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Avoids allocations and function calls if no extra data is present.

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This commit is contained in:
James Phillips 2016-08-12 10:29:57 -07:00
parent e05c77b9bf
commit 45e2879eb5
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GPG key ID: 77183E682AC5FC11
1 changed files with 14 additions and 3 deletions
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17
command/agent/dns.go
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@ -545,13 +545,22 @@ func syncExtra(index map[string]dns.RR, resp *dns.Msg) {
// records will be trimmed along with answers.
func trimUDPResponse(config *DNSConfig, resp *dns.Msg) (trimmed bool) {
numAnswers := len(resp.Answer)
index := indexRRs(resp.Extra)
hasExtra := len(resp.Extra) > 0
// We avoid some function calls and allocations by only handling the
// extra data when necessary.
var index map[string]dns.RR
if hasExtra {
index = indexRRs(resp.Extra)
}
// This cuts UDP responses to a useful but limited number of responses.
maxAnswers := lib.MinInt(maxUDPAnswerLimit, config.UDPAnswerLimit)
if numAnswers > maxAnswers {
resp.Answer = resp.Answer[:maxAnswers]
syncExtra(index, resp)
if hasExtra {
syncExtra(index, resp)
}
}
// This enforces the hard limit of 512 bytes per the RFC. Note that we
@ -563,7 +572,9 @@ func trimUDPResponse(config *DNSConfig, resp *dns.Msg) (trimmed bool) {
resp.Compress = false
for len(resp.Answer) > 0 && resp.Len() > 512 {
resp.Answer = resp.Answer[:len(resp.Answer)-1]
syncExtra(index, resp)
if hasExtra {
syncExtra(index, resp)
}
}
resp.Compress = compress