Merge pull request #842 from tmthrgd/compression-map-escaped
Put escaped names into compression map
This commit is contained in:
commit
fa589750ad
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@ -382,3 +382,26 @@ func TestMsgCompressLengthLargeRecordsAllValues(t *testing.T) {
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}
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}
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}
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func TestMsgCompressLengthEscapingMatch(t *testing.T) {
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// Although slightly non-optimal, "example.org." and "ex\\097mple.org."
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// are not considered equal in the compression map, even though \097 is
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// a valid escaping of a. This test ensures that the Len code and the
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// Pack code don't disagree on this.
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msg := new(Msg)
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msg.Compress = true
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msg.SetQuestion("www.example.org.", TypeA)
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msg.Answer = append(msg.Answer, &NS{Hdr: RR_Header{Name: "ex\\097mple.org.", Rrtype: TypeNS, Class: ClassINET}, Ns: "ns.example.org."})
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predicted := msg.Len()
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buf, err := msg.Pack()
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if err != nil {
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t.Error(err)
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}
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// Len doesn't account for escaping when calculating the length *yet* so
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// we're off by three here. This will be fixed in a follow up change.
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if predicted != len(buf)+3 {
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t.Fatalf("predicted compressed length is wrong: predicted %d, actual %d", predicted, len(buf))
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}
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}
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29
msg.go
29
msg.go
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@ -223,9 +223,11 @@ func packDomainName(s string, msg []byte, off int, compression map[string]int, c
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// Emit sequence of counted strings, chopping at dots.
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var (
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begin int
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bs []byte
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wasDot bool
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begin int
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compBegin int
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compOff int
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bs []byte
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wasDot bool
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)
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loop:
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for i := 0; i < ls; i++ {
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@ -251,9 +253,11 @@ loop:
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bs[i] = dddToByte(bs[i+1:])
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copy(bs[i+1:ls-3], bs[i+4:])
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ls -= 3
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compOff += 3
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} else {
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copy(bs[i:ls-1], bs[i+1:])
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ls--
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compOff++
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}
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wasDot = false
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@ -279,17 +283,7 @@ loop:
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// We should only compress when compress is true, but we should also still pick
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// up names that can be used for *future* compression(s).
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if compression != nil && !isRootLabel(s, bs, begin, ls) {
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var (
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p int
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ok bool
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)
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if bs == nil {
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p, ok = compression[s[begin:]]
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} else {
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p, ok = compression[string(bs[begin:ls])]
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}
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if ok {
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if p, ok := compression[s[compBegin:]]; ok {
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// The first hit is the longest matching dname
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// keep the pointer offset we get back and store
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// the offset of the current name, because that's
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@ -302,11 +296,7 @@ loop:
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}
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} else if off < maxCompressionOffset {
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// Only offsets smaller than maxCompressionOffset can be used.
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if bs == nil {
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compression[s[begin:]] = off
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} else {
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compression[string(bs[begin:ls])] = off
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}
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compression[s[compBegin:]] = off
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}
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}
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@ -324,6 +314,7 @@ loop:
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labels++
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begin = i + 1
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compBegin = begin + compOff
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default:
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wasDot = false
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}
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21
msg_test.go
21
msg_test.go
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@ -214,8 +214,15 @@ func TestUnpackDomainName(t *testing.T) {
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}
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func TestPackDomainNameCompressionMap(t *testing.T) {
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msg := make([]byte, 256)
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expected := map[string]struct{}{
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`www\.this.is.\131an.example.org.`: struct{}{},
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`is.\131an.example.org.`: struct{}{},
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`\131an.example.org.`: struct{}{},
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`example.org.`: struct{}{},
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`org.`: struct{}{},
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}
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msg := make([]byte, 256)
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for _, compress := range []bool{true, false} {
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compression := make(map[string]int)
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@ -224,16 +231,8 @@ func TestPackDomainNameCompressionMap(t *testing.T) {
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t.Fatalf("PackDomainName failed: %v", err)
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}
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for _, dname := range []string{
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`www.this.is.\131an.example.org.`,
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`is.\131an.example.org.`,
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"\x83an.example.org.",
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`example.org.`,
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`org.`,
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} {
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if _, ok := compression[dname]; !ok {
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t.Errorf("expected to find %q in compression map", dname)
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}
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if !compressionMapsEqual(expected, compression) {
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t.Errorf("expected compression maps to be equal; expected %v, got %v", expected, compression)
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}
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}
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}
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