.Closer
-	if err != nil {
+	addr := netutil.IPPort{IP: ip, Port: port}.String()
-		return err
+	switch network {
-	}
+	case "tcp":
-	_ = ln.Close()
+		c, err = net.Listen(network, addr)
-
+	case "udp":
-	// It seems that net.Listener.Close() doesn't close file descriptors right away.
+		c, err = net.ListenPacket(network, addr)
-	// We wait for some time and hope that this fd will be closed.
+	default:
-	time.Sleep(100 * time.Millisecond)
 		return nil
 	}
 
-// CheckPacketPortAvailable - check if UDP port is available
+	return errors.WithDeferred(err, closePortChecker(c))
-func CheckPacketPortAvailable(host net.IP, port int) error {
-	ln, err := net.ListenPacket("udp", netutil.JoinHostPort(host.String(), port))
-	if err != nil {
-		return err
-	}
-	_ = ln.Close()
-
-	// It seems that net.Listener.Close() doesn't close file descriptors right away.
-	// We wait for some time and hope that this fd will be closed.
-	time.Sleep(100 * time.Millisecond)
-	return err
 }
 
-// ErrorIsAddrInUse - check if error is "address already in use"
+// IsAddrInUse checks if err is about unsuccessful address binding.
-func ErrorIsAddrInUse(err error) bool {
+func IsAddrInUse(err error) (ok bool) {
-	errOpError, ok := err.(*net.OpError)
+	var sysErr syscall.Errno
-	if !ok {
+	if !errors.As(err, &sysErr) {
 		return false
 	}
 
-	errSyscallError, ok := errOpError.Err.(*os.SyscallError)
+	return isAddrInUse(sysErr)
-	if !ok {
-		return false
-	}
-
-	errErrno, ok := errSyscallError.Err.(syscall.Errno)
-	if !ok {
-		return false
-	}
-
-	if runtime.GOOS == "windows" {
-		const WSAEADDRINUSE = 10048
-		return errErrno == WSAEADDRINUSE
-	}
-
-	return errErrno == syscall.EADDRINUSE
 }
 
 // SplitHost is a wrapper for net.SplitHostPort for the cases when the hostport

internal/aghnet/net_others.go

@@ -1,20 +0,0 @@
-//go:build !(linux || darwin || freebsd || openbsd)
-// +build !linux,!darwin,!freebsd,!openbsd
-
-package aghnet
-
-import (
-	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
-)
-
-func canBindPrivilegedPorts() (can bool, err error) {
-	return aghos.HaveAdminRights()
-}
-
-func ifaceHasStaticIP(string) (ok bool, err error) {
-	return false, aghos.Unsupported("checking static ip")
-}
-
-func ifaceSetStaticIP(string) (err error) {
-	return aghos.Unsupported("setting static ip")
-}

internal/aghnet/net_unix.go

@@ -1,8 +1,19 @@
-//go:build openbsd || freebsd || linux
+//go:build openbsd || freebsd || linux || darwin
-// +build openbsd freebsd linux
+// +build openbsd freebsd linux darwin
 
 package aghnet
 
-// interfaceName is a string containing network interface's name.  The name is
+import (
-// used in file walking methods.
+	"io"
-type interfaceName string
+	"syscall"
+
+	"github.com/AdguardTeam/golibs/errors"
+)
+
+func closePortChecker(c io.Closer) (err error) {
+	return c.Close()
+}
+
+func isAddrInUse(err syscall.Errno) (ok bool) {
+	return errors.Is(err, syscall.EADDRINUSE)
+}

internal/aghnet/net_windows.go

@@ -0,0 +1,45 @@
+//go:build !(linux || darwin || freebsd || openbsd)
+// +build !linux,!darwin,!freebsd,!openbsd
+
+package aghnet
+
+import (
+	"io"
+	"syscall"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/golibs/errors"
+	"golang.org/x/sys/windows"
+)
+
+func canBindPrivilegedPorts() (can bool, err error) {
+	return aghos.HaveAdminRights()
+}
+
+func ifaceHasStaticIP(string) (ok bool, err error) {
+	return false, aghos.Unsupported("checking static ip")
+}
+
+func ifaceSetStaticIP(string) (err error) {
+	return aghos.Unsupported("setting static ip")
+}
+
+func closePortChecker(c io.Closer) (err error) {
+	if err = c.Close(); err != nil {
+		return err
+	}
+
+	// It seems that net.Listener.Close() doesn't close file descriptors right
+	// away.  We wait for some time and hope that this fd will be closed.
+	//
+	// TODO(e.burkov):  Investigate the purpose of the line and perhaps use more
+	// reliable approach.
+	time.Sleep(100 * time.Millisecond)
+
+	return nil
+}
+
+func isAddrInUse(err syscall.Errno) (ok bool) {
+	return errors.Is(err, windows.WSAEADDRINUSE)
+}

internal/dhcpd/http.go

@@ -10,18 +10,13 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/timeutil"
 )
 
-func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
-	text := fmt.Sprintf(format, args...)
-	log.Info("DHCP: %s %s: %s", r.Method, r.URL, text)
-	http.Error(w, text, code)
-}
-
 type v4ServerConfJSON struct {
 	GatewayIP     net.IP `json:"gateway_ip"`
 	SubnetMask    net.IP `json:"subnet_mask"`
@@ -87,8 +82,13 @@ func (s *Server) handleDHCPStatus(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	err := json.NewEncoder(w).Encode(status)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Unable to marshal DHCP status json: %s", err)
+		aghhttp.Error(
-		return
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Unable to marshal DHCP status json: %s",
+			err,
+		)
 	}
 }
 
@@ -211,36 +211,34 @@ func (s *Server) handleDHCPSetConfig(w http.ResponseWriter, r *http.Request) {
 
 	err := json.NewDecoder(r.Body).Decode(conf)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest,
+		aghhttp.Error(r, w, http.StatusBadRequest, "failed to parse new dhcp config json: %s", err)
-			"failed to parse new dhcp config json: %s", err)
 
 		return
 	}
 
 	srv4, v4Enabled, err := s.handleDHCPSetConfigV4(conf)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "bad dhcpv4 configuration: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "bad dhcpv4 configuration: %s", err)
 
 		return
 	}
 
 	srv6, v6Enabled, err := s.handleDHCPSetConfigV6(conf)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "bad dhcpv6 configuration: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "bad dhcpv6 configuration: %s", err)
 
 		return
 	}
 
 	if conf.Enabled == nbTrue && !v4Enabled && !v6Enabled {
-		httpError(r, w, http.StatusBadRequest,
+		aghhttp.Error(r, w, http.StatusBadRequest, "dhcpv4 or dhcpv6 configuration must be complete")
-			"dhcpv4 or dhcpv6 configuration must be complete")
 
 		return
 	}
 
 	err = s.Stop()
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "stopping dhcp: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "stopping dhcp: %s", err)
 
 		return
 	}
@@ -265,7 +263,7 @@ func (s *Server) handleDHCPSetConfig(w http.ResponseWriter, r *http.Request) {
 
 	err = s.dbLoad()
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "loading leases db: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "loading leases db: %s", err)
 
 		return
 	}
@@ -274,9 +272,7 @@ func (s *Server) handleDHCPSetConfig(w http.ResponseWriter, r *http.Request) {
 		var code int
 		code, err = s.enableDHCP(conf.InterfaceName)
 		if err != nil {
-			httpError(r, w, code, "enabling dhcp: %s", err)
+			aghhttp.Error(r, w, code, "enabling dhcp: %s", err)
-
-			return
 		}
 	}
 }
@@ -295,7 +291,8 @@ func (s *Server) handleDHCPInterfaces(w http.ResponseWriter, r *http.Request) {
 
 	ifaces, err := net.Interfaces()
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err)
+
 		return
 	}
 
@@ -312,7 +309,15 @@ func (s *Server) handleDHCPInterfaces(w http.ResponseWriter, r *http.Request) {
 		var addrs []net.Addr
 		addrs, err = iface.Addrs()
 		if err != nil {
-			httpError(r, w, http.StatusInternalServerError, "Failed to get addresses for interface %s: %s", iface.Name, err)
+			aghhttp.Error(
+				r,
+				w,
+				http.StatusInternalServerError,
+				"Failed to get addresses for interface %s: %s",
+				iface.Name,
+				err,
+			)
+
 			return
 		}
 
@@ -329,7 +334,13 @@ func (s *Server) handleDHCPInterfaces(w http.ResponseWriter, r *http.Request) {
 			ipnet, ok := addr.(*net.IPNet)
 			if !ok {
 				// not an IPNet, should not happen
-				httpError(r, w, http.StatusInternalServerError, "SHOULD NOT HAPPEN: got iface.Addrs() element %s that is not net.IPNet, it is %T", addr, addr)
+				aghhttp.Error(
+					r,
+					w,
+					http.StatusInternalServerError,
+					"got iface.Addrs() element %[1]s that is not net.IPNet, it is %[1]T",
+					addr)
+
 				return
 			}
 			// ignore link-local
@@ -350,8 +361,13 @@ func (s *Server) handleDHCPInterfaces(w http.ResponseWriter, r *http.Request) {
 
 	err = json.NewEncoder(w).Encode(response)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Failed to marshal json with available interfaces: %s", err)
+		aghhttp.Error(
-		return
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Failed to marshal json with available interfaces: %s",
+			err,
+		)
 	}
 }
 
@@ -455,9 +471,13 @@ func (s *Server) handleDHCPFindActiveServer(w http.ResponseWriter, r *http.Reque
 	w.Header().Set("Content-Type", "application/json")
 	err = json.NewEncoder(w).Encode(result)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Failed to marshal DHCP found json: %s", err)
+		aghhttp.Error(
-
+			r,
-		return
+			w,
+			http.StatusInternalServerError,
+			"Failed to marshal DHCP found json: %s",
+			err,
+		)
 	}
 }
 
@@ -465,13 +485,13 @@ func (s *Server) handleDHCPAddStaticLease(w http.ResponseWriter, r *http.Request
 	l := &Lease{}
 	err := json.NewDecoder(r.Body).Decode(l)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json.Decode: %s", err)
 
 		return
 	}
 
 	if l.IP == nil {
-		httpError(r, w, http.StatusBadRequest, "invalid IP")
+		aghhttp.Error(r, w, http.StatusBadRequest, "invalid IP")
 
 		return
 	}
@@ -483,7 +503,7 @@ func (s *Server) handleDHCPAddStaticLease(w http.ResponseWriter, r *http.Request
 
 		err = s.srv6.AddStaticLease(l)
 		if err != nil {
-			httpError(r, w, http.StatusBadRequest, "%s", err)
+			aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 		}
 
 		return
@@ -492,7 +512,7 @@ func (s *Server) handleDHCPAddStaticLease(w http.ResponseWriter, r *http.Request
 	l.IP = ip4
 	err = s.srv4.AddStaticLease(l)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
@@ -502,13 +522,13 @@ func (s *Server) handleDHCPRemoveStaticLease(w http.ResponseWriter, r *http.Requ
 	l := &Lease{}
 	err := json.NewDecoder(r.Body).Decode(l)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json.Decode: %s", err)
 
 		return
 	}
 
 	if l.IP == nil {
-		httpError(r, w, http.StatusBadRequest, "invalid IP")
+		aghhttp.Error(r, w, http.StatusBadRequest, "invalid IP")
 
 		return
 	}
@@ -520,7 +540,7 @@ func (s *Server) handleDHCPRemoveStaticLease(w http.ResponseWriter, r *http.Requ
 
 		err = s.srv6.RemoveStaticLease(l)
 		if err != nil {
-			httpError(r, w, http.StatusBadRequest, "%s", err)
+			aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 		}
 
 		return
@@ -529,7 +549,7 @@ func (s *Server) handleDHCPRemoveStaticLease(w http.ResponseWriter, r *http.Requ
 	l.IP = ip4
 	err = s.srv4.RemoveStaticLease(l)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
@@ -545,7 +565,7 @@ const (
 func (s *Server) handleReset(w http.ResponseWriter, r *http.Request) {
 	err := s.Stop()
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "stopping dhcp: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "stopping dhcp: %s", err)
 
 		return
 	}
@@ -583,7 +603,7 @@ func (s *Server) handleResetLeases(w http.ResponseWriter, r *http.Request) {
 	err := s.resetLeases()
 	if err != nil {
 		msg := "resetting leases: %s"
-		httpError(r, w, http.StatusInternalServerError, msg, err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, msg, err)
 
 		return
 	}

internal/dnsforward/access.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/netutil"
@@ -187,7 +188,7 @@ func (s *Server) handleAccessList(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	err := json.NewEncoder(w).Encode(j)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "encoding response: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "encoding response: %s", err)
 
 		return
 	}
@@ -251,14 +252,14 @@ func (s *Server) handleAccessSet(w http.ResponseWriter, r *http.Request) {
 	list := accessListJSON{}
 	err := json.NewDecoder(r.Body).Decode(&list)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "decoding request: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "decoding request: %s", err)
 
 		return
 	}
 
 	err = validateAccessSet(list)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, err.Error())
+		aghhttp.Error(r, w, http.StatusBadRequest, err.Error())
 
 		return
 	}
@@ -266,7 +267,7 @@ func (s *Server) handleAccessSet(w http.ResponseWriter, r *http.Request) {
 	var a *accessCtx
 	a, err = newAccessCtx(list.AllowedClients, list.DisallowedClients, list.BlockedHosts)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "creating access ctx: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "creating access ctx: %s", err)
 
 		return
 	}

internal/dnsforward/http.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/dnsproxy/proxy"
 	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/errors"
@@ -18,12 +19,6 @@ import (
 	"github.com/miekg/dns"
 )
 
-func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
-	text := fmt.Sprintf(format, args...)
-	log.Info("dns: %s %s: %s", r.Method, r.URL, text)
-	http.Error(w, text, code)
-}
-
 type dnsConfig struct {
 	Upstreams     *[]string `json:"upstream_dns"`
 	UpstreamsFile *string   `json:"upstream_dns_file"`
@@ -119,7 +114,8 @@ func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 
 	if err = json.NewEncoder(w).Encode(resp); err != nil {
-		httpError(r, w, http.StatusInternalServerError, "json.Encoder: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json.Encoder: %s", err)
+
 		return
 	}
 }
@@ -198,34 +194,52 @@ func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
 	req := dnsConfig{}
 	dec := json.NewDecoder(r.Body)
 	if err := dec.Decode(&req); err != nil {
-		httpError(r, w, http.StatusBadRequest, "json Encode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json Encode: %s", err)
+
 		return
 	}
 
 	if req.Upstreams != nil {
 		if err := ValidateUpstreams(*req.Upstreams); err != nil {
-			httpError(r, w, http.StatusBadRequest, "wrong upstreams specification: %s", err)
+			aghhttp.Error(r, w, http.StatusBadRequest, "wrong upstreams specification: %s", err)
+
 			return
 		}
 	}
 
 	if errBoot, err := req.checkBootstrap(); err != nil {
-		httpError(r, w, http.StatusBadRequest, "%s can not be used as bootstrap dns cause: %s", errBoot, err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"%s can not be used as bootstrap dns cause: %s",
+			errBoot,
+			err,
+		)
+
 		return
 	}
 
 	if !req.checkBlockingMode() {
-		httpError(r, w, http.StatusBadRequest, "blocking_mode: incorrect value")
+		aghhttp.Error(r, w, http.StatusBadRequest, "blocking_mode: incorrect value")
+
 		return
 	}
 
 	if !req.checkUpstreamsMode() {
-		httpError(r, w, http.StatusBadRequest, "upstream_mode: incorrect value")
+		aghhttp.Error(r, w, http.StatusBadRequest, "upstream_mode: incorrect value")
+
 		return
 	}
 
 	if !req.checkCacheTTL() {
-		httpError(r, w, http.StatusBadRequest, "cache_ttl_min must be less or equal than cache_ttl_max")
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"cache_ttl_min must be less or equal than cache_ttl_max",
+		)
+
 		return
 	}
 
@@ -234,8 +248,7 @@ func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
 
 	if restart {
 		if err := s.Reconfigure(nil); err != nil {
-			httpError(r, w, http.StatusInternalServerError, "%s", err)
+			aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
-			return
 		}
 	}
 }
@@ -582,7 +595,7 @@ func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 	req := &upstreamJSON{}
 	err := json.NewDecoder(r.Body).Decode(req)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "Failed to read request body: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to read request body: %s", err)
 
 		return
 	}
@@ -620,7 +633,13 @@ func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 
 	jsonVal, err := json.Marshal(result)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Unable to marshal status json: %s", err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Unable to marshal status json: %s",
+			err,
+		)
 
 		return
 	}
@@ -628,9 +647,7 @@ func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	_, err = w.Write(jsonVal)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Couldn't write body: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't write body: %s", err)
-
-		return
 	}
 }
 
@@ -641,12 +658,12 @@ func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 //  -> dnsforward.handleDNSRequest
 func (s *Server) handleDoH(w http.ResponseWriter, r *http.Request) {
 	if !s.conf.TLSAllowUnencryptedDoH && r.TLS == nil {
-		httpError(r, w, http.StatusNotFound, "Not Found")
+		aghhttp.Error(r, w, http.StatusNotFound, "Not Found")
 		return
 	}
 
 	if !s.IsRunning() {
-		httpError(r, w, http.StatusInternalServerError, "dns server is not running")
+		aghhttp.Error(r, w, http.StatusInternalServerError, "dns server is not running")
 		return
 	}
 

internal/filtering/blocked.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"net/http"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/urlfilter/rules"
 )
@@ -287,7 +288,8 @@ func (d *DNSFilter) handleBlockedServicesList(w http.ResponseWriter, r *http.Req
 	w.Header().Set("Content-Type", "application/json")
 	err := json.NewEncoder(w).Encode(list)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "json.Encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json.Encode: %s", err)
+
 		return
 	}
 }
@@ -296,7 +298,8 @@ func (d *DNSFilter) handleBlockedServicesSet(w http.ResponseWriter, r *http.Requ
 	list := []string{}
 	err := json.NewDecoder(r.Body).Decode(&list)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+
 		return
 	}
 

internal/filtering/filtering.go

@@ -864,8 +864,7 @@ func makeResult(matchedRules []rules.Rule, reason Reason) (res Result) {
 	}
 }
 
-// InitModule manually initializes blocked services map using blockedSvcListID
+// InitModule manually initializes blocked services map.
-// as list ID for the rules.
 func InitModule() {
 	initBlockedServices()
 }

internal/filtering/rewrites.go

@@ -9,6 +9,7 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/miekg/dns"
 )
@@ -206,7 +207,8 @@ func (d *DNSFilter) handleRewriteList(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	err := json.NewEncoder(w).Encode(arr)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "json.Encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json.Encode: %s", err)
+
 		return
 	}
 }
@@ -215,7 +217,8 @@ func (d *DNSFilter) handleRewriteAdd(w http.ResponseWriter, r *http.Request) {
 	jsent := rewriteEntryJSON{}
 	err := json.NewDecoder(r.Body).Decode(&jsent)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+
 		return
 	}
 
@@ -237,7 +240,8 @@ func (d *DNSFilter) handleRewriteDelete(w http.ResponseWriter, r *http.Request)
 	jsent := rewriteEntryJSON{}
 	err := json.NewDecoder(r.Body).Decode(&jsent)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json.Decode: %s", err)
+
 		return
 	}
 

internal/filtering/safebrowsing.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/cache"
 	"github.com/AdguardTeam/golibs/log"
@@ -368,12 +369,6 @@ func (d *DNSFilter) checkParental(
 	return check(sctx, res, d.parentalUpstream)
 }
 
-func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
-	text := fmt.Sprintf(format, args...)
-	log.Info("DNSFilter: %s %s: %s", r.Method, r.URL, text)
-	http.Error(w, text, code)
-}
-
 func (d *DNSFilter) handleSafeBrowsingEnable(w http.ResponseWriter, r *http.Request) {
 	d.Config.SafeBrowsingEnabled = true
 	d.Config.ConfigModified()
@@ -392,7 +387,8 @@ func (d *DNSFilter) handleSafeBrowsingStatus(w http.ResponseWriter, r *http.Requ
 		Enabled: d.Config.SafeBrowsingEnabled,
 	})
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
+
 		return
 	}
 }
@@ -415,8 +411,7 @@ func (d *DNSFilter) handleParentalStatus(w http.ResponseWriter, r *http.Request)
 		Enabled: d.Config.ParentalEnabled,
 	})
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
-		return
 	}
 }
 

internal/filtering/safesearch.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/cache"
 	"github.com/AdguardTeam/golibs/log"
 )
@@ -152,8 +153,13 @@ func (d *DNSFilter) handleSafeSearchStatus(w http.ResponseWriter, r *http.Reques
 		Enabled: d.Config.SafeSearchEnabled,
 	})
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
+		aghhttp.Error(
-		return
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Unable to write response json: %s",
+			err,
+		)
 	}
 }
 

internal/home/auth.go

@@ -13,6 +13,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/AdguardTeam/golibs/timeutil"
@@ -417,7 +418,7 @@ func handleLogin(w http.ResponseWriter, r *http.Request) {
 	req := loginJSON{}
 	err := json.NewDecoder(r.Body).Decode(&req)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "json decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json decode: %s", err)
 
 		return
 	}
@@ -429,7 +430,7 @@ func handleLogin(w http.ResponseWriter, r *http.Request) {
 	//
 	// TODO(e.burkov): Use realIP when the issue will be fixed.
 	if remoteAddr, err = netutil.SplitHost(r.RemoteAddr); err != nil {
-		httpError(w, http.StatusBadRequest, "auth: getting remote address: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "auth: getting remote address: %s", err)
 
 		return
 	}
@@ -437,7 +438,8 @@ func handleLogin(w http.ResponseWriter, r *http.Request) {
 	if blocker := Context.auth.blocker; blocker != nil {
 		if left := blocker.check(remoteAddr); left > 0 {
 			w.Header().Set("Retry-After", strconv.Itoa(int(left.Seconds())))
-			httpError(
+			aghhttp.Error(
+				r,
 				w,
 				http.StatusTooManyRequests,
 				"auth: blocked for %s",
@@ -451,7 +453,7 @@ func handleLogin(w http.ResponseWriter, r *http.Request) {
 	var cookie string
 	cookie, err = Context.auth.httpCookie(req, remoteAddr)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "crypto rand reader: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "crypto rand reader: %s", err)
 
 		return
 	}
@@ -480,7 +482,7 @@ func handleLogin(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Pragma", "no-cache")
 	w.Header().Set("Expires", "0")
 
-	returnOK(w)
+	aghhttp.OK(w)
 }
 
 func handleLogout(w http.ResponseWriter, r *http.Request) {

internal/home/clientshttp.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"net/http"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 )
 
@@ -58,7 +59,7 @@ type clientListJSON struct {
 }
 
 // respond with information about configured clients
-func (clients *clientsContainer) handleGetClients(w http.ResponseWriter, _ *http.Request) {
+func (clients *clientsContainer) handleGetClients(w http.ResponseWriter, r *http.Request) {
 	data := clientListJSON{}
 
 	clients.lock.Lock()
@@ -106,7 +107,14 @@ func (clients *clientsContainer) handleGetClients(w http.ResponseWriter, _ *http
 	w.Header().Set("Content-Type", "application/json")
 	e := json.NewEncoder(w).Encode(data)
 	if e != nil {
-		httpError(w, http.StatusInternalServerError, "Failed to encode to json: %v", e)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Failed to encode to json: %v",
+			e,
+		)
+
 		return
 	}
 }
@@ -154,7 +162,7 @@ func (clients *clientsContainer) handleAddClient(w http.ResponseWriter, r *http.
 	cj := clientJSON{}
 	err := json.NewDecoder(r.Body).Decode(&cj)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "failed to process request body: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "failed to process request body: %s", err)
 
 		return
 	}
@@ -162,11 +170,14 @@ func (clients *clientsContainer) handleAddClient(w http.ResponseWriter, r *http.
 	c := jsonToClient(cj)
 	ok, err := clients.Add(c)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
+
 		return
 	}
+
 	if !ok {
-		httpError(w, http.StatusBadRequest, "Client already exists")
+		aghhttp.Error(r, w, http.StatusBadRequest, "Client already exists")
+
 		return
 	}
 
@@ -178,19 +189,19 @@ func (clients *clientsContainer) handleDelClient(w http.ResponseWriter, r *http.
 	cj := clientJSON{}
 	err := json.NewDecoder(r.Body).Decode(&cj)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "failed to process request body: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "failed to process request body: %s", err)
 
 		return
 	}
 
 	if len(cj.Name) == 0 {
-		httpError(w, http.StatusBadRequest, "client's name must be non-empty")
+		aghhttp.Error(r, w, http.StatusBadRequest, "client's name must be non-empty")
 
 		return
 	}
 
 	if !clients.Del(cj.Name) {
-		httpError(w, http.StatusBadRequest, "Client not found")
+		aghhttp.Error(r, w, http.StatusBadRequest, "Client not found")
 		return
 	}
 
@@ -207,20 +218,22 @@ func (clients *clientsContainer) handleUpdateClient(w http.ResponseWriter, r *ht
 	dj := updateJSON{}
 	err := json.NewDecoder(r.Body).Decode(&dj)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "failed to process request body: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "failed to process request body: %s", err)
 
 		return
 	}
 
 	if len(dj.Name) == 0 {
-		httpError(w, http.StatusBadRequest, "Invalid request")
+		aghhttp.Error(r, w, http.StatusBadRequest, "Invalid request")
+
 		return
 	}
 
 	c := jsonToClient(dj.Data)
 	err = clients.Update(dj.Name, c)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
+
 		return
 	}
 
@@ -256,7 +269,7 @@ func (clients *clientsContainer) handleFindClient(w http.ResponseWriter, r *http
 	w.Header().Set("Content-Type", "application/json")
 	err := json.NewEncoder(w).Encode(data)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Couldn't write response: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't write response: %s", err)
 	}
 }
 

internal/home/config.go

@@ -1,7 +1,6 @@
 package home
 
 import (
-	"fmt"
 	"net"
 	"os"
 	"path/filepath"
@@ -274,17 +273,34 @@ func getLogSettings() logSettings {
 }
 
 // parseConfig loads configuration from the YAML file
-func parseConfig() error {
+func parseConfig() (err error) {
-	configFile := config.getConfigFilename()
+	var fileData []byte
-	log.Debug("Reading config file: %s", configFile)
+	fileData, err = readConfigFile()
-	yamlFile, err := readConfigFile()
 	if err != nil {
 		return err
 	}
+
 	config.fileData = nil
-	err = yaml.Unmarshal(yamlFile, &config)
+	err = yaml.Unmarshal(fileData, &config)
 	if err != nil {
-		log.Error("Couldn't parse config file: %s", err)
+		return err
+	}
+
+	pm := portsMap{}
+	pm.add(
+		config.BindPort,
+		config.BetaBindPort,
+		config.DNS.Port,
+	)
+	if config.TLS.Enabled {
+		pm.add(
+			config.TLS.PortHTTPS,
+			config.TLS.PortDNSOverTLS,
+			config.TLS.PortDNSOverQUIC,
+			config.TLS.PortDNSCrypt,
+		)
+	}
+	if err = pm.validate(); err != nil {
 		return err
 	}
 
@@ -299,18 +315,17 @@ func parseConfig() error {
 	return nil
 }
 
-// readConfigFile reads config file contents if it exists
+// readConfigFile reads configuration file contents.
-func readConfigFile() ([]byte, error) {
+func readConfigFile() (fileData []byte, err error) {
-	if len(config.fileData) != 0 {
+	if len(config.fileData) > 0 {
 		return config.fileData, nil
 	}
 
-	configFile := config.getConfigFilename()
+	name := config.getConfigFilename()
-	d, err := os.ReadFile(configFile)
+	log.Debug("reading config file: %s", name)
-	if err != nil {
+
-		return nil, fmt.Errorf("couldn't read config file %s: %w", configFile, err)
+	// Do not wrap the error because it's informative enough as is.
-	}
+	return os.ReadFile(name)
-	return d, nil
 }
 
 // Saves configuration to the YAML file and also saves the user filter contents to a file

internal/home/control.go

@@ -9,6 +9,7 @@ import (
 	"runtime"
 	"strings"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/AdGuardHome/internal/dnsforward"
 	"github.com/AdguardTeam/AdGuardHome/internal/version"
@@ -17,23 +18,6 @@ import (
 	"github.com/NYTimes/gziphandler"
 )
 
-// ----------------
-// helper functions
-// ----------------
-
-func returnOK(w http.ResponseWriter) {
-	_, err := fmt.Fprintf(w, "OK\n")
-	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Couldn't write body: %s", err)
-	}
-}
-
-func httpError(w http.ResponseWriter, code int, format string, args ...interface{}) {
-	text := fmt.Sprintf(format, args...)
-	log.Info(text)
-	http.Error(w, text, code)
-}
-
 // appendDNSAddrs is a convenient helper for appending a formatted form of DNS
 // addresses to a slice of strings.
 func appendDNSAddrs(dst []string, addrs ...net.IP) (res []string) {
@@ -125,12 +109,12 @@ type statusResponse struct {
 	Language        string `json:"language"`
 }
 
-func handleStatus(w http.ResponseWriter, _ *http.Request) {
+func handleStatus(w http.ResponseWriter, r *http.Request) {
 	dnsAddrs, err := collectDNSAddresses()
 	if err != nil {
 		// Don't add a lot of formatting, since the error is already
 		// wrapped by collectDNSAddresses.
-		httpError(w, http.StatusInternalServerError, "%s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
 
 		return
 	}
@@ -165,7 +149,7 @@ func handleStatus(w http.ResponseWriter, _ *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	err = json.NewEncoder(w).Encode(resp)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Unable to write response json: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
 
 		return
 	}
@@ -182,7 +166,7 @@ func handleGetProfile(w http.ResponseWriter, r *http.Request) {
 
 	data, err := json.Marshal(pj)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "json.Marshal: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json.Marshal: %s", err)
 		return
 	}
 	_, _ = w.Write(data)
@@ -295,7 +279,7 @@ func handleHTTPSRedirect(w http.ResponseWriter, r *http.Request) (ok bool) {
 
 	host, err := netutil.SplitHost(r.Host)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "bad host: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "bad host: %s", err)
 
 		return false
 	}

internal/home/controlfiltering.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/miekg/dns"
 )
@@ -49,7 +50,8 @@ func (f *Filtering) handleFilteringAddURL(w http.ResponseWriter, r *http.Request
 	fj := filterAddJSON{}
 	err := json.NewDecoder(r.Body).Decode(&fj)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to parse request body json: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to parse request body json: %s", err)
+
 		return
 	}
 
@@ -63,7 +65,8 @@ func (f *Filtering) handleFilteringAddURL(w http.ResponseWriter, r *http.Request
 
 	// Check for duplicates
 	if filterExists(fj.URL) {
-		httpError(w, http.StatusBadRequest, "Filter URL already added -- %s", fj.URL)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Filter URL already added -- %s", fj.URL)
+
 		return
 	}
 
@@ -79,17 +82,35 @@ func (f *Filtering) handleFilteringAddURL(w http.ResponseWriter, r *http.Request
 	// Download the filter contents
 	ok, err := f.update(&filt)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Couldn't fetch filter from url %s: %s", filt.URL, err)
+		aghhttp.Error(
-		return
+			r,
-	}
+			w,
-	if !ok {
+			http.StatusBadRequest,
-		httpError(w, http.StatusBadRequest, "Filter at the url %s is invalid (maybe it points to blank page?)", filt.URL)
+			"Couldn't fetch filter from url %s: %s",
+			filt.URL,
+			err,
+		)
+
 		return
 	}
 
-	// URL is deemed valid, append it to filters, update config, write new filter file and tell dns to reload it
+	if !ok {
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"Filter at the url %s is invalid (maybe it points to blank page?)",
+			filt.URL,
+		)
+
+		return
+	}
+
+	// URL is assumed valid so append it to filters, update config, write new
+	// file and reload it to engines.
 	if !filterAdd(filt) {
-		httpError(w, http.StatusBadRequest, "Filter URL already added -- %s", filt.URL)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Filter URL already added -- %s", filt.URL)
+
 		return
 	}
 
@@ -98,7 +119,7 @@ func (f *Filtering) handleFilteringAddURL(w http.ResponseWriter, r *http.Request
 
 	_, err = fmt.Fprintf(w, "OK %d rules\n", filt.RulesCount)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Couldn't write body: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't write body: %s", err)
 	}
 }
 
@@ -111,7 +132,8 @@ func (f *Filtering) handleFilteringRemoveURL(w http.ResponseWriter, r *http.Requ
 	req := request{}
 	err := json.NewDecoder(r.Body).Decode(&req)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "failed to parse request body json: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "failed to parse request body json: %s", err)
+
 		return
 	}
 
@@ -152,7 +174,7 @@ func (f *Filtering) handleFilteringRemoveURL(w http.ResponseWriter, r *http.Requ
 
 	_, err = fmt.Fprintf(w, "OK %d rules\n", deleted.RulesCount)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "couldn't write body: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "couldn't write body: %s", err)
 	}
 }
 
@@ -172,7 +194,8 @@ func (f *Filtering) handleFilteringSetURL(w http.ResponseWriter, r *http.Request
 	fj := filterURLReq{}
 	err := json.NewDecoder(r.Body).Decode(&fj)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "json decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json decode: %s", err)
+
 		return
 	}
 
@@ -228,7 +251,8 @@ func (f *Filtering) handleFilteringSetRules(w http.ResponseWriter, r *http.Reque
 	// This use of ReadAll is safe, because request's body is now limited.
 	body, err := io.ReadAll(r.Body)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to read request body: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to read request body: %s", err)
+
 		return
 	}
 
@@ -250,7 +274,8 @@ func (f *Filtering) handleFilteringRefresh(w http.ResponseWriter, r *http.Reques
 	req := Req{}
 	err = json.NewDecoder(r.Body).Decode(&req)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "json decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json decode: %s", err)
+
 		return
 	}
 
@@ -270,13 +295,15 @@ func (f *Filtering) handleFilteringRefresh(w http.ResponseWriter, r *http.Reques
 		resp.Updated, err = f.refreshFilters(flags|filterRefreshForce, false)
 	}()
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "%s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
+
 		return
 	}
 
 	js, err := json.Marshal(resp)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "json encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json encode: %s", err)
+
 		return
 	}
 	w.Header().Set("Content-Type", "application/json")
@@ -335,13 +362,14 @@ func (f *Filtering) handleFilteringStatus(w http.ResponseWriter, r *http.Request
 
 	jsonVal, err := json.Marshal(resp)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "json encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json encode: %s", err)
+
 		return
 	}
 	w.Header().Set("Content-Type", "application/json")
 	_, err = w.Write(jsonVal)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "http write: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "http write: %s", err)
 	}
 }
 
@@ -350,12 +378,14 @@ func (f *Filtering) handleFilteringConfig(w http.ResponseWriter, r *http.Request
 	req := filteringConfig{}
 	err := json.NewDecoder(r.Body).Decode(&req)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "json decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json decode: %s", err)
+
 		return
 	}
 
 	if !checkFiltersUpdateIntervalHours(req.Interval) {
-		httpError(w, http.StatusBadRequest, "Unsupported interval")
+		aghhttp.Error(r, w, http.StatusBadRequest, "Unsupported interval")
+
 		return
 	}
 
@@ -408,7 +438,15 @@ func (f *Filtering) handleCheckHost(w http.ResponseWriter, r *http.Request) {
 	Context.dnsFilter.ApplyBlockedServices(&setts, nil, true)
 	result, err := Context.dnsFilter.CheckHost(host, dns.TypeA, &setts)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "couldn't apply filtering: %s: %s", host, err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusInternalServerError,
+			"couldn't apply filtering: %s: %s",
+			host,
+			err,
+		)
+
 		return
 	}
 
@@ -433,7 +471,8 @@ func (f *Filtering) handleCheckHost(w http.ResponseWriter, r *http.Request) {
 
 	js, err := json.Marshal(resp)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "json encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json encode: %s", err)
+
 		return
 	}
 	w.Header().Set("Content-Type", "application/json")

internal/home/controlinstall.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
@@ -34,7 +35,8 @@ func (web *Web) handleInstallGetAddresses(w http.ResponseWriter, r *http.Request
 
 	ifaces, err := aghnet.GetValidNetInterfacesForWeb()
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err)
+
 		return
 	}
 
@@ -46,7 +48,14 @@ func (web *Web) handleInstallGetAddresses(w http.ResponseWriter, r *http.Request
 	w.Header().Set("Content-Type", "application/json")
 	err = json.NewEncoder(w).Encode(data)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Unable to marshal default addresses to json: %s", err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Unable to marshal default addresses to json: %s",
+			err,
+		)
+
 		return
 	}
 }
@@ -84,23 +93,32 @@ type checkConfigResp struct {
 func (web *Web) handleInstallCheckConfig(w http.ResponseWriter, r *http.Request) {
 	reqData := checkConfigReq{}
 	respData := checkConfigResp{}
+
 	err := json.NewDecoder(r.Body).Decode(&reqData)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to parse 'check_config' JSON data: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to parse 'check_config' JSON data: %s", err)
+
 		return
 	}
 
-	if reqData.Web.Port != 0 && reqData.Web.Port != config.BindPort && reqData.Web.Port != config.BetaBindPort {
+	pm := portsMap{}
-		err = aghnet.CheckPortAvailable(reqData.Web.IP, reqData.Web.Port)
+	pm.add(config.BindPort, config.BetaBindPort, reqData.Web.Port)
+	if err = pm.validate(); err != nil {
+		respData.Web.Status = err.Error()
+	} else if reqData.Web.Port != 0 {
+		err = aghnet.CheckPort("tcp", reqData.Web.IP, reqData.Web.Port)
 		if err != nil {
 			respData.Web.Status = err.Error()
 		}
 	}
 
-	if reqData.DNS.Port != 0 {
+	pm.add(reqData.DNS.Port)
-		err = aghnet.CheckPacketPortAvailable(reqData.DNS.IP, reqData.DNS.Port)
+	if err = pm.validate(); err != nil {
+		respData.DNS.Status = err.Error()
+	} else if reqData.DNS.Port != 0 {
+		err = aghnet.CheckPort("udp", reqData.DNS.IP, reqData.DNS.Port)
 
-		if aghnet.ErrorIsAddrInUse(err) {
+		if aghnet.IsAddrInUse(err) {
 			canAutofix := checkDNSStubListener()
 			if canAutofix && reqData.DNS.Autofix {
 
@@ -109,7 +127,7 @@ func (web *Web) handleInstallCheckConfig(w http.ResponseWriter, r *http.Request)
 					log.Error("Couldn't disable DNSStubListener: %s", err)
 				}
 
-				err = aghnet.CheckPacketPortAvailable(reqData.DNS.IP, reqData.DNS.Port)
+				err = aghnet.CheckPort("udp", reqData.DNS.IP, reqData.DNS.Port)
 				canAutofix = false
 			}
 
@@ -117,7 +135,7 @@ func (web *Web) handleInstallCheckConfig(w http.ResponseWriter, r *http.Request)
 		}
 
 		if err == nil {
-			err = aghnet.CheckPortAvailable(reqData.DNS.IP, reqData.DNS.Port)
+			err = aghnet.CheckPort("tcp", reqData.DNS.IP, reqData.DNS.Port)
 		}
 
 		if err != nil {
@@ -130,7 +148,8 @@ func (web *Web) handleInstallCheckConfig(w http.ResponseWriter, r *http.Request)
 	w.Header().Set("Content-Type", "application/json")
 	err = json.NewEncoder(w).Encode(respData)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Unable to marshal JSON: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Unable to marshal JSON: %s", err)
+
 		return
 	}
 }
@@ -287,21 +306,21 @@ func shutdownSrv(ctx context.Context, srv *http.Server) {
 func (web *Web) handleInstallConfigure(w http.ResponseWriter, r *http.Request) {
 	req, restartHTTP, err := decodeApplyConfigReq(r.Body)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
 
-	err = aghnet.CheckPacketPortAvailable(req.DNS.IP, req.DNS.Port)
+	err = aghnet.CheckPort("udp", req.DNS.IP, req.DNS.Port)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
 
-	err = aghnet.CheckPortAvailable(req.DNS.IP, req.DNS.Port)
+	err = aghnet.CheckPort("tcp", req.DNS.IP, req.DNS.Port)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
@@ -315,28 +334,29 @@ func (web *Web) handleInstallConfigure(w http.ResponseWriter, r *http.Request) {
 	config.DNS.BindHosts = []net.IP{req.DNS.IP}
 	config.DNS.Port = req.DNS.Port
 
-	// TODO(e.burkov): StartMods() should be put in a separate goroutine at
+	// TODO(e.burkov): StartMods() should be put in a separate goroutine at the
-	// the moment we'll allow setting up TLS in the initial configuration or
+	// moment we'll allow setting up TLS in the initial configuration or the
-	// the configuration itself will use HTTPS protocol, because the
+	// configuration itself will use HTTPS protocol, because the underlying
-	// underlying functions potentially restart the HTTPS server.
+	// functions potentially restart the HTTPS server.
 	err = StartMods()
 	if err != nil {
 		Context.firstRun = true
 		copyInstallSettings(config, curConfig)
-		httpError(w, http.StatusInternalServerError, "%s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
 
 		return
 	}
 
-	u := User{}
+	u := &User{
-	u.Name = req.Username
+		Name: req.Username,
-	Context.auth.UserAdd(&u, req.Password)
+	}
+	Context.auth.UserAdd(u, req.Password)
 
 	err = config.write()
 	if err != nil {
 		Context.firstRun = true
 		copyInstallSettings(config, curConfig)
-		httpError(w, http.StatusInternalServerError, "Couldn't write config: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't write config: %s", err)
 
 		return
 	}
@@ -347,7 +367,7 @@ func (web *Web) handleInstallConfigure(w http.ResponseWriter, r *http.Request) {
 
 	registerControlHandlers()
 
-	returnOK(w)
+	aghhttp.OK(w)
 	if f, ok := w.(http.Flusher); ok {
 		f.Flush()
 	}
@@ -386,7 +406,7 @@ func decodeApplyConfigReq(r io.Reader) (req *applyConfigReq, restartHTTP bool, e
 
 	restartHTTP = !config.BindHost.Equal(req.Web.IP) || config.BindPort != req.Web.Port
 	if restartHTTP {
-		err = aghnet.CheckPortAvailable(req.Web.IP, req.Web.Port)
+		err = aghnet.CheckPort("tcp", req.Web.IP, req.Web.Port)
 		if err != nil {
 			return nil, false, fmt.Errorf(
 				"checking address %s:%d: %w",
@@ -437,12 +457,14 @@ func (web *Web) handleInstallCheckConfigBeta(w http.ResponseWriter, r *http.Requ
 	reqData := checkConfigReqBeta{}
 	err := json.NewDecoder(r.Body).Decode(&reqData)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to parse 'check_config' JSON data: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to parse 'check_config' JSON data: %s", err)
+
 		return
 	}
 
 	if len(reqData.DNS.IP) == 0 || len(reqData.Web.IP) == 0 {
-		httpError(w, http.StatusBadRequest, http.StatusText(http.StatusBadRequest))
+		aghhttp.Error(r, w, http.StatusBadRequest, http.StatusText(http.StatusBadRequest))
+
 		return
 	}
 
@@ -464,7 +486,14 @@ func (web *Web) handleInstallCheckConfigBeta(w http.ResponseWriter, r *http.Requ
 
 	err = json.NewEncoder(nonBetaReqBody).Encode(nonBetaReqData)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to encode 'check_config' JSON data: %s", err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"Failed to encode 'check_config' JSON data: %s",
+			err,
+		)
+
 		return
 	}
 	body := nonBetaReqBody.String()
@@ -505,12 +534,14 @@ func (web *Web) handleInstallConfigureBeta(w http.ResponseWriter, r *http.Reques
 	reqData := applyConfigReqBeta{}
 	err := json.NewDecoder(r.Body).Decode(&reqData)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to parse 'check_config' JSON data: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to parse 'check_config' JSON data: %s", err)
+
 		return
 	}
 
 	if len(reqData.DNS.IP) == 0 || len(reqData.Web.IP) == 0 {
-		httpError(w, http.StatusBadRequest, http.StatusText(http.StatusBadRequest))
+		aghhttp.Error(r, w, http.StatusBadRequest, http.StatusText(http.StatusBadRequest))
+
 		return
 	}
 
@@ -531,7 +562,14 @@ func (web *Web) handleInstallConfigureBeta(w http.ResponseWriter, r *http.Reques
 
 	err = json.NewEncoder(nonBetaReqBody).Encode(nonBetaReqData)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to encode 'check_config' JSON data: %s", err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"Failed to encode 'check_config' JSON data: %s",
+			err,
+		)
+
 		return
 	}
 	body := nonBetaReqBody.String()
@@ -564,7 +602,8 @@ func (web *Web) handleInstallGetAddressesBeta(w http.ResponseWriter, r *http.Req
 
 	ifaces, err := aghnet.GetValidNetInterfacesForWeb()
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err)
+
 		return
 	}
 
@@ -573,7 +612,14 @@ func (web *Web) handleInstallGetAddressesBeta(w http.ResponseWriter, r *http.Req
 	w.Header().Set("Content-Type", "application/json")
 	err = json.NewEncoder(w).Encode(data)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Unable to marshal default addresses to json: %s", err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Unable to marshal default addresses to json: %s",
+			err,
+		)
+
 		return
 	}
 }

internal/home/controlupdate.go

@@ -11,6 +11,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/AdGuardHome/internal/updater"
 	"github.com/AdguardTeam/golibs/errors"
@@ -43,7 +44,8 @@ func handleGetVersionJSON(w http.ResponseWriter, r *http.Request) {
 	if r.ContentLength != 0 {
 		err = json.NewDecoder(r.Body).Decode(req)
 		if err != nil {
-			httpError(w, http.StatusBadRequest, "JSON parse: %s", err)
+			aghhttp.Error(r, w, http.StatusBadRequest, "JSON parse: %s", err)
+
 			return
 		}
 	}
@@ -77,7 +79,15 @@ func handleGetVersionJSON(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		vcu := Context.updater.VersionCheckURL()
 		// TODO(a.garipov): Figure out the purpose of %T verb.
-		httpError(w, http.StatusBadGateway, "Couldn't get version check json from %s: %T %s\n", vcu, err, err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadGateway,
+			"Couldn't get version check json from %s: %T %s\n",
+			vcu,
+			err,
+			err,
+		)
 
 		return
 	}
@@ -87,24 +97,26 @@ func handleGetVersionJSON(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	err = json.NewEncoder(w).Encode(resp)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Couldn't write body: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't write body: %s", err)
 	}
 }
 
 // handleUpdate performs an update to the latest available version procedure.
-func handleUpdate(w http.ResponseWriter, _ *http.Request) {
+func handleUpdate(w http.ResponseWriter, r *http.Request) {
 	if Context.updater.NewVersion() == "" {
-		httpError(w, http.StatusBadRequest, "/update request isn't allowed now")
+		aghhttp.Error(r, w, http.StatusBadRequest, "/update request isn't allowed now")
+
 		return
 	}
 
 	err := Context.updater.Update()
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "%s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
+
 		return
 	}
 
-	returnOK(w)
+	aghhttp.OK(w)
 	if f, ok := w.(http.Flusher); ok {
 		f.Flush()
 	}

internal/home/home.go

@@ -159,14 +159,11 @@ func setupContext(args options) {
 	}
 
 	if !Context.firstRun {
-		// Do the upgrade if necessary
+		// Do the upgrade if necessary.
 		err := upgradeConfig()
-		if err != nil {
+		fatalOnError(err)
-			log.Fatal(err)
-		}
 
-		err = parseConfig()
+		if err = parseConfig(); err != nil {
-		if err != nil {
 			log.Error("parsing configuration file: %s", err)
 
 			os.Exit(1)
@@ -186,15 +183,15 @@ func setupContext(args options) {
 // unsupported errors and returns nil.  If err is nil, logIfUnsupported returns
 // nil.  Otherise, it returns err.
 func logIfUnsupported(msg string, err error) (outErr error) {
-	if unsupErr := (&aghos.UnsupportedError{}); errors.As(err, &unsupErr) {
+	if errors.As(err, new(*aghos.UnsupportedError)) {
 		log.Debug(msg, err)
-	} else if err != nil {
-		return err
-	}
 
 		return nil
 	}
 
+	return err
+}
+
 // configureOS sets the OS-related configuration.
 func configureOS(conf *configuration) (err error) {
 	osConf := conf.OSConfig
@@ -297,13 +294,32 @@ func setupConfig(args options) (err error) {
 
 	Context.clients.Init(config.Clients, Context.dhcpServer, Context.etcHosts)
 
+	if args.bindPort != 0 {
+		pm := portsMap{}
+		pm.add(
+			args.bindPort,
+			config.BetaBindPort,
+			config.DNS.Port,
+		)
+		if config.TLS.Enabled {
+			pm.add(
+				config.TLS.PortHTTPS,
+				config.TLS.PortDNSOverTLS,
+				config.TLS.PortDNSOverQUIC,
+				config.TLS.PortDNSCrypt,
+			)
+		}
+		if err = pm.validate(); err != nil {
+			return err
+		}
+
+		config.BindPort = args.bindPort
+	}
+
 	// override bind host/port from the console
 	if args.bindHost != nil {
 		config.BindHost = args.bindHost
 	}
-	if args.bindPort != 0 {
-		config.BindPort = args.bindPort
-	}
 	if len(args.pidFile) != 0 && writePIDFile(args.pidFile) {
 		Context.pidFileName = args.pidFile
 	}
@@ -766,8 +782,7 @@ func printHTTPAddresses(proto string) {
 		port = tlsConf.PortHTTPS
 	}
 
-	// TODO(e.burkov): Inspect and perhaps merge with the previous
+	// TODO(e.burkov): Inspect and perhaps merge with the previous condition.
-	// condition.
 	if proto == schemeHTTPS && tlsConf.ServerName != "" {
 		printWebAddrs(proto, tlsConf.ServerName, tlsConf.PortHTTPS, 0)
 

internal/home/i18n.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/stringutil"
 )
@@ -96,5 +97,5 @@ func handleI18nChangeLanguage(w http.ResponseWriter, r *http.Request) {
 	}()
 
 	onConfigModified()
-	returnOK(w)
+	aghhttp.OK(w)
 }

internal/home/portsmap.go

@@ -0,0 +1,63 @@
+package home
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/stringutil"
+)
+
+// portsMap is a helper type for mapping a network port to the number of its
+// users.
+type portsMap map[int]int
+
+// add binds each of ps.  Zeroes are skipped.
+func (pm portsMap) add(ps ...int) {
+	for _, p := range ps {
+		if p == 0 {
+			continue
+		}
+
+		pm[p]++
+	}
+}
+
+// validate returns an error about all the ports bound several times.
+func (pm portsMap) validate() (err error) {
+	overbound := []int{}
+	for p, num := range pm {
+		if num > 1 {
+			overbound = append(overbound, p)
+			pm[p] = 1
+		}
+	}
+
+	switch len(overbound) {
+	case 0:
+		return nil
+	case 1:
+		return fmt.Errorf("port %d is already used", overbound[0])
+	default:
+		b := &strings.Builder{}
+
+		// TODO(e.burkov, a.garipov):  Add JoinToBuilder helper to stringutil.
+		stringutil.WriteToBuilder(b, "ports ", strconv.Itoa(overbound[0]))
+		for _, p := range overbound[1:] {
+			stringutil.WriteToBuilder(b, ", ", strconv.Itoa(p))
+		}
+		stringutil.WriteToBuilder(b, " are already used")
+
+		return errors.Error(b.String())
+	}
+}
+
+// validatePorts is a helper function for a single-step ports binding
+// validation.
+func validatePorts(ps ...int) (err error) {
+	pm := portsMap{}
+	pm.add(ps...)
+
+	return pm.validate()
+}

internal/home/tls.go

@@ -20,6 +20,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/AdGuardHome/internal/dnsforward"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
@@ -224,7 +225,7 @@ type tlsConfigSettingsExt struct {
 	PrivateKeySaved bool `yaml:"-" json:"private_key_saved,inline"`
 }
 
-func (t *TLSMod) handleTLSStatus(w http.ResponseWriter, _ *http.Request) {
+func (t *TLSMod) handleTLSStatus(w http.ResponseWriter, r *http.Request) {
 	t.confLock.Lock()
 	data := tlsConfig{
 		tlsConfigSettingsExt: tlsConfigSettingsExt{
@@ -233,13 +234,14 @@ func (t *TLSMod) handleTLSStatus(w http.ResponseWriter, _ *http.Request) {
 		tlsConfigStatus: t.status,
 	}
 	t.confLock.Unlock()
-	marshalTLS(w, data)
+	marshalTLS(w, r, data)
 }
 
 func (t *TLSMod) handleTLSValidate(w http.ResponseWriter, r *http.Request) {
 	setts, err := unmarshalTLS(r)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to unmarshal TLS config: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to unmarshal TLS config: %s", err)
+
 		return
 	}
 
@@ -247,8 +249,31 @@ func (t *TLSMod) handleTLSValidate(w http.ResponseWriter, r *http.Request) {
 		setts.PrivateKey = t.conf.PrivateKey
 	}
 
+	if setts.Enabled {
+		if err = validatePorts(
+			config.BindPort,
+			config.BetaBindPort,
+			config.DNS.Port,
+			setts.PortHTTPS,
+			setts.PortDNSOverTLS,
+			setts.PortDNSOverQUIC,
+			setts.PortDNSCrypt,
+		); err != nil {
+			aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
+
+			return
+		}
+	}
+
 	if !WebCheckPortAvailable(setts.PortHTTPS) {
-		httpError(w, http.StatusBadRequest, "port %d is not available, cannot enable HTTPS on it", setts.PortHTTPS)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"port %d is not available, cannot enable HTTPS on it",
+			setts.PortHTTPS,
+		)
+
 		return
 	}
 
@@ -261,7 +286,8 @@ func (t *TLSMod) handleTLSValidate(w http.ResponseWriter, r *http.Request) {
 		tlsConfigSettingsExt: setts,
 		tlsConfigStatus:      status,
 	}
-	marshalTLS(w, data)
+
+	marshalTLS(w, r, data)
 }
 
 func (t *TLSMod) setConfig(newConf tlsConfigSettings, status tlsConfigStatus) (restartHTTPS bool) {
@@ -302,7 +328,8 @@ func (t *TLSMod) setConfig(newConf tlsConfigSettings, status tlsConfigStatus) (r
 func (t *TLSMod) handleTLSConfigure(w http.ResponseWriter, r *http.Request) {
 	data, err := unmarshalTLS(r)
 	if err != nil {
-		httpError(w, http.StatusBadRequest, "Failed to unmarshal TLS config: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "Failed to unmarshal TLS config: %s", err)
+
 		return
 	}
 
@@ -310,8 +337,32 @@ func (t *TLSMod) handleTLSConfigure(w http.ResponseWriter, r *http.Request) {
 		data.PrivateKey = t.conf.PrivateKey
 	}
 
+	if data.Enabled {
+		if err = validatePorts(
+			config.BindPort,
+			config.BetaBindPort,
+			config.DNS.Port,
+			data.PortHTTPS,
+			data.PortDNSOverTLS,
+			data.PortDNSOverQUIC,
+			data.PortDNSCrypt,
+		); err != nil {
+			aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
+
+			return
+		}
+	}
+
+	// TODO(e.burkov):  Investigate and perhaps check other ports.
 	if !WebCheckPortAvailable(data.PortHTTPS) {
-		httpError(w, http.StatusBadRequest, "port %d is not available, cannot enable HTTPS on it", data.PortHTTPS)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusBadRequest,
+			"port %d is not available, cannot enable HTTPS on it",
+			data.PortHTTPS,
+		)
+
 		return
 	}
 
@@ -321,7 +372,7 @@ func (t *TLSMod) handleTLSConfigure(w http.ResponseWriter, r *http.Request) {
 			tlsConfigSettingsExt: data,
 			tlsConfigStatus:      t.status,
 		}
-		marshalTLS(w, data2)
+		marshalTLS(w, r, data2)
 
 		return
 	}
@@ -334,7 +385,7 @@ func (t *TLSMod) handleTLSConfigure(w http.ResponseWriter, r *http.Request) {
 
 	err = reconfigureDNSServer()
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "%s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
 
 		return
 	}
@@ -344,15 +395,15 @@ func (t *TLSMod) handleTLSConfigure(w http.ResponseWriter, r *http.Request) {
 		tlsConfigStatus:      t.status,
 	}
 
-	marshalTLS(w, data2)
+	marshalTLS(w, r, data2)
 	if f, ok := w.(http.Flusher); ok {
 		f.Flush()
 	}
 
-	// The background context is used because the TLSConfigChanged wraps
+	// The background context is used because the TLSConfigChanged wraps context
-	// context with timeout on its own and shuts down the server, which
+	// with timeout on its own and shuts down the server, which handles current
-	// handles current request. It is also should be done in a separate
+	// request. It is also should be done in a separate goroutine due to the
-	// goroutine due to the same reason.
+	// same reason.
 	if restartHTTPS {
 		go func() {
 			Context.web.TLSConfigChanged(context.Background(), data.tlsConfigSettings)
@@ -595,7 +646,7 @@ func unmarshalTLS(r *http.Request) (tlsConfigSettingsExt, error) {
 	return data, nil
 }
 
-func marshalTLS(w http.ResponseWriter, data tlsConfig) {
+func marshalTLS(w http.ResponseWriter, r *http.Request, data tlsConfig) {
 	w.Header().Set("Content-Type", "application/json")
 
 	if data.CertificateChain != "" {
@@ -610,8 +661,13 @@ func marshalTLS(w http.ResponseWriter, data tlsConfig) {
 
 	err := json.NewEncoder(w).Encode(data)
 	if err != nil {
-		httpError(w, http.StatusInternalServerError, "Failed to marshal json with TLS status: %s", err)
+		aghhttp.Error(
-		return
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Failed to marshal json with TLS status: %s",
+			err,
+		)
 	}
 }
 

internal/home/web.go

@@ -114,17 +114,8 @@ func CreateWeb(conf *webConfig) *Web {
 // WebCheckPortAvailable - check if port is available
 // BUT: if we are already using this port, no need
 func WebCheckPortAvailable(port int) bool {
-	alreadyRunning := false
+	return Context.web.httpsServer.server != nil ||
-	if Context.web.httpsServer.server != nil {
+		aghnet.CheckPort("tcp", config.BindHost, port) == nil
-		alreadyRunning = true
-	}
-	if !alreadyRunning {
-		err := aghnet.CheckPortAvailable(config.BindHost, port)
-		if err != nil {
-			return false
-		}
-	}
-	return true
 }
 
 // TLSConfigChanged updates the TLS configuration and restarts the HTTPS server

internal/querylog/http.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/jsonutil"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/stringutil"
@@ -33,18 +34,11 @@ func (l *queryLog) initWeb() {
 	l.conf.HTTPRegister(http.MethodPost, "/control/querylog_config", l.handleQueryLogConfig)
 }
 
-func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
-	text := fmt.Sprintf(format, args...)
-
-	log.Info("QueryLog: %s %s: %s", r.Method, r.URL, text)
-
-	http.Error(w, text, code)
-}
-
 func (l *queryLog) handleQueryLog(w http.ResponseWriter, r *http.Request) {
 	params, err := l.parseSearchParams(r)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "failed to parse params: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "failed to parse params: %s", err)
+
 		return
 	}
 
@@ -56,14 +50,21 @@ func (l *queryLog) handleQueryLog(w http.ResponseWriter, r *http.Request) {
 
 	jsonVal, err := json.Marshal(data)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Couldn't marshal data into json: %s", err)
+		aghhttp.Error(
+			r,
+			w,
+			http.StatusInternalServerError,
+			"Couldn't marshal data into json: %s",
+			err,
+		)
+
 		return
 	}
 
 	w.Header().Set("Content-Type", "application/json")
 	_, err = w.Write(jsonVal)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "Unable to write response json: %s", err)
 	}
 }
 
@@ -80,13 +81,15 @@ func (l *queryLog) handleQueryLogInfo(w http.ResponseWriter, r *http.Request) {
 
 	jsonVal, err := json.Marshal(resp)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "json encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json encode: %s", err)
+
 		return
 	}
+
 	w.Header().Set("Content-Type", "application/json")
 	_, err = w.Write(jsonVal)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "http write: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "http write: %s", err)
 	}
 }
 
@@ -109,13 +112,15 @@ func (l *queryLog) handleQueryLogConfig(w http.ResponseWriter, r *http.Request)
 	d := &qlogConfig{}
 	req, err := jsonutil.DecodeObject(d, r.Body)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "%s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
+
 		return
 	}
 
 	ivl := time.Duration(float64(timeutil.Day) * d.Interval)
 	if req.Exists("interval") && !checkInterval(ivl) {
-		httpError(r, w, http.StatusBadRequest, "Unsupported interval")
+		aghhttp.Error(r, w, http.StatusBadRequest, "Unsupported interval")
+
 		return
 	}
 

internal/stats/http.go

@@ -4,21 +4,13 @@ package stats
 
 import (
 	"encoding/json"
-	"fmt"
 	"net/http"
 	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
 	"github.com/AdguardTeam/golibs/log"
 )
 
-func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) {
-	text := fmt.Sprintf(format, args...)
-
-	log.Info("Stats: %s %s: %s", r.Method, r.URL, text)
-
-	http.Error(w, text, code)
-}
-
 // topAddrs is an alias for the types of the TopFoo fields of statsResponse.
 // The key is either a client's address or a requested address.
 type topAddrs = map[string]uint64
@@ -71,7 +63,7 @@ func (s *statsCtx) handleStats(w http.ResponseWriter, r *http.Request) {
 		log.Debug("stats: prepared data in %v", time.Since(start))
 
 		if !ok {
-			httpError(r, w, http.StatusInternalServerError, "Couldn't get statistics data")
+			aghhttp.Error(r, w, http.StatusInternalServerError, "Couldn't get statistics data")
 
 			return
 		}
@@ -81,7 +73,7 @@ func (s *statsCtx) handleStats(w http.ResponseWriter, r *http.Request) {
 
 	err := json.NewEncoder(w).Encode(resp)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "json encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json encode: %s", err)
 
 		return
 	}
@@ -98,13 +90,14 @@ func (s *statsCtx) handleStatsInfo(w http.ResponseWriter, r *http.Request) {
 
 	data, err := json.Marshal(resp)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "json encode: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "json encode: %s", err)
+
 		return
 	}
 	w.Header().Set("Content-Type", "application/json")
 	_, err = w.Write(data)
 	if err != nil {
-		httpError(r, w, http.StatusInternalServerError, "http write: %s", err)
+		aghhttp.Error(r, w, http.StatusInternalServerError, "http write: %s", err)
 	}
 }
 
@@ -113,12 +106,14 @@ func (s *statsCtx) handleStatsConfig(w http.ResponseWriter, r *http.Request) {
 	reqData := config{}
 	err := json.NewDecoder(r.Body).Decode(&reqData)
 	if err != nil {
-		httpError(r, w, http.StatusBadRequest, "json decode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "json decode: %s", err)
+
 		return
 	}
 
 	if !checkInterval(reqData.IntervalDays) {
-		httpError(r, w, http.StatusBadRequest, "Unsupported interval")
+		aghhttp.Error(r, w, http.StatusBadRequest, "Unsupported interval")
+
 		return
 	}
 

main.go

@@ -6,6 +6,10 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/internal/home"
 )
 
+// 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 build2
 var clientBuildFS embed.FS