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plugin/cache: fix TTL for negative DNS responses (#2197)

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Ruslan Drozhdzh 2018-10-19 21:10:08 +03:00 • committed by Chris O'Haver
parent 54df160aa4
commit dbc2efc49a
3 changed files with 14 additions and 35 deletions
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3
plugin/cache/README.md vendored
View file

@ -24,7 +24,6 @@ cache [TTL] [ZONES...]
* **ZONES** zones it should cache for. If empty, the zones from the configuration block are used. * **ZONES** zones it should cache for. If empty, the zones from the configuration block are used.
Each element in the cache is cached according to its TTL (with **TTL** as the max). Each element in the cache is cached according to its TTL (with **TTL** as the max).
For the negative cache, the SOA's MinTTL value is used. A TTL of zero is not allowed.
A cache is divided into 256 shards, each holding up to 512 items by default - for a total size A cache is divided into 256 shards, each holding up to 512 items by default - for a total size
of 256 * 512 = 131,072 items. of 256 * 512 = 131,072 items.
@ -101,4 +100,4 @@ Enable caching for all zones, keep a positive cache size of 5000 and a negative
denial 2500 denial 2500
} }
} }
~~~ ~~~

38
plugin/pkg/dnsutil/ttl.go
View file

@ -14,34 +14,21 @@ func MinimalTTL(m *dns.Msg, mt response.Type) time.Duration {
return MinimalDefaultTTL return MinimalDefaultTTL
} }
// No data to examine, return a short ttl as a fail safe. // No records or OPT is the only record, return a short ttl as a fail safe.
if len(m.Answer)+len(m.Ns)+len(m.Extra) == 0 { if len(m.Answer)+len(m.Ns) == 0 &&
(len(m.Extra) == 0 || (len(m.Extra) == 1 && m.Extra[0].Header().Rrtype == dns.TypeOPT)) {
return MinimalDefaultTTL return MinimalDefaultTTL
} }
minTTL := MaximumDefaulTTL minTTL := MaximumDefaulTTL
for _, r := range m.Answer { for _, r := range m.Answer {
switch mt { if r.Header().Ttl < uint32(minTTL.Seconds()) {
case response.NameError, response.NoData: minTTL = time.Duration(r.Header().Ttl) * time.Second
if r.Header().Rrtype == dns.TypeSOA {
minTTL = time.Duration(r.(*dns.SOA).Minttl) * time.Second
}
case response.NoError, response.Delegation:
if r.Header().Ttl < uint32(minTTL.Seconds()) {
minTTL = time.Duration(r.Header().Ttl) * time.Second
}
} }
} }
for _, r := range m.Ns { for _, r := range m.Ns {
switch mt { if r.Header().Ttl < uint32(minTTL.Seconds()) {
case response.NameError, response.NoData: minTTL = time.Duration(r.Header().Ttl) * time.Second
if r.Header().Rrtype == dns.TypeSOA {
minTTL = time.Duration(r.(*dns.SOA).Minttl) * time.Second
}
case response.NoError, response.Delegation:
if r.Header().Ttl < uint32(minTTL.Seconds()) {
minTTL = time.Duration(r.Header().Ttl) * time.Second
}
} }
} }
@ -50,15 +37,8 @@ func MinimalTTL(m *dns.Msg, mt response.Type) time.Duration {
// OPT records use TTL field for extended rcode and flags // OPT records use TTL field for extended rcode and flags
continue continue
} }
switch mt { if r.Header().Ttl < uint32(minTTL.Seconds()) {
case response.NameError, response.NoData: minTTL = time.Duration(r.Header().Ttl) * time.Second
if r.Header().Rrtype == dns.TypeSOA {
minTTL = time.Duration(r.(*dns.SOA).Minttl) * time.Second
}
case response.NoError, response.Delegation:
if r.Header().Ttl < uint32(minTTL.Seconds()) {
minTTL = time.Duration(r.Header().Ttl) * time.Second
}
} }
} }
return minTTL return minTTL

8
plugin/pkg/dnsutil/ttl_test.go
View file

@ -26,8 +26,8 @@ func TestMinimalTTL(t *testing.T) {
t.Fatalf("Expected type to be response.NoData, got %s", mt) t.Fatalf("Expected type to be response.NoData, got %s", mt)
} }
dur := MinimalTTL(m, mt) // minTTL on msg is 3600 (neg. ttl on SOA) dur := MinimalTTL(m, mt) // minTTL on msg is 3600 (neg. ttl on SOA)
if dur != time.Duration(3600*time.Second) { if dur != time.Duration(1800*time.Second) {
t.Fatalf("Expected minttl duration to be %d, got %d", 3600, dur) t.Fatalf("Expected minttl duration to be %d, got %d", 1800, dur)
} }
m.Rcode = dns.RcodeNameError m.Rcode = dns.RcodeNameError
@ -36,8 +36,8 @@ func TestMinimalTTL(t *testing.T) {
t.Fatalf("Expected type to be response.NameError, got %s", mt) t.Fatalf("Expected type to be response.NameError, got %s", mt)
} }
dur = MinimalTTL(m, mt) // minTTL on msg is 3600 (neg. ttl on SOA) dur = MinimalTTL(m, mt) // minTTL on msg is 3600 (neg. ttl on SOA)
if dur != time.Duration(3600*time.Second) { if dur != time.Duration(1800*time.Second) {
t.Fatalf("Expected minttl duration to be %d, got %d", 3600, dur) t.Fatalf("Expected minttl duration to be %d, got %d", 1800, dur)
} }
} }