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plugin/cache: cap TTL on first answer (#1092)

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Cache would let the first response through and would then cap subsequent
ones to whatever the cache duration was. This would lead to huge drops
in TTL values: 3600 -> 20 for instance, which is not only bad, but can
mess up your careful TTL planning business.

This PR fixes that and applies the cache duration to all replies. As a
bonus I could remove a time.Sleep() from the cache test and just check
for the cache duration as the TTL on the reply.

Fixes #1038
This commit is contained in:
Miek Gieben
2017-09-20 11:36:41 +01:00
committed by GitHub
parent be47709270
commit cd5879f866
3 changed files with 17 additions and 23 deletions
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13
plugin/cache/cache.go vendored
View File

@@ -117,6 +117,19 @@ func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
return nil
}
// Apply capped TTL to this reply to avoid jarring TTL experience 1799 -> 8 (e.g.)
ttl := uint32(duration.Seconds())
for i := range res.Answer {
res.Answer[i].Header().Ttl = ttl
}
for i := range res.Ns {
res.Ns[i].Header().Ttl = ttl
}
for i := range res.Extra {
if res.Extra[i].Header().Rrtype != dns.TypeOPT {
res.Extra[i].Header().Ttl = ttl
}
}
return w.ResponseWriter.WriteMsg(res)
}

2
plugin/cache/handler.go vendored
View File

@@ -19,7 +19,7 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
qtype := state.QType()
zone := plugin.Zones(c.Zones).Matches(qname)
if zone == "" {
return c.Next.ServeDNS(ctx, w, r)
return plugin.NextOrFailure(c.Name(), c.Next, ctx, w, r)
}
do := state.Do() // TODO(): might need more from OPT record? Like the actual bufsize?