AdGuardHome/internal/dhcpd/helpers.go

package dhcpd

import (
	"encoding/binary"
	"fmt"
	"net"
)

func isTimeout(err error) bool {
	operr, ok := err.(*net.OpError)
	if !ok {
		return false
	}
	return operr.Timeout()
}

// Get IPv4 address list
func getIfaceIPv4(iface net.Interface) []net.IP {
	addrs, err := iface.Addrs()
	if err != nil {
		return nil
	}

	var res []net.IP
	for _, a := range addrs {
		ipnet, ok := a.(*net.IPNet)
		if !ok {
			continue
		}
		if ipnet.IP.To4() != nil {
			res = append(res, ipnet.IP.To4())
		}
	}
	return res
}

func parseIPv4(text string) (net.IP, error) {
	result := net.ParseIP(text)
	if result == nil {
		return nil, fmt.Errorf("%s is not an IP address", text)
	}
	if result.To4() == nil {
		return nil, fmt.Errorf("%s is not an IPv4 address", text)
	}
	return result.To4(), nil
}

// Return TRUE if subnet mask is correct (e.g. 255.255.255.0)
func isValidSubnetMask(mask net.IP) bool {
	var n uint32
	n = binary.BigEndian.Uint32(mask)
	for i := 0; i != 32; i++ {
		if n == 0 {
			break
		}
		if (n & 0x80000000) == 0 {
			return false
		}
		n <<= 1
	}
	return true
}