On 10/17/22 22:50, Chris Johns wrote:
On 18/10/2022 4:42 pm, Sebastian Huber wrote:
On 18/10/2022 06:15, Chris Johns wrote:
On 18/10/2022 2:22 pm, Michael Davidsaver wrote:
On 10/17/22 16:20, Chris Johns wrote:
2. Look at kqueue, it is a better interface for this type of blocking
Maybe not relevant in Miroslaw's application, but I've found
that the RTEMS kqueue implementation doesn't notify when a
TCP connection is closed by reset. I think this is a lack
of NOTE_EOF *.
Thanks. I cannot find a ticket for this? Do you know if one has been created?
Not by me. I ran into this incidentally while testing some
new networking code using libevent, which helped me towards
finding:
https://www.mail-archive.com/freebsd-hackers@freebsd.org/msg43808.html
Which leads with a reasonably clear statement that kqueue
is/was not 100% functionally equivalent to select()/poll().
At that point I configured libevent to use poll() and
continued with my own troubleshooting. Then unfortunately,
I forgot about it until I read this thread.
https://github.com/mdavidsaver/pvxs/blob/6ee82fac6533d6551b18aa489cb263adc1333018/src/evhelper.cpp#L171-L178
That freebsd thread is 19 years old, and I haven't spent the
time to investigate what happened since then.
libevent has:
#ifdef NOTE_EOF
/* Make it behave like select() and poll() */
if (filter == EVFILT_READ)
out->fflags = NOTE_EOF;
#endif
https://github.com/libevent/libevent/blob/8f47d8de281b877450474734594fdc0a60ee35d1/kqueue.c#L193-L197
This looks like a general FreeBSD limitation.
This was my general assessment at the time.
Is NOTE_EOF the same as EV_EOF? I noticed EV_EOF in the FreeBSD man page for
kqueue.
I'm no expert on the kqueue mechanism, but I think not.
https://man.openbsd.org/kqueue.2
This openbsd manpage mentions both, although 'NOTE_EOF' is
only mentioned in passing, with no definition given.
Some searching leads me to think that EV_EOF is a "flag"
while NOTE_EOF is an "fflag" (filter flag). I have not
investigated the precise distinction between the two.
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