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Re: [SCTP-Discussion] ch_enterPRSCTPfromInit infinite loop.


Chronological Thread 
  • From: Thomas Dreibholz <dreibh AT iem.uni-due.de>
  • To: sctp-discussion AT sctp.de
  • Cc: Nils Olav Selåsdal - Utel Systems <nos AT utel.no>, "discussion AT sctp.de" <discussion AT sctp.de>
  • Subject: Re: [SCTP-Discussion] ch_enterPRSCTPfromInit infinite loop.
  • Date: Wed, 09 May 2012 09:36:14 +0200
  • List-archive: <http://lists.franken.de/pipermail/sctp-discussion>
  • List-id: SCTP Discussions <sctp-discussion.sctp.de>
  • Organization: University of Duisburg-Essen, Institute for Experimental Mathematics
Am Freitag 27 April 2012, 15:25:07 schrieb Michael Tuexen:
> On Apr 27, 2012, at 1:10 PM, Nils Olav Selåsdal - Utel Systems wrote:
> > Hi,
> > We got into an infinite loop just now, ch_enterPRSCTPfromInit() got stuck
> > with pLen being 0 in this loop,
> >
> > while (curs < vlp_totalLength) {
> >
> > ack_string = &((SCTP_init
> > *)chunks[initAckCID])->variableParams[writeCursor[initAckCID]];
> > vl_initPtr = (SCTP_vlparam_header *) & init_string[curs];
> > pType = ntohs(vl_initPtr->param_type);
> > pLen = ntohs(vl_initPtr->param_length);
> >
> > if (pLen < 4) result = -1; /* peer error - ignore - should send an
> > error notification */
> >
> > event_logiii(VERBOSE, "Scan variable parameters: Got type %u, len:
> > %u, position %u",pType, pLen, curs);
> >
> > if (pType == VLPARAM_PRSCTP) {
> >
> > /* ha, we got one ! */
> >
> > if (pLen == 4) result = 0; /* peer supports it, but doesn't
> > send anything unreliably */ if (pLen > 4) result = 1; /*
> > peer supports it, and does send some */ memcpy(ack_string,
> > vl_initPtr, pLen);
> > writeCursor[initAckCID] += pLen;
> >
> > }
> > curs += pLen;
> > while ((curs % 4) != 0) curs++;
> >
> > }
> >
> > I’d assume it’ll be safe to change if (pLen < 4) result = -1; to if(pLen
> > < 4) return -1; here ?
> That seems correct. However, checking for pLen > 4 seems suspicious. I guess
> the sctplib implements some draft version, not PR-SCTP as specified in RFC
> 3758.

Did you any updates and testing of the change?

If it is working, please send us a patch. Then, we can include it in the next
release of sctplib.

--
Best regards / Mit freundlichen Grüßen / Med vennlig hilsen

====================================================================== Thomas
Dreibholz

Simula Research Laboratory
Simula Innovation AS, Network Systems Group
Visiting address: Martin Linges vei 17, 1364 Fornebu, Norway
Mailing address: P.O.Box 134, 1325 Lysaker, Norway
-----------------------------------------------------------------------
E-Mail:
dreibh AT simula.no
Homepage: http://simula.no/people/dreibh
=====================================================================

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