add all files from Hong

plugins/netmask/plugin.go

@@ -0,0 +1,62 @@
+// 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
+}