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Ethereal-users: RE: [Ethereal-users] Filters and airodump captures

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From: "Guy Harris" <gharris@xxxxxxxxx>
Date: Fri, 15 Jul 2005 16:34:08 -0700 (PDT)
Charsley, Troy (Sudbury) said:
> Here is an example of a filter I am using:
> eth.src == 00:12:7f:ce:8d:70

    ...

> This is a beacon packet.

There's no such thing as a "beacon packet" on Ethernet, so this isn't an
Ethernet packet; "eth.src" is an Ethernet-specific field, and, as such,
appears only in Ethernet packets.  Any comparison of a field that doesn't
exist in a packet returns "false".

This has nothing to do with airodump - the same problem would occur with
any other type of 802.11 capture (and would occur with FDDI captures,
Token Ring captures,etc.).

The MAC-address fields you can filter on in 802.11 packets are:

    wlan.da - the DA field
    wlan.sa - the SA field
    wlan.ra - the RA field
    wlan.TA - the TA field
    wlan.bssid - the BSSID field

Perhaps we need, for example, some "pseudo-fields" that correspond to
source and destination addresses as displayed in the columns in the packet
list, so that you could do "src == foo" (which would match packets with a
source address corresponding to the host name "foo", where that could be
*any* type of host name, i.e. one corresponding to a MAC address or an
IPv4 address or an IPv6 address or...), "dst == 127.0.0.1" (which would
match only IPv4 packets; we'd need a syntax for addresses that lets us
infer the address type or types from the address string), and "addr ==
fe80::1" (which would match anything with a source *or* destination IPv6
address of fe80::1).