Fix #1764

+ rewrites: support IP exception; support "pass A only" case

* commit '32610840f9a0769bb58c7443a485c5e5b0cd2b68':
  + rewrites: support IP exception; support "pass A only" case

AGHTechDoc.md

@@ -986,6 +986,110 @@ Response:
 This section allows the administrator to easily configure custom DNS response for a specific domain name.
 A, AAAA and CNAME records are supported.
 
+Syntax:
+
+	key -> value
+
+where `key` is a host name or a wild card that matches Question in DNS request
+and `value` is either:
+* IPv4 address: use this IP in A response
+* IPv6 address: use this IP in AAAA response
+* canonical name: add CNAME record
+* "<key>": CNAME exception - pass request to upstream
+* "A": A exception - pass A request to upstream
+* "AAAA": AAAA exception - pass AAAA request to upstream
+
+
+#### Example: A record
+
+	host.com -> 1.2.3.4
+
+Response:
+
+	A:
+		A = 1.2.3.4
+	AAAA:
+		<empty>
+
+#### Example: AAAA record
+
+	host.com -> ::1
+
+Response:
+
+	A:
+		<empty>
+	AAAA:
+		AAAA = ::1
+
+#### Example: CNAME record
+
+	sub.host.com -> host.com
+
+Response:
+
+	A:
+		CNAME = host.com
+		A = <IPv4 address of host.com>
+	AAAA:
+		CNAME = host.com
+		AAAA = <IPv6 address of host.com>
+
+#### Example: CNAME+A records
+
+	sub.host.com -> host.com
+	host.com -> 1.2.3.4
+
+Response:
+
+	A:
+		CNAME = host.com
+		A = 1.2.3.4
+	AAAA:
+		CNAME = host.com
+
+#### Example: Wildcard CNAME+A record with CNAME exception
+
+	*.host.com -> 1.2.3.4
+	pass.host.com -> pass.host.com
+
+Response to `my.host.com`:
+
+	A:
+		A = 1.2.3.4
+	AAAA:
+		<empty>
+
+Response to `pass.host.com`:
+
+	A:
+		A = <IPv4 address of pass.host.com>
+	AAAA:
+		AAAA = <IPv6 address of pass.host.com>
+
+#### Example: A record with AAAA exception
+
+	host.com -> 1.2.3.4
+	host.com -> AAAA
+
+Response:
+
+	A:
+		A = 1.2.3.4
+	AAAA:
+		AAAA = <IPv6 address of host.com>
+
+#### Example: pass A only
+
+	host.com -> A
+
+Response:
+
+	A:
+		A = <IPv4 address of host.com>
+	AAAA:
+		<empty>
+
 
 ### API: List rewrite entries
 

dnsfilter/dnsfilter.go

@@ -316,7 +316,7 @@ func (d *Dnsfilter) CheckHost(host string, qtype uint16, setts *RequestFiltering
 	var result Result
 	var err error
 
-	result = d.processRewrites(host)
+	result = d.processRewrites(host, qtype)
 	if result.Reason == ReasonRewrite {
 		return result, nil
 	}
@@ -398,8 +398,8 @@ func (d *Dnsfilter) CheckHost(host string, qtype uint16, setts *RequestFiltering
 //  . if found, set domain name to canonical name
 //  . repeat for the new domain name (Note: we return only the last CNAME)
 // . Find A or AAAA record for a domain name (exact match or by wildcard)
-//  . if found, return IP addresses (both IPv4 and IPv6)
+//  . if found, set IP addresses (IPv4 or IPv6 depending on qtype) in Result.IPList array
-func (d *Dnsfilter) processRewrites(host string) Result {
+func (d *Dnsfilter) processRewrites(host string, qtype uint16) Result {
 	var res Result
 
 	d.confLock.RLock()
@@ -432,7 +432,14 @@ func (d *Dnsfilter) processRewrites(host string) Result {
 	}
 
 	for _, r := range rr {
-		if r.Type != dns.TypeCNAME {
+		if (r.Type == dns.TypeA && qtype == dns.TypeA) ||
+			(r.Type == dns.TypeAAAA && qtype == dns.TypeAAAA) {
+
+			if r.IP == nil { // IP exception
+				res.Reason = 0
+				return res
+			}
+
 			res.IPList = append(res.IPList, r.IP)
 			log.Debug("Rewrite: A/AAAA for %s is %s", host, r.IP)
 		}

dnsfilter/rewrites.go

@@ -69,6 +69,16 @@ func (a rewritesArray) Less(i, j int) bool {
 
 // Prepare entry for use
 func (r *RewriteEntry) prepare() {
+	if r.Answer == "AAAA" {
+		r.IP = nil
+		r.Type = dns.TypeAAAA
+		return
+	} else if r.Answer == "A" {
+		r.IP = nil
+		r.Type = dns.TypeA
+		return
+	}
+
 	ip := net.ParseIP(r.Answer)
 	if ip == nil {
 		r.Type = dns.TypeCNAME

dnsfilter/rewrites_test.go

@@ -4,6 +4,7 @@ import (
 	"net"
 	"testing"
 
+	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -20,16 +21,21 @@ func TestRewrites(t *testing.T) {
 		RewriteEntry{"www.host.com", "host.com", 0, nil},
 	}
 	d.prepareRewrites()
-	r := d.processRewrites("host2.com")
+	r := d.processRewrites("host2.com", dns.TypeA)
 	assert.Equal(t, NotFilteredNotFound, r.Reason)
 
-	r = d.processRewrites("www.host.com")
+	r = d.processRewrites("www.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, "host.com", r.CanonName)
-	assert.True(t, len(r.IPList) == 3)
+	assert.Equal(t, 2, len(r.IPList))
 	assert.True(t, r.IPList[0].Equal(net.ParseIP("1.2.3.4")))
 	assert.True(t, r.IPList[1].Equal(net.ParseIP("1.2.3.5")))
-	assert.True(t, r.IPList[2].Equal(net.ParseIP("1:2:3::4")))
+
+	r = d.processRewrites("www.host.com", dns.TypeAAAA)
+	assert.Equal(t, ReasonRewrite, r.Reason)
+	assert.Equal(t, "host.com", r.CanonName)
+	assert.Equal(t, 1, len(r.IPList))
+	assert.True(t, r.IPList[0].Equal(net.ParseIP("1:2:3::4")))
 
 	// wildcard
 	d.Rewrites = []RewriteEntry{
@@ -37,15 +43,15 @@ func TestRewrites(t *testing.T) {
 		RewriteEntry{"*.host.com", "1.2.3.5", 0, nil},
 	}
 	d.prepareRewrites()
-	r = d.processRewrites("host.com")
+	r = d.processRewrites("host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.True(t, r.IPList[0].Equal(net.ParseIP("1.2.3.4")))
 
-	r = d.processRewrites("www.host.com")
+	r = d.processRewrites("www.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.True(t, r.IPList[0].Equal(net.ParseIP("1.2.3.5")))
 
-	r = d.processRewrites("www.host2.com")
+	r = d.processRewrites("www.host2.com", dns.TypeA)
 	assert.Equal(t, NotFilteredNotFound, r.Reason)
 
 	// override a wildcard
@@ -54,7 +60,7 @@ func TestRewrites(t *testing.T) {
 		RewriteEntry{"*.host.com", "1.2.3.5", 0, nil},
 	}
 	d.prepareRewrites()
-	r = d.processRewrites("a.host.com")
+	r = d.processRewrites("a.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.True(t, len(r.IPList) == 1)
 	assert.True(t, r.IPList[0].Equal(net.ParseIP("1.2.3.4")))
@@ -65,7 +71,7 @@ func TestRewrites(t *testing.T) {
 		RewriteEntry{"*.host.com", "host.com", 0, nil},
 	}
 	d.prepareRewrites()
-	r = d.processRewrites("www.host.com")
+	r = d.processRewrites("www.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, "host.com", r.CanonName)
 	assert.True(t, r.IPList[0].Equal(net.ParseIP("1.2.3.4")))
@@ -77,7 +83,7 @@ func TestRewrites(t *testing.T) {
 		RewriteEntry{"host.com", "1.2.3.4", 0, nil},
 	}
 	d.prepareRewrites()
-	r = d.processRewrites("b.host.com")
+	r = d.processRewrites("b.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, "host.com", r.CanonName)
 	assert.True(t, len(r.IPList) == 1)
@@ -90,7 +96,7 @@ func TestRewrites(t *testing.T) {
 		RewriteEntry{"*.somehost.com", "1.2.3.4", 0, nil},
 	}
 	d.prepareRewrites()
-	r = d.processRewrites("b.host.com")
+	r = d.processRewrites("b.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, "x.somehost.com", r.CanonName)
 	assert.True(t, len(r.IPList) == 1)
@@ -108,25 +114,25 @@ func TestRewritesLevels(t *testing.T) {
 	d.prepareRewrites()
 
 	// match exact
-	r := d.processRewrites("host.com")
+	r := d.processRewrites("host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, 1, len(r.IPList))
 	assert.Equal(t, "1.1.1.1", r.IPList[0].String())
 
 	// match L2
-	r = d.processRewrites("sub.host.com")
+	r = d.processRewrites("sub.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, 1, len(r.IPList))
 	assert.Equal(t, "2.2.2.2", r.IPList[0].String())
 
 	// match L3
-	r = d.processRewrites("my.sub.host.com")
+	r = d.processRewrites("my.sub.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, 1, len(r.IPList))
 	assert.Equal(t, "3.3.3.3", r.IPList[0].String())
 }
 
-func TestRewritesException(t *testing.T) {
+func TestRewritesExceptionCNAME(t *testing.T) {
 	d := Dnsfilter{}
 	// wildcard; exception for a sub-domain
 	d.Rewrites = []RewriteEntry{
@@ -136,13 +142,13 @@ func TestRewritesException(t *testing.T) {
 	d.prepareRewrites()
 
 	// match sub-domain
-	r := d.processRewrites("my.host.com")
+	r := d.processRewrites("my.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, 1, len(r.IPList))
 	assert.Equal(t, "2.2.2.2", r.IPList[0].String())
 
 	// match sub-domain, but handle exception
-	r = d.processRewrites("sub.host.com")
+	r = d.processRewrites("sub.host.com", dns.TypeA)
 	assert.Equal(t, NotFilteredNotFound, r.Reason)
 }
 
@@ -156,12 +162,54 @@ func TestRewritesExceptionWC(t *testing.T) {
 	d.prepareRewrites()
 
 	// match sub-domain
-	r := d.processRewrites("my.host.com")
+	r := d.processRewrites("my.host.com", dns.TypeA)
 	assert.Equal(t, ReasonRewrite, r.Reason)
 	assert.Equal(t, 1, len(r.IPList))
 	assert.Equal(t, "2.2.2.2", r.IPList[0].String())
 
 	// match sub-domain, but handle exception
-	r = d.processRewrites("my.sub.host.com")
+	r = d.processRewrites("my.sub.host.com", dns.TypeA)
 	assert.Equal(t, NotFilteredNotFound, r.Reason)
 }
+
+func TestRewritesExceptionIP(t *testing.T) {
+	d := Dnsfilter{}
+	// exception for AAAA record
+	d.Rewrites = []RewriteEntry{
+		RewriteEntry{"host.com", "1.2.3.4", 0, nil},
+		RewriteEntry{"host.com", "AAAA", 0, nil},
+		RewriteEntry{"host2.com", "::1", 0, nil},
+		RewriteEntry{"host2.com", "A", 0, nil},
+		RewriteEntry{"host3.com", "A", 0, nil},
+	}
+	d.prepareRewrites()
+
+	// match domain
+	r := d.processRewrites("host.com", dns.TypeA)
+	assert.Equal(t, ReasonRewrite, r.Reason)
+	assert.Equal(t, 1, len(r.IPList))
+	assert.Equal(t, "1.2.3.4", r.IPList[0].String())
+
+	// match exception
+	r = d.processRewrites("host.com", dns.TypeAAAA)
+	assert.Equal(t, NotFilteredNotFound, r.Reason)
+
+	// match exception
+	r = d.processRewrites("host2.com", dns.TypeA)
+	assert.Equal(t, NotFilteredNotFound, r.Reason)
+
+	// match domain
+	r = d.processRewrites("host2.com", dns.TypeAAAA)
+	assert.Equal(t, ReasonRewrite, r.Reason)
+	assert.Equal(t, 1, len(r.IPList))
+	assert.Equal(t, "::1", r.IPList[0].String())
+
+	// match exception
+	r = d.processRewrites("host3.com", dns.TypeA)
+	assert.Equal(t, NotFilteredNotFound, r.Reason)
+
+	// match domain
+	r = d.processRewrites("host3.com", dns.TypeAAAA)
+	assert.Equal(t, ReasonRewrite, r.Reason)
+	assert.Equal(t, 0, len(r.IPList))
+}

dnsforward/filter.go

@@ -65,12 +65,11 @@ func (s *Server) filterDNSRequest(ctx *dnsContext) (*dnsfilter.Result, error) {
 		}
 
 		for _, ip := range res.IPList {
-			ip4 := ip.To4()
+			if req.Question[0].Qtype == dns.TypeA {
-			if req.Question[0].Qtype == dns.TypeA && ip4 != nil {
+				a := s.genAAnswer(req, ip.To4())
-				a := s.genAAnswer(req, ip4)
 				a.Hdr.Name = dns.Fqdn(name)
 				resp.Answer = append(resp.Answer, a)
-			} else if req.Question[0].Qtype == dns.TypeAAAA && ip4 == nil {
+			} else if req.Question[0].Qtype == dns.TypeAAAA {
 				a := s.genAAAAAnswer(req, ip)
 				a.Hdr.Name = dns.Fqdn(name)
 				resp.Answer = append(resp.Answer, a)