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seemoo-lab / nexmon_csi

Channel State Information Extraction on Various Broadcom Wi-Fi Chips
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CSI packets are captured but pcap file is empty #204

Open dejavo4e opened 3 years ago

dejavo4e commented 3 years ago

hi; I tried to capture CSI packets using "tcpdump -i wlan0 dst port 5500 -vv -w output.pcap -c 1000" the result shows that 1000 CSI packets were captured. I mount my usb flash drive and "cp" the pcap file. But the files are either 0kb or 325kb. I didn't find similar problem . I don't know whether others have encountered this problem or not. Thank you for your respond.

parisafm commented 3 years ago

Hi there; Try to reinstall raspian and nexmon. Be sure that you are using the right kernel version. Check the version of kernel header. It should be 5.4. U can check its version by this command: uname -r

By the way, I recommend u to do as it is said in https://github.com/zeroby0/nexmon_csi/tree/pi-4.19.97 This link is for 4.19 version. Change branches for other versions

dejavo4e commented 3 years ago

@parisafm Thanks for your respond. I have checked my kernel by using "uname -a" . it is 5.4.79. still i get empty pcap files. here is my results: tcpdump: listening on wlan0, link-type EN10MB (Ethernet), capture size 262144 bytes
1000 packets captured 1120 packets received by filter 0 packets dropped by kernel root@raspberrypi:/home/pi# du -h a20.pcap 328K a20.pcap

yujianyuanhaha commented 3 years ago

@dejavo4e what about longer time capture, mine is like ./tcpdump -i eth6 dst port 5500 -vv -G 5 -W 1 -w /mnt/MYDISK/test.pcap; where -G 5 mean 5 seconds collection.

Best

zeroby0 commented 3 years ago

Are you sure the pcap file is empty?

If your WiFi bandwidth is 20 MHz, the ~300KB file size seems reasonable. An 80 MHz file with 1000 samples is about 1 MB.

You can use CSI-Explorer to inspect your CSI files and see whether they're really empty. Or you can open them up in Wireshark.

dejavo4e commented 3 years ago

@dejavo4e what about longer time capture, mine is like ./tcpdump -i eth6 dst port 5500 -vv -G 5 -W 1 -w /mnt/MYDISK/test.pcap; where -G 5 mean 5 seconds collection.

Best

same as before. pcap file is empty

dejavo4e commented 3 years ago

Are you sure the pcap file is empty?

If your WiFi bandwidth is 20 MHz, the ~300KB file size seems reasonable. An 80 MHz file with 1000 samples is about 1 MB.

You can use CSI-Explorer to inspect your CSI files and see whether they're really empty. Or you can open them up in Wireshark.

yeah i tried wireshark. still pcap file is empty. I reinstalled raspian but it didn't work as expected...

zeroby0 commented 3 years ago

Just to confirm, the 325 kb file had no data? It might be a problem with tcpdump or your setup. Try using channel 36, and make sure there is wireless traffic in that channel when you collect. Can you post your file?

I'm using kernel 5.4.51, I created a fresh install of nexmon_csi and it works as expected. https://github.com/nexmonster/nexmon_csi/tree/pi-5.4.51-plus

yjxb1 commented 1 year ago

Hello, have you solved the problem? The bag I caught is also empty。