func()

in pcap-cli/internal/transformer/json_translator.go [732:809]

• 56 lines of code
• 4 McCabe index (conditional complexity)

func (t *JSONPcapTranslator) translateTCPLayer(
	ctx context.Context,
	tcp *layers.TCP,
) fmt.Stringer {
	json := gabs.New()

	// https://github.com/google/gopacket/blob/master/layers/tcp.go#L19-L35

	L4, _ := json.Object("L4")

	L4.Set(strconv.FormatInt(int64(len(tcp.Payload)), 10), "len")

	L4.Set(tcp.Seq, "seq")
	L4.Set(tcp.Ack, "ack")
	L4.Set(tcp.DataOffset, "off")
	L4.Set(tcp.Window, "win")
	L4.Set(tcp.Checksum, "xsum")
	L4.Set(tcp.Urgent, "urg")

	flags, _ := L4.Object("flags")

	setFlags := parseTCPflags(tcp)

	flags.Set(setFlags, "dec")

	if flagsStr, ok := tcpFlagsStr[setFlags]; ok {
		flags.Set(flagsStr, "str")
	} else {
		// this scenario is slow, but it should also be exceedingly rare
		t.addTCPflags(ctx, tcp, flags)
	}

	t.addTCPoptions(ctx, tcp, L4)

	L4.Set(tcp.SrcPort, "src")
	L4.Set(tcp.DstPort, "dst")

	// TCP(6) (0x06) | `SrcPort` and `DstPort` are `uint8`
	flowID := fnv1a.HashUint64(uint64(6) + uint64(tcp.SrcPort) + uint64(tcp.DstPort))
	flowIDstr := strconv.FormatUint(flowID, 10)
	L4.Set(flowIDstr, "flow")

	atDebugVerbosity(ctx,
		t.pcapTranslator,
		func(
			ctx context.Context,
			translator *pcapTranslator,
		) {
			if name, ok := layers.TCPPortNames[tcp.SrcPort]; ok {
				L4.Set(name, "sproto")
			}

			if name, ok := layers.TCPPortNames[tcp.DstPort]; ok {
				L4.Set(name, "dproto")
			}

			transportFlow := tcp.TransportFlow()
			t.addEndpoints(L4, &transportFlow)

			flagsMap, _ := flags.Object("map")

			flagsMap.Set(tcp.SYN, "SYN")
			flagsMap.Set(tcp.ACK, "ACK")
			flagsMap.Set(tcp.PSH, "PSH")
			flagsMap.Set(tcp.FIN, "FIN")
			flagsMap.Set(tcp.RST, "RST")
			flagsMap.Set(tcp.URG, "URG")
			flagsMap.Set(tcp.ECE, "ECE")
			flagsMap.Set(tcp.CWR, "CWR")

			flagsMap.Set(tcp.NS, "NS")

			flags.Set("0b"+strconv.FormatUint(uint64(setFlags), 2), "bin")
			flags.Set("0x"+strconv.FormatUint(uint64(setFlags), 16), "hex")
		})

	return json
}