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

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This commit is contained in:
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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38
plugin/pkg/dnsutil/ttl.go
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@@ -14,34 +14,21 @@ func MinimalTTL(m *dns.Msg, mt response.Type) time.Duration {
return MinimalDefaultTTL
}
// No data to examine, return a short ttl as a fail safe.
if len(m.Answer)+len(m.Ns)+len(m.Extra) == 0 {
// No records or OPT is the only record, return a short ttl as a fail safe.
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
}
minTTL := MaximumDefaulTTL
for _, r := range m.Answer {
switch mt {
case response.NameError, response.NoData:
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
}
if r.Header().Ttl < uint32(minTTL.Seconds()) {
minTTL = time.Duration(r.Header().Ttl) * time.Second
}
}
for _, r := range m.Ns {
switch mt {
case response.NameError, response.NoData:
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
}
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
continue
}
switch mt {
case response.NameError, response.NoData:
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
}
if r.Header().Ttl < uint32(minTTL.Seconds()) {
minTTL = time.Duration(r.Header().Ttl) * time.Second
}
}
return minTTL