add all files from Hong

plugins/mtu/plugin.go

@@ -0,0 +1,50 @@
+// 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 mtu
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+
+	"github.com/coredhcp/coredhcp/handler"
+	"github.com/coredhcp/coredhcp/logger"
+	"github.com/coredhcp/coredhcp/plugins"
+)
+
+var log = logger.GetLogger("plugins/mtu")
+
+// Plugin wraps the MTU plugin information.
+var Plugin = plugins.Plugin{
+	Name:   "mtu",
+	Setup4: setup4,
+	// No Setup6 since DHCPv6 does not have MTU-related options
+}
+
+var (
+	mtu int
+)
+
+func setup4(args ...string) (handler.Handler4, error) {
+	if len(args) != 1 {
+		return nil, errors.New("need one mtu value")
+	}
+	var err error
+	if mtu, err = strconv.Atoi(args[0]); err != nil {
+		return nil, fmt.Errorf("invalid mtu: %v", args[0])
+	}
+	log.Infof("loaded mtu %d.", mtu)
+	return Handler4, nil
+}
+
+// Handler4 handles DHCPv4 packets for the mtu plugin
+func Handler4(req, resp *dhcpv4.DHCPv4) (*dhcpv4.DHCPv4, bool) {
+	if req.IsOptionRequested(dhcpv4.OptionInterfaceMTU) {
+		resp.Options.Update(dhcpv4.Option{Code: dhcpv4.OptionInterfaceMTU, Value: dhcpv4.Uint16(mtu)})
+	}
+	return resp, false
+}