Add system stack

internal/clashtcpip/icmp.go

@@ -0,0 +1,40 @@
+package clashtcpip
+
+import (
+	"encoding/binary"
+)
+
+type ICMPType = byte
+
+const (
+	ICMPTypePingRequest  byte = 0x8
+	ICMPTypePingResponse byte = 0x0
+)
+
+type ICMPPacket []byte
+
+func (p ICMPPacket) Type() ICMPType {
+	return p[0]
+}
+
+func (p ICMPPacket) SetType(v ICMPType) {
+	p[0] = v
+}
+
+func (p ICMPPacket) Code() byte {
+	return p[1]
+}
+
+func (p ICMPPacket) Checksum() uint16 {
+	return binary.BigEndian.Uint16(p[2:])
+}
+
+func (p ICMPPacket) SetChecksum(sum [2]byte) {
+	p[2] = sum[0]
+	p[3] = sum[1]
+}
+
+func (p ICMPPacket) ResetChecksum() {
+	p.SetChecksum(zeroChecksum)
+	p.SetChecksum(Checksum(0, p))
+}