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feat: add cache entire DNS response (#833) #909

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merged 1 commit into from
Mar 3, 2023
Merged

feat: add cache entire DNS response (#833) #909

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47 changes: 20 additions & 27 deletions resolver/caching_resolver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,8 @@ type CachingResolver struct {

// cacheValue includes query answer and prefetch flag
type cacheValue struct {
answer []dns.RR
prefetch bool
resultMsg *dns.Msg
prefetch bool
}

// NewCachingResolver creates a new resolver instance
Expand Down Expand Up @@ -124,7 +124,7 @@ func (r *CachingResolver) onExpired(cacheKey string) (val interface{}, ttl time.
if response.Res.Rcode == dns.RcodeSuccess {
evt.Bus().Publish(evt.CachingDomainPrefetched, domainName)

return cacheValue{response.Res.Answer, true}, r.adjustTTLs(response.Res.Answer)
return cacheValue{response.Res, true}, r.adjustTTLs(response.Res.Answer)
}
} else {
util.LogOnError(fmt.Sprintf("can't prefetch '%s' ", domainName), err)
Expand Down Expand Up @@ -170,9 +170,6 @@ func (r *CachingResolver) Resolve(request *model.Request) (response *model.Respo
return r.next.Resolve(request)
}

resp := new(dns.Msg)
resp.SetReply(request.Req)

for _, question := range request.Req.Question {
domain := util.ExtractDomain(question)
cacheKey := util.GenerateCacheKey(dns.Type(question.Qtype), domain)
Expand All @@ -187,26 +184,24 @@ func (r *CachingResolver) Resolve(request *model.Request) (response *model.Respo

evt.Bus().Publish(evt.CachingResultCacheHit, domain)

v, ok := val.(cacheValue)
if ok {
if v.prefetch {
// Hit from prefetch cache
evt.Bus().Publish(evt.CachingPrefetchCacheHit, domain)
}
v := val.(cacheValue)
if v.prefetch {
// Hit from prefetch cache
evt.Bus().Publish(evt.CachingPrefetchCacheHit, domain)
}

// Answer from successful request
for _, rr := range v.answer {
// make copy here since entries in cache can be modified by other goroutines (e.g. redis cache)
cp := dns.Copy(rr)
cp.Header().Ttl = uint32(ttl.Seconds())
resp := v.resultMsg.Copy()
resp.SetReply(request.Req)
resp.Rcode = v.resultMsg.Rcode

resp.Answer = append(resp.Answer, cp)
}
// Adjust TTL
for _, rr := range resp.Answer {
rr.Header().Ttl = uint32(ttl.Seconds())
}

if resp.Rcode == dns.RcodeSuccess {
return &model.Response{Res: resp, RType: model.ResponseTypeCACHED, Reason: "CACHED"}, nil
}
// Answer with response code != OK
resp.Rcode = val.(int)

return &model.Response{Res: resp, RType: model.ResponseTypeCACHED, Reason: "CACHED NEGATIVE"}, nil
}
Expand Down Expand Up @@ -241,23 +236,21 @@ func (r *CachingResolver) trackQueryDomainNameCount(domain, cacheKey string, log
}

func (r *CachingResolver) putInCache(cacheKey string, response *model.Response, prefetch, publish bool) {
answer := response.Res.Answer

if response.Res.Rcode == dns.RcodeSuccess {
// put value into cache
r.resultCache.Put(cacheKey, cacheValue{answer, prefetch}, r.adjustTTLs(answer))
r.resultCache.Put(cacheKey, cacheValue{response.Res, prefetch}, r.adjustTTLs(response.Res.Answer))
} else if response.Res.Rcode == dns.RcodeNameError {
if r.cacheTimeNegative > 0 {
// put return code if NXDOMAIN
r.resultCache.Put(cacheKey, response.Res.Rcode, r.cacheTimeNegative)
// put negative cache if result code is NXDOMAIN
r.resultCache.Put(cacheKey, cacheValue{response.Res, prefetch}, r.cacheTimeNegative)
}
}

evt.Bus().Publish(evt.CachingResultCacheChanged, r.resultCache.TotalCount())

if publish && r.redisClient != nil {
res := *response.Res
res.Answer = answer
res.Answer = response.Res.Answer
r.redisClient.PublishCache(cacheKey, &res)
}
}
Expand Down