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Re: [RSPlib-Discusssion] fail-over problems


Chronological Thread 
  • From: "Marjan Bozinovski" <marjanb AT cpk.auc.dk>
  • To: "Thomas Dreibholz" <dreibh AT exp-math.uni-essen.de>, <rsplib-discussion AT sctp.de>
  • Subject: Re: [RSPlib-Discusssion] fail-over problems
  • Date: Mon Sep 16 11:47:01 2002
  • List-id: RSPlib Discussions <rsplib-discussion.sctp.de>
Hi Thomas,

In the logfile I sent you on Friday, one can see that the problem occurs
with the rspSelect(). These are the suspicious debugging output line:

-----------------------
select: adding FD 0 (0) with mask $0003
select: registering user callback for socket 0...
Sending Break via break pipe...
F0008: User Callback, mask=$1
Break via break pipe received
Break Pipe: 1 calls
select: adding FD 1020 for read
select: adding FD 1020 for except
select: adding FD 1021 for read
select: waiting...
A0003 S00: Data Arrive Notification, Length = 392
select: wake-up
----------------------

It's strange, there is Data Arrive Notification, but rspSelect() returns
zero. What is the problem? This does not happen when examplepu is run.

Best regards,
Marjan


----- Original Message -----
From: "Marjan Bozinovski"
<marjanb AT cpk.auc.dk>
To: "Thomas Dreibholz"
<dreibh AT exp-math.uni-essen.de>;
<rsplib-discussion AT sctp.de>
Sent: Friday, September 13, 2002 6:42 PM
Subject: Re: [RSPlib-Discusssion] fail-over problems


> Thomas, I didn't receive your last two mails. An hour ago, I accidently
> checked the rsplib mailing list archive, and I saw you messages. So, I did
> as you recommended and in the attached file I put the debug output I get
on
> the screen after turning on the socket API debugging output.
>
> Note that I set my program to exit automatically if rspSelect() does not
> report any arrived message (i.e., result=0).
>
> Please check it out and see if there is something suspicious.
>
> Regards,
> Marjan
>
> ----- Original Message -----
> From: "Marjan Bozinovski"
> <marjanb AT cpk.auc.dk>
> To: "Thomas Dreibholz"
> <dreibh AT exp-math.uni-essen.de>;
> <rsplib-discussion AT sctp.de>
> Sent: Thursday, September 12, 2002 3:20 PM
> Subject: Re: [RSPlib-Discusssion] fail-over problems
>
>
> > I understand that a simpler program can facilitate the debugging but I
> > couldn't do that. On the other hand, today I think at least I localized
> the
> > problem. It seems that it has something to do with rspSelect() and the
> > socket opened by connectToPoolElement().
> >
> > I will outline a piece of the pseudo code:
> >
> > 1. First I start with:
> >
> > beginLogging();
> > initAll();
> > connectToPoolElement();
> > //as a result, a global DataSocket is created which is nonzero. This
> is
> > the same as in examplepu().
> >
> > 2. I send some data 'buffer'.
> >
> > sendToPoolElement(buffer);
> > //this is successfully transmitted as I can see with Ethereal. Also,
> the
> > SCTP receiver responds back with SACK + echoed 'buffer'.
> >
> > 3. I start listening to incoming messages:
> >
> > FD_ZERO(&readfdset);
> > FD_SET(DataSocket, &readfdset);
> >
> > timeout.tv_sec = 2;
> > timeout.tv_usec = 0;
> >
> > result = rspSelect(DataSocket + 1, &readfdset, NULL, NULL,
&timeout);
> > //exactly as in the examplepu();
> >
> > After this I always get result=0, there are no incoming messages at
> > DataSocket.
> > Why? I am supposed to receive the echoed message from the
echo_server.
> > Where do I make the mistake?
> >
> > /Marjan
> >
> >
> > ----- Original Message -----
> > From: "Thomas Dreibholz"
> > <dreibh AT exp-math.uni-essen.de>
> > To: "Marjan Bozinovski"
> > <marjanb AT cpk.auc.dk>;
<rsplib-discussion AT sctp.de>
> > Sent: Wednesday, September 11, 2002 5:34 PM
> > Subject: Re: [RSPlib-Discusssion] fail-over problems
> >
> >
> > > -----BEGIN PGP SIGNED MESSAGE-----
> > > Hash: SHA1
> > >
> > > Am Dienstag, 10. September 2002 23:14 schrieb Marjan Bozinovski:
> > > > Hi,
> > > >
> > > > In my SIP client application I have included a fail-over mechanism.
> For
> > > > instance, if the application does not receive a response to a
> particular
> > > > request after a timer expiration, the request has to be resent to
> > another
> > > > active pool element. In principle, my ultimate goal is if the ASAP
> level
> > > > does the fail-over by using a notification either: a) from the SCTP
> > layer
> > > > that the message could not be delivered to the peer endpoint or b)
> from
> > the
> > > > ASAP user layer using timer mechanisms as it is at the moment.
> > > >
> > > > Now, the problem is the following. Whenever a timer activated per
SIP
> > > > request fires, it is a signal for a failure, and therefore a
fail-over
> > is
> > > > made by using the existing function connectToPoolElement() (in
> > > > examplepu.c). Here is what I notice: First, it prints on the screen
> that
> > > > the connection to the second PE is successfully established and
> > > > connectToPoolElement() is finished. But, when seeing the packets
with
> > > > Ethereal I realize that the SCTP association is actually not
> > established.
> > > > On the contrary, the SCTP client side sends an INIT but immediately
> > after
> > > > that it sends an ABORT in which it reports zero error causes with
the
> T
> > bit
> > > > set to 0. Due to the abortion, the SCTP association has never been
> > > > established although connectToPoolElement() notifies successful
> > association
> > > > startup.
> > > >
> > > > I also expected that the SCTP association with the previous SCTP
> > endpoint
> > > > will be shutdown, but that does not happen.
> > > >
> > > > After the connectToPoolElement(), I put sendToPoolElement(), but
> > naturally
> > > > it only says "writing to data socket failed".
> > > >
> > > > I hope that I described this problem clearly.
> > >
> > > What do you use to realize your timer, Unix signals (SIGALRM, etc.)?
The
> > > socket API is thread-safe but not signal safe. You can not use socket
> API
> > > functions from a signal handler.
> > >
> > > Turn on loglevel 9 for your rsplib program and let it write the
output,
> > > including your program's output, to a file, that is "-loglevel=9
> > > - -logcolor=off" (see examplepe and examplepu) and ">logfile 2>&1".
> Then,
> > send
> > > me this file with a description what you have done to produce this
> output.
> > >
> > > It would be very helpful if you can reproduce the error in a very
simple
> > > program without your SIP library. The simpler the program, the more
> easily
> > I
> > > can identify the problem.
> > >
> > >
> > > Best regards
> > > - --
> > >
=======================================================================
> > > Dipl.-Inform. Thomas Dreibholz
> > >
> > > University of Essen, Room ES210
> > > Inst. for Experimental Mathematics Ellernstraße 29
> > > Computer Networking Technology Group D-45326 Essen/Germany
> >
>
> - -----------------------------------------------------------------------
> > > E-Mail:
> > > dreibh AT exp-math.uni-essen.de
> > > Homepage: http://www.exp-math.uni-essen.de/~dreibh
> > >
=======================================================================
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