Create question pipeline filter #257
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This will ensure that there's only one question at a given time. If a message has no question, it will return immediately; if it has more than one, it will discard all the tail questions and raise and event as a warning.
NelsonVides
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enhancement
Pull Request Test Coverage Report for Build 16137529487Details
💛 - Coveralls |
DXTimer
reviewed
Jul 8, 2025
| Labels = dns:dname_to_lower_labels(Q1#dns_query.name), | ||
| Measurements = #{count => 1 + length(Rest)}, | ||
| Metadata = #{host => Host, questions => [Q1, Q2 | Rest]}, | ||
| telemetry:execute([erldns, pipeline, questions], Measurements, Metadata), |
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Multi-question messages are not of great interest to us, since in practice we only support a single question, and any additional questions can be ignored safely.
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I know, the idea is that an attacking client can wilfully submit messages with many many questions, which no real DNS server really supports so very likely this is either a buggy client or a carefully crafted packet for evil purposes, which we will waste resources parsing, and we never drop them, the answer will contain them so again we waste resources encoding them. We might just drop them early enough and if it is of any interest for DDoS ideas this can be analysed.
DXTimer
approved these changes
Jul 8, 2025
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This will ensure that there's only one question at a given time. If a message has no question, it will return immediately; if it has more than one, it will discard all the tail questions and raise and event as a warning.