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// Copyright 2018-present the CoreDHCP Authors. All rights reserved
// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.
package netmask
import (
"encoding/binary"
"errors"
"net"
"github.com/coredhcp/coredhcp/handler"
"github.com/coredhcp/coredhcp/logger"
"github.com/coredhcp/coredhcp/plugins"
"github.com/insomniacslk/dhcp/dhcpv4"
)
var log = logger.GetLogger("plugins/netmask")
// Plugin wraps plugin registration information
var Plugin = plugins.Plugin{
Name: "netmask",
Setup4: setup4,
}
var (
netmask net.IPMask
)
func setup4(args ...string) (handler.Handler4, error) {
log.Printf("loaded plugin for DHCPv4.")
if len(args) != 1 {
return nil, errors.New("need at least one netmask IP address")
}
netmaskIP := net.ParseIP(args[0])
if netmaskIP.IsUnspecified() {
return nil, errors.New("netmask is not valid, got: " + args[0])
}
netmaskIP = netmaskIP.To4()
if netmaskIP == nil {
return nil, errors.New("expected an netmask address, got: " + args[0])
}
netmask = net.IPv4Mask(netmaskIP[0], netmaskIP[1], netmaskIP[2], netmaskIP[3])
if !checkValidNetmask(netmask) {
return nil, errors.New("netmask is not valid, got: " + args[0])
}
log.Printf("loaded client netmask")
return Handler4, nil
}
//Handler4 handles DHCPv4 packets for the netmask plugin
func Handler4(req, resp *dhcpv4.DHCPv4) (*dhcpv4.DHCPv4, bool) {
resp.Options.Update(dhcpv4.OptSubnetMask(netmask))
return resp, false
}
func checkValidNetmask(netmask net.IPMask) bool {
netmaskInt := binary.BigEndian.Uint32(netmask)
x := ^netmaskInt
y := x + 1
return (y & x) == 0
}
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