Fix dns sniffer

common/sniff/dns.go

@@ -11,6 +11,7 @@ import (
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/buf"
+	M "github.com/sagernet/sing/common/metadata"
 	"github.com/sagernet/sing/common/task"
 
 	mDNS "github.com/miekg/dns"
@@ -49,5 +50,8 @@ func DomainNameQuery(ctx context.Context, packet []byte) (*adapter.InboundContex
 	if err != nil {
 		return nil, err
 	}
+	if len(msg.Question) == 0 || msg.Question[0].Qclass != mDNS.ClassINET || !M.IsDomainName(msg.Question[0].Name) {
+		return nil, os.ErrInvalid
+	}
 	return &adapter.InboundContext{Protocol: C.ProtocolDNS}, nil
 }

common/sniff/domain.go

@@ -1,6 +0,0 @@
-package sniff
-
-import _ "unsafe" // for linkname
-
-//go:linkname IsDomainName net.isDomainName
-func IsDomainName(domain string) bool