Wireshark-dev: Re: [Wireshark-dev] dfilter functions
From: Michael Mann <[email protected]>
Date: Sun, 6 Jan 2019 14:20:22 +0000 (UTC)
len - Checks the string length of "string types" (FT_STRING, FT_STRINGZ, FT_UINT_STRING, FT_STRINGZPAD) or array length of "byte types" (FT_BYTES, FT_UINT_BYTES) and does a compare.

Examples:
len(smpp.message_id)  > 10
len(smpp.message) > 25

size - Checks the size of the field in a packet.  Can be used for strings/bytes like len() above, but can also be used for integer fields that vary in length (1-4 bytes)

Examples:
size(eth.type) == 2       (This is just for demonstration purposes.  Obviously the size of the eth.type field could only be 2 but I couldn't quickly think of a "popular" field with varying integer length)    
size(tcp.options) > 7

count - Number of times a field is found in a single frame.  This can be used to help identify "tunneling" or if multiple PDUs are in a single frame.

Examples:
count(ip.src) > 1
count(smpp.sequence_number) > 1    (Since sequence_number is required for the packet, having more than one shows frames with multiple PDUs.


-----Original Message-----
From: Dario Lombardo <[email protected]>
To: Developer support list for Wireshark <[email protected]>
Sent: Sun, Jan 6, 2019 4:35 am
Subject: [Wireshark-dev] dfilter functions

Hi
I've noticed that the online documentation about dfilter functions just talks about 2 of them, upper and lower:


but there are more that are undocumented AFAICS:

- len
- size
- count

Can someone explain me their purpose and give a working example on some protocol?
Thanks.
Dario.

--
Naima is online.
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