Re: Patches for wlan filtering

["Gianluca Varenni" <gianluca.varenni () cacetech com>]

The attachment got somewhat dropped.

You can find it here

http://www.winpcap.org/gianluca/wlan_filtering.patch

GV


----- Original Message ----- 
From: "Gianluca Varenni" <gianluca.varenni () cacetech com>
To: <tcpdump-workers () lists tcpdump org>
Sent: Thursday, June 14, 2007 2:19 PM
Subject: [tcpdump-workers] Patches for wlan filtering


> Guys,
>
> the attached patch fixes some of the problems in the current wlan code 
> generation of pcap_compile.
> In particular it should fix these problems:
>
> 1. the 802.11 header size of a data frame has not a fixed size. When the 
> QoS bit is set in the subtype field (QoS DATA frame), the header is two 
> bytes longer. You can clearly see this on 802.11n APs, that usually use 
> QoS DATA frames. The code does not take into consideration
>   * 802.11n frames containing the HT control field
>   * frames in a WDS (wireless bridges)
> 2. The optimizer generates buggy code when compiling filters in the form 
> "wlan dst ...." or similar. The optimizer gets disabled in these cases.
> 3. Added some code that verifies that a packet is a data frame when 
> accessing the LLC and above protocol fields.
>
> Modifications related to 1. and 3. generate code that is not compatible 
> with the optimizer, as gen_load_ll_XXX() generate slist*'s of instructions 
> (where I added the code to verify if a packet is a data/QoS data frame), 
> and not block* chunks. So optimization gets disabled.
>
> I'm planning to commit them on the libpcap CVS as disabled patches, and 
> also planning to enable them for the win32 build (winpcap) in the next 
> version that is probably due within some weeks.
>
> Any comment/test is more than welcome. Please apply the patch with 
> "patch -p0 gencode.c < wlan_filtering.patch". The patch should work on 
> both HEAD and the libpcap_0_9 branch (I developed it on the libpcap_0_9 
> branch).
>
> Have a nice day
> GV
>
>
>
>
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