Wireshark · Wireshark-users: Re: [Wireshark-users] Editcap 100 argument limitation? (Jeff Morriss)

["Rob Campbell" <a.robcampbell@xxxxxxxxx>]

> Message: 2
> Date: Wed, 20 Jun 2007 16:06:25 -0400
> From: Jeff Morriss <jeff.morriss@xxxxxxxxxxx>
> Subject: Re: [Wireshark-users] Editcap 100 argument limitation?
> To: Community support list for Wireshark
>        <wireshark-users@xxxxxxxxxxxxx>
> Message-ID: <467988C1.7030803@xxxxxxxxxxx>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
>
>
> Stephen Fisher wrote:
> > On Tue, Jun 19, 2007 at 04:48:15PM -0400, Rob Campbell wrote:
> >
> >> I did some experimenting and the problem seems to lie in that editcap
> >> seems to only read the first 100 arguments (be it individual packet
> >> numbers or sets of packet numbers).
> >>
> >> Is this limit intentional or can it be removed?  Is this a unix/linux
> >> limitation?
> >
> > This is an arbitrary limit compiled into the editcap program:
> >
> > Line 109 of editcap.c:
> >
> >   static struct select_item selectfrm[100];
> >
> > How many arguments do you need to pass to editcap?  We could look into
> > changing this limit or removing it entirely to make it dynamically
> > allocate space for as many arguments as fit on the command-line.
>
> I went ahead and (in rev 22145) increased the size of the array (up to
> 512).  If that's not enough we can always go to a dynamically sized
> array, but that seems like overkill to me (now).
>
> More importantly, I also made 'editcap' tell you when it runs out of
> room for packet selections.

Thanks Jeff!  512 should be tons.  I was unaware of the ability to
use tethereal/tshark to read in from one pcap and output to a
different file using a wireshark display filter.

 I was using tethereal to dump the pcaps to XML/Text and then parsing
the XML/Text files collecting all of the packet numbers that belonged
to a flow based on IP/Port information, and then using regular
expressions I was creating the sets of packet numbers to allow me for
than 100 packets.  Everything was done using tcl scripts so it's not
like I was manually entering 100 arguments or anything, but the silent
failure when it hit the 100 argument mark took me a little while to
figure out :)

 Had I have known that tethereal could do it for me by just passing
it the IP/Port information as a filter than I likely would never have
needed this, but reporting that it hit the limit is definately a great
improvement as I'm sure someone will hit this again.

Thanks again,
Rob


---------------------------------------
Rob Campbell
a.robcampbell@xxxxxxxxx