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 }