package ip

import (
	"math/big"
	"net"
)

type IPv4HeaderBitOffset uint32

const (
	// see IPv4 Header (RFC 791) - https://wiki.sans.blue/Tools/tcpip/ip.html
	SrcAddressBitOffset IPv4HeaderBitOffset = 12
	DstAddressBitOffset IPv4HeaderBitOffset = 16
	OptionsBitOffset    IPv4HeaderBitOffset = 20
)

var (
	DstPortMask uint32 = 0x0000ffff
	SrcPortMask uint32 = 0xffff0000
)

var (
	IPIPHeaderSize = 20 // IPIP header 20 bytes length
)

// converts ipv4 address to unsigned, 32 bit integer
func IPv4ToUInt32(ip net.IP) uint32 {
	ipv4 := ip.To4()
	ipInt := big.NewInt(0)
	ipInt.SetBytes(ipv4)
	return uint32(ipInt.Uint64()) /* #nosec G115 */
}