Date: Sun, 25 Sep 2022 23:12:38 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] [draft] dns tcp fallback On Thu, Sep 22, 2022 at 04:28:34PM -0400, Rich Felker wrote: > Here is my first draft of the DNS TCP fallback support that seems to > be basically working. There may of course be bugs, and there are cases > where I probably don't want it to fall back like it's doing, but it's > at a stage where review and [smoke-]testing would be helpful. > > Some known issues: > > - getaddrinfo should use larger buffers (probably 640-768 bytes) or > the "huge CNAME" problem iss not solved. > > - If res_send is used to send EDNS0 queries crafted by the caller and > the caller provides a buffer smaller than what the OPT header > advertises, the answer will be silently truncated to the caller's > buffer size. > > I've tested querying TXT for locations.publicdns.goog (>7k RRset) and > basic non-fallback usage. Further large-answer query test cases would > be appreciated, especially names where one or both of the A or AAAA > RRset are large so that fallback in parallel lookup can be tested, and > later so that getaddrinfo buffer size increase can be tested. OK, I have patches for both of the above now. View attachment "0004-getaddrinfo-dns-lookup-use-larger-answer-buffer-to-h.patch" of type "text/plain" (2283 bytes) View attachment "0005-dns-query-core-detect-udp-truncation-at-recv-time.patch" of type "text/plain" (2416 bytes)
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