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-rw-r--r--middleware/backend_lookup.go452
1 files changed, 452 insertions, 0 deletions
diff --git a/middleware/backend_lookup.go b/middleware/backend_lookup.go
new file mode 100644
index 000000000..a9a5e03fd
--- /dev/null
+++ b/middleware/backend_lookup.go
@@ -0,0 +1,452 @@
+package middleware
+
+import (
+ "fmt"
+ "math"
+ "net"
+ "time"
+
+ "github.com/miekg/coredns/middleware/etcd/msg"
+ "github.com/miekg/coredns/middleware/pkg/dnsutil"
+ "github.com/miekg/coredns/request"
+
+ "github.com/miekg/dns"
+)
+
+// A returns A records from Backend or an error.
+func A(b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, false, opt)
+ if err != nil {
+ return nil, debug, err
+ }
+
+ for _, serv := range services {
+ ip := net.ParseIP(serv.Host)
+ switch {
+ case ip == nil:
+ if Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
+ // x CNAME x is a direct loop, don't add those
+ continue
+ }
+
+ newRecord := serv.NewCNAME(state.QName(), serv.Host)
+ if len(previousRecords) > 7 {
+ // don't add it, and just continue
+ continue
+ }
+ if dnsutil.DuplicateCNAME(newRecord, previousRecords) {
+ continue
+ }
+
+ state1 := state.NewWithQuestion(serv.Host, state.QType())
+ nextRecords, nextDebug, err := A(b, zone, state1, append(previousRecords, newRecord), opt)
+
+ if err == nil {
+ // Not only have we found something we should add the CNAME and the IP addresses.
+ if len(nextRecords) > 0 {
+ records = append(records, newRecord)
+ records = append(records, nextRecords...)
+ debug = append(debug, nextDebug...)
+ }
+ continue
+ }
+ // This means we can not complete the CNAME, try to look else where.
+ target := newRecord.Target
+ if dns.IsSubDomain(zone, target) {
+ // We should already have found it
+ continue
+ }
+ // Lookup
+ m1, e1 := b.Lookup(state, target, state.QType())
+ if e1 != nil {
+ debugMsg := msg.Service{Key: msg.Path(target, b.Debug()), Host: target, Text: " IN " + state.Type() + ": " + e1.Error()}
+ debug = append(debug, debugMsg)
+ continue
+ }
+ // Len(m1.Answer) > 0 here is well?
+ records = append(records, newRecord)
+ records = append(records, m1.Answer...)
+ continue
+ case ip.To4() != nil:
+ records = append(records, serv.NewA(state.QName(), ip.To4()))
+ case ip.To4() == nil:
+ // nodata?
+ }
+ }
+ return records, debug, nil
+}
+
+// AAAA returns AAAA records from Backend or an error.
+func AAAA(b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, false, opt)
+ if err != nil {
+ return nil, debug, err
+ }
+
+ for _, serv := range services {
+ ip := net.ParseIP(serv.Host)
+ switch {
+ case ip == nil:
+ // Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
+ if Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
+ // x CNAME x is a direct loop, don't add those
+ continue
+ }
+
+ newRecord := serv.NewCNAME(state.QName(), serv.Host)
+ if len(previousRecords) > 7 {
+ // don't add it, and just continue
+ continue
+ }
+ if dnsutil.DuplicateCNAME(newRecord, previousRecords) {
+ continue
+ }
+
+ state1 := state.NewWithQuestion(serv.Host, state.QType())
+ nextRecords, nextDebug, err := AAAA(b, zone, state1, append(previousRecords, newRecord), opt)
+
+ if err == nil {
+ // Not only have we found something we should add the CNAME and the IP addresses.
+ if len(nextRecords) > 0 {
+ records = append(records, newRecord)
+ records = append(records, nextRecords...)
+ debug = append(debug, nextDebug...)
+ }
+ continue
+ }
+ // This means we can not complete the CNAME, try to look else where.
+ target := newRecord.Target
+ if dns.IsSubDomain(zone, target) {
+ // We should already have found it
+ continue
+ }
+ m1, e1 := b.Lookup(state, target, state.QType())
+ if e1 != nil {
+ debugMsg := msg.Service{Key: msg.Path(target, b.Debug()), Host: target, Text: " IN " + state.Type() + ": " + e1.Error()}
+ debug = append(debug, debugMsg)
+ continue
+ }
+ // Len(m1.Answer) > 0 here is well?
+ records = append(records, newRecord)
+ records = append(records, m1.Answer...)
+ continue
+ // both here again
+ case ip.To4() != nil:
+ // nada?
+ case ip.To4() == nil:
+ records = append(records, serv.NewAAAA(state.QName(), ip.To16()))
+ }
+ }
+ return records, debug, nil
+}
+
+// SRV returns SRV records from the Backend.
+// If the Target is not a name but an IP address, a name is created on the fly.
+func SRV(b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, false, opt)
+ if err != nil {
+ return nil, nil, nil, err
+ }
+
+ // Looping twice to get the right weight vs priority
+ w := make(map[int]int)
+ for _, serv := range services {
+ weight := 100
+ if serv.Weight != 0 {
+ weight = serv.Weight
+ }
+ if _, ok := w[serv.Priority]; !ok {
+ w[serv.Priority] = weight
+ continue
+ }
+ w[serv.Priority] += weight
+ }
+ lookup := make(map[string]bool)
+ for _, serv := range services {
+ w1 := 100.0 / float64(w[serv.Priority])
+ if serv.Weight == 0 {
+ w1 *= 100
+ } else {
+ w1 *= float64(serv.Weight)
+ }
+ weight := uint16(math.Floor(w1))
+ ip := net.ParseIP(serv.Host)
+ switch {
+ case ip == nil:
+ srv := serv.NewSRV(state.QName(), weight)
+ records = append(records, srv)
+
+ if _, ok := lookup[srv.Target]; ok {
+ break
+ }
+
+ lookup[srv.Target] = true
+
+ if !dns.IsSubDomain(zone, srv.Target) {
+ m1, e1 := b.Lookup(state, srv.Target, dns.TypeA)
+ if e1 == nil {
+ extra = append(extra, m1.Answer...)
+ } else {
+ debugMsg := msg.Service{Key: msg.Path(srv.Target, b.Debug()), Host: srv.Target, Text: " IN A: " + e1.Error()}
+ debug = append(debug, debugMsg)
+ }
+
+ m1, e1 = b.Lookup(state, srv.Target, dns.TypeAAAA)
+ if e1 == nil {
+ // If we have seen CNAME's we *assume* that they are already added.
+ for _, a := range m1.Answer {
+ if _, ok := a.(*dns.CNAME); !ok {
+ extra = append(extra, a)
+ }
+ }
+ } else {
+ debugMsg := msg.Service{Key: msg.Path(srv.Target, b.Debug()), Host: srv.Target, Text: " IN AAAA: " + e1.Error()}
+ debug = append(debug, debugMsg)
+ }
+ break
+ }
+ // Internal name, we should have some info on them, either v4 or v6
+ // Clients expect a complete answer, because we are a recursor in their view.
+ state1 := state.NewWithQuestion(srv.Target, dns.TypeA)
+ addr, debugAddr, e1 := A(b, zone, state1, nil, Options(opt))
+ if e1 == nil {
+ extra = append(extra, addr...)
+ debug = append(debug, debugAddr...)
+ }
+ // IPv6 lookups here as well? AAAA(zone, state1, nil).
+ case ip.To4() != nil:
+ serv.Host = msg.Domain(serv.Key)
+ srv := serv.NewSRV(state.QName(), weight)
+
+ records = append(records, srv)
+ extra = append(extra, serv.NewA(srv.Target, ip.To4()))
+ case ip.To4() == nil:
+ serv.Host = msg.Domain(serv.Key)
+ srv := serv.NewSRV(state.QName(), weight)
+
+ records = append(records, srv)
+ extra = append(extra, serv.NewAAAA(srv.Target, ip.To16()))
+ }
+ }
+ return records, extra, debug, nil
+}
+
+// MX returns MX records from the Backend. If the Target is not a name but an IP address, a name is created on the fly.
+func MX(b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, false, opt)
+ if err != nil {
+ return nil, nil, debug, err
+ }
+
+ lookup := make(map[string]bool)
+ for _, serv := range services {
+ if !serv.Mail {
+ continue
+ }
+ ip := net.ParseIP(serv.Host)
+ switch {
+ case ip == nil:
+ mx := serv.NewMX(state.QName())
+ records = append(records, mx)
+ if _, ok := lookup[mx.Mx]; ok {
+ break
+ }
+
+ lookup[mx.Mx] = true
+
+ if !dns.IsSubDomain(zone, mx.Mx) {
+ m1, e1 := b.Lookup(state, mx.Mx, dns.TypeA)
+ if e1 == nil {
+ extra = append(extra, m1.Answer...)
+ } else {
+ debugMsg := msg.Service{Key: msg.Path(mx.Mx, b.Debug()), Host: mx.Mx, Text: " IN A: " + e1.Error()}
+ debug = append(debug, debugMsg)
+ }
+ m1, e1 = b.Lookup(state, mx.Mx, dns.TypeAAAA)
+ if e1 == nil {
+ // If we have seen CNAME's we *assume* that they are already added.
+ for _, a := range m1.Answer {
+ if _, ok := a.(*dns.CNAME); !ok {
+ extra = append(extra, a)
+ }
+ }
+ } else {
+ debugMsg := msg.Service{Key: msg.Path(mx.Mx, b.Debug()), Host: mx.Mx, Text: " IN AAAA: " + e1.Error()}
+ debug = append(debug, debugMsg)
+ }
+ break
+ }
+ // Internal name
+ state1 := state.NewWithQuestion(mx.Mx, dns.TypeA)
+ addr, debugAddr, e1 := A(b, zone, state1, nil, opt)
+ if e1 == nil {
+ extra = append(extra, addr...)
+ debug = append(debug, debugAddr...)
+ }
+ // e.AAAA as well
+ case ip.To4() != nil:
+ serv.Host = msg.Domain(serv.Key)
+ records = append(records, serv.NewMX(state.QName()))
+ extra = append(extra, serv.NewA(serv.Host, ip.To4()))
+ case ip.To4() == nil:
+ serv.Host = msg.Domain(serv.Key)
+ records = append(records, serv.NewMX(state.QName()))
+ extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
+ }
+ }
+ return records, extra, debug, nil
+}
+
+// CNAME returns CNAME records from the backend or an error.
+func CNAME(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, true, opt)
+ if err != nil {
+ return nil, debug, err
+ }
+
+ if len(services) > 0 {
+ serv := services[0]
+ if ip := net.ParseIP(serv.Host); ip == nil {
+ records = append(records, serv.NewCNAME(state.QName(), serv.Host))
+ }
+ }
+ return records, debug, nil
+}
+
+// TXT returns TXT records from Backend or an error.
+func TXT(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, false, opt)
+ if err != nil {
+ return nil, debug, err
+ }
+
+ for _, serv := range services {
+ if serv.Text == "" {
+ continue
+ }
+ records = append(records, serv.NewTXT(state.QName()))
+ }
+ return records, debug, nil
+}
+
+// PTR returns the PTR records from the backend, only services that have a domain name as host are included.
+// TODO(miek|infoblox): move k8s to this as well.
+func PTR(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
+ services, debug, err := b.Services(state, true, opt)
+ if err != nil {
+ return nil, debug, err
+ }
+
+ for _, serv := range services {
+ if ip := net.ParseIP(serv.Host); ip == nil {
+ records = append(records, serv.NewPTR(state.QName(), serv.Host))
+ }
+ }
+ return records, debug, nil
+}
+
+// NS returns NS records from the backend
+func NS(b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, debug []msg.Service, err error) {
+ // NS record for this zone live in a special place, ns.dns.<zone>. Fake our lookup.
+ // only a tad bit fishy...
+ old := state.QName()
+
+ state.Clear()
+ state.Req.Question[0].Name = "ns.dns." + zone
+ services, debug, err := b.Services(state, false, opt)
+ if err != nil {
+ return nil, nil, debug, err
+ }
+ // ... and reset
+ state.Req.Question[0].Name = old
+
+ for _, serv := range services {
+ ip := net.ParseIP(serv.Host)
+ switch {
+ case ip == nil:
+ return nil, nil, debug, fmt.Errorf("NS record must be an IP address: %s", serv.Host)
+ case ip.To4() != nil:
+ serv.Host = msg.Domain(serv.Key)
+ records = append(records, serv.NewNS(state.QName()))
+ extra = append(extra, serv.NewA(serv.Host, ip.To4()))
+ case ip.To4() == nil:
+ serv.Host = msg.Domain(serv.Key)
+ records = append(records, serv.NewNS(state.QName()))
+ extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
+ }
+ }
+ return records, extra, debug, nil
+}
+
+// SOA returns a SOA record from the backend.
+func SOA(b ServiceBackend, zone string, state request.Request, opt Options) ([]dns.RR, []msg.Service, error) {
+ header := dns.RR_Header{Name: zone, Rrtype: dns.TypeSOA, Ttl: 300, Class: dns.ClassINET}
+
+ soa := &dns.SOA{Hdr: header,
+ Mbox: hostmaster + "." + zone,
+ Ns: "ns.dns." + zone,
+ Serial: uint32(time.Now().Unix()),
+ Refresh: 7200,
+ Retry: 1800,
+ Expire: 86400,
+ Minttl: minTTL,
+ }
+ // TODO(miek): fake some msg.Service here when returning?
+ return []dns.RR{soa}, nil, nil
+}
+
+// BackendError writes an error response to the client.
+func BackendError(b ServiceBackend, zone string, rcode int, state request.Request, debug []msg.Service, err error, opt Options) (int, error) {
+ m := new(dns.Msg)
+ m.SetRcode(state.Req, rcode)
+ m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
+ m.Ns, _, _ = SOA(b, zone, state, opt)
+ if opt.Debug != "" {
+ m.Extra = ServicesToTxt(debug)
+ txt := ErrorToTxt(err)
+ if txt != nil {
+ m.Extra = append(m.Extra, ErrorToTxt(err))
+ }
+ }
+ state.SizeAndDo(m)
+ state.W.WriteMsg(m)
+ // Return success as the rcode to signal we have written to the client.
+ return dns.RcodeSuccess, nil
+}
+
+// ServicesToTxt puts debug in TXT RRs.
+func ServicesToTxt(debug []msg.Service) []dns.RR {
+ if debug == nil {
+ return nil
+ }
+
+ rr := make([]dns.RR, len(debug))
+ for i, d := range debug {
+ rr[i] = d.RR()
+ }
+ return rr
+}
+
+// ErrorToTxt puts in error's text into an TXT RR.
+func ErrorToTxt(err error) dns.RR {
+ if err == nil {
+ return nil
+ }
+ msg := err.Error()
+ if len(msg) > 255 {
+ msg = msg[:255]
+ }
+ t := new(dns.TXT)
+ t.Hdr.Class = dns.ClassCHAOS
+ t.Hdr.Ttl = 0
+ t.Hdr.Rrtype = dns.TypeTXT
+ t.Hdr.Name = "."
+
+ t.Txt = []string{msg}
+ return t
+}
+
+const (
+ minTTL = 60
+ hostmaster = "hostmaster"
+)
generated by cgit v1.2.3 (git 2.39.1) at 2025-07-30 10:44:49 +0000