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package network
/*
The code in this was kindly contributed by Dan Williams(dcbw@redhat.com). Many thanks
for his contributions.
*/
import (
"fmt"
"net"
)
func incByte(subnet *net.IPNet, idx int, shift uint) error {
if idx < 0 {
return fmt.Errorf("no more subnets left")
}
if subnet.IP[idx] == 255 {
subnet.IP[idx] = 0
return incByte(subnet, idx-1, 0)
}
subnet.IP[idx] += (1 << shift)
return nil
}
// NextSubnet returns subnet incremented by 1
func NextSubnet(subnet *net.IPNet) (*net.IPNet, error) {
newSubnet := &net.IPNet{
IP: subnet.IP,
Mask: subnet.Mask,
}
ones, bits := newSubnet.Mask.Size()
if ones == 0 {
return nil, fmt.Errorf("%s has only one subnet", subnet.String())
}
zeroes := uint(bits - ones)
shift := zeroes % 8
idx := ones/8 - 1
if idx < 0 {
idx = 0
}
if err := incByte(newSubnet, idx, shift); err != nil {
return nil, err
}
return newSubnet, nil
}
// LastIPInSubnet gets the last IP in a subnet
func LastIPInSubnet(addr *net.IPNet) (net.IP, error) { //nolint:interfacer
// re-parse to ensure clean network address
_, cidr, err := net.ParseCIDR(addr.String())
if err != nil {
return nil, err
}
ones, bits := cidr.Mask.Size()
if ones == bits {
return FirstIPInSubnet(cidr)
}
hostStart := ones / 8
// Handle the first host byte
cidr.IP[hostStart] |= (0xff & cidr.Mask[hostStart])
// Fill the rest with ones
for i := hostStart; i < len(cidr.IP); i++ {
cidr.IP[i] = 0xff
}
return cidr.IP, nil
}
// FirstIPInSubnet gets the first IP in a subnet
func FirstIPInSubnet(addr *net.IPNet) (net.IP, error) { //nolint:interfacer
// re-parse to ensure clean network address
_, cidr, err := net.ParseCIDR(addr.String())
if err != nil {
return nil, err
}
cidr.IP[len(cidr.IP)-1]++
return cidr.IP, nil
}
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