Re: libpcap and tc filters

[jamal <hadi@cyberus.ca>]

On Tue, 2011-07-05 at 06:56 -0400, jamal wrote:

> I downloaded tcpreplay and reproduced the issue with your rules.
> Will look into it..

Ok - found out whats going on. 
tcprelay sendpacket_open_pf() does bind to ETH_P_ALL.
You are sending IP packets (the name tcpreplay is misleading,
this thing replays anything). 
Your filters are for ip packets as in:
---
sudo tc filter add dev eth0 protocol ip parent 1: prio 1 u32 match ip
dport 22 0xffff flowid 1:1
---

You have two options:

1) If you change that to capture ETH_P_ALL it works.
i.e

---
sudo tc filter add dev eth0 protocol all parent 1: prio 1 u32 match ip
dport 22 0xffff flowid 1:1
---

Of course this is nasty if you are in a busy network, because _all_
packets not just ip will look at your filters. If it is just an
experimental setup, it may be a non-issue

2) Change tcpreplay to take an additional option so it binds to 
ETH_P_IP (and default stays as is today). The authors of the app
may not like that option - but it is sensible if you know you are
replaying ip packets.

cheers,
jamal