Hundreds of crypto file descriptors for Apache httpd

[Frank Wille <frank%phoenix.owl.de@localhost>]

Hi,

I am running "Horde webmail" with Apache 2.4.33 and PHP5.6 (both from
pkgsrc) on a NetBSD 8.1 server, which usually works pretty well, although a
little bit slow when dealing with bigger mails.

Today it became extremely slow. It requires nearly 60 seconds just to log
in. And any small action within Horde also takes between 10 and 30 seconds.
Other pages on this server are still fast (for example Typo3), so I was
looking for a problem with Horde and found this in /var/log/messages:

Mar  9 20:07:14 nerthus HORDE: [horde] PHP ERROR: stream_select(): You MUST
recompile PHP with a larger value of FD_SETSIZE. It is set to 256, but you
have descriptors numbered at least as high as 269. 
--enable-fd-setsize=1024 is recommended, but you may want to set it to
equal the maximum number of open files supported by your system, in order
to avoid seeing this error again at a later date. [pid 19351 on line 218 of
"/var/www/vhosts/www.xxxxx.de/webmail/pear/php/Net/DNS2/Socket/Streams.php"]

I wonder why there are so many file descriptors in use, so I checked with
fstat(1). Indeed, all httpd processes showed around 264 file descriptors in
use and 227 of them were "crypto" file descriptors:
[...]
apache   httpd       5661  229* crypto 0xfffffe83c27af9d8
apache   httpd       5661  230* crypto 0xfffffe83c27af930
apache   httpd       5661  231* crypto 0xfffffe83c27af888
[...]

Were do they come from? Is that some kind of leak? What can I do (besides
restarting Apache or the whole server)?

Thanks in advance!

-- 
Frank Wille