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Date: Thu, 5 Nov 2015 16:01:22 +0100 (CET)
From: elof2@sentor.se
To: freebsd-net <freebsd-net@freebsd.org>
Subject: ngrep/ixgbe bpf bug
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Hi all!

Why don't ngrep work on ix interfaces?


It shows nice values if I sniff on other interfaces, e.g. igb0 and
bridge0:

# ngrep -d igb0 "q" ip
I see some matching packets. Everything looks good.

# netstat -B
   Pid  Netif   Flags      Recv      Drop     Match Sblen Hblen Command
  1800   igb0 p--s---       135         0       129   380     0 ngrep
The BPF stats show Recv and Match values. Good.


# ngrep -d bridge0 "q" ip
   I see some matching packets. Good.

# netstat -B
   Pid  Netif      Flags    Recv     Drop     Match  Sblen Hblen Command
  1901  bridge0  p--s---  661897        0    659170 425606     0 ngrep
Again, the BPF stats show Recv and Match values. Good.



However, if I sniff on an ix interface:

# ngrep -d ix1 "q" ip
I get no matching packets!

# netstat -B
   Pid  Netif   Flags      Recv      Drop     Match Sblen Hblen Command
  1816    ix1 p--s---     45340         0         0     0     0 ngrep
                                                 ^^^
...and the BPF stats always show zero Matches.


Bug in the ixgbe driver or in ngrep?

/Elof