[Ns-bugs] [Bug 443] Net device pcap traces arent consistent with what tcpdump would display

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=443


Mathieu Lacage <mathieu.lacage at sophia.inria.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mathieu.lacage at sophia.inria.
                   |                            |fr




--- Comment #4 from Mathieu Lacage <mathieu.lacage at sophia.inria.fr>  2009-03-01 03:39:49 EDT ---
Ok, I looked at the wifi patches (generated with hg diff -r 4252 -r tip
src/devices/wifi from craigdo/ns-3-traces):

1) You can't just add a tx completed event in MacLow. The whole codebase was
designed to not use a tx completed event to 'optimize' that event. If we find
out that we really need to have a tx completed event for tracing purposes,
then, we have to restructure entirely the codebase because a lot of code is
there just to work without a tx completed event so, if there is one, a lot of
code must disappear.

2) In wifi-mac.h: please, don't make the traces protected: if you need to
trigger them from subclasses, use a protected Notify method. The same goes for
wifi-phy.h.

3) WifiNetDevice::SniffPacket ?? You are making an extra copy of the packet
just for tracing, even if there are no connected trace sinks ? This really does
not look like a good idea because it is emulating something really stupid/bad
from linux (which, incidentely, I believe got fixed in recent wifi stacks) and
because its performance cost is a bit horrid.

To summarize, 2) appears easily fixable, the part of 3) which makes use of an
ethernet header for tracing looks like a really, _really_ bad idea, and 1)
worries me because it would be a lot of work to adjust the current codebase to
the presence of a tx completed event.


Sorry for not sounding too enthusiastic.


-- 
Configure bugmail: http://www.nsnam.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.