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Merge pull request #4215 from hashicorp/feature/config-node-meta-dns-txt 

Add configuration entry to control including TXT records for node meta in DNS responses
This commit is contained in:
Matt Keeler 2018-06-20 08:53:04 -04:00 committed by GitHub
parent 894667b87a 7f7c703118
commit 0d4e8676d1
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 216 additions and 10 deletions
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10
agent/config/builder.go
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@ -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
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@ -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:"enable_additional_node_meta_txt,omitempty" hcl:"enable_additional_node_meta_txt" mapstructure:"enable_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.
//

2
agent/config/runtime_test.go
View File

@ -3371,6 +3371,7 @@ func TestFullConfig(t *testing.T) {
DNSRecursors: []string{"63.38.39.58", "92.49.18.18"},
DNSServiceTTL: map[string]time.Duration{"*": 32030 * time.Second},
DNSUDPAnswerLimit: 29909,
DNSNodeMetaTXT: true,
DataDir: dataDir,
Datacenter: "rzo029wg",
DevMode: true,
@ -4043,6 +4044,7 @@ func TestSanitize(t *testing.T) {
"DNSDomain": "",
"DNSEnableTruncate": false,
"DNSMaxStale": "0s",
"DNSNodeMetaTXT": false,
"DNSNodeTTL": "0s",
"DNSOnlyPassing": false,
"DNSPort": 0,

31
agent/dns.go
View File

@ -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,
}
}
@ -374,7 +376,7 @@ 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)
glue := d.formatNodeRecord(nil, addr, fqdn, dns.TypeANY, d.config.NodeTTL, edns, false)
extra = append(extra, glue...)
// don't provide more than 3 servers
@ -582,7 +584,7 @@ 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)
records := d.formatNodeRecord(out.NodeServices.Node, addr, req.Question[0].Name, qType, d.config.NodeTTL, edns, true)
if records != nil {
resp.Answer = append(resp.Answer, records...)
}
@ -610,7 +612,7 @@ func encodeKVasRFC1464(key, value string) (txt string) {
}
// 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 bool) (records []dns.RR) {
func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qType uint16, ttl time.Duration, edns, answer bool) (records []dns.RR) {
// Parse the IP
ip := net.ParseIP(addr)
var ipv4 net.IP
@ -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 := 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 {
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
@ -1143,7 +1158,7 @@ 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)
records := d.formatNodeRecord(node.Node, addr, qName, qType, ttl, edns, true)
if records != nil {
resp.Answer = append(resp.Answer, records...)
count++
@ -1192,7 +1207,7 @@ 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)
records := d.formatNodeRecord(node.Node, addr, srvRec.Target, dns.TypeANY, ttl, edns, false)
if len(records) > 0 {
// Use the node address if it doesn't differ from the service address
if addr == node.Node.Address {

171
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 = { enable_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()
@ -510,7 +555,46 @@ func TestDNS_NodeLookup_ANY(t *testing.T) {
},
}
verify.Values(t, "answer", in.Answer, wantAnswer)
}
func TestDNS_NodeLookup_ANY_DontSuppressTXT(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{}
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
},
&dns.TXT{
Hdr: dns.RR_Header{Name: "bar.node.consul.", Rrtype: dns.TypeTXT, Class: dns.ClassINET, Rdlength: 0xa},
Txt: []string{"key=value"},
},
}
verify.Values(t, "answer", in.Answer, wantAnswer)
}
func TestDNS_EDNS0(t *testing.T) {
@ -4613,6 +4697,93 @@ func TestDNS_ServiceLookup_FilterACL(t *testing.T) {
}
}
func TestDNS_ServiceLookup_MetaTXT(t *testing.T) {
a := NewTestAgent(t.Name(), `dns_config = { enable_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 = { enable_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(), "")

6
website/source/docs/agent/options.html.md
View File

@ -777,6 +777,12 @@ 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="enable_additional_node_meta_txt"></a><a href="#enable_additional_node_meta_txt">`enable_additional_node_meta_txt`</a> -
When set to true, Consul will add TXT records for Node metadata into the Additional section of the DNS responses for several
query types such as SRV queries. When set to false those records are emitted. This does not impact the behavior of those
same TXT records when they would be added to the Answer section of the response like when querying with type TXT or ANY. This
defaults to true.
* <a name="domain"></a><a href="#domain">`domain`</a> Equivalent to the
[`-domain` command-line flag](#_domain).