On Jul 29, 2010, at 8:02 AM, César Gomes wrote:

> I'm currently working on a dissector, and I need to make so that one variable 
> has the same value at the begining of a capture, the value then can change, 
> but in the beginning it has to be the same, how can I do that?

Note that there is no guarantee that, in Wireshark, after the file has been 
read in for the first time, your packets will be dissected in order.  When the 
file is read in, each packet is dissected in order (note, however, that there 
is no guarantee that you will be asked to build a protocol tree on that first 
dissection, so don't build state only if the tree argument is non-null!), and 
you can use that pass to build state.  After that, users can click on whatever 
packets they want, in whatever order they want, and, when a packet is clicked 
on, it is dissected.

In other words, do *NOT* maintain, in a global variable, state that changes 
from packet to packet, and assume that, when a packet is dissected, the state 
will reflect only the packets before the packet in question.  You might have to 
attach state information to packets in order to dissect them after the first 
pass.
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