Viktor Dukhovni via Postfix-users:
> On Sat, Feb 15, 2025 at 10:54:58AM +0200, Nikolaos Milas via Postfix-users
> wrote:
>
> > On 15/2/2025 1:45 ?.?., Wietse Venema via Postfix-users wrote:
> > > It is possible to override these system library functions by providing
> > > your own alternatives with LD_PRELOAD.
> >
> > Thanks Wietse, it makes sense.
> >
> > Would it be sufficient to LD_PRELOAD 2.34 libs for smptd or we should do so
> > for other executables like postscreen?
>
> No, this is at best going to work for a diagnostic test. Not suitable
> for "production".
>
> I don't recall seeing you testing with "getaddrinfo" (and perhaps also
> "getnameinfo" to see whether it is slow PTR lookup that is the problem).
> It may also help to perform tcpdumps to see how long the delay is
> between that client connecting and the Postfix 220 greeting.
>
> Until you understand the problem, there's no solution.
To preload:
main.cf:
import_environment = MAIL_CONFIG MAIL_DEBUG MAIL_LOGTAG TZ XAUTHORITY
DISPLAY LANG=C POSTLOG_SERVICE POSTLOG_HOSTNAME LD_PRELOAD=/path/to/file
This requires a postfix stop and start.
However Linux glibc has dependencies on other files (/lib64/ld-linux-whatever)
and implicit dependencies on nsswitch shared objects (/lib64/libnss_whatever)
and so on. The 'bug' can be at any level in this software stack.
Wietse
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