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unix/dgram: return EAGAIN instead of ENOBUFS when O_NONBLOCK set
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Authored by glebius on Feb 6 2022, 6:33 PM.
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Summary

This is behavior what some programs expect and what Linux does. For
example nginx expects EAGAIN when sending messages to /var/run/log,
which it connects to with O_NONBLOCK. Particularly with nginx the
problem is magnified by the fact that a ENOBUFS on send(2) is also
logged, so situation creates a log-bomb - a failed log message
triggers another log message.

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I think this is probably ok. EAGAIN is the usual error value for this case. I thought this would break our syslog(3), which explicitly checks for ENOBUFS, but it uses a blocking socket.

This revision is now accepted and ready to land.Feb 6 2022, 10:35 PM