all: rm aghos unsupported err

internal/aghos/os.go

@@ -19,25 +19,9 @@ import (
 	"github.com/AdguardTeam/golibs/log"
 )
 
-// UnsupportedError is returned by functions and methods when a particular
-// operation Op cannot be performed on the current OS.
-type UnsupportedError struct {
-	Op string
-	OS string
-}
-
-// Error implements the error interface for *UnsupportedError.
-func (err *UnsupportedError) Error() (msg string) {
-	return fmt.Sprintf("%s is unsupported on %s", err.Op, err.OS)
-}
-
-// Unsupported is a helper that returns an *UnsupportedError with the Op field
-// set to op and the OS field set to the current OS.
+// Unsupported is a helper that returns a wrapped [errors.ErrUnsupported].
 func Unsupported(op string) (err error) {
-	return &UnsupportedError{
-		Op: op,
-		OS: runtime.GOOS,
-	}
+	return fmt.Errorf("%s: not supported on %s: %w", op, runtime.GOOS, errors.ErrUnsupported)
 }
 
 // SetRlimit sets user-specified limit of how many fd's we can use.

internal/dnsforward/ipset.go

@@ -6,7 +6,6 @@ import (
 	"os"
 	"strings"
 
-	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/AdGuardHome/internal/ipset"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
@@ -35,7 +34,7 @@ func (c *ipsetCtx) init(ipsetConf []string) (err error) {
 		log.Info("ipset: warning: cannot initialize: %s", err)
 
 		return nil
-	} else if unsupErr := (&aghos.UnsupportedError{}); errors.As(err, &unsupErr) {
+	} else if errors.Is(err, errors.ErrUnsupported) {
 		log.Info("ipset: warning: %s", err)
 
 		return nil

internal/home/home.go

@@ -178,7 +178,7 @@ func setupContext(opts options) (err error) {
 // unsupported errors and returns nil.  If err is nil, logIfUnsupported returns
 // nil.  Otherwise, it returns err.
 func logIfUnsupported(msg string, err error) (outErr error) {
-	if errors.As(err, new(*aghos.UnsupportedError)) {
+	if errors.Is(err, errors.ErrUnsupported) {
 		log.Debug(msg, err)
 
 		return nil

internal/ipset/ipset.go

@@ -22,8 +22,8 @@ type Manager interface {
 //
 //	DOMAIN[,DOMAIN].../IPSET_NAME[,IPSET_NAME]...
 //
-// If ipsetConf is empty, msg and err are nil.  The error is of type
-// *aghos.UnsupportedError if the OS is not supported.
+// If ipsetConf is empty, msg and err are nil.  The error's chain contains
+// [errors.UnsupportedError] if current OS is not supported.
 func NewManager(ipsetConf []string) (mgr Manager, err error) {
 	if len(ipsetConf) == 0 {
 		return nil, nil