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dnsdist: Handle ENOTCONN on read() over TCP #8030

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merged 1 commit into from Aug 9, 2019

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@rgacogne rgacogne commented Jul 5, 2019

Short description

When a non-blocking connect() has returned EINPROGRESS, it looks like BSD can return ENOTCONN on read() even after a write() succeeded.
We did not get a trace confirming that read() can indeed return ENOTCONN in that case yet, though.

Fixes #8021.

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I have:

  • read the CONTRIBUTING.md document
  • compiled this code
  • tested this code
  • included documentation (including possible behaviour changes)
  • documented the code
  • added or modified regression test(s)
  • added or modified unit test(s)
When a non-blocking connect() has returned `EINPROGRESS`, it looks
like BSD can return `ENOTCONN` on `read()` even after a `write()`
succeeded.
@rgacogne
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@rgacogne rgacogne commented Aug 9, 2019

Confirmed on FreeBSD via a PoC, see #8021 (comment). After reading the source code of NetBSD and OpenBSD I believe we can get ENOTCONN on the first sendmsg() if the handshake has not been completed yet. Based on #7685 it looks like we actually experienced that on MacOS as well.

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@rgacogne rgacogne merged commit 91287ec into PowerDNS:master Aug 9, 2019
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@rgacogne rgacogne deleted the ddist-tcp-enotconn-read-bsd branch Aug 9, 2019
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