Avoid calling RR.Header more than once per RR (#891)

* Avoid calling RR.Header more than once per RR

Header is an interface method so there's non-zero overhead when calling
it.

* Reset entire RR_Header in SIG.Sign

This is equivilant (while also clearing Rdlength) while being simpler.

dnssec.go

@@ -262,16 +262,17 @@ func (rr *RRSIG) Sign(k crypto.Signer, rrset []RR) error {
 		return ErrKey
 	}
 
+	h0 := rrset[0].Header()
 	rr.Hdr.Rrtype = TypeRRSIG
-	rr.Hdr.Name = rrset[0].Header().Name
-	rr.Hdr.Class = rrset[0].Header().Class
+	rr.Hdr.Name = h0.Name
+	rr.Hdr.Class = h0.Class
 	if rr.OrigTtl == 0 { // If set don't override
-		rr.OrigTtl = rrset[0].Header().Ttl
+		rr.OrigTtl = h0.Ttl
 	}
-	rr.TypeCovered = rrset[0].Header().Rrtype
-	rr.Labels = uint8(CountLabel(rrset[0].Header().Name))
+	rr.TypeCovered = h0.Rrtype
+	rr.Labels = uint8(CountLabel(h0.Name))
 
-	if strings.HasPrefix(rrset[0].Header().Name, "*") {
+	if strings.HasPrefix(h0.Name, "*") {
 		rr.Labels-- // wildcard, remove from label count
 	}
 
@@ -405,10 +406,7 @@ func (rr *RRSIG) Verify(k *DNSKEY, rrset []RR) error {
 	// IsRRset checked that we have at least one RR and that the RRs in
 	// the set have consistent type, class, and name. Also check that type and
 	// class matches the RRSIG record.
-	if rrset[0].Header().Class != rr.Hdr.Class {
-		return ErrRRset
-	}
-	if rrset[0].Header().Rrtype != rr.TypeCovered {
+	if h0 := rrset[0].Header(); h0.Class != rr.Hdr.Class || h0.Rrtype != rr.TypeCovered {
 		return ErrRRset
 	}
 
@@ -652,15 +650,16 @@ func rawSignatureData(rrset []RR, s *RRSIG) (buf []byte, err error) {
 	wires := make(wireSlice, len(rrset))
 	for i, r := range rrset {
 		r1 := r.copy()
-		r1.Header().Ttl = s.OrigTtl
-		labels := SplitDomainName(r1.Header().Name)
+		h := r1.Header()
+		h.Ttl = s.OrigTtl
+		labels := SplitDomainName(h.Name)
 		// 6.2. Canonical RR Form. (4) - wildcards
 		if len(labels) > int(s.Labels) {
 			// Wildcard
-			r1.Header().Name = "*." + strings.Join(labels[len(labels)-int(s.Labels):], ".") + "."
+			h.Name = "*." + strings.Join(labels[len(labels)-int(s.Labels):], ".") + "."
 		}
 		// RFC 4034: 6.2.  Canonical RR Form. (2) - domain name to lowercase
-		r1.Header().Name = strings.ToLower(r1.Header().Name)
+		h.Name = strings.ToLower(h.Name)
 		// 6.2. Canonical RR Form. (3) - domain rdata to lowercase.
 		//   NS, MD, MF, CNAME, SOA, MB, MG, MR, PTR,
 		//   HINFO, MINFO, MX, RP, AFSDB, RT, SIG, PX, NXT, NAPTR, KX,

sanitize.go

@@ -15,10 +15,11 @@ func Dedup(rrs []RR, m map[string]RR) []RR {
 	for _, r := range rrs {
 		key := normalizedString(r)
 		keys = append(keys, &key)
-		if _, ok := m[key]; ok {
+		if mr, ok := m[key]; ok {
 			// Shortest TTL wins.
-			if m[key].Header().Ttl > r.Header().Ttl {
-				m[key].Header().Ttl = r.Header().Ttl
+			rh, mrh := r.Header(), mr.Header()
+			if mrh.Ttl > rh.Ttl {
+				mrh.Ttl = rh.Ttl
 			}
 			continue
 		}

sig0.go

@@ -21,13 +21,9 @@ func (rr *SIG) Sign(k crypto.Signer, m *Msg) ([]byte, error) {
 	if rr.KeyTag == 0 || len(rr.SignerName) == 0 || rr.Algorithm == 0 {
 		return nil, ErrKey
 	}
-	rr.Header().Rrtype = TypeSIG
-	rr.Header().Class = ClassANY
-	rr.Header().Ttl = 0
-	rr.Header().Name = "."
-	rr.OrigTtl = 0
-	rr.TypeCovered = 0
-	rr.Labels = 0
+
+	rr.Hdr = RR_Header{Name: ".", Rrtype: TypeSIG, Class: ClassANY, Ttl: 0}
+	rr.OrigTtl, rr.TypeCovered, rr.Labels = 0, 0, 0
 
 	buf := make([]byte, m.Len()+Len(rr))
 	mbuf, err := m.PackBuffer(buf)

update.go

@@ -44,7 +44,8 @@ func (u *Msg) RRsetUsed(rr []RR) {
 		u.Answer = make([]RR, 0, len(rr))
 	}
 	for _, r := range rr {
-		u.Answer = append(u.Answer, &ANY{Hdr: RR_Header{Name: r.Header().Name, Ttl: 0, Rrtype: r.Header().Rrtype, Class: ClassANY}})
+		h := r.Header()
+		u.Answer = append(u.Answer, &ANY{Hdr: RR_Header{Name: h.Name, Ttl: 0, Rrtype: h.Rrtype, Class: ClassANY}})
 	}
 }
 
@@ -55,7 +56,8 @@ func (u *Msg) RRsetNotUsed(rr []RR) {
 		u.Answer = make([]RR, 0, len(rr))
 	}
 	for _, r := range rr {
-		u.Answer = append(u.Answer, &ANY{Hdr: RR_Header{Name: r.Header().Name, Ttl: 0, Rrtype: r.Header().Rrtype, Class: ClassNONE}})
+		h := r.Header()
+		u.Answer = append(u.Answer, &ANY{Hdr: RR_Header{Name: h.Name, Ttl: 0, Rrtype: h.Rrtype, Class: ClassNONE}})
 	}
 }
 
@@ -79,7 +81,8 @@ func (u *Msg) RemoveRRset(rr []RR) {
 		u.Ns = make([]RR, 0, len(rr))
 	}
 	for _, r := range rr {
-		u.Ns = append(u.Ns, &ANY{Hdr: RR_Header{Name: r.Header().Name, Ttl: 0, Rrtype: r.Header().Rrtype, Class: ClassANY}})
+		h := r.Header()
+		u.Ns = append(u.Ns, &ANY{Hdr: RR_Header{Name: h.Name, Ttl: 0, Rrtype: h.Rrtype, Class: ClassANY}})
 	}
 }
 
@@ -99,8 +102,9 @@ func (u *Msg) Remove(rr []RR) {
 		u.Ns = make([]RR, 0, len(rr))
 	}
 	for _, r := range rr {
-		r.Header().Class = ClassNONE
-		r.Header().Ttl = 0
+		h := r.Header()
+		h.Class = ClassNONE
+		h.Ttl = 0
 		u.Ns = append(u.Ns, r)
 	}
 }