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Add configuration entry to control including TXT records for node meta in DNS responses 

If set to false, the only way to retrieve TXT records for node meta is to specifically query for TXT records.
This commit is contained in:
Matt Keeler 2018-06-11 11:49:04 -04:00
parent 6e9cbeecd0
commit 6cc0422408
6 changed files with 205 additions and 5 deletions
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10
agent/config/builder.go
View File

@ -592,6 +592,7 @@ func (b *Builder) Build() (rt RuntimeConfig, err error) {
DNSRecursors: dnsRecursors,
DNSServiceTTL: dnsServiceTTL,
DNSUDPAnswerLimit: b.intVal(c.DNS.UDPAnswerLimit),
DNSNodeMetaTXT: b.boolValWithDefault(c.DNS.NodeMetaTXT, true),
// HTTP
HTTPPort: httpPort,
@ -1010,13 +1011,18 @@ func (b *Builder) serviceVal(v *ServiceDefinition) *structs.ServiceDefinition {
}
}
func (b *Builder) boolVal(v *bool) bool {
func (b *Builder) boolValWithDefault(v *bool, default_val bool) bool {
if v == nil {
return false
return default_val
}
return *v
}
func (b *Builder) boolVal(v *bool) bool {
return b.boolValWithDefault(v, false)
}
func (b *Builder) durationVal(name string, v *string) (d time.Duration) {
if v == nil {
return 0

1
agent/config/config.go
View File

@ -360,6 +360,7 @@ type DNS struct {
RecursorTimeout *string `json:"recursor_timeout,omitempty" hcl:"recursor_timeout" mapstructure:"recursor_timeout"`
ServiceTTL map[string]string `json:"service_ttl,omitempty" hcl:"service_ttl" mapstructure:"service_ttl"`
UDPAnswerLimit *int `json:"udp_answer_limit,omitempty" hcl:"udp_answer_limit" mapstructure:"udp_answer_limit"`
NodeMetaTXT *bool `json:"additional_node_meta_txt,omitempty" hcl:"additional_node_meta_txt" mapstructure:"additional_node_meta_txt"`
}
type HTTPConfig struct {

5
agent/config/runtime.go
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@ -281,6 +281,11 @@ type RuntimeConfig struct {
// hcl: dns_config { udp_answer_limit = int }
DNSUDPAnswerLimit int
// DNSNodeMetaTXT controls whether DNS queries will synthesize
// TXT records for the node metadata and add them when not specifically
// request (query type = TXT). If unset this will default to true
DNSNodeMetaTXT bool
// DNSRecursors can be set to allow the DNS servers to recursively
// resolve non-consul domains.
//

21
agent/dns.go
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@ -51,6 +51,7 @@ type dnsConfig struct {
ServiceTTL map[string]time.Duration
UDPAnswerLimit int
ARecordLimit int
NodeMetaTXT bool
}
// DNSServer is used to wrap an Agent and expose various
@ -109,6 +110,7 @@ func GetDNSConfig(conf *config.RuntimeConfig) *dnsConfig {
SegmentName: conf.SegmentName,
ServiceTTL: conf.DNSServiceTTL,
UDPAnswerLimit: conf.DNSUDPAnswerLimit,
NodeMetaTXT: conf.DNSNodeMetaTXT,
}
}
@ -671,7 +673,20 @@ func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qTy
}
}
if node != nil && (qType == dns.TypeANY || qType == dns.TypeTXT) {
node_meta_txt := true
if node == nil {
node_meta_txt = false
} else if qType == dns.TypeANY {
// Since any RR type is requested allow the configuration to
// determine whether or not node meta gets added as TXT records
node_meta_txt = d.config.NodeMetaTXT
} else if qType != dns.TypeTXT {
// qType isn't TXT or ANY so avoid emitting the TXT records
node_meta_txt = false
}
if node_meta_txt {
for key, value := range node.Meta {
txt := value
if !strings.HasPrefix(strings.ToLower(key), "rfc1035-") {
@ -782,8 +797,8 @@ func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
originalNumRecords := len(resp.Answer)
// It is not possible to return more than 4k records even with compression
// Since we are performing binary search it is not a big deal, but it
// improves a bit performance, even with binary search
// Since we are performing binary search it is not a big deal, but it
// improves a bit performance, even with binary search
truncateAt := 4096
if req.Question[0].Qtype == dns.TypeSRV {
// More than 1024 SRV records do not fit in 64k

168
agent/dns_test.go
View File

@ -472,6 +472,51 @@ func TestDNS_NodeLookup_TXT(t *testing.T) {
}
}
func TestDNS_NodeLookup_TXT_DontSuppress(t *testing.T) {
a := NewTestAgent(t.Name(), `dns_config = { additional_node_meta_txt = false }`)
defer a.Shutdown()
args := &structs.RegisterRequest{
Datacenter: "dc1",
Node: "google",
Address: "127.0.0.1",
NodeMeta: map[string]string{
"rfc1035-00": "value0",
"key0": "value1",
},
}
var out struct{}
if err := a.RPC("Catalog.Register", args, &out); err != nil {
t.Fatalf("err: %v", err)
}
m := new(dns.Msg)
m.SetQuestion("google.node.consul.", dns.TypeTXT)
c := new(dns.Client)
in, _, err := c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", err)
}
// Should have the 1 TXT record reply
if len(in.Answer) != 2 {
t.Fatalf("Bad: %#v", in)
}
txtRec, ok := in.Answer[0].(*dns.TXT)
if !ok {
t.Fatalf("Bad: %#v", in.Answer[0])
}
if len(txtRec.Txt) != 1 {
t.Fatalf("Bad: %#v", in.Answer[0])
}
if txtRec.Txt[0] != "value0" && txtRec.Txt[0] != "key0=value1" {
t.Fatalf("Bad: %#v", in.Answer[0])
}
}
func TestDNS_NodeLookup_ANY(t *testing.T) {
a := NewTestAgent(t.Name(), ``)
defer a.Shutdown()
@ -513,6 +558,42 @@ func TestDNS_NodeLookup_ANY(t *testing.T) {
}
func TestDNS_NodeLookup_ANY_SuppressTXT(t *testing.T) {
a := NewTestAgent(t.Name(), `dns_config = { 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{}
if err := a.RPC("Catalog.Register", args, &out); err != nil {
t.Fatalf("err: %v", err)
}
m := new(dns.Msg)
m.SetQuestion("bar.node.consul.", dns.TypeANY)
c := new(dns.Client)
in, _, err := c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", 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)
}
func TestDNS_EDNS0(t *testing.T) {
t.Parallel()
a := NewTestAgent(t.Name(), "")
@ -4613,6 +4694,93 @@ func TestDNS_ServiceLookup_FilterACL(t *testing.T) {
}
}
func TestDNS_ServiceLookup_MetaTXT(t *testing.T) {
a := NewTestAgent(t.Name(), `dns_config = { additional_node_meta_txt = true }`)
defer a.Shutdown()
args := &structs.RegisterRequest{
Datacenter: "dc1",
Node: "bar",
Address: "127.0.0.1",
NodeMeta: map[string]string{
"key": "value",
},
Service: &structs.NodeService{
Service: "db",
Tags: []string{"master"},
Port: 12345,
},
}
var out struct{}
if err := a.RPC("Catalog.Register", args, &out); err != nil {
t.Fatalf("err: %v", err)
}
m := new(dns.Msg)
m.SetQuestion("db.service.consul.", dns.TypeSRV)
c := new(dns.Client)
in, _, err := c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", err)
}
wantAdditional := []dns.RR{
&dns.A{
Hdr: dns.RR_Header{Name: "bar.node.dc1.consul.", Rrtype: dns.TypeA, Class: dns.ClassINET, Rdlength: 0x4},
A: []byte{0x7f, 0x0, 0x0, 0x1}, // 127.0.0.1
},
&dns.TXT{
Hdr: dns.RR_Header{Name: "bar.node.dc1.consul.", Rrtype: dns.TypeTXT, Class: dns.ClassINET, Rdlength: 0xa},
Txt: []string{"key=value"},
},
}
verify.Values(t, "additional", in.Extra, wantAdditional)
}
func TestDNS_ServiceLookup_SuppressTXT(t *testing.T) {
a := NewTestAgent(t.Name(), `dns_config = { additional_node_meta_txt = false }`)
defer a.Shutdown()
// Register a node with a service.
args := &structs.RegisterRequest{
Datacenter: "dc1",
Node: "bar",
Address: "127.0.0.1",
NodeMeta: map[string]string{
"key": "value",
},
Service: &structs.NodeService{
Service: "db",
Tags: []string{"master"},
Port: 12345,
},
}
var out struct{}
if err := a.RPC("Catalog.Register", args, &out); err != nil {
t.Fatalf("err: %v", err)
}
m := new(dns.Msg)
m.SetQuestion("db.service.consul.", dns.TypeSRV)
c := new(dns.Client)
in, _, err := c.Exchange(m, a.DNSAddr())
if err != nil {
t.Fatalf("err: %v", err)
}
wantAdditional := []dns.RR{
&dns.A{
Hdr: dns.RR_Header{Name: "bar.node.dc1.consul.", Rrtype: dns.TypeA, Class: dns.ClassINET, Rdlength: 0x4},
A: []byte{0x7f, 0x0, 0x0, 0x1}, // 127.0.0.1
},
}
verify.Values(t, "additional", in.Extra, wantAdditional)
}
func TestDNS_AddressLookup(t *testing.T) {
t.Parallel()
a := NewTestAgent(t.Name(), "")

5
website/source/docs/agent/options.html.md
View File

@ -777,6 +777,11 @@ Consul will not enable TLS for the HTTP API unless the `https` port has been ass
[RFC 6724](https://tools.ietf.org/html/rfc6724) and as a result it should
be increasingly uncommon to need to change this value with modern
resolvers).
* <a name="additional_node_meta_txt"></a><a href="#additional_node_meta_txt">`additional_node_meta_txt`</a> - If set
to false, node metadata will not be synthesized into TXT records and returned except for queries specifically for
TXT records. By default, TXT records will be generated for node queries with an ANY query type or for SRV queries
of services.
* <a name="domain"></a><a href="#domain">`domain`</a> Equivalent to the
[`-domain` command-line flag](#_domain).