From postfix-users  Fri Aug 16 13:50:45 2019
From: Wietse Venema <wietse () porcupine ! org>
Date: Fri, 16 Aug 2019 13:50:45 +0000
To: postfix-users
Subject: Re: postfix milter body chunk length
Message-Id: <4694Td0s4SzJrNt () spike ! porcupine ! org>
X-MARC-Message: https://marc.info/?l=postfix-users&m=156596350932260

Viktor Dukhovni:
> > On Aug 16, 2019, at 10:33 PM, Matthias Schneider <matthias.schneider@rmail.de> wrote:
> > 
> > I was wondering why the transfer of a 100mb mail to my milter application was slow, i found the bottleneck in the body chunk transfer.
> > 
> > The maximum packet length seems to be fixed to 64k, it would be great if we could make that configurable in postfix (uint32 is possible).
> 
> https://github.com/avar/sendmail-pmilter/blob/master/doc/milter-protocol.txt#L182-L213
> 
> http://ftp.sendmail.org/KNOWNBUGS
> 
> * milter communication fails if a single header is larger than 64K.
> 
>   If a single header is larger than 64KB (which is not possible in the
>   default configuration) then it cannot be transferred in one block to
>   libmilter and hence the communication fails.  This can be avoided by
>   increasing the constant MILTER_CHUNK_SIZE in
>   include/libmilter/mfdef.h and recompiling sendmail, libmilter, and
>   all (statically linked) milters (or by using undocumented compile
>   time options: _FFR_MAXDATASIZE/_FFR_MDS_NEGOTIATE; you have to
>   read the source code in order to use these properly).

On the Postfix side, edit src/milter/milter8.c and update its
MILTER_CHUNK_SIZE definition accordingly. It's only compile-time
configurable in Postfix, because it's only compile-time configurable
in libmilter.

	Wietse