Ethereal-users: RE: [Ethereal-users] Out of order reception woes
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From: "Stock, Stuart [TKY]" <Stuart.Stock@xxxxxxxx>
Date: Tue, 25 May 2004 11:46:13 +0900
Thank you. -----Original Message----- From: ethereal-users-bounces@xxxxxxxxxxxx [mailto:ethereal-users-bounces@xxxxxxxxxxxx]On Behalf Of Guy Harris Sent: 2004 5 25 11:44 To: Ethereal user support Subject: Re: [Ethereal-users] Out of order reception woes On Tue, May 25, 2004 at 11:25:06AM +0900, Stock, Stuart [TKY] wrote: > This is a bit complicated, so please bear with me. The short version is: we > have 3 instances of the same application all consuming the same low rate > (max 1.5 MBps) multicast data. Randomly one of the instances will report > out-of-order reception of the data while the other 2 see the data correctly > ordered. All of the instances are on the same switch and consume data from > the same source. Ethereal dumps of these events consistently show a negative > frame.time_delta for the instance reporting the problem and normally ordered > data for the 2 others. > > I would think that the issue lies somewhere with the kernel or ethernet > driver since the timestamps show the data was received off-the-wire > correctly, but is mixed-up before being handed to libpcap/my application. > The OS is Red Hat Linux AS 2.1 x386. > > My questions are: > 1. Anybody experienced similar out-of-order problems and might be able to > shed some light on this? I haven't dealt with such a problem myself, so I can't help you there. > 2. Where do the libpcap timestamps really come from? Looking at my libpcap > sources I see pcap_pkthdr.ts getting its value from ioctl(handle->fd, > SIOCGSTAMP, &pcap_header.ts) but I'm not sure if it's the file handle that > supplies the timestamp or the underlying driver. It's OS-dependent, but, in Linux, it's ultimately done somewhere in the networking stack, either in the driver or in routines the driver calls - I forget which. Libpcap receives packets from a socket, just as your application presumably does; as such, if there's something in the networking stack causing packets to be delivered to sockets out of order, it might affect both Ethereal (or tcpdump or some other libpcap-based application) and your application. You should probably ask the Linux network stack developers about this. _______________________________________________ Ethereal-users mailing list Ethereal-users@xxxxxxxxxxxx http://www.ethereal.com/mailman/listinfo/ethereal-users ---------------------------------------------------------------------- The information contained herein is confidential and is intended solely for the addressee. Access by any other party is unauthorised without the express written permission of the sender. If you are not the intended recipient, please contact the sender either via the company switchboard on +44 (0)20 7623 8000, or via e-mail return. If you have received this e-mail in error or wish to read our e-mail disclaimer statement and monitoring policy, please refer to http://www.drkw.com/disc/email/ or contact the sender. ----------------------------------------------------------------------
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