Add tracked vpnruntime implementation for CI guard tests

agents/rap-node-agent/internal/vpnruntime/checksum.go

@@ -0,0 +1,77 @@
+package vpnruntime
+
+import "encoding/binary"
+
+func normalizeIPv4PacketChecksums(packet []byte) bool {
+	if len(packet) < 20 || packet[0]>>4 != 4 {
+		return false
+	}
+	ihl := int(packet[0]&0x0f) * 4
+	if ihl < 20 || len(packet) < ihl {
+		return false
+	}
+	totalLen := int(binary.BigEndian.Uint16(packet[2:4]))
+	if totalLen <= 0 || totalLen > len(packet) {
+		totalLen = len(packet)
+	}
+	if totalLen < ihl {
+		return false
+	}
+
+	packet[10], packet[11] = 0, 0
+	binary.BigEndian.PutUint16(packet[10:12], checksum(packet[:ihl]))
+
+	proto := packet[9]
+	payload := packet[ihl:totalLen]
+	switch proto {
+	case 6:
+		if len(payload) < 20 {
+			return true
+		}
+		payload[16], payload[17] = 0, 0
+		binary.BigEndian.PutUint16(payload[16:18], transportChecksum(packet, payload, proto))
+	case 17:
+		if len(payload) < 8 {
+			return true
+		}
+		payload[6], payload[7] = 0, 0
+		sum := transportChecksum(packet, payload, proto)
+		if sum == 0 {
+			sum = 0xffff
+		}
+		binary.BigEndian.PutUint16(payload[6:8], sum)
+	case 1:
+		if len(payload) < 4 {
+			return true
+		}
+		payload[2], payload[3] = 0, 0
+		binary.BigEndian.PutUint16(payload[2:4], checksum(payload))
+	}
+	return true
+}
+
+func transportChecksum(ipHeader []byte, payload []byte, proto byte) uint16 {
+	pseudo := make([]byte, 12+len(payload))
+	copy(pseudo[0:4], ipHeader[12:16])
+	copy(pseudo[4:8], ipHeader[16:20])
+	pseudo[8] = 0
+	pseudo[9] = proto
+	binary.BigEndian.PutUint16(pseudo[10:12], uint16(len(payload)))
+	copy(pseudo[12:], payload)
+	return checksum(pseudo)
+}
+
+func checksum(data []byte) uint16 {
+	var sum uint32
+	for len(data) >= 2 {
+		sum += uint32(binary.BigEndian.Uint16(data[:2]))
+		data = data[2:]
+	}
+	if len(data) == 1 {
+		sum += uint32(data[0]) << 8
+	}
+	for (sum >> 16) != 0 {
+		sum = (sum & 0xffff) + (sum >> 16)
+	}
+	return ^uint16(sum)
+}