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+ DHCP: add ra_slaac_only, ra_allow_slaac config settings

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Close # 2076

Squashed commit of the following:

commit 7a938fc6ffa0adc1e705f59778d7e7442b83d4b9
Merge: 3db2605e 6222d17d
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Thu Sep 24 16:34:23 2020 +0300

    Merge remote-tracking branch 'origin/master' into 2076-dhcp-ra-slaac

commit 3db2605efda79e8d361fb46c32bb9ec753de0e02
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Thu Sep 24 16:21:36 2020 +0300

    minor

commit de31c6aeebd78dce54ca54fbff010f3dd50ce974
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Thu Sep 24 12:23:09 2020 +0300

    don't initialize DHCPv6 server if we must force the clients to use SLAAC

commit 7c4239899c85880641dc5b4826ae34386bc5ee94
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Tue Sep 22 19:34:27 2020 +0300

    minor

commit 2b57688ce4c31d45d2236bd397e0b3041dac68c1
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Sep 21 19:50:11 2020 +0300

    + DHCP: add ra_slaac_only, ra_allow_slaac config settings
This commit is contained in:
Simon Zolin
2020-09-24 18:33:11 +03:00
parent 6222d17d86
commit 990f531f54
6 changed files with 379 additions and 8 deletions
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23
dhcpd/README.md
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@@ -30,6 +30,10 @@ To set up a test environment for DHCP server you need:
3. Start your VM, install an OS. Configure your network interface to use DHCP and the OS should ask for a IP address from our DHCP server.
4. To see the current IP address on client OS you can use `ip a` command on Linux or `ipconfig` on Windows.
5. To force the client OS to request an IP from DHCP server again, you can use `dhclient` on Linux or `ipconfig /release` on Windows.
### Configure server
1. Edit server configuration file 'AdGuardHome.yaml', for example:
@@ -37,12 +41,19 @@ To set up a test environment for DHCP server you need:
dhcp:
enabled: true
interface_name: vboxnet0
gateway_ip: 192.168.56.1
subnet_mask: 255.255.255.0
range_start: 192.168.56.2
range_end: 192.168.56.2
lease_duration: 86400
icmp_timeout_msec: 1000
dhcpv4:
gateway_ip: 192.168.56.1
subnet_mask: 255.255.255.0
range_start: 192.168.56.2
range_end: 192.168.56.2
lease_duration: 86400
icmp_timeout_msec: 1000
options: []
dhcpv6:
range_start: 2001::1
lease_duration: 86400
ra_slaac_only: false
ra_allow_slaac: false
2. Start the server

239
dhcpd/router_adv.go Normal file
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@@ -0,0 +1,239 @@
package dhcpd
import (
"encoding/binary"
"fmt"
"net"
"sync/atomic"
"time"
"github.com/AdguardTeam/golibs/log"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv6"
)
type raCtx struct {
raAllowSlaac bool // send RA packets without MO flags
raSlaacOnly bool // send RA packets with MO flags
ipAddr net.IP // source IP address (link-local-unicast)
dnsIPAddr net.IP // IP address for DNS Server option
prefixIPAddr net.IP // IP address for Prefix option
ifaceName string
iface *net.Interface
packetSendPeriod time.Duration // how often RA packets are sent
conn *icmp.PacketConn // ICMPv6 socket
stop atomic.Value // stop the packet sending loop
}
type icmpv6RA struct {
managedAddressConfiguration bool
otherConfiguration bool
prefix net.IP
prefixLen int
sourceLinkLayerAddress net.HardwareAddr
recursiveDNSServer net.IP
mtu uint32
}
// Create an ICMPv6.RouterAdvertisement packet with all necessary options.
//
// ICMPv6:
// type[1]
// code[1]
// chksum[2]
// body (RouterAdvertisement):
// Cur Hop Limit[1]
// Flags[1]: MO......
// Router Lifetime[2]
// Reachable Time[4]
// Retrans Timer[4]
// Option=Prefix Information(3):
// Type[1]
// Length * 8bytes[1]
// Prefix Length[1]
// Flags[1]: LA......
// Valid Lifetime[4]
// Preferred Lifetime[4]
// Reserved[4]
// Prefix[16]
// Option=MTU(5):
// Type[1]
// Length * 8bytes[1]
// Reserved[2]
// MTU[4]
// Option=Source link-layer address(1):
// Link-Layer Address[6]
// Option=Recursive DNS Server(25):
// Type[1]
// Length * 8bytes[1]
// Reserved[2]
// Lifetime[4]
// Addresses of IPv6 Recursive DNS Servers[16]
func createICMPv6RAPacket(params icmpv6RA) []byte {
data := make([]byte, 88)
i := 0
// ICMPv6:
data[i] = 134 // type
data[i+1] = 0 // code
data[i+2] = 0 // chksum
data[i+3] = 0
i += 4
// RouterAdvertisement:
data[i] = 64 // Cur Hop Limit[1]
i++
data[i] = 0 // Flags[1]: MO......
if params.managedAddressConfiguration {
data[i] |= 0x80
}
if params.otherConfiguration {
data[i] |= 0x40
}
i++
binary.BigEndian.PutUint16(data[i:], 1800) // Router Lifetime[2]
i += 2
binary.BigEndian.PutUint32(data[i:], 0) // Reachable Time[4]
i += 4
binary.BigEndian.PutUint32(data[i:], 0) // Retrans Timer[4]
i += 4
// Option=Prefix Information:
data[i] = 3 // Type
data[i+1] = 4 // Length
i += 2
data[i] = byte(params.prefixLen) // Prefix Length[1]
i++
data[i] = 0xc0 // Flags[1]
i++
binary.BigEndian.PutUint32(data[i:], 3600) // Valid Lifetime[4]
i += 4
binary.BigEndian.PutUint32(data[i:], 3600) // Preferred Lifetime[4]
i += 4
binary.BigEndian.PutUint32(data[i:], 0) // Reserved[4]
i += 4
copy(data[i:], params.prefix[:8]) // Prefix[16]
binary.BigEndian.PutUint32(data[i+8:], 0)
binary.BigEndian.PutUint32(data[i+12:], 0)
i += 16
// Option=MTU:
data[i] = 5 // Type
data[i+1] = 1 // Length
i += 2
binary.BigEndian.PutUint16(data[i:], 0) // Reserved[2]
i += 2
binary.BigEndian.PutUint32(data[i:], params.mtu) // MTU[4]
i += 4
// Option=Source link-layer address:
data[i] = 1 // Type
data[i+1] = 1 // Length
i += 2
copy(data[i:], params.sourceLinkLayerAddress) // Link-Layer Address[6]
i += 6
// Option=Recursive DNS Server:
data[i] = 25 // Type
data[i+1] = 3 // Length
i += 2
binary.BigEndian.PutUint16(data[i:], 0) // Reserved[2]
i += 2
binary.BigEndian.PutUint32(data[i:], 3600) // Lifetime[4]
i += 4
copy(data[i:], params.recursiveDNSServer) // Addresses of IPv6 Recursive DNS Servers[16]
return data
}
// Init - initialize RA module
func (ra *raCtx) Init() error {
ra.stop.Store(0)
ra.conn = nil
if !(ra.raAllowSlaac || ra.raSlaacOnly) {
return nil
}
log.Debug("DHCPv6 RA: source IP address: %s DNS IP address: %s",
ra.ipAddr, ra.dnsIPAddr)
params := icmpv6RA{
managedAddressConfiguration: !ra.raSlaacOnly,
otherConfiguration: !ra.raSlaacOnly,
mtu: uint32(ra.iface.MTU),
prefixLen: 64,
recursiveDNSServer: ra.dnsIPAddr,
sourceLinkLayerAddress: ra.iface.HardwareAddr,
}
params.prefix = make([]byte, 16)
copy(params.prefix, ra.prefixIPAddr[:8]) // /64
data := createICMPv6RAPacket(params)
var err error
ipAndScope := ra.ipAddr.String() + "%" + ra.ifaceName
ra.conn, err = icmp.ListenPacket("ip6:ipv6-icmp", ipAndScope)
if err != nil {
return fmt.Errorf("DHCPv6 RA: icmp.ListenPacket: %s", err)
}
success := false
defer func() {
if !success {
ra.Close()
}
}()
con6 := ra.conn.IPv6PacketConn()
if err := con6.SetHopLimit(255); err != nil {
return fmt.Errorf("DHCPv6 RA: SetHopLimit: %s", err)
}
if err := con6.SetMulticastHopLimit(255); err != nil {
return fmt.Errorf("DHCPv6 RA: SetMulticastHopLimit: %s", err)
}
msg := &ipv6.ControlMessage{
HopLimit: 255,
Src: ra.ipAddr,
IfIndex: ra.iface.Index,
}
addr := &net.UDPAddr{
IP: net.ParseIP("ff02::1"),
}
go func() {
log.Debug("DHCPv6 RA: starting to send periodic RouterAdvertisement packets")
for ra.stop.Load() == 0 {
_, err = con6.WriteTo(data, msg, addr)
if err != nil {
log.Error("DHCPv6 RA: WriteTo: %s", err)
}
time.Sleep(ra.packetSendPeriod)
}
log.Debug("DHCPv6 RA: loop exit")
}()
success = true
return nil
}
// Close - close module
func (ra *raCtx) Close() {
log.Debug("DHCPv6 RA: closing")
ra.stop.Store(1)
if ra.conn != nil {
ra.conn.Close()
}
}

31
dhcpd/router_adv_test.go Normal file
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@@ -0,0 +1,31 @@
package dhcpd
import (
"bytes"
"net"
"testing"
"github.com/stretchr/testify/assert"
)
func TestRA(t *testing.T) {
ra := icmpv6RA{
managedAddressConfiguration: false,
otherConfiguration: true,
mtu: 1500,
prefix: net.ParseIP("1234::"),
prefixLen: 64,
recursiveDNSServer: net.ParseIP("fe80::800:27ff:fe00:0"),
sourceLinkLayerAddress: []byte{0x0a, 0x00, 0x27, 0x00, 0x00, 0x00},
}
data := createICMPv6RAPacket(ra)
dataCorrect := []byte{
0x86, 0x00, 0x00, 0x00, 0x40, 0x40, 0x07, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x03, 0x04, 0x40, 0xc0, 0x00, 0x00, 0x0e, 0x10, 0x00, 0x00, 0x0e, 0x10, 0x00, 0x00, 0x00, 0x00,
0x12, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x05, 0xdc, 0x01, 0x01, 0x0a, 0x00, 0x27, 0x00, 0x00, 0x00,
0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x10, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x08, 0x00, 0x27, 0xff, 0xfe, 0x00, 0x00, 0x00,
}
assert.True(t, bytes.Equal(data, dataCorrect))
}

3
dhcpd/server.go
View File

@@ -83,6 +83,9 @@ type V6ServerConf struct {
LeaseDuration uint32 `yaml:"lease_duration"` // in seconds
RaSlaacOnly bool `yaml:"ra_slaac_only"` // send ICMPv6.RA packets without MO flags
RaAllowSlaac bool `yaml:"ra_allow_slaac"` // send ICMPv6.RA packets with MO flags
ipStart net.IP // starting IP address for dynamic leases
leaseTime time.Duration // the time during which a dynamic lease is considered valid
dnsIPAddrs []net.IP // IPv6 addresses to return to DHCP clients as DNS server addresses

43
dhcpd/v6.go
View File

@@ -25,6 +25,8 @@ type v6Server struct {
ipAddrs [256]byte
sid dhcpv6.Duid
ra raCtx // RA module
conf V6ServerConf
}
@@ -557,6 +559,27 @@ func getIfaceIPv6(iface net.Interface) []net.IP {
return res
}
// initialize RA module
func (s *v6Server) initRA(iface *net.Interface) error {
// choose the source IP address - should be link-local-unicast
s.ra.ipAddr = s.conf.dnsIPAddrs[0]
for _, ip := range s.conf.dnsIPAddrs {
if ip.IsLinkLocalUnicast() {
s.ra.ipAddr = ip
break
}
}
s.ra.raAllowSlaac = s.conf.RaAllowSlaac
s.ra.raSlaacOnly = s.conf.RaSlaacOnly
s.ra.dnsIPAddr = s.ra.ipAddr
s.ra.prefixIPAddr = s.conf.ipStart
s.ra.ifaceName = s.conf.InterfaceName
s.ra.iface = iface
s.ra.packetSendPeriod = 1 * time.Second
return s.ra.Init()
}
// Start - start server
func (s *v6Server) Start() error {
if !s.conf.Enabled {
@@ -568,13 +591,25 @@ func (s *v6Server) Start() error {
return wrapErrPrint(err, "Couldn't find interface by name %s", s.conf.InterfaceName)
}
log.Debug("DHCPv6: starting...")
s.conf.dnsIPAddrs = getIfaceIPv6(*iface)
if len(s.conf.dnsIPAddrs) == 0 {
log.Debug("DHCPv6: no IPv6 address for interface %s", iface.Name)
return nil
}
err = s.initRA(iface)
if err != nil {
return err
}
// don't initialize DHCPv6 server if we must force the clients to use SLAAC
if s.conf.RaSlaacOnly {
log.Debug("DHCPv6: not starting DHCPv6 server due to ra_slaac_only=true")
return nil
}
log.Debug("DHCPv6: starting...")
if len(iface.HardwareAddr) != 6 {
return fmt.Errorf("DHCPv6: invalid MAC %s", iface.HardwareAddr)
}
@@ -598,11 +633,15 @@ func (s *v6Server) Start() error {
err = s.srv.Serve()
log.Debug("DHCPv6: srv.Serve: %s", err)
}()
return nil
}
// Stop - stop server
func (s *v6Server) Stop() {
s.ra.Close()
// DHCPv6 server may not be initialized if ra_slaac_only=true
if s.srv == nil {
return
}
@@ -626,7 +665,7 @@ func v6Create(conf V6ServerConf) (DHCPServer, error) {
}
s.conf.ipStart = net.ParseIP(conf.RangeStart)
if s.conf.ipStart == nil {
if s.conf.ipStart == nil || s.conf.ipStart.To16() == nil {
return s, fmt.Errorf("DHCPv6: invalid range-start IP: %s", conf.RangeStart)
}