func NextIP()

in plugins/ipam/ipstore/ipstore.go [244:278]

• 27 lines of code
• 9 McCabe index (conditional complexity)

func NextIP(ip net.IP, subnet net.IPNet) (net.IP, error) {
	if ones, _ := subnet.Mask.Size(); ones > MaxMask {
		return nil, errors.Errorf("nextIP ipstore: no available ip in the subnet: %v", subnet)
	}

	// currently only ipv4 is supported
	ipv4 := ip.To4()
	if ipv4 == nil {
		return nil, errors.Errorf("nextIP ipstore: invalid ipv4 address: %v", ipv4)
	}

	if !subnet.Contains(ipv4) {
		return nil, errors.Errorf("nextIP ipstore: ip %v is not within subnet %s", ipv4.String(), subnet.String())
	}

	minIP := subnet.IP.Mask(subnet.Mask)
	maxIP := net.IP(make([]byte, 4))
	for i := range ipv4 {
		maxIP[i] = minIP[i] | ^subnet.Mask[i]
	}

	nextIP := ipv4
	// Reserve the broadcast address(all 1) and the network address(all 0)
	for nextIP.Equal(ipv4) || nextIP.Equal(minIP) || nextIP.Equal(maxIP) {
		if nextIP.Equal(maxIP) {
			nextIP = minIP
		}
		// convert the IP into Int for easily calculation
		nextIPInBytes := big.NewInt(0).SetBytes(nextIP)
		nextIPInBytes.Add(nextIPInBytes, big.NewInt(1))
		nextIP = net.IP(nextIPInBytes.Bytes())
	}

	return nextIP, nil
}