Address commments from Alex
This commit is contained in:
Miek Gieben
parent
6cf1a0db58
commit
0206070abf
101
sanitize.go
101
sanitize.go
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@ -1,26 +1,13 @@
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package dns
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import "strings"
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// Dedup removes identical RRs from rrs. It preserves the original ordering.
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// The lowest TTL of any duplicates is used in the remaining one.
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//
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// TODO(miek): This function will be extended to also look for CNAMEs and DNAMEs.
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// if found, it will prune rrs from the "other data" that can exist. Example:
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// if it finds a: a.miek.nl. CNAME foo, all other RRs with the ownername a.miek.nl.
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// will be removed. When a DNAME is found all RRs with an ownername below that of
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// the DNAME will be removed.
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func Dedup(rrs []RR) []RR {
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m := make(map[string]RR)
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keys := make([]string, 0, len(rrs))
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// Save possible cname and dname domainnames. Currently a slice, don't
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// expect millions here..
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cname := []string{}
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dname := []string{}
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for _, r := range rrs {
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key, end := normalizedString(r)
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key := normalizedString(r)
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keys = append(keys, key)
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if _, ok := m[key]; ok {
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// Shortest TTL wins.
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@ -30,37 +17,18 @@ func Dedup(rrs []RR) []RR {
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continue
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}
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if r.Header().Rrtype == TypeCNAME {
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// we do end+3 here, so we capture the full domain name *and*
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// the class field which mnemonic is always two chars.
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cname = append(cname, key[:end+3])
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}
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if r.Header().Rrtype == TypeDNAME {
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dname = append(dname, key[:end+3])
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}
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m[key] = r
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}
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// If the length of the result map equals the amount of RRs we got,
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// it means they were all different. We can then just return the original rrset.
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// We can only do this when we haven't found a CNAME or DNAME.
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if len(m) == len(rrs) && len(cname) == 0 && len(dname) == 0 {
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if len(m) == len(rrs) {
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return rrs
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}
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ret := make([]RR, 0, len(rrs))
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for i, r := range rrs {
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// If keys[i] lives in the map, we should copy it and remove
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// it from the map.
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// If keys[i] lives in the map, we should copy and remove it.
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if _, ok := m[keys[i]]; ok {
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if needsDeletion(r, keys[i], cname, dname) {
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// It the RR is masked by an CNAME or DNAME, we only
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// delete it from the map, but don't copy it.
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delete(m, keys[i])
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continue
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}
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delete(m, keys[i])
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ret = append(ret, r)
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}
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@ -74,70 +42,37 @@ func Dedup(rrs []RR) []RR {
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}
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// normalizedString returns a normalized string from r. The TTL
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// is removed and the domain name is lowercased. The returned integer
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// is the index where the domain name ends + 1.
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func normalizedString(r RR) (string, int) {
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// is removed and the domain name is lowercased. We go from this:
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// DomainName<TAB>TTL<TAB>CLASS<TAB>TYPE<TAB>RDATA to:
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// lowercasename<TAB>CLASS<TAB>TYPE...
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func normalizedString(r RR) string {
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// A string Go DNS makes has: domainname<TAB>TTL<TAB>...
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b := []byte(r.String())
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// find the first non-escaped tab, then another, so we capture
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// where the TTL lives.
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// find the first non-escaped tab, then another, so we capture where the TTL lives.
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esc := false
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ttlStart, ttlEnd := 0, 0
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for i, c := range b {
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if c == '\\' {
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esc = true
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continue
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}
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if esc {
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esc = false
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continue
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}
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if c == '\t' {
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for i := 0; i < len(b) && ttlEnd == 0; i++ {
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switch {
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case b[i] == '\\':
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esc = !esc
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case b[i] == '\t' && !esc:
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if ttlStart == 0 {
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ttlStart = i
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continue
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}
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if ttlEnd == 0 {
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ttlEnd = i
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break
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}
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}
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if c >= 'A' && c <= 'Z' {
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b[i] = c + 32
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case b[i] >= 'A' && b[i] <= 'Z' && !esc:
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b[i] += 32
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default:
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esc = false
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}
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}
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// remove TTL.
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copy(b[ttlStart:], b[ttlEnd:])
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cut := ttlEnd - ttlStart
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// ttlStart + 3 puts us on the start of the rdata
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return string(b[:len(b)-cut]), ttlStart
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}
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// needsDeletion checks if the RR is masked by either a CNAME or a DNAME.
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// If so it return true.
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func needsDeletion(r RR, s string, cname, dname []string) bool {
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// For CNAME we can do strings.HasPrefix with s.
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// For DNAME we can do strings.Contains with s.
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// Either signals a removal of this RR.
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for _, c := range cname {
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if strings.HasPrefix(s, c) {
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if r.Header().Rrtype == TypeCNAME {
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// don't delete yourself
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continue
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}
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return true
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}
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}
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for _, d := range dname {
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if strings.Contains(s, d) {
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if r.Header().Rrtype == TypeDNAME && strings.HasPrefix(s, d) {
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// don't delete yourself
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continue
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}
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return true
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}
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}
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return false
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return string(b[:len(b)-cut])
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}
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@ -49,55 +49,17 @@ func TestDedup(t *testing.T) {
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}
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}
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func TestDedupWithCNAMEDNAME(t *testing.T) {
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testcases := map[[4]RR][]string{
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[...]RR{
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newRR(t, "miek.Nl. CNAME a."),
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newRR(t, "miEk.nl. IN A 127.0.0.1"),
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newRR(t, "miek.Nl. IN A 127.0.0.1"),
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newRR(t, "miek.de. IN A 127.0.0.1"),
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}: []string{"miek.Nl.\t3600\tIN\tCNAME\ta.",
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"miek.de.\t3600\tIN\tA\t127.0.0.1"},
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[...]RR{
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newRR(t, "Miek.nl. CNAME a."),
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newRR(t, "mIek.nl. CNAME a."),
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newRR(t, "miEk.nl. CNAME a."),
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newRR(t, "mieK.nl. CNAME a."),
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}: []string{"Miek.nl.\t3600\tIN\tCNAME\ta."},
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[...]RR{
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newRR(t, "miek.nl. CNAME a."),
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newRR(t, "a.miek.nl. CNAME a."),
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newRR(t, "a.miek.nl. CNAME a."),
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newRR(t, "a.miek.nl. CNAME a."),
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}: []string{"miek.nl.\t3600\tIN\tCNAME\ta.",
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"a.miek.nl.\t3600\tIN\tCNAME\ta."},
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[...]RR{
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newRR(t, "miek.nl. DNAME a."),
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newRR(t, "a.miek.nl. CNAME a."),
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newRR(t, "b.miek.nl. IN A 127.0.0.1"),
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newRR(t, "a.miek.de. IN A 127.0.0.1"),
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}: []string{"miek.nl.\t3600\tIN\tDNAME\ta.",
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"a.miek.de.\t3600\tIN\tA\t127.0.0.1"},
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[...]RR{
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newRR(t, "miek.nl. DNAME a."),
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newRR(t, "a.miek.nl. DNAME a."),
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newRR(t, "b.miek.nl. DNAME b."),
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newRR(t, "a.b.miek.nl. DNAME a.b"),
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}: []string{"miek.nl.\t3600\tIN\tDNAME\ta."},
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func BenchmarkDedup(b *testing.B) {
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rrs := []RR{
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newRR(nil, "miEk.nl. 2000 IN A 127.0.0.1"),
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newRR(nil, "mieK.Nl. 1000 IN A 127.0.0.1"),
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newRR(nil, "Miek.nL. 500 IN A 127.0.0.1"),
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}
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for rr, expected := range testcases {
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out := Dedup([]RR{rr[0], rr[1], rr[2], rr[3]})
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for i, o := range out {
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if o.String() != expected[i] {
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t.Fatalf("expected %v, got %v", expected[i], o.String())
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}
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}
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for i := 0; i < b.N; i++ {
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Dedup(rrs)
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}
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}
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// BenchMark test as well TODO(miek)
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func TestNormalizedString(t *testing.T) {
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tests := map[RR]string{
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newRR(t, "mIEk.Nl. 3600 IN A 127.0.0.1"): "miek.nl.\tIN\tA\t127.0.0.1",
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@ -105,9 +67,9 @@ func TestNormalizedString(t *testing.T) {
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newRR(t, "m\\\tIeK.nl. 3600 in A 127.0.0.1"): "m\\tiek.nl.\tIN\tA\t127.0.0.1",
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}
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for tc, expected := range tests {
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a1, _ := normalizedString(tc)
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if a1 != expected {
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t.Logf("expected %s, got %s", expected, a1)
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n := normalizedString(tc)
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if n != expected {
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t.Logf("expected %s, got %s", expected, n)
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t.Fail()
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}
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}
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