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Merge pull request #4362 from hashicorp/bugfix/gh-4354
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Ensure TXT RRs always end up in the Additional section except for ANY or TXT queries
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@mkeeler
mkeeler authored Jul 10, 2018
2 parents efa13a1 + cbf8f14 commit d066fb7
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Showing 2 changed files with 121 additions and 69 deletions.
60 changes: 38 additions & 22 deletions agent/dns.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -376,8 +376,11 @@ func (d *DNSServer) nameservers(edns bool) (ns []dns.RR, extra []dns.RR) {
}
ns = append(ns, nsrr)

glue := d.formatNodeRecord(nil, addr, fqdn, dns.TypeANY, d.config.NodeTTL, edns, false)
glue, meta := d.formatNodeRecord(nil, addr, fqdn, dns.TypeANY, d.config.NodeTTL, edns)
extra = append(extra, glue...)
if meta != nil && d.config.NodeMetaTXT {
extra = append(extra, meta...)
}

// don't provide more than 3 servers
if len(ns) >= 3 {
Expand Down Expand Up @@ -592,10 +595,15 @@ RPC:
n := out.NodeServices.Node
edns := req.IsEdns0() != nil
addr := d.agent.TranslateAddress(datacenter, n.Address, n.TaggedAddresses)
records := d.formatNodeRecord(out.NodeServices.Node, addr, req.Question[0].Name, qType, d.config.NodeTTL, edns, true)
records, meta := d.formatNodeRecord(out.NodeServices.Node, addr, req.Question[0].Name, qType, d.config.NodeTTL, edns)
if records != nil {
resp.Answer = append(resp.Answer, records...)
}
if meta != nil && (qType == dns.TypeANY || qType == dns.TypeTXT) {
resp.Answer = append(resp.Answer, meta...)
} else if meta != nil && d.config.NodeMetaTXT {
resp.Extra = append(resp.Extra, meta...)
}
}

// encodeKVasRFC1464 encodes a key-value pair according to RFC1464
Expand All @@ -619,8 +627,12 @@ func encodeKVasRFC1464(key, value string) (txt string) {
return key + "=" + value
}

// formatNodeRecord takes a Node and returns an A, AAAA, TXT or CNAME record
func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qType uint16, ttl time.Duration, edns, answer bool) (records []dns.RR) {
// formatNodeRecord takes a Node and returns the RRs associated with that node
//
// The return value is two slices. The first slice is the main answer slice (containing the A, AAAA, CNAME) RRs for the node
// and the second slice contains any TXT RRs created from the node metadata. It is up to the caller to determine where the
// generated RRs should go and if they should be used at all.
func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qType uint16, ttl time.Duration, edns bool) (records, meta []dns.RR) {
// Parse the IP
ip := net.ParseIP(addr)
var ipv4 net.IP
Expand Down Expand Up @@ -681,26 +693,14 @@ func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qTy
}
}

node_meta_txt := false

if node == nil {
node_meta_txt = false
} else if answer {
node_meta_txt = true
} else {
// Use configuration when the TXT RR would
// end up in the Additional section of the
// DNS response
node_meta_txt = d.config.NodeMetaTXT
}

if node_meta_txt {
if node != nil {
for key, value := range node.Meta {
txt := value
if !strings.HasPrefix(strings.ToLower(key), "rfc1035-") {
txt = encodeKVasRFC1464(key, value)
}
records = append(records, &dns.TXT{

meta = append(meta, &dns.TXT{
Hdr: dns.RR_Header{
Name: qName,
Rrtype: dns.TypeTXT,
Expand All @@ -712,7 +712,7 @@ func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qTy
}
}

return records
return records, meta
}

// indexRRs populates a map which indexes a given list of RRs by name. NOTE that
Expand Down Expand Up @@ -1167,9 +1167,21 @@ func (d *DNSServer) serviceNodeRecords(dc string, nodes structs.CheckServiceNode
handled[addr] = struct{}{}

// Add the node record
records := d.formatNodeRecord(node.Node, addr, qName, qType, ttl, edns, true)
had_answer := false
records, meta := d.formatNodeRecord(node.Node, addr, qName, qType, ttl, edns)
if records != nil {
resp.Answer = append(resp.Answer, records...)
had_answer = true
}

if meta != nil && (qType == dns.TypeANY || qType == dns.TypeTXT) {
resp.Answer = append(resp.Answer, meta...)
had_answer = true
} else if meta != nil && d.config.NodeMetaTXT {
resp.Extra = append(resp.Extra, meta...)
}

if had_answer {
count++
if count == d.config.ARecordLimit {
// We stop only if greater than 0 or we reached the limit
Expand Down Expand Up @@ -1216,7 +1228,7 @@ func (d *DNSServer) serviceSRVRecords(dc string, nodes structs.CheckServiceNodes
}

// Add the extra record
records := d.formatNodeRecord(node.Node, addr, srvRec.Target, dns.TypeANY, ttl, edns, false)
records, meta := d.formatNodeRecord(node.Node, addr, srvRec.Target, dns.TypeANY, ttl, edns)
if len(records) > 0 {
// Use the node address if it doesn't differ from the service address
if addr == node.Node.Address {
Expand Down Expand Up @@ -1246,6 +1258,10 @@ func (d *DNSServer) serviceSRVRecords(dc string, nodes structs.CheckServiceNodes
resp.Extra = append(resp.Extra, records...)
}
}

if meta != nil && d.config.NodeMetaTXT {
resp.Extra = append(resp.Extra, meta...)
}
}
}
}
Expand Down
130 changes: 83 additions & 47 deletions agent/dns_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,9 @@ func TestDNS_NodeLookup(t *testing.T) {
TaggedAddresses: map[string]string{
"wan": "127.0.0.2",
},
NodeMeta: map[string]string{
"key": "value",
},
}

var out struct{}
Expand All @@ -190,72 +193,70 @@ func TestDNS_NodeLookup(t *testing.T) {

c := new(dns.Client)
in, _, err := c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", err)
}

if len(in.Answer) != 1 {
t.Fatalf("Bad: %#v", in)
}
require.NoError(t, err)
require.Len(t, in.Answer, 2)
require.Len(t, in.Extra, 0)

aRec, ok := in.Answer[0].(*dns.A)
if !ok {
t.Fatalf("Bad: %#v", in.Answer[0])
}
if aRec.A.String() != "127.0.0.1" {
t.Fatalf("Bad: %#v", in.Answer[0])
}
if aRec.Hdr.Ttl != 0 {
t.Fatalf("Bad: %#v", in.Answer[0])
}
require.True(t, ok, "First answer is not an A record")
require.Equal(t, "127.0.0.1", aRec.A.String())
require.Equal(t, uint32(0), aRec.Hdr.Ttl)

txt, ok := in.Answer[1].(*dns.TXT)
require.True(t, ok, "Second answer is not a TXT record")
require.Len(t, txt.Txt, 1)
require.Equal(t, "key=value", txt.Txt[0])

// Re-do the query, but only for an A RR

m = new(dns.Msg)
m.SetQuestion("foo.node.consul.", dns.TypeA)

c = new(dns.Client)
in, _, err = c.Exchange(m, a.DNSAddr())
require.NoError(t, err)
require.Len(t, in.Answer, 1)
require.Len(t, in.Extra, 1)

aRec, ok = in.Answer[0].(*dns.A)
require.True(t, ok, "Answer is not an A record")
require.Equal(t, "127.0.0.1", aRec.A.String())
require.Equal(t, uint32(0), aRec.Hdr.Ttl)

txt, ok = in.Extra[0].(*dns.TXT)
require.True(t, ok, "Extra record is not a TXT record")
require.Len(t, txt.Txt, 1)
require.Equal(t, "key=value", txt.Txt[0])

// Re-do the query, but specify the DC
m = new(dns.Msg)
m.SetQuestion("foo.node.dc1.consul.", dns.TypeANY)

c = new(dns.Client)
in, _, err = c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", err)
}

if len(in.Answer) != 1 {
t.Fatalf("Bad: %#v", in)
}
require.NoError(t, err)
require.Len(t, in.Answer, 2)
require.Len(t, in.Extra, 0)

aRec, ok = in.Answer[0].(*dns.A)
if !ok {
t.Fatalf("Bad: %#v", in.Answer[0])
}
if aRec.A.String() != "127.0.0.1" {
t.Fatalf("Bad: %#v", in.Answer[0])
}
if aRec.Hdr.Ttl != 0 {
t.Fatalf("Bad: %#v", in.Answer[0])
}
require.True(t, ok, "First answer is not an A record")
require.Equal(t, "127.0.0.1", aRec.A.String())
require.Equal(t, uint32(0), aRec.Hdr.Ttl)

txt, ok = in.Answer[1].(*dns.TXT)
require.True(t, ok, "Second answer is not a TXT record")

// lookup a non-existing node, we should receive a SOA
m = new(dns.Msg)
m.SetQuestion("nofoo.node.dc1.consul.", dns.TypeANY)

c = new(dns.Client)
in, _, err = c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", err)
}

if len(in.Ns) != 1 {
t.Fatalf("Bad: %#v %#v", in, len(in.Answer))
}

require.NoError(t, err)
require.Len(t, in.Ns, 1)
soaRec, ok := in.Ns[0].(*dns.SOA)
if !ok {
t.Fatalf("Bad: %#v", in.Ns[0])
}
if soaRec.Hdr.Ttl != 0 {
t.Fatalf("Bad: %#v", in.Ns[0])
}

require.True(t, ok, "NS RR is not a SOA record")
require.Equal(t, uint32(0), soaRec.Hdr.Ttl)
}

func TestDNS_CaseInsensitiveNodeLookup(t *testing.T) {
Expand Down Expand Up @@ -598,6 +599,41 @@ func TestDNS_NodeLookup_ANY_DontSuppressTXT(t *testing.T) {
verify.Values(t, "answer", in.Answer, wantAnswer)
}

func TestDNS_NodeLookup_A_SuppressTXT(t *testing.T) {
a := NewTestAgent(t.Name(), `dns_config = { enable_additional_node_meta_txt = false }`)
defer a.Shutdown()

args := &structs.RegisterRequest{
Datacenter: "dc1",
Node: "bar",
Address: "127.0.0.1",
NodeMeta: map[string]string{
"key": "value",
},
}

var out struct{}
require.NoError(t, a.RPC("Catalog.Register", args, &out))

m := new(dns.Msg)
m.SetQuestion("bar.node.consul.", dns.TypeA)

c := new(dns.Client)
in, _, err := c.Exchange(m, a.DNSAddr())
require.NoError(t, err)

wantAnswer := []dns.RR{
&dns.A{
Hdr: dns.RR_Header{Name: "bar.node.consul.", Rrtype: dns.TypeA, Class: dns.ClassINET, Rdlength: 0x4},
A: []byte{0x7f, 0x0, 0x0, 0x1}, // 127.0.0.1
},
}
verify.Values(t, "answer", in.Answer, wantAnswer)

// ensure TXT RR suppression
require.Len(t, in.Extra, 0)
}

func TestDNS_EDNS0(t *testing.T) {
t.Parallel()
a := NewTestAgent(t.Name(), "")
Expand Down

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