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Date:      Fri, 26 Oct 2001 18:06:59 +0300
From:      Maxim Sobolev <sobomax@FreeBSD.org>
To:        Peter Pentchev <roam@ringlet.net>
Cc:        Ian Dowse <iedowse@maths.tcd.ie>, hackers@FreeBSD.org
Subject:   Re: cvs commit: ports/devel/ORBit Makefile ports/devel/ORBit/files  patch-src::IIOP::giop-msg-buffer.c
Message-ID:  <3BD97C13.81DF3E6F@FreeBSD.org>
References:  <200110261421.aa89321@salmon.maths.tcd.ie> <3BD977E4.DA2F224B@FreeBSD.org> <20011026175819.G33751@straylight.oblivion.bg>

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Peter Pentchev wrote:
> 
> On Fri, Oct 26, 2001 at 05:49:08PM +0300, Maxim Sobolev wrote:
> > Ian Dowse wrote:
> > >
> > > In message <200110261306.f9QD61O73080@freefall.freebsd.org>, Maxim Sobolev writ
> > > es:
> > > >  Nautilus from working properly. The problem disappeared when I've replaced
> > > >  writev(2) call with appropriate loop based around ordinary write(2). Perhaps
> > > >  this should be investigated and the real source of the problem fixed instead,
> > > >  but I do not have a time for this right now. For those who interested I'm
> > > >  ready to provide a step-by step instruction on how to reproduce the bug.
> > >
> > > Hi,
> > >
> > > If you have the details handy, a post to -hackers is likely to be
> > > quite constructive at getting the problem analysed and resolved.
> >
> > Ok, details are below.
> >
> > GNOME oaf is a CORBA-based RPC framework. It uses UNIX
> > domain sockets to communicate between client application and
> > oafd daemon that serves requests. Usually the communication
> > looks like the following:
> >
> > 1. Client connects to the oafd daemon via domain socket and
> > sends marshalled RPC request.
> > 2. The daemon reads request, demarshalls it and executes
> > either internally or by invoking external program/shared
> > library.
> > 3. The daemon marshalls result of the call and passes it
> > back to the client via the same socket.
> >
> > On the step 3, when marshalling results of the call, daemon
> > creates a large collection of small buffers (usually 5-10
> > bytes long each) arranged as array of struct iovec and then
> > sends this whole buffer to the client using writev(2) call.
> > In my particular case there were some 2,800 entries in the
> > buffer and when the daemon tried to send it to the client
> > writev(2) was returning -1 and setting errno to be EINVAL,
> > which confused the server and the client causing RPC to
> > fail.
> 
> 2800 entries?  Well, from the writev(2) manual page:
> 
>      In addition, writev() may return one of the following errors:
> 
>      ...
> 
>      [EINVAL]           Iovcnt was less than or equal to 0, or greater than
>                         UIO_MAXIOV.
> 
> And at least on -stable, UIO_MAXIOV is defined as 1024..

Ah, ok. I've overlooked it somehow.

-Maxim

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