OpenWrt/LEDE Project

  • Status Unconfirmed
  • Percent Complete
    0%
  • Task Type Bug Report
  • Category Kernel
  • Assigned To No-one
  • Operating System All
  • Severity Low
  • Priority Very Low
  • Reported Version openwrt-19.07
  • Due in Version Undecided
  • Due Date Undecided
  • Private
Attached to Project: OpenWrt/LEDE Project
Opened by Cristian Morales Vega - 25.04.2020

FS#3045 - In kernel WiFi pcap filters filter too much

In an Archer C7 just flashed with https://downloads.openwrt.org/releases/19.07.2/targets/ath79/generic/openwrt-19.07.2-ath79-generic-tplink_archer-c7-v2-squashfs-factory.bin (also with a custom build of the HEAD of the openwrt-19.07 branch) I find that “tcpdump -i wlan1 | grep Beacon” shows a lot of packets but “tcpdump -i wlan1 ‘type mgt subtype beacon’” doesn’t show anything (a packet from time to time, but very rarely and way less than without the filter). Doing the same after patching libpcap to force it to do the filtering in user-space fixes the issue.

Cristian Morales Vega commented on 25.04.2020 21:43
Cristian Morales Vega commented on 25.04.2020 21:52

I have not seen any other bug report, but in the forum there is https://forum.openwrt.org/t/unable-to-filter-for-beacon-frames-with-tcpdump-bug/47841/5, which says the problem happens with both "Archer C7 v2 (QCA9558) and Asus RT-AC51U(MT7620)".

Cristian Morales Vega commented on 01.05.2020 09:50

The problem disappears in master (f57230c) doing this

echo 0 > /proc/sys/net/core/bpf_jit_enable

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