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