Ethereal-users: [Ethereal-users] Specifying filters in tethereal

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From: Vaidehi Kasarekar <vaidehi_30@xxxxxxxxx>
Date: Wed, 4 Jun 2003 18:26:50 -0700 (PDT)
Hello,
 
Suppose i have a frame like:
Frame 363 (90 on wire, 90 captured)
    Arrival Time: Jun  4, 2003 18:16:20.623654000
    Time delta from previous packet: 0.002625000 seconds
    Time relative to first packet: 13.375884000 seconds
    Frame Number: 363
    Packet Length: 90 bytes
    Capture Length: 90 bytes
IEEE 802.11
    Type/Subtype: Data (32)
    Frame Control: 0x0108
        Version: 0
        Type: Data frame (2)
        Subtype: 0
        Flags: 0x1
            DS status: Frame is entering DS (To DS: 1  From DS: 0) (0x01)
            .... .0.. = Fragments: No fragments
            .... 0... = Retry: Frame is not being retransmitted
            ...0 .... = PWR MGT: STA will stay up
            ..0. .... = More Data: No data buffered
            .0.. .... = WEP flag: WEP is disabled
            0... .... = Order flag: Not strictly ordered
    Duration: 258
    BSS Id: 00:02:2d:0d:fc:5b (Agere_0d:fc:5b)
    Source address: 00:02:2d:20:e1:d0 (Agere_20:e1:d0)
    Destination address: 00:02:2d:0d:fc:5b (Agere_0d:fc:5b)
    Fragment number: 0
    Sequence number: 2090
Logical-Link Control
    DSAP: SNAP (0xaa)
    IG Bit: Individual
    SSAP: SNAP (0xaa)
    CR Bit: Command
    Control field: U, func = UI (0x03)
        000. 00.. = Unnumbered Information
        .... ..11 = Unnumbered frame
    Organization Code: Unknown (0x00601d)
    Protocol ID: 0x0001
Data (58 bytes)
If i want to specify a filter in tethereal in such a way that, it will filter out packets, where
Frame Type match: "data" and the some more fields of the header. what is the syntax? How do i specify that???
 
If i specify:
[vaidehi@base-station log]$ tethereal -i eth2 -f 'wlan.fc.type_subtype eq 0x08' -V
I get an error:
 
tethereal: Unable to parse filter string (parse error).
Can anybody guide me writing rules to filter out packets based on certain header information. I am interested in the syntax. Or any document describing the filters or examples of filters would be useful.
 
Thanks
-Vaidehi


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