func scanTCPStats()

in container/libcontainer/handler.go [630:691]

• 50 lines of code
• 5 McCabe index (conditional complexity)

func scanTCPStats(tcpStatsFile string) (info.TcpStat, error) {
	var stats info.TcpStat

	data, err := os.ReadFile(tcpStatsFile)
	if err != nil {
		return stats, fmt.Errorf("failure opening %s: %v", tcpStatsFile, err)
	}

	tcpStateMap := map[string]uint64{
		"01": 0, // ESTABLISHED
		"02": 0, // SYN_SENT
		"03": 0, // SYN_RECV
		"04": 0, // FIN_WAIT1
		"05": 0, // FIN_WAIT2
		"06": 0, // TIME_WAIT
		"07": 0, // CLOSE
		"08": 0, // CLOSE_WAIT
		"09": 0, // LAST_ACK
		"0A": 0, // LISTEN
		"0B": 0, // CLOSING
	}

	reader := strings.NewReader(string(data))
	scanner := bufio.NewScanner(reader)

	scanner.Split(bufio.ScanLines)

	// Discard header line
	if b := scanner.Scan(); !b {
		return stats, scanner.Err()
	}

	for scanner.Scan() {
		line := scanner.Text()

		state := strings.Fields(line)
		// TCP state is the 4th field.
		// Format: sl local_address rem_address st tx_queue rx_queue tr tm->when retrnsmt  uid timeout inode
		tcpState := state[3]
		_, ok := tcpStateMap[tcpState]
		if !ok {
			return stats, fmt.Errorf("invalid TCP stats line: %v", line)
		}
		tcpStateMap[tcpState]++
	}

	stats = info.TcpStat{
		Established: tcpStateMap["01"],
		SynSent:     tcpStateMap["02"],
		SynRecv:     tcpStateMap["03"],
		FinWait1:    tcpStateMap["04"],
		FinWait2:    tcpStateMap["05"],
		TimeWait:    tcpStateMap["06"],
		Close:       tcpStateMap["07"],
		CloseWait:   tcpStateMap["08"],
		LastAck:     tcpStateMap["09"],
		Listen:      tcpStateMap["0A"],
		Closing:     tcpStateMap["0B"],
	}

	return stats, nil
}