From 3cadbdd7aa2350b8e4846c8b5576025c9ef2a079 Mon Sep 17 00:00:00 2001
From: Michael Stapelberg <stapelberg@google.com>
Date: Sat, 2 Jun 2018 21:00:56 +0200
Subject: [PATCH] dhcp6: hook up SIGUSR2 to DHCPRELEASE

---
 cmd/dhcp6/dhcp6.go        | 28 ++++++++++++++++++++++------
 integrationdhcpv6_test.go |  4 ++++
 internal/dhcp6/dhcp6.go   | 20 +++++++++++++++++++-
 3 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/cmd/dhcp6/dhcp6.go b/cmd/dhcp6/dhcp6.go
index c887516..5e3f3b3 100644
--- a/cmd/dhcp6/dhcp6.go
+++ b/cmd/dhcp6/dhcp6.go
@@ -5,37 +5,45 @@ package main
 import (
 	"encoding/json"
 	"flag"
-	"fmt"
 	"io/ioutil"
-	"log"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"router7/internal/dhcp6"
 	"router7/internal/notify"
+	"router7/internal/teelogger"
 	"syscall"
 	"time"
 )
 
+var log = teelogger.NewConsole()
+
 func logic() error {
 	const configPath = "/perm/dhcp6/wire/lease.json"
 	if err := os.MkdirAll(filepath.Dir(configPath), 0755); err != nil {
 		return err
 	}
 
+	duid, err := ioutil.ReadFile("/perm/dhcp6/duid")
+	if err != nil {
+		log.Printf("could not read /perm/dhcp6/duid (%v), proceeding with DUID-LLT")
+	}
+
 	c, err := dhcp6.NewClient(dhcp6.ClientConfig{
 		InterfaceName: "uplink0",
+		DUID:          duid,
 	})
 	if err != nil {
 		return err
 	}
+	usr2 := make(chan os.Signal, 1)
+	signal.Notify(usr2, syscall.SIGUSR2)
 	for c.ObtainOrRenew() {
 		if err := c.Err(); err != nil {
 			log.Printf("Temporary error: %v", err)
 			continue
 		}
-		// TODO: use a logger which writes to /dev/console
 		log.Printf("lease: %+v", c.Config())
-		ioutil.WriteFile("/dev/console", []byte(fmt.Sprintf("lease: %+v\n", c.Config())), 0600)
 		b, err := json.Marshal(c.Config())
 		if err != nil {
 			return err
@@ -45,9 +53,17 @@ func logic() error {
 		}
 		if err := notify.Process("/user/netconfi", syscall.SIGUSR1); err != nil {
 			log.Printf("notifying netconfig: %v", err)
-			ioutil.WriteFile("/dev/console", []byte(fmt.Sprintf("notifying netconfigd: %+v\n", err)), 0600)
 		}
-		time.Sleep(time.Until(c.Config().RenewAfter))
+		select {
+		case <-time.After(time.Until(c.Config().RenewAfter)):
+			// fallthrough and renew the DHCP lease
+		case <-usr2:
+			log.Printf("SIGUSR2 received, sending DHCPRELEASE")
+			if _, _, err := c.Release(); err != nil {
+				return err
+			}
+			os.Exit(125) // quit supervision by gokrazy
+		}
 	}
 	return c.Err() // permanent error
 }
diff --git a/integrationdhcpv6_test.go b/integrationdhcpv6_test.go
index e58f99e..10312e3 100644
--- a/integrationdhcpv6_test.go
+++ b/integrationdhcpv6_test.go
@@ -99,13 +99,17 @@ func TestDHCPv6(t *testing.T) {
 		t.Fatalf("unexpected config: diff (-got +want):\n%s", diff)
 	}
 
+	c.Release()
+
 	{
+		dnsmasq.Kill() // flush log
 		got := dnsmasq.Actions()
 		want := []string{
 			"DHCPSOLICIT(veth0b) 00:0a:00:03:00:01:4c:5e:0c:41:bf:39",
 			"DHCPADVERTISE(veth0b) 2001:db8::c 00:0a:00:03:00:01:4c:5e:0c:41:bf:39",
 			"DHCPREQUEST(veth0b) 00:0a:00:03:00:01:4c:5e:0c:41:bf:39",
 			"DHCPREPLY(veth0b) 2001:db8::c 00:0a:00:03:00:01:4c:5e:0c:41:bf:39",
+			"DHCPRELEASE(veth0b) 00:0a:00:03:00:01:4c:5e:0c:41:bf:39",
 		}
 		withoutMac := func(line string) string {
 			return v6AddrRe.ReplaceAllString(strings.TrimSpace(line), "")
diff --git a/internal/dhcp6/dhcp6.go b/internal/dhcp6/dhcp6.go
index 4671f8c..b1abd4a 100644
--- a/internal/dhcp6/dhcp6.go
+++ b/internal/dhcp6/dhcp6.go
@@ -47,6 +47,7 @@ type Client struct {
 	raddr         *net.UDPAddr
 	timeNow       func() time.Time
 	duid          *dhcpv6.Duid
+	advertise     dhcpv6.DHCPv6
 
 	cfg Config
 	err error
@@ -249,7 +250,8 @@ func (c *Client) ObtainOrRenew() bool {
 		return true
 	}
 
-	_, reply, err := c.request(advertise, nil)
+	c.advertise = advertise
+	_, reply, err := c.request(advertise)
 	if err != nil {
 		c.err = err
 		return true
@@ -291,6 +293,22 @@ func (c *Client) ObtainOrRenew() bool {
 	return true
 }
 
+func (c *Client) Release() (release dhcpv6.DHCPv6, reply dhcpv6.DHCPv6, err error) {
+	release, err = dhcpv6.NewRequestFromAdvertise(c.advertise, dhcpv6.WithClientID(*c.duid))
+	if err != nil {
+		return nil, nil, err
+	}
+	release.(*dhcpv6.DHCPv6Message).SetMessage(dhcpv6.RELEASE)
+
+	if len(c.transactionIDs) > 0 {
+		id := c.transactionIDs[0]
+		c.transactionIDs = c.transactionIDs[1:]
+		release.(*dhcpv6.DHCPv6Message).SetTransactionID(id)
+	}
+	reply, err = c.sendReceive(release, dhcpv6.MSGTYPE_NONE)
+	return release, reply, err
+}
+
 func (c *Client) Err() error {
 	return c.err
 }