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Re-Enable compression while computing Len(), so we can send more answers 

This will fix https://github.com/hashicorp/consul/issues/4071
This commit is contained in:
Pierre Souchay 2018-05-16 11:00:51 +02:00
parent 61e7d06174
commit 7e8878df0b
1 changed files with 8 additions and 8 deletions
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16
agent/dns.go
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@ -745,9 +745,6 @@ func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
hasExtra := len(resp.Extra) > 0
// There is some overhead, 65535 does not work
maxSize := 65533 // 64k - 2 bytes
// In order to compute properly, we have to avoid compress first
compressed := resp.Compress
resp.Compress = false
// We avoid some function calls and allocations by only handling the
// extra data when necessary.
@ -790,8 +787,6 @@ func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
req.Question,
len(resp.Answer), originalNumRecords, resp.Len(), originalSize)
}
// Restore compression if any
resp.Compress = compressed
return truncated
}
@ -821,7 +816,10 @@ func trimUDPResponse(req, resp *dns.Msg, udpAnswerLimit int) (trimmed bool) {
// This cuts UDP responses to a useful but limited number of responses.
maxAnswers := lib.MinInt(maxUDPAnswerLimit, udpAnswerLimit)
compress := resp.Compress
if maxSize == defaultMaxUDPSize && numAnswers > maxAnswers {
// We disable computation of Len ONLY for non-eDNS request (512 bytes)
resp.Compress = false
resp.Answer = resp.Answer[:maxAnswers]
if hasExtra {
syncExtra(index, resp)
@ -834,9 +832,9 @@ func trimUDPResponse(req, resp *dns.Msg, udpAnswerLimit int) (trimmed bool) {
// that will not exceed 512 bytes uncompressed, which is more conservative and
// will allow our responses to be compliant even if some downstream server
// uncompresses them.
compress := resp.Compress
resp.Compress = false
for len(resp.Answer) > 0 && resp.Len() > maxSize {
// Even when size is too big for one single record, try to send it anyway
// (usefull for 512 bytes messages)
for len(resp.Answer) > 1 && resp.Len() > maxSize {
// More than 100 bytes, find with a binary search
if resp.Len()-maxSize > 100 {
bestIndex := dnsBinaryTruncate(resp, maxSize, index, hasExtra)
@ -848,6 +846,8 @@ func trimUDPResponse(req, resp *dns.Msg, udpAnswerLimit int) (trimmed bool) {
syncExtra(index, resp)
}
}
// For 512 non-eDNS responses, while we compute size non-compressed,
// we send result compressed
resp.Compress = compress
return len(resp.Answer) < numAnswers