From 9fcbef5edc09c495bbc2fcaa1b4a03c7f5fe5647 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Mon, 22 Aug 2011 14:51:10 +0200
Subject: [PATCH] Add dynamic update support

---
 update.go | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 update.go

diff --git a/update.go b/update.go
new file mode 100644
index 00000000..e8ae0d65
--- /dev/null
+++ b/update.go
@@ -0,0 +1,91 @@
+package dns
+
+import ()
+
+// Implements wrapper functions for dealing with dynamic update packets.
+// Dynamic update packets are identical to normal DNS messages, but the
+// names are redefined. See RFC 2136 for the details.
+
+type Update struct{ Msg }
+
+// Not sure if I want to keep these functions, but they
+// may help a programmer
+
+func (u *Update) Zone() []Question {
+	return u.Msg.Question
+}
+
+func (u *Update) Prereq() []RR {
+	return u.Msg.Answer
+}
+
+func (u *Update) Update() []RR {
+	return u.Msg.Ns
+}
+
+func (u *Update) Additional() []RR {
+	return u.Msg.Extra
+}
+
+// 3.2.4 - Table Of Metavalues Used In Prerequisite Section
+//
+//   CLASS    TYPE     RDATA    Meaning
+//   ------------------------------------------------------------
+//   ANY      ANY      empty    Name is in use
+//   ANY      rrset    empty    RRset exists (value independent)
+//   NONE     ANY      empty    Name is not in use
+//   NONE     rrset    empty    RRset does not exist
+//   zone     rrset    rr       RRset exists (value dependent)
+
+// PrereqNameUsed sets the RRs in the prereq section to
+// "Name is in use" RRs. RFC 2136 section 2.4.4.
+func (u *Update) PrereqNameUsed(rr []RR) {
+	u.Msg.Answer = make([]RR, len(rr))
+	for i, r := range rr {
+		u.Msg.Answer[i] = &RR_ANY{Hdr: RR_Header{Name: r.Header().Name, Ttl: 0, Rrtype: TypeANY, Class: ClassANY}}
+	}
+}
+
+// PrereqNameNotUsed sets the RRs in the prereq section to
+// "Name is in not use" RRs. RFC 2136 section 2.4.5.
+func (u *Update) PrereqNameNotUsed(rr []RR) {
+	u.Msg.Answer = make([]RR, len(rr))
+	for i, r := range rr {
+                u.Msg.Answer[i] = &RR_ANY{Hdr: RR_Header{Name: r.Header().Name, Ttl: 0, Rrtype: TypeANY, Class: ClassNONE}}
+	}
+}
+
+// PrereqRRsetUsedFull sets the RRs in the prereq section to
+// "RRset exists (value dependent -- with rdata)" RRs. RFC 2136 section 2.4.2.
+func (u *Update) PrereqRRsetUsedFull(rr []RR) {
+	u.Msg.Answer = make([]RR, len(rr))
+	for i, r := range rr {
+                u.Msg.Answer[i] = r
+                u.Msg.Answer[i].Header().Class = u.Msg.Question[0].Qclass       // TODO crashes if question is zero
+	}
+}
+
+// PrereqRRsetUsed sets the RRs in the prereq section to
+// "RRset exists (value independent -- no rdata)" RRs. RFC 2136 section 2.4.1.
+func (u *Update) PrereqRRsetUsed(rr []RR) {
+	u.Msg.Answer = make([]RR, len(rr))
+	for i, r := range rr {
+                u.Msg.Answer[i] = r
+                u.Msg.Answer[i].Header().Class = ClassANY
+                /* rdata should be cleared */
+	}
+}
+
+// PrereqRRsetNotUsed sets the RRs in the prereq section to
+// "RRset does not exist" RRs. RFC 2136 section 2.4.3.
+func (u *Update) PrereqRRsetNotUsed(rr []RR) {
+	u.Msg.Answer = make([]RR, len(rr))
+	for i, r := range rr {
+                u.Msg.Answer[i] = r
+                u.Msg.Answer[i].Header().Class = ClassNONE
+                /* rdata should be cleared */
+	}
+}
+
+
+