agent: Fixing DNS CNAME recursion
This commit is contained in:
Armon Dadgar
parent
8c314d3041
commit
141086eee8
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@ -16,6 +16,7 @@ const (
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testQuery = "_test.consul."
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consulDomain = "consul."
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maxServiceResponses = 3 // For UDP only
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maxRecurseRecords = 3
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)
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// DNSServer is used to wrap an Agent and expose various
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@ -175,7 +176,7 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
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m := new(dns.Msg)
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m.SetReply(req)
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m.Authoritative = true
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m.RecursionAvailable = true
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m.RecursionAvailable = (d.recursor != "")
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// Only add the SOA if requested
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if req.Question[0].Qtype == dns.TypeSOA {
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@ -313,22 +314,14 @@ func (d *DNSServer) nodeLookup(network, datacenter, node string, req, resp *dns.
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}
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// Add the node record
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record := formatNodeRecord(&out.NodeServices.Node, req.Question[0].Name, qType)
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if record != nil {
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resp.Answer = append(resp.Answer, record)
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// Try to recursively resolve the CNAME
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if cnRec, ok := record.(*dns.CNAME); ok {
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aRecs := d.resolveCNAME(cnRec.Target)
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if len(aRecs) > 0 {
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resp.Extra = append(resp.Extra, aRecs[0])
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}
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}
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records := d.formatNodeRecord(&out.NodeServices.Node, req.Question[0].Name, qType)
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if records != nil {
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resp.Answer = append(resp.Answer, records...)
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}
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}
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// formatNodeRecord takes a Node and returns an A, AAAA, or CNAME record
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func formatNodeRecord(node *structs.Node, qName string, qType uint16) dns.RR {
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func (d *DNSServer) formatNodeRecord(node *structs.Node, qName string, qType uint16) (records []dns.RR) {
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// Parse the IP
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ip := net.ParseIP(node.Address)
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var ipv4 net.IP
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@ -337,7 +330,7 @@ func formatNodeRecord(node *structs.Node, qName string, qType uint16) dns.RR {
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}
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switch {
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case ipv4 != nil && (qType == dns.TypeANY || qType == dns.TypeA):
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return &dns.A{
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return []dns.RR{&dns.A{
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Hdr: dns.RR_Header{
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Name: qName,
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Rrtype: dns.TypeA,
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@ -345,10 +338,10 @@ func formatNodeRecord(node *structs.Node, qName string, qType uint16) dns.RR {
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Ttl: 0,
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},
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A: ip,
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}
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}}
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case ip != nil && ipv4 == nil && (qType == dns.TypeANY || qType == dns.TypeAAAA):
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return &dns.AAAA{
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return []dns.RR{&dns.AAAA{
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Hdr: dns.RR_Header{
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Name: qName,
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Rrtype: dns.TypeAAAA,
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@ -356,10 +349,12 @@ func formatNodeRecord(node *structs.Node, qName string, qType uint16) dns.RR {
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Ttl: 0,
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},
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AAAA: ip,
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}
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}}
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case ip == nil && (qType == dns.TypeANY || qType == dns.TypeCNAME):
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return &dns.CNAME{
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case ip == nil && (qType == dns.TypeANY || qType == dns.TypeCNAME ||
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qType == dns.TypeA || qType == dns.TypeAAAA):
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// Get the CNAME
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cnRec := &dns.CNAME{
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Hdr: dns.RR_Header{
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Name: qName,
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Rrtype: dns.TypeCNAME,
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@ -368,9 +363,26 @@ func formatNodeRecord(node *structs.Node, qName string, qType uint16) dns.RR {
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},
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Target: dns.Fqdn(node.Address),
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}
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default:
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return nil
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records = append(records, cnRec)
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// Recurse
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more := d.resolveCNAME(cnRec.Target)
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extra := 0
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MORE_REC:
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for _, rr := range more {
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switch rr.Header().Rrtype {
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case dns.TypeA:
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fallthrough
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case dns.TypeAAAA:
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records = append(records, rr)
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extra++
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if extra == maxRecurseRecords {
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break MORE_REC
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}
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}
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}
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}
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return records
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}
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// serviceLookup is used to handle a service query
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@ -410,12 +422,9 @@ func (d *DNSServer) serviceLookup(network, datacenter, service, tag string, req,
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qType := req.Question[0].Qtype
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d.serviceNodeRecords(out.Nodes, req, resp)
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if qType == dns.TypeANY || qType == dns.TypeSRV {
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if qType == dns.TypeSRV {
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d.serviceSRVRecords(datacenter, out.Nodes, req, resp)
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}
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// Cleanup duplicate extra entries
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resp.Extra = removeDuplicates(resp.Extra)
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}
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// filterServiceNodes is used to filter out nodes that are failing
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@ -460,17 +469,9 @@ func (d *DNSServer) serviceNodeRecords(nodes structs.CheckServiceNodes, req, res
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handled[addr] = struct{}{}
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// Add the node record
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record := formatNodeRecord(&node.Node, qName, qType)
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if record != nil {
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resp.Answer = append(resp.Answer, record)
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// Try to recursively resolve the CNAME
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if cnRec, ok := record.(*dns.CNAME); ok {
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aRecs := d.resolveCNAME(cnRec.Target)
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if len(aRecs) > 0 {
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resp.Extra = append(resp.Extra, aRecs[0])
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}
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}
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records := d.formatNodeRecord(&node.Node, qName, qType)
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if records != nil {
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resp.Answer = append(resp.Answer, records...)
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}
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}
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}
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@ -502,26 +503,10 @@ func (d *DNSServer) serviceSRVRecords(dc string, nodes structs.CheckServiceNodes
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}
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resp.Answer = append(resp.Answer, srvRec)
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// Avoid duplicate extra records, possible if a node has
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// the same service on multiple ports, etc.
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addr := node.Node.Address
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if _, ok := handled[addr]; ok {
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continue
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}
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handled[addr] = struct{}{}
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// Add the extra record
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record := formatNodeRecord(&node.Node, srvRec.Target, dns.TypeANY)
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if record != nil {
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resp.Extra = append(resp.Extra, record)
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// Try to recursively resolve the CNAME
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if cnRec, ok := record.(*dns.CNAME); ok {
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aRecs := d.resolveCNAME(cnRec.Target)
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if len(aRecs) > 0 {
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resp.Extra = append(resp.Extra, aRecs[0])
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}
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}
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records := d.formatNodeRecord(&node.Node, srvRec.Target, dns.TypeANY)
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if records != nil {
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resp.Extra = append(resp.Extra, records...)
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}
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}
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}
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@ -584,23 +569,3 @@ func (d *DNSServer) resolveCNAME(name string) []dns.RR {
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// Return all the answers
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return r.Answer
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}
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// removeDuplicates is used to remove the duplicate entries.
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// This only deduplicates on the QName and QType
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func removeDuplicates(rr []dns.RR) []dns.RR {
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handled := make(map[string]struct{})
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n := len(rr)
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for i := 0; i < n; i++ {
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rec := rr[i]
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hdr := rec.Header()
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key := fmt.Sprintf("%s:%d", hdr.Name, hdr.Rrtype)
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if _, ok := handled[key]; ok {
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// Remove duplicate
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rr[i], rr[n-1] = rr[n-1], nil
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n--
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i--
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}
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handled[key] = struct{}{}
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}
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return rr[:n]
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}
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@ -190,7 +190,8 @@ func TestDNS_NodeLookup_CNAME(t *testing.T) {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 1 {
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// Should have the CNAME record + a few A records
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if len(in.Answer) < 2 {
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t.Fatalf("Bad: %#v", in)
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}
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@ -228,7 +229,7 @@ func TestDNS_ServiceLookup(t *testing.T) {
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}
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m := new(dns.Msg)
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m.SetQuestion("db.service.consul.", dns.TypeANY)
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m.SetQuestion("db.service.consul.", dns.TypeSRV)
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c := new(dns.Client)
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in, _, err := c.Exchange(m, srv.agent.config.DNSAddr)
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@ -236,22 +237,14 @@ func TestDNS_ServiceLookup(t *testing.T) {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 2 {
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if len(in.Answer) != 1 {
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t.Fatalf("Bad: %#v", in)
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}
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aRec, ok := in.Answer[0].(*dns.A)
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srvRec, ok := in.Answer[0].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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if aRec.A.String() != "127.0.0.1" {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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srvRec, ok := in.Answer[1].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[1])
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}
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if srvRec.Port != 12345 {
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t.Fatalf("Bad: %#v", srvRec)
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}
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@ -259,7 +252,7 @@ func TestDNS_ServiceLookup(t *testing.T) {
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t.Fatalf("Bad: %#v", srvRec)
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}
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aRec, ok = in.Extra[0].(*dns.A)
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aRec, ok := in.Extra[0].(*dns.A)
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if !ok {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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@ -334,7 +327,7 @@ func TestDNS_ServiceLookup_Dedup(t *testing.T) {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 3 {
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if len(in.Answer) != 1 {
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t.Fatalf("Bad: %#v", in)
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}
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@ -345,10 +338,78 @@ func TestDNS_ServiceLookup_Dedup(t *testing.T) {
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if aRec.A.String() != "127.0.0.1" {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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}
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srvRec, ok := in.Answer[1].(*dns.SRV)
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func TestDNS_ServiceLookup_Dedup_SRV(t *testing.T) {
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dir, srv := makeDNSServer(t)
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defer os.RemoveAll(dir)
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defer srv.agent.Shutdown()
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// Wait for leader
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time.Sleep(100 * time.Millisecond)
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// Register node
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args := &structs.RegisterRequest{
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Datacenter: "dc1",
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Node: "foo",
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Address: "127.0.0.1",
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Service: &structs.NodeService{
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Service: "db",
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Tag: "master",
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Port: 12345,
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},
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}
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var out struct{}
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if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
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t.Fatalf("err: %v", err)
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}
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args = &structs.RegisterRequest{
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Datacenter: "dc1",
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Node: "foo",
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Address: "127.0.0.1",
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Service: &structs.NodeService{
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ID: "db2",
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Service: "db",
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Tag: "slave",
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Port: 12345,
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},
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}
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if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
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t.Fatalf("err: %v", err)
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}
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args = &structs.RegisterRequest{
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Datacenter: "dc1",
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Node: "foo",
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Address: "127.0.0.1",
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Service: &structs.NodeService{
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ID: "db3",
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Service: "db",
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Tag: "slave",
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Port: 12346,
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},
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}
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if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
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t.Fatalf("err: %v", err)
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}
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m := new(dns.Msg)
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m.SetQuestion("db.service.consul.", dns.TypeSRV)
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c := new(dns.Client)
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in, _, err := c.Exchange(m, srv.agent.config.DNSAddr)
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if err != nil {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 2 {
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t.Fatalf("Bad: %#v", in)
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}
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srvRec, ok := in.Answer[0].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[1])
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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if srvRec.Port != 12345 && srvRec.Port != 12346 {
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t.Fatalf("Bad: %#v", srvRec)
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@ -357,21 +418,21 @@ func TestDNS_ServiceLookup_Dedup(t *testing.T) {
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t.Fatalf("Bad: %#v", srvRec)
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}
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srvRec, ok = in.Answer[2].(*dns.SRV)
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srvRec, ok = in.Answer[1].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[1])
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}
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if srvRec.Port != 12346 && srvRec.Port != 12345 {
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t.Fatalf("Bad: %#v", srvRec)
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}
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if srvRec.Port == in.Answer[1].(*dns.SRV).Port {
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if srvRec.Port == in.Answer[0].(*dns.SRV).Port {
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t.Fatalf("should be a different port")
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}
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if srvRec.Target != "foo.node.dc1.consul." {
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t.Fatalf("Bad: %#v", srvRec)
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}
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aRec, ok = in.Extra[0].(*dns.A)
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aRec, ok := in.Extra[0].(*dns.A)
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if !ok {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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@ -507,8 +568,8 @@ func TestDNS_ServiceLookup_Randomize(t *testing.T) {
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}
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// Response length should be truncated
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// We should get an SRV + A record for each response (hence 2x)
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if len(in.Answer) != 2*maxServiceResponses {
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// We should get an A record for each response
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if len(in.Answer) != maxServiceResponses {
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t.Fatalf("Bad: %#v", len(in.Answer))
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}
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@ -564,10 +625,11 @@ func TestDNS_ServiceLookup_CNAME(t *testing.T) {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 2 {
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if len(in.Answer) != 4 {
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t.Fatalf("Bad: %#v", in)
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}
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// Should have google CNAME
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cnRec, ok := in.Answer[0].(*dns.CNAME)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[0])
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@ -576,33 +638,10 @@ func TestDNS_ServiceLookup_CNAME(t *testing.T) {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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srvRec, ok := in.Answer[1].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[1])
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}
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if srvRec.Port != 80 {
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t.Fatalf("Bad: %#v", srvRec)
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}
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if srvRec.Target != "google.node.dc1.consul." {
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t.Fatalf("Bad: %#v", srvRec)
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}
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aRec, ok := in.Extra[0].(*dns.A)
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if !ok {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.Hdr.Name != "www.google.com." {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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cnRec, ok = in.Extra[1].(*dns.CNAME)
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if !ok {
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t.Fatalf("Bad: %#v", in.Extra[1])
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}
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if cnRec.Hdr.Name != "google.node.dc1.consul." {
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t.Fatalf("Bad: %#v", in.Extra[1])
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}
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if cnRec.Target != "www.google.com." {
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t.Fatalf("Bad: %#v", in.Extra[1])
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// Check we recursively resolve
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for i := 1; i < 4; i++ {
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if _, ok := in.Answer[i].(*dns.A); !ok {
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t.Fatalf("Bad: %#v", in.Answer[i])
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}
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}
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}
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