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Dimitri Herzog
db8d889b7b
* fix(server): compress responses larger than 512 bytes Since #2102 the server lets Truncate decide compression, and Truncate clears Compress whenever the message already fits uncompressed. Fitting the buffer the client advertised is not sufficient: that client may be a forwarder relaying our answer to a stub resolver with a smaller buffer, and it can only truncate what it received. A query arriving via such a forwarder carries the forwarder's OPT record, so getMaxResponseSize returns its buffer (1232 or more) rather than 512. An eight-record A answer for a 45-byte name is 562 bytes uncompressed and 202 compressed: both fit 1232, so we now send the uncompressed one, and the forwarder has to truncate it for its non-EDNS0 clients -- typically by dropping every section, leaving them with TC and no answer at all. Before #2102 the same answer went out compressed, fit 512, and was relayed intact. Compress anything that would not fit a bare 512-byte UDP message so it survives that hop. Below that threshold there is nothing to gain, so the compression-map alloc #2102 set out to avoid is still skipped for the short responses that make up the bulk of the traffic. Fixes #2212 * test(server): guard that the compression regression test stays meaningful Assert the answer really exceeds 512 bytes uncompressed, so shrinking the RR set can't leave the test passing without exercising the scenario.