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ipcalc.go
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ipcalc.go
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package ipcalc
import (
"encoding/binary"
"fmt"
"net/netip"
)
type CIDR struct {
Address netip.Addr
Bits int
Netmask netip.Addr
WildcardMask netip.Addr
MaximumSubnets int
MaximumAddresses int
NetworkAddress netip.Addr
BroadcastAddress netip.Addr
}
func NetmaskStringToBits(mask string) int {
maskAddr, err := netip.ParseAddr(mask)
if err != nil {
fmt.Println(err)
}
return NetmaskToBits(maskAddr)
}
func NetmaskToBits(mask netip.Addr) int {
maskBytes := mask.As4()
var bits int
for _, maskByte := range maskBytes {
for maskByte > 0 {
if maskByte&1 > 0 {
bits++
}
maskByte >>= 1
}
}
return bits
}
func CIDRNetmask(maskBits int) netip.Addr {
mask := 0xffffffff << (32 - maskBits)
bytes := make([]byte, 4)
binary.BigEndian.PutUint32(bytes, uint32(mask))
bmask := [4]byte{bytes[0], bytes[1], bytes[2], bytes[3]}
return netip.AddrFrom4(bmask)
}
func WildcardMask(maskBits int) netip.Addr {
mask := 0xffffffff >> maskBits
bytes := make([]byte, 4)
binary.BigEndian.PutUint32(bytes, uint32(mask))
bmask := [4]byte{bytes[0], bytes[1], bytes[2], bytes[3]}
return netip.AddrFrom4(bmask)
}
func MaximumSubnets(maskBits int) int {
return 1 << (32 - maskBits)
}
func MaximumAddresses(maskBits int) int {
if maskBits >= 31 {
return MaximumSubnets(maskBits)
} else {
return MaximumSubnets(maskBits) - 2
}
}
func AddrToBinary(addr [4]byte) uint32 {
return binary.BigEndian.Uint32(addr[:])
}
func BinaryToAddr(addr uint32) netip.Addr {
bytes := make([]byte, 4)
binary.BigEndian.PutUint32(bytes, uint32(addr))
bmask := [4]byte{bytes[0], bytes[1], bytes[2], bytes[3]}
return netip.AddrFrom4(bmask)
}
func CIDRAddress(addr string, bits int) CIDR {
cidrAddr, _ := netip.ParseAddr(addr)
cidrBits := bits
netMask := CIDRNetmask(cidrBits)
// cidr calculation
cidrAddrBinary := AddrToBinary(cidrAddr.As4())
netMaskBinary := AddrToBinary(netMask.As4())
cidrNetworkBinary := cidrAddrBinary & netMaskBinary
cidrBroadcastBinary := cidrNetworkBinary | ^netMaskBinary
return CIDR{
Address: cidrAddr,
Bits: cidrBits,
Netmask: netMask,
WildcardMask: WildcardMask(cidrBits),
MaximumSubnets: MaximumSubnets(cidrBits),
MaximumAddresses: MaximumAddresses(cidrBits),
NetworkAddress: BinaryToAddr(cidrNetworkBinary),
BroadcastAddress: BinaryToAddr(cidrBroadcastBinary),
}
}
func CIDRAddressFromString(cidr string) CIDR {
pfx, _ := netip.ParsePrefix(cidr)
cidrAddr := pfx.Addr()
cidrBits := pfx.Bits()
netMask := CIDRNetmask(cidrBits)
// cidr calculation
cidrAddrBinary := AddrToBinary(cidrAddr.As4())
netMaskBinary := AddrToBinary(netMask.As4())
cidrNetworkBinary := cidrAddrBinary & netMaskBinary
cidrBroadcastBinary := cidrNetworkBinary | ^netMaskBinary
return CIDR{
Address: cidrAddr,
Bits: cidrBits,
Netmask: netMask,
WildcardMask: WildcardMask(cidrBits),
MaximumSubnets: MaximumSubnets(cidrBits),
MaximumAddresses: MaximumAddresses(cidrBits),
NetworkAddress: BinaryToAddr(cidrNetworkBinary),
BroadcastAddress: BinaryToAddr(cidrBroadcastBinary),
}
}