95 lines
2.2 KiB
Go
95 lines
2.2 KiB
Go
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Binary dhcp4d hands out DHCPv4 leases to clients.
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package main
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import (
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"encoding/json"
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"flag"
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"io/ioutil"
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"os"
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"syscall"
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"router7/internal/dhcp4d"
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"router7/internal/notify"
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"router7/internal/teelogger"
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"github.com/krolaw/dhcp4"
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"github.com/krolaw/dhcp4/conn"
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)
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var log = teelogger.NewConsole()
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func loadLeases(h *dhcp4d.Handler, fn string) error {
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b, err := ioutil.ReadFile(fn)
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if err != nil {
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if os.IsNotExist(err) {
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return nil
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}
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return err
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}
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var leases []*dhcp4d.Lease
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if err := json.Unmarshal(b, &leases); err != nil {
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return err
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}
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h.SetLeases(leases)
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return nil
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}
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func logic() error {
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if err := os.MkdirAll("/perm/dhcp4d", 0755); err != nil {
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return err
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}
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errs := make(chan error)
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handler, err := dhcp4d.NewHandler("/perm", nil, nil)
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if err != nil {
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return err
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}
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if err := loadLeases(handler, "/perm/dhcp4d/leases.json"); err != nil {
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return err
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}
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handler.Leases = func(leases []*dhcp4d.Lease, latest *dhcp4d.Lease) {
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log.Printf("DHCPACK %+v", latest)
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b, err := json.Marshal(leases)
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if err != nil {
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errs <- err
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return
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}
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// TODO: write atomically
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if err := ioutil.WriteFile("/perm/dhcp4d/leases.json", b, 0644); err != nil {
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errs <- err
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}
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if err := notify.Process("/user/dnsd", syscall.SIGUSR1); err != nil {
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log.Printf("notifying dnsd: %v", err)
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}
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}
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conn, err := conn.NewUDP4BoundListener("lan0", ":67") // TODO: customizeable
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if err != nil {
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return err
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}
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go func() {
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errs <- dhcp4.Serve(conn, handler)
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}()
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return <-errs
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}
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func main() {
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// TODO: drop privileges, run as separate uid?
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flag.Parse()
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if err := logic(); err != nil {
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log.Fatal(err)
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}
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}
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