github.com/mysteriumnetwork/node@v0.0.0-20240516044423-365054f76801/utils/netutil/subnet.go (about)

     1  /*
     2   * Copyright (C) 2019 The "MysteriumNetwork/node" Authors.
     3   *
     4   * This program is free software: you can redistribute it and/or modify
     5   * it under the terms of the GNU General Public License as published by
     6   * the Free Software Foundation, either version 3 of the License, or
     7   * (at your option) any later version.
     8   *
     9   * This program is distributed in the hope that it will be useful,
    10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    12   * GNU General Public License for more details.
    13   *
    14   * You should have received a copy of the GNU General Public License
    15   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    16   */
    17  
    18  package netutil
    19  
    20  import "net"
    21  
    22  // FirstIP returns a first IP from the subnet.
    23  func FirstIP(subnet net.IPNet) net.IP {
    24  	ip := make(net.IP, len(subnet.IP))
    25  	copy(ip, subnet.IP)
    26  	dup := ip.Mask(subnet.Mask)
    27  	inc(dup)
    28  	if subnet.Contains(dup) {
    29  		return dup
    30  	}
    31  	return ip
    32  }
    33  
    34  func inc(ip net.IP) {
    35  	for j := len(ip) - 1; j >= 0; j-- {
    36  		ip[j]++
    37  		if ip[j] > 0 {
    38  			break
    39  		}
    40  	}
    41  }