Fix errors usage

Author: nekohasekai

common/baderror/baderror.go

@@ -2,11 +2,10 @@ package baderror
 
 import (
 	"context"
+	"errors"
 	"io"
 	"net"
 	"strings"
-
-	E "github.com/sagernet/sing/common/exceptions"
 )
 
 func Contains(err error, msgList ...string) bool {
@@ -22,8 +21,7 @@ func WrapH2(err error) error {
 	if err == nil {
 		return nil
 	}
-	err = E.Unwrap(err)
-	if err == io.ErrUnexpectedEOF {
+	if errors.Is(err, io.ErrUnexpectedEOF) {
 		return io.EOF
 	}
 	if Contains(err, "client disconnected", "body closed by handler", "response body closed", "; CANCEL") {

common/exceptions/inner.go

@@ -1,24 +1,14 @@
 package exceptions
 
-import "github.com/sagernet/sing/common"
+import (
+	"errors"
 
-type HasInnerError interface {
-	Unwrap() error
-}
+	"github.com/sagernet/sing/common"
+)
 
+// Deprecated: Use errors.Unwrap instead.
 func Unwrap(err error) error {
-	for {
-		inner, ok := err.(HasInnerError)
-		if !ok {
-			break
-		}
-		innerErr := inner.Unwrap()
-		if innerErr == nil {
-			break
-		}
-		err = innerErr
-	}
-	return err
+	return errors.Unwrap(err)
 }
 
 func Cast[T any](err error) (T, bool) {

common/exceptions/multi.go

@@ -63,12 +63,5 @@ func IsMulti(err error, targetList ...error) bool {
 			return true
 		}
 	}
-	err = Unwrap(err)
-	multiErr, isMulti := err.(MultiError)
-	if !isMulti {
-		return false
-	}
-	return common.All(multiErr.Unwrap(), func(it error) bool {
-		return IsMulti(it, targetList...)
-	})
+	return false
 }