Ah, I should have mentioned that this is not a new application, it has and does run regularly and successfully taking live multicast data via either kernel sockets, or OpenOnload or ef_vi kernel bypass. The packet replay is a new feature however, and works fine unless the application is configured to use kernel sockets, in which case the kernel currently drops all the replayed packets. Of course I confirm that the associated multicast group membership is as expected prior to launching the replay.
To confirm then, are you saying that tcpreplay should not interfere with the IP stack in the scenario described; that being tcpreplay and application running concurrently on the same box, tcpreplay out eth1 to switch, back to eth2, kernel, and (hopefully) application? Thanks! ________________________________________ From: Aaron Turner <synfina...@gmail.com> Sent: Saturday, July 9, 2016 12:30:07 AM To: Main forum for tcpreplay Subject: Re: [Tcpreplay-users] replayed multicast packets dropped by ip stack The linux kernel IP stack won't deliver multicast packets unless you open the appropriate listener socket. Obviously, without looking at your application code I have no idea if that's your problem, but from the sounds of it that is the most likely issue. Nothing you've said sounds like a tcpreplay bug to me. -- Aaron Turner https://synfin.net/ Twitter: @synfinatic Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. -- Benjamin Franklin On Fri, Jul 8, 2016 at 1:53 PM, James deCocq <dotmar...@hotmail.com> wrote: > Hi all, > > NICETIES > tcpreplay version: 4.1.0; CentOS 6.7; x86_64 > Multiple Solarflare SFC9120 > > BACKGROUND: > Our application can be built to use one of: > * kernel sockets > * OpenOnload (bespoke network stack, kernel bypass) > * ef_vi (direct to/from VNICs, no stack) > > PROBLEM: > * We test using tcpreplay of captured live multicast packets. > * Replayed packets go out eth1 to the switch and back to eth2. > * When application is built to use onload or ef_vi, it works as expected. > * However when built for kernel stack, replayed packets arrive at eth2 > as expected, but are subsequently dropped by kernel. > > DETAIL: > * Multicast drops appear to originate from 2 spots in the linux stack: > most from ip_rcv(), and some in tpacket_rcv() (the AF_PACKET stuff) > * Captured live data is massaged for playback thusly, addresses redacted: > tcprewrite -C --srcipmap=nnn.nnn.nnn.nnn/26:nnn.nnn.nnn.nnn > --dstipmap=nnn.nnn.nnn.nnn/24:nnn.nnn.nnn.nnn/24 > --enet-smac=00:0F:53:xx:yy:zz --enet-vlan=del -i in.pcap -o out.pcap > * All mods and IP checksums look good in Wireshark, and again, > the application receives expected flow if the kernel stack is not involved. > > QUESTION: > * Of course I noted the caveat about replay on the same box; however > I was not certain that the caveat applied to our use case, > tcpreplay -> eth1 -> switch -> eth2 ->kernel; > however drops from kernel's tpacket_rcv() would seem to suggest yes? > * So is tcpreplay running concurrently with our application likely to be > the cause of the kernel dropping multicast packets in this situation? > > Thanks very much for any assistance you can provide. > > james > > ------------------------------------------------------------------------------ > Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San > Francisco, CA to explore cutting-edge tech and listen to tech luminaries > present their vision of the future. This family event has something for > everyone, including kids. Get more information and register today. > http://sdm.link/attshape > _______________________________________________ > Tcpreplay-users mailing list > Tcpreplay-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/tcpreplay-users > Support Information: http://tcpreplay.synfin.net/trac/wiki/Support ------------------------------------------------------------------------------ Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San Francisco, CA to explore cutting-edge tech and listen to tech luminaries present their vision of the future. This family event has something for everyone, including kids. Get more information and register today. http://sdm.link/attshape _______________________________________________ Tcpreplay-users mailing list Tcpreplay-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tcpreplay-users Support Information: http://tcpreplay.synfin.net/trac/wiki/Support ------------------------------------------------------------------------------ Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San Francisco, CA to explore cutting-edge tech and listen to tech luminaries present their vision of the future. This family event has something for everyone, including kids. Get more information and register today. http://sdm.link/attshape _______________________________________________ Tcpreplay-users mailing list Tcpreplay-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tcpreplay-users Support Information: http://tcpreplay.synfin.net/trac/wiki/Support
