From d21822f531b186e64e117cadf24fed7c541f0f00 Mon Sep 17 00:00:00 2001
From: Michael Stapelberg <stapelberg@google.com>
Date: Sat, 9 Jun 2018 15:10:11 +0200
Subject: [PATCH] dhcp4d: implement loading leases files from persistent
 storage

---
 cmd/dhcp4d/dhcp4d.go           | 25 ++++++++++++++++++++++---
 internal/dhcp4d/dhcp4d.go      | 23 +++++++++++++++++------
 internal/dhcp4d/dhcp4d_test.go | 24 +++++++++++++++++++++++-
 3 files changed, 62 insertions(+), 10 deletions(-)

diff --git a/cmd/dhcp4d/dhcp4d.go b/cmd/dhcp4d/dhcp4d.go
index 6936196..81413b9 100644
--- a/cmd/dhcp4d/dhcp4d.go
+++ b/cmd/dhcp4d/dhcp4d.go
@@ -4,19 +4,36 @@ package main
 import (
 	"encoding/json"
 	"flag"
-	"fmt"
 	"io/ioutil"
-	"log"
 	"os"
 	"syscall"
 
 	"router7/internal/dhcp4d"
 	"router7/internal/notify"
+	"router7/internal/teelogger"
 
 	"github.com/krolaw/dhcp4"
 	"github.com/krolaw/dhcp4/conn"
 )
 
+var log = teelogger.NewConsole()
+
+func loadLeases(h *dhcp4d.Handler, fn string) error {
+	b, err := ioutil.ReadFile(fn)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	var leases []*dhcp4d.Lease
+	if err := json.Unmarshal(b, leases); err != nil {
+		return err
+	}
+	h.SetLeases(leases)
+	return nil
+}
+
 func logic() error {
 	if err := os.MkdirAll("/perm/dhcp4d", 0755); err != nil {
 		return err
@@ -26,6 +43,9 @@ func logic() error {
 	if err != nil {
 		return err
 	}
+	if err := loadLeases(handler, "/perm/dhcp4d/leases.json"); err != nil {
+		return err
+	}
 	handler.Leases = func(leases []*dhcp4d.Lease) {
 		b, err := json.Marshal(leases)
 		if err != nil {
@@ -38,7 +58,6 @@ func logic() error {
 		}
 		if err := notify.Process("/user/dnsd", syscall.SIGUSR1); err != nil {
 			log.Printf("notifying dnsd: %v", err)
-			ioutil.WriteFile("/dev/console", []byte(fmt.Sprintf("notifying dnsd: %+v\n", err)), 0600)
 		}
 	}
 	conn, err := conn.NewUDP4BoundListener("lan0", ":67") // TODO: customizeable
diff --git a/internal/dhcp4d/dhcp4d.go b/internal/dhcp4d/dhcp4d.go
index fa5855d..c0d5153 100644
--- a/internal/dhcp4d/dhcp4d.go
+++ b/internal/dhcp4d/dhcp4d.go
@@ -14,11 +14,11 @@ import (
 )
 
 type Lease struct {
-	Num          int
-	Addr         net.IP
-	HardwareAddr string
-	Hostname     string
-	Expiry       time.Time
+	Num          int       `json:"num"` // relative to Handler.start
+	Addr         net.IP    `json:"addr"`
+	HardwareAddr string    `json:"hardware_addr"`
+	Hostname     string    `json:"hostname"`
+	Expiry       time.Time `json:"expiry"`
 }
 
 type Handler struct {
@@ -36,7 +36,6 @@ type Handler struct {
 	Leases func([]*Lease)
 }
 
-// TODO: restore leases from permanent storage
 func NewHandler(dir string) (*Handler, error) {
 	serverIP, err := netconfig.LinkAddress(dir, "lan0")
 	if err != nil {
@@ -64,6 +63,18 @@ func NewHandler(dir string) (*Handler, error) {
 	}, nil
 }
 
+// SetLeases overwrites the leases database with the specified leases, typically
+// loaded from persistent storage. There is no locking, so SetLeases must be
+// called before Serve.
+func (h *Handler) SetLeases(leases []*Lease) {
+	h.leasesHW = make(map[string]*Lease)
+	h.leasesIP = make(map[int]*Lease)
+	for _, l := range leases {
+		h.leasesHW[l.HardwareAddr] = l
+		h.leasesIP[l.Num] = l
+	}
+}
+
 func (h *Handler) findLease() int {
 	now := h.timeNow()
 	if len(h.leasesIP) < h.leaseRange {
diff --git a/internal/dhcp4d/dhcp4d_test.go b/internal/dhcp4d/dhcp4d_test.go
index c619190..201f96b 100644
--- a/internal/dhcp4d/dhcp4d_test.go
+++ b/internal/dhcp4d/dhcp4d_test.go
@@ -316,4 +316,26 @@ func TestServerID(t *testing.T) {
 	}
 }
 
-// TODO: test persistent storage
+func TestPersistentStorage(t *testing.T) {
+	handler, cleanup := testHandler(t)
+	defer cleanup()
+
+	var (
+		addr         = net.IP{192, 168, 42, 4}
+		hardwareAddr = net.HardwareAddr{0x11, 0x22, 0x33, 0x44, 0x55, 0x66}
+	)
+
+	handler.SetLeases([]*Lease{
+		{
+			Num:          2,
+			Addr:         addr,
+			HardwareAddr: hardwareAddr.String(),
+		},
+	})
+
+	p := request(net.IPv4zero, hardwareAddr)
+	resp := handler.ServeDHCP(p, dhcp4.Discover, p.ParseOptions())
+	if got, want := resp.YIAddr().To4(), addr.To4(); !bytes.Equal(got, want) {
+		t.Errorf("DHCPOFFER for wrong IP: got %v, want %v", got, want)
+	}
+}