Networking frame loss in transmission

[Julian Elischer]

> Message: 2
> Date: Fri, 15 Apr 2011 18:57:19 -0500
> From: Alex Anagnos<woodshop2300 at gmail.com>
> Subject: Networking frame loss in transmission
> To: freebsd-emulation at freebsd.org
> Message-ID:<BANLkTik92Eg0hrHsaK0J8yh3vibuyRDZew at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> FreeBSD 8.0-RELEASE w/ VirtualBox 3.2.12.
>
> The setup is a small application in a Guest OS that is sending UDP
> Ethernet frames.
> I Am capturing on FreeBSD on the device with both Wireshark, and a
> custom written program that uses BPF zero copy.
>
> What i'm seeing is that when the application send data that is beyond
> the MTU the data is fragmented.
> However, sometimes, the first few fragments never show up in the
> capture, and indeed the receiving app never gets the message
> (reassembly fails).

maybe it was waiting for arp?
> So when I call send with an 8192 payload, i see,  frames 1 and 2 go
> missing, but 3, 4, and , 5 get out fine. (1500 MTU)
do you see an arp reply wbetween 2 and 3?

> When calling send 2 times in rapid succession, all fragments of the
> first send go missing as well as 1, and 2 of the 2nd send. 3, 4, and 5
> get out fine.
> When calling send 3 times in rapid succession, all fragments of send 1
> &  2 get lost as well as fragment 1&  2 of the 3rd send. Frags 3, 4,
> and 5 are fine.

makes arp less likely but not impossible.
> When sending this at like 1 Message per second, things occasionally don't work.
> When going at 3000FPS, it has so far always been the first few frames,
> after that the rest of the stream gets through ok almost like the
> driver has to warm up or something..
>
> The issue happens sending from both a Linux guest and from a Windows Guest.
> The issue does not care about the speed of the traffic, it happens at
> 1FPS and at 3000FPS.
have you tried a freebsd guest? at least we can debug that.. :-)

> The issue does seam to occur less often the smaller the message sent.
> When the message does not require fragmentation I have not seen the
> issue happen but i'm not going to guarantee it does not happen.
>
> The problem happens using Bridged, VDE, and Host-Only.
> The problem happens using the FastPCI driver, intel e1000, and para-virtualized.
> The problem happens with any number of the above 3 combos.
>
> The problem happens in Version 3.2.6 and inversion 3.2.12.
>
> The problem looks to be somewhere in the VirtualBox box code, or maybe
> in the VirtualBox kernel module integration with FreeBSD