How to list subnets in a network using golang?

php editor Banana will introduce you how to use Golang to list subnets in the network. Golang is a powerful programming language that provides many features and libraries to easily handle network-related tasks. To list subnets in a network, we can use Golang’s net package and CIDR (Classless Inter-Domain Routing) library. By parsing the IP address and subnet mask, we can calculate all the subnets in the network. Next, we will explain in detail how to use Golang to write code to implement this function.

Question content

I want to list it. subnet in network, I have sample working code in python but need it in golang.

NETWORK="192.168.0.0/16"
subnet_prefix=22
net = ipaddress.ip_network(NETWORK)
for subnet in net.subnets(new_prefix=subnet_prefix):
    net = ipaddress.ip_interface(subnet)
    print(net)

192.168.0.0/22 ​​192.168.4.0/22 ​​192.168.8.0/22 ​​192.168.12.0/22 ​​192.168.16.0/22 ​​192.168.20.0/22 ​​192.168.24.0/22 ​​192.168 . 28.0/22 ​​192.168.32.0/ 22 192.168.36.0/22 ​​192.168.40.0/22 ​​192.168.44.0/22 ​​192.168.48.0/22 ​​192.168.52.0/22 ​​192.168.56.0/22 ​​192.168.60.0/22 ​​192.168. 64. 0/22 192.168.68.0/22 ​​192.168.72.0/22 ​​192.168.76.0/22 ​​192.168.80.0/22 ​​192.168.84.0/22 ​​192.168.88.0/22 ​​192.168.92.0/22 ​​192.16 8.96.0/22 ​​192.168.100.0/22 ​​192.168. 10 4.0/22 ​​192.168.108.0/22 ​​192.168.112.0/22 ​​192.168.116.0/22 ​​192.168.120.0/22 ​​192.168.124.0/22 ​​192.168.128.0/22 ​​192.168.132 .0/22 ​​192.168.136.0/22 ​​192.168.140.0/22 ​​192 . 168.144.0/22 ​​192.168.148.0/22 ​​192.168.152.0/22 ​​192.168.156.0/22 ​​192.168.160.0/22 ​​192.168.164.0/22 ​​192.168.168.0/22 ​​192.168. 172.0/22 ​​192.168.176.0/22 ​​192.168.180.0/22 192. 168.184.0/22 ​​192.168.188.0/22 ​​192.168.192.0/22 ​​192.168.196.0/22 ​​192.168.200.0/22 ​​192.168.204.0/22 ​​192.168.208.0/22 ​​192.168. 212.0/22 ​​192.168.216.0/22 ​​192.168.220.0/22 192. 168.224.0/22 ​​192.168.228.0/22 ​​192.168.232.0/22 ​​192.168.236.0/22 ​​192.168.240.0/22 ​​192.168.244.0/22 ​​192.168.248.0/22 ​​192 .168.252.0/22

Solution

The function I wrote generates all subnets that can be created within a given netcidr given a subnetmasksize. Networks and subnets are represented in cidr notation.

For example:

func runner() {
    fmt.println(gensubnetsinnetwork("192.168.0.0/24", 26))
}

=== run   testrunner/run_me
[192.168.0.0/26 192.168.0.64/26 192.168.0.128/26 192.168.0.192/26] <nil>
--- pass: testrunner (0.00s)

I chose arithmetic operations so it's easier to understand (for better performance, use bitwise operations).

This function computes some facts about a given network and subnet mask, then generates all subnet cidrs.

func GenSubnetsInNetwork(netCIDR string, subnetMaskSize int) ([]string, error) {
    ip, ipNet, err := net.ParseCIDR(netCIDR)
    if err != nil {
        return nil, err
    }
    if !ip.Equal(ipNet.IP) {
        return nil, errors.New("netCIDR is not a valid network address")
    }
    netMaskSize, _ := ipNet.Mask.Size()
    if netMaskSize > int(subnetMaskSize) {
        return nil, errors.New("subnetMaskSize must be greater or equal than netMaskSize")
    }

    totalSubnetsInNetwork := math.Pow(2, float64(subnetMaskSize)-float64(netMaskSize))
    totalHostsInSubnet := math.Pow(2, 32-float64(subnetMaskSize))
    subnetIntAddresses := make([]uint32, int(totalSubnetsInNetwork))
    // first subnet address is same as the network address
    subnetIntAddresses[0] = ip2int(ip.To4())
    for i := 1; i < int(totalSubnetsInNetwork); i++ {
        subnetIntAddresses[i] = subnetIntAddresses[i-1] + uint32(totalHostsInSubnet)
    }

    subnetCIDRs := make([]string, 0)
    for _, sia := range subnetIntAddresses {
        subnetCIDRs = append(
            subnetCIDRs,
            int2ip(sia).String()+"/"+strconv.Itoa(int(subnetMaskSize)),
        )
    }
    return subnetCIDRs, nil
}

func ip2int(ip net.IP) uint32 {
    if len(ip) == 16 {
        panic("cannot convert IPv6 into uint32")
    }
    return binary.BigEndian.Uint32(ip)
}
func int2ip(nn uint32) net.IP {
    ip := make(net.IP, 4)
    binary.BigEndian.PutUint32(ip, nn)
    return ip
}

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