How to verify the validity of IP address in golang

In golang, verifying the validity of an IP address usually requires the use of some functions and structures in the net package. In this article, we will introduce how to use these functions and structures to verify the validity of an IP address.

First, we need to use the net.ParseIP() function to parse the IP address and convert it to the net.IP type. This function accepts a string parameter and returns a value of type net.IP. If the string is a valid IP address, returns the net.IP type value for that IP address. If the string is not a valid IP address, a nil value is returned.

For example, the following code parses the string "192.168.1.1" into a value of type net.IP and assigns it to the variable ip:

ip := net.ParseIP("192.168.1.1")

If the string is not a valid IP address , then ip will be nil. Therefore, when verifying the validity of an IP address, we need to check if the ip variable is nil.

Next, we can use the net.IP.IsIPv4() and net.IP.IsIPv6() functions to determine whether the IP address is an IPv4 address or an IPv6 address. If the IP address is an IPv4 address, the IsIPv4() function returns true, while the IsIPv6() function returns false. If the IP address is an IPv6 address, the IsIPv4() function returns false and the IsIPv6() function returns true.

For example, the following code checks whether the variable ip is an IPv4 address and assigns the result to the variable isIPv4:

isIPv4 := ip != nil && ip.IsIPv4()

If the variable ip is a valid IPv4 address, isIPv4 will be true. Otherwise, isIPv4 will be false.

In addition, when verifying the validity of the IP address, we also need to check whether the IP address is within a specific IP address range. In golang, we can use the net.IPNet type to represent an IP address range. net.IPNet consists of an IP address and a subnet mask, which is used to identify an IP address range.

For example, the following code uses the net.ParseCIDR() function to parse the string "192.168.1.0/24" and convert it to the net.IPNet type:

ip, subnet, _ := net.ParseCIDR("192.168.1.0/24")

where, ip is a net A value of .IP type, indicating the IP address "192.168.1.0". subnet is a value of type net.IPMask, representing the subnet mask. This function also returns a value of type error to indicate whether an error occurred. In this example, we ignore this value.

Next, we can use the net.IPNet.Contains() function to check whether an IP address is within the specified IP address range. For example, the following code checks whether the IP address "192.168.1.100" falls within the 192.168.1.0/24 range:

isInRange := subnet.Contains(net.ParseIP("192.168.1.100"))

If the IP address falls within the specified IP address range, isInRange will be true. Otherwise, isInRange will be false.

To sum up, we can use these functions and structures in the net package to verify the validity of the IP address. The following code demonstrates how to use them together:

func validateIP(ipStr string) bool {
    ip := net.ParseIP(ipStr)
    if ip == nil {
        return false
    }

    if ip.IsIPv4() {
        subnet := net.IPv4(192, 168, 1, 0).Mask(net.CIDRMask(24, 32))
        return subnet.Contains(ip)
    }

    if ip.IsIPv6() {
        subnet := &net.IPNet{
            IP:   net.ParseIP("2001:db8::"),
            Mask: net.CIDRMask(64, 128),
        }
        return subnet.Contains(ip)
    }

    return false
}

This function accepts a string parameter ipStr representing the IP address to be verified. It first parses the string and converts it into a value of type net.IP. If the value is nil, it means that the IP address is invalid and the function returns false. Otherwise, the function selects the corresponding IP address range based on whether the IP address is an IPv4 or IPv6 address, and uses the net.IPNet.Contains() function to check whether the IP address is within the range. The function returns true if the IP address falls within the specified IP address range. Otherwise, the function returns false.

By using these functions and structures in the net package, we can easily verify the validity of the IP address and ensure that the application is handling the network connection correctly.

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