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+ dns: respond to PTR requests for internal IP addresses from DHCP
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Close #1682

Squashed commit of the following:

commit 2fad354
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Jun 22 17:32:45 2020 +0300

    minor

commit 7c17992
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Jun 22 16:09:34 2020 +0300

    build

commit 16a52e1
Merge: 7b6a73c 2c47053
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Jun 22 16:08:32 2020 +0300

    Merge remote-tracking branch 'origin/master' into 1682-dhcp-resolve

commit 7b6a73c
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Jun 22 16:01:34 2020 +0300

    tests

commit c2654ab
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Jun 1 15:15:13 2020 +0300

    + dnsforward: respond to PTR requests for internal IP addresses

    {[IP] => "host"} <- DNSforward <-(leases)-- DHCP
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@szolin
szolin committed Jun 23, 2020
1 parent 2c47053 commit 49a9260
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Showing 9 changed files with 237 additions and 90 deletions.
10 changes: 6 additions & 4 deletions dhcpd/dhcpd.go
View file
Expand Up @@ -92,7 +92,7 @@ type Server struct {
conf ServerConfig

// Called when the leases DB is modified
onLeaseChanged onLeaseChangedT
onLeaseChanged []onLeaseChangedT
}

// Print information about the available network interfaces
Expand Down Expand Up @@ -146,14 +146,16 @@ func (s *Server) Init(config ServerConfig) error {

// SetOnLeaseChanged - set callback
func (s *Server) SetOnLeaseChanged(onLeaseChanged onLeaseChangedT) {
s.onLeaseChanged = onLeaseChanged
s.onLeaseChanged = append(s.onLeaseChanged, onLeaseChanged)
}

func (s *Server) notify(flags int) {
if s.onLeaseChanged == nil {
if len(s.onLeaseChanged) == 0 {
return
}
s.onLeaseChanged(flags)
for _, f := range s.onLeaseChanged {
f(flags)
}
}

// WriteDiskConfig - write configuration
Expand Down
37 changes: 28 additions & 9 deletions dnsforward/dnsforward.go
View file
Expand Up @@ -8,6 +8,7 @@ import (
"sync"
"time"

"github.com/AdguardTeam/AdGuardHome/dhcpd"
"github.com/AdguardTeam/AdGuardHome/dnsfilter"
"github.com/AdguardTeam/AdGuardHome/querylog"
"github.com/AdguardTeam/AdGuardHome/stats"
Expand Down Expand Up @@ -43,11 +44,15 @@ var webRegistered bool
//
// The zero Server is empty and ready for use.
type Server struct {
dnsProxy *proxy.Proxy // DNS proxy instance
dnsFilter *dnsfilter.Dnsfilter // DNS filter instance
queryLog querylog.QueryLog // Query log instance
stats stats.Stats
access *accessCtx
dnsProxy *proxy.Proxy // DNS proxy instance
dnsFilter *dnsfilter.Dnsfilter // DNS filter instance
dhcpServer *dhcpd.Server // DHCP server instance (optional)
queryLog querylog.QueryLog // Query log instance
stats stats.Stats
access *accessCtx

tablePTR map[string]string // "IP -> hostname" table for reverse lookup
tablePTRLock sync.Mutex

// DNS proxy instance for internal usage
// We don't Start() it and so no listen port is required.
Expand All @@ -59,13 +64,27 @@ type Server struct {
conf ServerConfig
}

// DNSCreateParams - parameters for NewServer()
type DNSCreateParams struct {
DNSFilter *dnsfilter.Dnsfilter
Stats stats.Stats
QueryLog querylog.QueryLog
DHCPServer *dhcpd.Server
}

// NewServer creates a new instance of the dnsforward.Server
// Note: this function must be called only once
func NewServer(dnsFilter *dnsfilter.Dnsfilter, stats stats.Stats, queryLog querylog.QueryLog) *Server {
func NewServer(p DNSCreateParams) *Server {
s := &Server{}
s.dnsFilter = dnsFilter
s.stats = stats
s.queryLog = queryLog
s.dnsFilter = p.DNSFilter
s.stats = p.Stats
s.queryLog = p.QueryLog
s.dhcpServer = p.DHCPServer

if s.dhcpServer != nil {
s.dhcpServer.SetOnLeaseChanged(s.onDHCPLeaseChanged)
s.onDHCPLeaseChanged(dhcpd.LeaseChangedAdded)
}

if runtime.GOARCH == "mips" || runtime.GOARCH == "mipsle" {
// Use plain DNS on MIPS, encryption is too slow
Expand Down
43 changes: 40 additions & 3 deletions dnsforward/dnsforward_test.go
View file
Expand Up @@ -15,6 +15,7 @@ import (
"testing"
"time"

"github.com/AdguardTeam/AdGuardHome/dhcpd"
"github.com/AdguardTeam/AdGuardHome/dnsfilter"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/dnsproxy/upstream"
Expand Down Expand Up @@ -496,7 +497,7 @@ func TestBlockedCustomIP(t *testing.T) {
c := dnsfilter.Config{}

f := dnsfilter.New(&c, filters)
s := NewServer(f, nil, nil)
s := NewServer(DNSCreateParams{DNSFilter: f})
conf := ServerConfig{}
conf.UDPListenAddr = &net.UDPAddr{Port: 0}
conf.TCPListenAddr = &net.TCPAddr{Port: 0}
Expand Down Expand Up @@ -648,7 +649,7 @@ func TestRewrite(t *testing.T) {
}

f := dnsfilter.New(&c, nil)
s := NewServer(f, nil, nil)
s := NewServer(DNSCreateParams{DNSFilter: f})
conf := ServerConfig{}
conf.UDPListenAddr = &net.UDPAddr{Port: 0}
conf.TCPListenAddr = &net.TCPAddr{Port: 0}
Expand Down Expand Up @@ -705,7 +706,7 @@ func createTestServer(t *testing.T) *Server {
c.CacheTime = 30

f := dnsfilter.New(&c, filters)
s := NewServer(f, nil, nil)
s := NewServer(DNSCreateParams{DNSFilter: f})
s.conf.UDPListenAddr = &net.UDPAddr{Port: 0}
s.conf.TCPListenAddr = &net.TCPAddr{Port: 0}
s.conf.UpstreamDNS = []string{"8.8.8.8:53", "8.8.4.4:53"}
Expand Down Expand Up @@ -1012,3 +1013,39 @@ func TestMatchDNSName(t *testing.T) {
assert.True(t, !matchDNSName(dnsNames, ""))
assert.True(t, !matchDNSName(dnsNames, "*.host2"))
}

func TestPTRResponse(t *testing.T) {
dhcp := &dhcpd.Server{}
dhcp.IPpool = make(map[[4]byte]net.HardwareAddr)

c := dnsfilter.Config{}
f := dnsfilter.New(&c, nil)
s := NewServer(DNSCreateParams{DNSFilter: f, DHCPServer: dhcp})
s.conf.UDPListenAddr = &net.UDPAddr{Port: 0}
s.conf.TCPListenAddr = &net.TCPAddr{Port: 0}
s.conf.UpstreamDNS = []string{"127.0.0.1:53"}
s.conf.FilteringConfig.ProtectionEnabled = true
err := s.Prepare(nil)
assert.True(t, err == nil)
assert.Nil(t, s.Start())

l := dhcpd.Lease{}
l.IP = net.ParseIP("127.0.0.1").To4()
l.HWAddr, _ = net.ParseMAC("aa:aa:aa:aa:aa:aa")
l.Hostname = "localhost"
dhcp.AddStaticLease(l)

addr := s.dnsProxy.Addr(proxy.ProtoUDP)
req := createTestMessage("1.0.0.127.in-addr.arpa.")
req.Question[0].Qtype = dns.TypePTR

resp, err := dns.Exchange(req, addr.String())
assert.Nil(t, err)
assert.Equal(t, 1, len(resp.Answer))
assert.Equal(t, dns.TypePTR, resp.Answer[0].Header().Rrtype)
assert.Equal(t, "1.0.0.127.in-addr.arpa.", resp.Answer[0].Header().Name)
ptr := resp.Answer[0].(*dns.PTR)
assert.Equal(t, "localhost.", ptr.Ptr)

s.Close()
}
75 changes: 75 additions & 0 deletions dnsforward/handle_dns.go
View file
@@ -1,9 +1,12 @@
package dnsforward

import (
"strings"
"time"

"github.com/AdguardTeam/AdGuardHome/dhcpd"
"github.com/AdguardTeam/AdGuardHome/dnsfilter"
"github.com/AdguardTeam/AdGuardHome/util"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/golibs/log"
"github.com/miekg/dns"
Expand Down Expand Up @@ -39,6 +42,7 @@ func (s *Server) handleDNSRequest(_ *proxy.Proxy, d *proxy.DNSContext) error {
type modProcessFunc func(ctx *dnsContext) int
mods := []modProcessFunc{
processInitial,
processInternalIPAddrs,
processFilteringBeforeRequest,
processUpstream,
processDNSSECAfterResponse,
Expand Down Expand Up @@ -88,11 +92,82 @@ func processInitial(ctx *dnsContext) int {
return resultDone
}

func (s *Server) onDHCPLeaseChanged(flags int) {
switch flags {
case dhcpd.LeaseChangedAdded,
dhcpd.LeaseChangedAddedStatic,
dhcpd.LeaseChangedRemovedStatic:
//
default:
return
}

m := make(map[string]string)
ll := s.dhcpServer.Leases(dhcpd.LeasesAll)
for _, l := range ll {
if len(l.Hostname) == 0 {
continue
}
m[l.IP.String()] = l.Hostname
}
log.Debug("DNS: added %d PTR entries from DHCP", len(m))
s.tablePTRLock.Lock()
s.tablePTR = m
s.tablePTRLock.Unlock()
}

// Respond to PTR requests if the target IP address is leased by our DHCP server
func processInternalIPAddrs(ctx *dnsContext) int {
s := ctx.srv
req := ctx.proxyCtx.Req
if req.Question[0].Qtype != dns.TypePTR {
return resultDone
}

arpa := req.Question[0].Name
arpa = strings.TrimSuffix(arpa, ".")
arpa = strings.ToLower(arpa)
ip := util.DNSUnreverseAddr(arpa)
if ip == nil {
return resultDone
}

s.tablePTRLock.Lock()
if s.tablePTR == nil {
s.tablePTRLock.Unlock()
return resultDone
}
host, ok := s.tablePTR[ip.String()]
s.tablePTRLock.Unlock()
if !ok {
return resultDone
}

log.Debug("DNS: reverse-lookup: %s -> %s", arpa, host)

resp := s.makeResponse(req)
ptr := &dns.PTR{}
ptr.Hdr = dns.RR_Header{
Name: req.Question[0].Name,
Rrtype: dns.TypePTR,
Ttl: s.conf.BlockedResponseTTL,
Class: dns.ClassINET,
}
ptr.Ptr = host + "."
resp.Answer = append(resp.Answer, ptr)
ctx.proxyCtx.Res = resp
return resultDone
}

// Apply filtering logic
func processFilteringBeforeRequest(ctx *dnsContext) int {
s := ctx.srv
d := ctx.proxyCtx

if d.Res != nil {
return resultDone // response is already set - nothing to do
}

s.RLock()
// Synchronize access to s.dnsFilter so it won't be suddenly uninitialized while in use.
// This could happen after proxy server has been stopped, but its workers are not yet exited.
Expand Down
8 changes: 7 additions & 1 deletion home/dns.go
View file
Expand Up @@ -61,7 +61,13 @@ func initDNSServer() error {
filterConf.HTTPRegister = httpRegister
Context.dnsFilter = dnsfilter.New(&filterConf, nil)

Context.dnsServer = dnsforward.NewServer(Context.dnsFilter, Context.stats, Context.queryLog)
p := dnsforward.DNSCreateParams{
DNSFilter: Context.dnsFilter,
Stats: Context.stats,
QueryLog: Context.queryLog,
DHCPServer: Context.dhcpServer,
}
Context.dnsServer = dnsforward.NewServer(p)
dnsConfig := generateServerConfig()
err = Context.dnsServer.Prepare(&dnsConfig)
if err != nil {
Expand Down
2 changes: 1 addition & 1 deletion home/whois_test.go
View file
Expand Up @@ -9,7 +9,7 @@ import (

func prepareTestDNSServer() error {
config.DNS.Port = 1234
Context.dnsServer = dnsforward.NewServer(nil, nil, nil)
Context.dnsServer = dnsforward.NewServer(dnsforward.DNSCreateParams{})
conf := &dnsforward.ServerConfig{}
conf.UpstreamDNS = []string{"8.8.8.8"}
return Context.dnsServer.Prepare(conf)
Expand Down
66 changes: 1 addition & 65 deletions util/auto_hosts.go
View file
Expand Up @@ -296,78 +296,14 @@ func (a *AutoHosts) Process(host string, qtype uint16) []net.IP {
return ipsCopy
}

// convert character to hex number
func charToHex(n byte) int8 {
if n >= '0' && n <= '9' {
return int8(n) - '0'
} else if (n|0x20) >= 'a' && (n|0x20) <= 'f' {
return (int8(n) | 0x20) - 'a' + 10
}
return -1
}

// parse IPv6 reverse address
func ipParseArpa6(s string) net.IP {
if len(s) != 63 {
return nil
}
ip6 := make(net.IP, 16)

for i := 0; i != 64; i += 4 {

// parse "0.1."
n := charToHex(s[i])
n2 := charToHex(s[i+2])
if s[i+1] != '.' || (i != 60 && s[i+3] != '.') ||
n < 0 || n2 < 0 {
return nil
}

ip6[16-i/4-1] = byte(n2<<4) | byte(n&0x0f)
}
return ip6
}

// ipReverse - reverse IP address: 1.0.0.127 -> 127.0.0.1
func ipReverse(ip net.IP) net.IP {
n := len(ip)
r := make(net.IP, n)
for i := 0; i != n; i++ {
r[i] = ip[n-i-1]
}
return r
}

// Convert reversed ARPA address to a normal IP address
func dnsUnreverseAddr(s string) net.IP {
const arpaV4 = ".in-addr.arpa"
const arpaV6 = ".ip6.arpa"

if strings.HasSuffix(s, arpaV4) {
ip := strings.TrimSuffix(s, arpaV4)
ip4 := net.ParseIP(ip).To4()
if ip4 == nil {
return nil
}

return ipReverse(ip4)

} else if strings.HasSuffix(s, arpaV6) {
ip := strings.TrimSuffix(s, arpaV6)
return ipParseArpa6(ip)
}

return nil // unknown suffix
}

// ProcessReverse - process PTR request
// Return "" if not found or an error occurred
func (a *AutoHosts) ProcessReverse(addr string, qtype uint16) string {
if qtype != dns.TypePTR {
return ""
}

ipReal := dnsUnreverseAddr(addr)
ipReal := DNSUnreverseAddr(addr)
if ipReal == nil {
return "" // invalid IP in question
}
Expand Down
16 changes: 9 additions & 7 deletions util/auto_hosts_test.go
View file
Expand Up @@ -104,11 +104,13 @@ func TestAutoHostsFSNotify(t *testing.T) {
}

func TestIP(t *testing.T) {
assert.True(t, dnsUnreverseAddr("1.0.0.127.in-addr.arpa").Equal(net.ParseIP("127.0.0.1").To4()))
assert.True(t, dnsUnreverseAddr("4.3.2.1.d.c.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa").Equal(net.ParseIP("::abcd:1234")))

assert.True(t, dnsUnreverseAddr("1.0.0.127.in-addr.arpa.") == nil)
assert.True(t, dnsUnreverseAddr(".0.0.127.in-addr.arpa") == nil)
assert.True(t, dnsUnreverseAddr(".3.2.1.d.c.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") == nil)
assert.True(t, dnsUnreverseAddr("4.3.2.1.d.c.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0..ip6.arpa") == nil)
assert.Equal(t, "127.0.0.1", DNSUnreverseAddr("1.0.0.127.in-addr.arpa").String())
assert.Equal(t, "::abcd:1234", DNSUnreverseAddr("4.3.2.1.d.c.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa").String())
assert.Equal(t, "::abcd:1234", DNSUnreverseAddr("4.3.2.1.d.c.B.A.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa").String())

assert.Nil(t, DNSUnreverseAddr("1.0.0.127.in-addr.arpa."))
assert.Nil(t, DNSUnreverseAddr(".0.0.127.in-addr.arpa"))
assert.Nil(t, DNSUnreverseAddr(".3.2.1.d.c.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa"))
assert.Nil(t, DNSUnreverseAddr("4.3.2.1.d.c.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0..ip6.arpa"))
assert.Nil(t, DNSUnreverseAddr("4.3.2.1.d.c.b. .0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa"))
}

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