ping: Fix not handling reject

stack.go

@@ -12,7 +12,10 @@ import (
 	"github.com/sagernet/sing/common/logger"
 )
 
-var ErrDrop = E.New("drop connections by rule")
+var (
+	ErrDrop  = E.New("drop by rule")
+	ErrReset = E.New("reset by rule")
+)
 
 type Stack interface {
 	Start() error

stack_gvisor_icmp.go

@@ -4,6 +4,7 @@ package tun
 
 import (
 	"context"
+	"errors"
 	"net/netip"
 	"sync"
 	"time"
@@ -73,7 +74,10 @@ func (f *ICMPForwarder) HandlePacket(id stack.TransportEndpointID, pkt *stack.Pa
 					timeout,
 				)
 			})
-			if err != nil {
+			if errors.Is(err, ErrReset) {
+				gWriteUnreachable(f.stack, pkt)
+				return true
+			} else if errors.Is(err, ErrDrop) {
 				return true
 			}
 			if action != nil {
@@ -132,7 +136,10 @@ func (f *ICMPForwarder) HandlePacket(id stack.TransportEndpointID, pkt *stack.Pa
 					timeout,
 				)
 			})
-			if err != nil {
+			if errors.Is(err, ErrReset) {
+				gWriteUnreachable(f.stack, pkt)
+				return true
+			} else if errors.Is(err, ErrDrop) {
 				return true
 			}
 			if action != nil {

stack_system.go

@@ -668,7 +668,11 @@ func (s *System) processIPv4ICMP(ipHdr header.IPv4, icmpHdr header.ICMPv4) (bool
 			)
 		})
 		if err != nil {
-			return false, nil
+			if errors.Is(err, ErrReset) {
+				return false, s.rejectIPv4WithICMP(ipHdr, header.ICMPv4PortUnreachable)
+			} else if errors.Is(err, ErrDrop) {
+				return false, nil
+			}
 		}
 		if action != nil {
 			return false, action.WritePacket(buf.As(ipHdr).ToOwned())
@@ -739,7 +743,9 @@ func (s *System) processIPv6ICMP(ipHdr header.IPv6, icmpHdr header.ICMPv6) (bool
 				timeout,
 			)
 		})
-		if err != nil {
+		if errors.Is(err, ErrReset) {
+			return false, s.rejectIPv6WithICMP(ipHdr, header.ICMPv6PortUnreachable)
+		} else if errors.Is(err, ErrDrop) {
 			return false, nil
 		}
 		if action != nil {