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path: root/plugin/file/xfr.go
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Diffstat (limited to 'plugin/file/xfr.go')
-rw-r--r--plugin/file/xfr.go41
1 files changed, 41 insertions, 0 deletions
diff --git a/plugin/file/xfr.go b/plugin/file/xfr.go
index b2dbd1458..f5f803d11 100644
--- a/plugin/file/xfr.go
+++ b/plugin/file/xfr.go
@@ -26,6 +26,15 @@ func (x Xfr) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (in
return 0, plugin.Error(x.Name(), fmt.Errorf("xfr called with non transfer type: %d", state.QType()))
}
+ // For IXFR we take the SOA in the IXFR message (if there), compare it what we have and then decide to do an
+ // AXFR or just reply with one SOA message back.
+ if state.QType() == dns.TypeIXFR {
+ code, _ := x.ServeIxfr(ctx, w, r)
+ if plugin.ClientWrite(code) {
+ return code, nil
+ }
+ }
+
records := x.All()
if len(records) == 0 {
return dns.RcodeServerFailure, nil
@@ -63,4 +72,36 @@ func (x Xfr) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (in
// Name implements the plugin.Handler interface.
func (x Xfr) Name() string { return "xfr" }
+// ServeIxfr checks if we need to serve a simpler IXFR for the incoming message.
+// See RFC 1995 Section 3: "... and the authority section containing the SOA record of client's version of the zone."
+// and Section 2, paragraph 4 where we only need to echo the SOA record back.
+// This function must be called when the qtype is IXFR. It returns a plugin.ClientWrite(code) == false, when it didn't
+// write anything and we should perform an AXFR.
+func (x Xfr) ServeIxfr(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+ if len(r.Ns) != 1 {
+ return dns.RcodeServerFailure, nil
+ }
+ soa, ok := r.Ns[0].(*dns.SOA)
+ if !ok {
+ return dns.RcodeServerFailure, nil
+ }
+
+ x.RLock()
+ if x.Apex.SOA == nil {
+ x.RUnlock()
+ return dns.RcodeServerFailure, nil
+ }
+ serial := x.Apex.SOA.Serial
+ x.RUnlock()
+
+ if soa.Serial == serial { // Section 2, para 4; echo SOA back. We have the same zone
+ m := new(dns.Msg)
+ m.SetReply(r)
+ m.Answer = []dns.RR{soa}
+ w.WriteMsg(m)
+ return 0, nil
+ }
+ return dns.RcodeServerFailure, nil
+}
+
const transferLength = 1000 // Start a new envelop after message reaches this size in bytes. Intentionally small to test multi envelope parsing.