Parse dynamic update RR in presentation format

Don't panic when encountering dynamic update RRs in zonefiles.
There are some other failure cases when parsing, those will be
fixed in subsequent commits.

Closes #110

parse_test.go

@@ -1173,6 +1173,7 @@ func TestTxtLong(t *testing.T) {
 	}
 }
 
+// Basically, don't crash.
 func TestMalformedPackets(t *testing.T) {
 	var packets = []string{
 		"0021641c0000000100000000000078787878787878787878787303636f6d0000100001",
@@ -1192,9 +1193,7 @@ func TestMalformedPackets(t *testing.T) {
 
 func TestDynamicUpdateParsing(t *testing.T) {
 	prefix := "example.com. IN "
-	// TODO(miek): extend to all types.
+	for _, typ := range TypeToString {
-	//for _, typ := range TypeToString {
-	for _, typ := range []string{"PTR", "A"} {
 		r, e := NewRR(prefix + typ)
 		if e != nil {
 			t.Log("failure to parse: " + prefix + typ)

zscan_rr.go

@@ -296,6 +296,9 @@ func setNS(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Ns = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Ns = o
 		return rr, nil
@@ -339,6 +342,9 @@ func setNSAPPTR(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Ptr = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Ptr = o
 		return rr, nil
@@ -359,6 +365,9 @@ func setRP(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Mbox = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Mbox = o
 	} else {
@@ -393,6 +402,9 @@ func setMR(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Mr = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Mr = o
 		return rr, nil
@@ -413,6 +425,9 @@ func setMB(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Mb = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Mb = o
 		return rr, nil
@@ -433,6 +448,9 @@ func setMG(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Mg = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Mg = o
 		return rr, nil
@@ -466,6 +484,9 @@ func setMINFO(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Rmail = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Rmail = o
 	} else {
@@ -500,6 +521,9 @@ func setMF(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Mf = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Mf = o
 		return rr, nil
@@ -520,6 +544,9 @@ func setMD(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Md = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Md = o
 		return rr, nil
@@ -657,6 +684,9 @@ func setCNAME(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Target = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Target = o
 		return rr, nil
@@ -677,6 +707,9 @@ func setDNAME(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Target = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Target = o
 		return rr, nil
@@ -697,6 +730,9 @@ func setSOA(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.Ns = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	<-c // _BLANK
 	if l.token == "@" {
 		rr.Ns = o
@@ -901,6 +937,9 @@ func setTALINK(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 
 	l := <-c
 	rr.PreviousName = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.PreviousName = o
 	} else {
@@ -1247,6 +1286,9 @@ func setNSEC(h RR_Header, c chan lex, o, f string) (RR, *ParseError, string) {
 
 	l := <-c
 	rr.NextDomain = l.token
+	if l.length == 0 {
+		return rr, nil, l.comment
+	}
 	if l.token == "@" {
 		rr.NextDomain = o
 	} else {
@@ -2004,6 +2046,9 @@ func setLP(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 	<-c     // _BLANK
 	l = <-c // _STRING
 	rr.Fqdn = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Fqdn = o
 		return rr, nil
@@ -2086,6 +2131,9 @@ func setPX(h RR_Header, c chan lex, o, f string) (RR, *ParseError) {
 	<-c     // _BLANK
 	l = <-c // _STRING
 	rr.Map822 = l.token
+	if l.length == 0 {
+		return rr, nil
+	}
 	if l.token == "@" {
 		rr.Map822 = o
 		return rr, nil