There is a possibility that the 1st frame is retried. Can you check for the "retry bit" in the sniffer capture.
Regards, Thomas. On Wed, Mar 25, 2015 at 1:05 AM, Mark Gannon <[email protected]> wrote: > I'm currently troubleshooting a problem using the ath9k driver where by > packets injected via libpcap are sent twice with slightly different > radiotap > headers. The issue happens with different software injecting the packets. > > The system is an up to date Gentoo box where uname -a shows: > Linux scooby 3.18.5-gentoo #1 SMP PREEMPT Wed Feb 4 16:54:06 EST 2015 > x86_64 > AMD A6-3650 APU with Radeon(tm) HD Graphics AuthenticAMD GNU/Linux > > lspci shows the card as: > 02:00.0 Network controller: Qualcomm Atheros AR93xx Wireless Network > Adapter > (rev 01) > > In order to create the problem: > > 1. Load the driver: modprobe ath9k debug=0x00000282 > Note: The problem happens with or without the debug parameters > 2. Create the monitor interface using: > iw dev wlan0 interface add fish0 type monitor flags none > iw reg set US > ifconfig fish0 up > > 3. Download and build the packetspammer application from: > https://wireless.wiki.kernel.org/en/users/Documentation/packetspammer > Note: I edited Makefile to remove the -werror that was causing the make to > fail. > 4. Start Wireshark listening to the fish0 interface. > 5. Run packetspammer: ./packetspammer -d 1000000000000000000000000000 > fish0 > Note: The long delay is to make the issue easier to see in the trace. > > Result: > Wireshark shows two packets with slightly different lengths due to > differences > in the radiotap header. The second packet has a much smaller radiotap > header > only setting the speed. > > In examining the driver code in the kernel tree, there appears to be a > difference between main.c and htc_drv_main.c with regard to packet > injection. > The latter includes a section with the comment: "Associate a station with > the > interface for packet injection." After the comment, is code to associate a > station with the interface. As near as I can tell, this process doesn't > occur > in main.c, which is the code being executed for my NIC. Could this be the > reason for the duplicate packets? > > Any help addressing this issue is greatly appreciated. > > Regards, > > Mark Gannon > > -- > You have to accept whatever comes, and the only important thing is that you > meet it with the best you have to give. > > — Eleanor Roosevelt > _______________________________________________ > ath9k-devel mailing list > [email protected] > https://lists.ath9k.org/mailman/listinfo/ath9k-devel > >
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