#41 Errors under load (try to use poll instead of select)

[Stijn van der Ree]

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We're using opendkim with postfix (multi-instance), for signing outgoing mail. At busy moments, opendkim logs the following error:

warning: milter unix:/var/run/opendkim/opendkim.sock: read error in initial handshake
Sep 8 16:00:14 telemann postfix-15/smtpd[24178]: warning: milter unix:/var/run/opendkim/opendkim.sock: can't read SMFIC_OPTNEG reply packet header: Connection reset by peer

And this:

opendkim[14581]: OpenDKIM Filter: accept() returned invalid socket (Numerical result out of range), try again

I understand this can be solved by using using poll() instead of select(), so I've compiled opendkim with --enable-poll, but this does't help.

When stracing the binary, it seems to be still using select:

strace -p 14581
Process 14581 attached
select(6, [5], NULL, [5], {2, 959258}) = 0 (Timeout)
select(6, [5], NULL, [5], {5, 0}) = 0 (Timeout)

How can I check if the binary is using poll? If not, how should I compile opendkim? Or is there another way to solve this?

(I'm not very good at C/C++ unfortunately).

[Dilian Wesselinov Palauzov]

Does compiling libmilter with SM_CONF_POLL before linking it with opendkim help?

Looking at the code of opendkim the only impact of specifying ./configure --enable-poll is that opendkim -V prints POLL. The last calls within opendkim for poll were removed by commit b6967980bee : Feature request #SF3544764: Support for libar has been discontinued.

opendkim[14581]: OpenDKIM Filter: accept() returned invalid socket (Numerical result out of range), try again is generated by libmilter and according to my understanding, looking at its source means:

• "Numerical result out of range" - accept() returned a number higher thant 256, so that at that time probably for some reason the system had allocated more than 265 file descriptors
• try again - the connection was closed by the milter and the accept() call will be retried (for a new connection)

[Stijn van der Ree]

Hi Dilian,

Thanks, yes, we did it like this (enable polling):

./configure --with-odbx --with-openssl=/usr/include/openssl
--enable-poll --prefix=/opt/opendkim --exec-prefix=/opt/opendkim
CFLAGS=-g -O2 -w -DFD_SETSIZE=8192 -FD_SETSIZE=8192
LDFLAGS=-L/home/blah/src/sendmail-xxxx/obj.Linux.3.xxxxxxxx/libmilter/
-lmilter --with-milter=/home/blah/src/sendmail-xxxxxxx

Met vriendelijke groet,
Stijn van der Ree

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On Sun, Nov 12, 2017, at 18:06, Dilian Wesselinov Palauzov wrote:

Does compiling libmilter with _FFR_WORKERS_POOL before linking it with
opendkim help?

---

** [support-requests:#41] Errors under load (try to use poll instead of
select)**

Status: open
Group: 2.10.3
Created: Wed Sep 13, 2017 10:50 AM UTC by Stijn van der Ree
Last Updated: Wed Sep 13, 2017 10:50 AM UTC
Owner: nobody

0
down vote
favorite

We're using opendkim with postfix (multi-instance), for signing outgoing
mail. At busy moments, opendkim logs the following error:

warning: milter unix:/var/run/opendkim/opendkim.sock: read error in
initial handshake
Sep 8 16:00:14 telemann postfix-15/smtpd[24178]: warning: milter
unix:/var/run/opendkim/opendkim.sock: can't read SMFIC_OPTNEG reply
packet header: Connection reset by peer

And this:

opendkim[14581]: OpenDKIM Filter: accept() returned invalid socket
(Numerical result out of range), try again

I understand this can be solved by using using poll() instead of
select(), so I've compiled opendkim with --enable-poll, but this does't
help.

When stracing the binary, it seems to be still using select:

strace -p 14581
Process 14581 attached
select(6, [5], NULL, [5], {2, 959258}) = 0 (Timeout)
select(6, [5], NULL, [5], {5, 0}) = 0 (Timeout)

How can I check if the binary is using poll? If not, how should I compile
opendkim? Or is there another way to solve this?

(I'm not very good at C/C++ unfortunately).

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[Dilian Wesselinov Palauzov]

--enable-poll doesn't do anything.

From your message it is unclear, whether you #define SM_CONF_POLL while you build libmilter and whether this helps, hence the problem is within libmilter using select instead of poll.