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

route/router.go

@@ -554,7 +554,7 @@ func (r *Router) RouteConnection(ctx context.Context, conn net.Conn, metadata ad
 		if err == nil {
 			metadata.Protocol = sniffMetadata.Protocol
 			metadata.Domain = sniffMetadata.Domain
-			if metadata.SniffOverrideDestination && sniff.IsDomainName(metadata.Domain) {
+			if metadata.SniffOverrideDestination && M.IsDomainName(metadata.Domain) {
 				metadata.Destination = M.Socksaddr{
 					Fqdn: metadata.Domain,
 					Port: metadata.Destination.Port,
@@ -631,7 +631,7 @@ func (r *Router) RoutePacketConnection(ctx context.Context, conn N.PacketConn, m
 		if err == nil {
 			metadata.Protocol = sniffMetadata.Protocol
 			metadata.Domain = sniffMetadata.Domain
-			if metadata.SniffOverrideDestination && sniff.IsDomainName(metadata.Domain) {
+			if metadata.SniffOverrideDestination && M.IsDomainName(metadata.Domain) {
 				metadata.Destination = M.Socksaddr{
 					Fqdn: metadata.Domain,
 					Port: metadata.Destination.Port,