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package util
import (
"crypto/rand"
"errors"
"fmt"
"net"
)
func incByte(subnet *net.IPNet, idx int, shift uint) error {
if idx < 0 {
return errors.New("no more subnets left")
}
var val byte = 1 << shift
// if overflow we have to inc the previous byte
if uint(subnet.IP[idx])+uint(val) > 255 {
if err := incByte(subnet, idx-1, 0); err != nil {
return err
}
}
subnet.IP[idx] += val
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 - 1) / 8
if err := incByte(newSubnet, idx, shift); err != nil {
return nil, err
}
return newSubnet, nil
}
func NetworkIntersectsWithNetworks(n *net.IPNet, networklist []*net.IPNet) bool {
for _, nw := range networklist {
if networkIntersect(n, nw) {
return true
}
}
return false
}
func networkIntersect(n1, n2 *net.IPNet) bool {
return n2.Contains(n1.IP) || n1.Contains(n2.IP)
}
// getRandomIPv6Subnet returns a random internal ipv6 subnet as described in RFC3879.
func getRandomIPv6Subnet() (net.IPNet, error) {
ip := make(net.IP, 8, net.IPv6len)
// read 8 random bytes
_, err := rand.Read(ip)
if err != nil {
return net.IPNet{}, err
}
// first byte must be FD as per RFC3879
ip[0] = 0xfd
// add 8 zero bytes
ip = append(ip, make([]byte, 8)...)
return net.IPNet{IP: ip, Mask: net.CIDRMask(64, 128)}, nil
}
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