Avoids allocations and function calls if no extra data is present.
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@ -545,13 +545,22 @@ func syncExtra(index map[string]dns.RR, resp *dns.Msg) {
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// records will be trimmed along with answers.
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func trimUDPResponse(config *DNSConfig, resp *dns.Msg) (trimmed bool) {
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numAnswers := len(resp.Answer)
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index := indexRRs(resp.Extra)
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hasExtra := len(resp.Extra) > 0
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// We avoid some function calls and allocations by only handling the
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// extra data when necessary.
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var index map[string]dns.RR
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if hasExtra {
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index = indexRRs(resp.Extra)
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}
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// This cuts UDP responses to a useful but limited number of responses.
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maxAnswers := lib.MinInt(maxUDPAnswerLimit, config.UDPAnswerLimit)
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if numAnswers > maxAnswers {
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resp.Answer = resp.Answer[:maxAnswers]
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syncExtra(index, resp)
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if hasExtra {
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syncExtra(index, resp)
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}
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}
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// This enforces the hard limit of 512 bytes per the RFC. Note that we
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@ -563,7 +572,9 @@ func trimUDPResponse(config *DNSConfig, resp *dns.Msg) (trimmed bool) {
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resp.Compress = false
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for len(resp.Answer) > 0 && resp.Len() > 512 {
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resp.Answer = resp.Answer[:len(resp.Answer)-1]
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syncExtra(index, resp)
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if hasExtra {
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syncExtra(index, resp)
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}
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}
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resp.Compress = compress
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