TUN inbound: Reply fake pong to ICMP ping (#6015)

https://github.com/XTLS/Xray-core/pull/6015#issuecomment-4321525342
2026-07-02 17:58:46 +00:00 · 2026-05-02 06:51:42 +08:00
parent 7f7fc5a829
commit 2fff03720d
5 changed files with 386 additions and 3 deletions
@@ -0,0 +1,106 @@
+package icmp
+
+import (
+	"github.com/xtls/xray-core/common/errors"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/checksum"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+)
+
+func ProtocolLabel(netProto tcpip.NetworkProtocolNumber) string {
+	switch netProto {
+	case header.IPv4ProtocolNumber:
+		return "ipv4"
+	case header.IPv6ProtocolNumber:
+		return "ipv6"
+	default:
+		return "unknown"
+	}
+}
+
+func ParseEchoRequest(netProto tcpip.NetworkProtocolNumber, message []byte) (uint16, uint16, bool) {
+	switch netProto {
+	case header.IPv4ProtocolNumber:
+		if len(message) < header.ICMPv4MinimumSize {
+			return 0, 0, false
+		}
+		icmpHdr := header.ICMPv4(message)
+		if icmpHdr.Type() != header.ICMPv4Echo || icmpHdr.Code() != header.ICMPv4UnusedCode {
+			return 0, 0, false
+		}
+		return icmpHdr.Ident(), icmpHdr.Sequence(), true
+	case header.IPv6ProtocolNumber:
+		if len(message) < header.ICMPv6MinimumSize {
+			return 0, 0, false
+		}
+		icmpHdr := header.ICMPv6(message)
+		if icmpHdr.Type() != header.ICMPv6EchoRequest || icmpHdr.Code() != header.ICMPv6UnusedCode {
+			return 0, 0, false
+		}
+		return icmpHdr.Ident(), icmpHdr.Sequence(), true
+	default:
+		return 0, 0, false
+	}
+}
+
+func RewriteChecksum(netProto tcpip.NetworkProtocolNumber, message []byte, srcIP, dstIP tcpip.Address) error {
+	switch netProto {
+	case header.IPv4ProtocolNumber:
+		if len(message) < header.ICMPv4MinimumSize {
+			return errors.New("invalid icmpv4 packet")
+		}
+		icmpHdr := header.ICMPv4(message)
+		icmpHdr.SetChecksum(0)
+		icmpHdr.SetChecksum(header.ICMPv4Checksum(icmpHdr[:header.ICMPv4MinimumSize], checksum.Checksum(icmpHdr.Payload(), 0)))
+		return nil
+	case header.IPv6ProtocolNumber:
+		if len(message) < header.ICMPv6MinimumSize {
+			return errors.New("invalid icmpv6 packet")
+		}
+		icmpHdr := header.ICMPv6(message)
+		icmpHdr.SetChecksum(0)
+		icmpHdr.SetChecksum(header.ICMPv6Checksum(header.ICMPv6ChecksumParams{
+			Header:      icmpHdr[:header.ICMPv6MinimumSize],
+			Src:         srcIP,
+			Dst:         dstIP,
+			PayloadCsum: checksum.Checksum(icmpHdr.Payload(), 0),
+			PayloadLen:  len(icmpHdr.Payload()),
+		}))
+		return nil
+	default:
+		return errors.New("unsupported icmp network protocol")
+	}
+}
+
+func BuildLocalEchoReply(netProto tcpip.NetworkProtocolNumber, request []byte, srcIP, dstIP tcpip.Address) ([]byte, error) {
+	reply := append([]byte(nil), request...)
+
+	switch netProto {
+	case header.IPv4ProtocolNumber:
+		if len(reply) < header.ICMPv4MinimumSize {
+			return nil, errors.New("invalid icmpv4 echo packet")
+		}
+		icmpHdr := header.ICMPv4(reply)
+		if icmpHdr.Type() != header.ICMPv4Echo || icmpHdr.Code() != header.ICMPv4UnusedCode {
+			return nil, errors.New("not an icmpv4 echo request")
+		}
+		reply[0] = byte(header.ICMPv4EchoReply)
+	case header.IPv6ProtocolNumber:
+		if len(reply) < header.ICMPv6MinimumSize {
+			return nil, errors.New("invalid icmpv6 echo packet")
+		}
+		icmpHdr := header.ICMPv6(reply)
+		if icmpHdr.Type() != header.ICMPv6EchoRequest || icmpHdr.Code() != header.ICMPv6UnusedCode {
+			return nil, errors.New("not an icmpv6 echo request")
+		}
+		reply[0] = byte(header.ICMPv6EchoReply)
+	default:
+		return nil, errors.New("unsupported icmp network protocol")
+	}
+
+	if err := RewriteChecksum(netProto, reply, srcIP, dstIP); err != nil {
+		return nil, err
+	}
+
+	return reply, nil
+}