[Click] FromDump restart

Tue Nov 20 11:09:36 EST 2007

That was the problem.  I wasn't aware order of declaration mattered, but
apparently it does when dealing with scripts.  The declaration of my
FromDump elements was after the declaration of my Script element in the
configuration.  I moved the FromDump elements above my Script
declaration and filepos now reports "24".  Thanks!

Robert Ross
DSCI Inc.
Office: 732.542.3113 x173
Home: 609.702.8114
Cell: 609.509.5139
Fax: 253.550.6198

-----Original Message-----
From: Beyers Cronje [mailto:bcronje at gmail.com] 
Sent: Tuesday, November 20, 2007 11:07 AM
To: Robert Ross
Cc: Eddie Kohler; click at pdos.csail.mit.edu
Subject: Re: [Click] FromDump restart

Hi Robert,

Running your config below and pcap file I get:

click conf/fromdump.click
First Offset:  24
1194550918.323930:   66 | 00180125 a9fb0017 3f525f52 08004500 0034829e
40003006
1194550918.384094:   54 | 00180125 a9fb0017 3f525f52 08004500 0028829f
40003006
1194550918.444360:   66 | 00180125 a9fb0017 3f525f52 08004500 003482a4
40003006
......

I'm running git version from a few weeks back. I wonder if it is
possible that your script element is getting initialized before your
FromDump element?

Beyers

On Nov 20, 2007 4:25 PM, Robert Ross <rross at dsci.com> wrote:
> I tried this and, as I said before, the position returned is "0":
>
> fd::FromDump(/tmp/foo.trace,
>         TIMING true, FORCE_IP false, ACTIVE false, END_CALL
> restarter.step)
>         -> Print(TIMESTAMP true) -> Discard;
>
> restarter::Script(init first_offset $(fd.filepos),
>         print "First Offset: " $first_offset ,
>         write fd.active true,
>         pause,
>         write fd.filepos $first_offset,
>         write fd.reset_timing,
>         loop)
>
>
> This prints:
>
> First Offset: 0
>
>
>
> Robert Ross
> DSCI Inc.
> Office: 732.542.3113 x173
> Home: 609.702.8114
> Cell: 609.509.5139
> Fax: 253.550.6198
>
> -----Original Message-----
> From: Eddie Kohler [mailto:kohler at cs.ucla.edu]
> Sent: Monday, November 19, 2007 1:38 PM
> To: Robert Ross
> Cc: click at amsterdam.lcs.mit.edu
> Subject: Re: [Click] FromDump restart
>
> I think you did not try this, because it should have worked, but who 
> knows?  I checked in an update so that TIMING and FORCE_IP are 
> compatible, and added a "FromDump::reset_timing" handler so that you 
> can reset timing information when looping back into the file.
>
> fd::FromDump(/tmp/foo.trace,
>         TIMING true, FORCE_IP false, ACTIVE false, END_CALL
> restarter.step)
>         -> Print(TIMESTAMP true) -> Discard;
>
> restarter::Script(init first_offset $(fd.filepos),
>         write fd.active true,
>         pause,
>         write fd.filepos $first_offset,
>         write fd.reset_timing,
>         loop)
>
>
> Eddie
>
>
> Robert Ross wrote:
> >
> > I thought I had tried this already.  When I tried it, fd.filepose 
> > returned "0" as the starting position.  The only difference I see is

> > that I did not use "FORCE_IP true" because need to use the "TIMING"
> > keyword.  The two are apparently mutually exclusive.
> >
> > Robert Ross
> > DSCI Inc.
> > Office: 732.542.3113 x173
> > Home: 609.702.8114
> > Cell: 609.509.5139
> > Fax: 253.550.6198
> >
> > -----Original Message-----
> > From: Eddie Kohler [mailto:kohler at cs.ucla.edu]
> > Sent: Saturday, November 17, 2007 10:03 PM
> > To: Robert Ross
> > Cc: click at amsterdam.lcs.mit.edu
> > Subject: Re: [Click] FromDump restart
> >
> > Hi Robert,
> >
> > The problem with filepos is that filepos=0 is the pcap file header.
> > You need to set it to the first byte of actual packet data, which 
> > might be
> > 24 or 28 depending on pcap version.
> >
> > This script works for me.  It relies on the fact that FromDump skips

> > the header at initialization time, but does not actually read any 
> > packets until ACTIVE is true.
> >
> >
> > fd::FromDump(~/src/ipsumdump/test/one-byte-payload.trace,
> >       FORCE_IP true, ACTIVE false, END_CALL restarter.step)
> >       -> IPPrint -> Discard;
> >
> > restarter::Script(init first_offset $(fd.filepos),
> >       write fd.active true,
> >       pause,
> >       write fd.filepos $first_offset,
> >       loop)
> >
> >
> > Eddie
> >
> >
> > Robert Ross wrote:
> >> I'm trying to use a Script element along with a FromDump to loop a
> > small PCAP file several times with a delay between replays.  The 
> > script basically works except for one critical element:  I cannot 
> > seem
>
> > to reset the FromDump "filepos" handler to the beginning of the
file.
>
> > As indicated in the documentation, the issue appears to be 
> > determining
>
> > the correct byte offset for the beginning of the first packet in the
> file.
> > I've tried the following with no luck:
> >>
> >> 1.  Setting filepos=0.  If only it were that simple...
> >> 2.  Wait until the first packet has come out and "poke" the script
> > using a Counter element.  Then use the script to calculate various 
> > starting positions using a combination of read handlers from 
> > FromDump and Counter.
> >>
> >> Some of the questions I have are:
> >>
> >> 1.  Both packet_filepos and filepos provide byte offsets, but the
> > documentation does not adequately describe what these offsets
> represent.
> > Is packet_filepos the end point of the last packet read?  The start 
> > point of the last packet read?  The start point of the next packet 
> > to be read?  Something else?  What is the difference between filepos

> > and packet_filepos?
> >> 2.  Is there another simpler way to loop a PCAP file that I'm
> missing?
> >> 3.  Assuming I knew the correct offset, is it even possible to 
> >> reset
> > the filepos and re-play the PCAP file again?
> >>
> >> As a general suggestion, added LOOP and LOOP_INTERVAL keywords to 
> >> the
> > various dump elements could be extremely useful.  In the absence of 
> > those, at the very least a "restart" or "start_pos" handler would be

> > equally useful.  I'm currently wondering why the "filepos" handler 
> > is even writeable...
> >>
> >> Thanks,
> >> Robert A. Ross
> >> DSCI Inc.
> >> 609-509-5139
> >> _______________________________________________
> >> click mailing list
> >> click at amsterdam.lcs.mit.edu
> >> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>
> _______________________________________________
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>