[Winpcap-users] How canigetthenew-estpacketfrombuffer?HELPPLEASE~!

[Alan Jay Weiner]

Thanks for jumping in and correcting my misconception!  I was following an
earlier comment about that; I should have checked that the information was
correct.

 

- Al -

 

 

----------------------------------------------------------------------------
Alan Jay Weiner / Valid8.com, Inc. - Conform, Perform & Excel(tm)
500 W Cummings Park, Suite #2700, Woburn, MA 01801, USA
a.weiner at valid8.com / Tel:+1-781-938-1221 x112, Fax +1-781-207-0550
http://www.VALID8.com 

 

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From: winpcap-users-bounces at winpcap.org
[mailto:winpcap-users-bounces at winpcap.org] On Behalf Of Gianluca Varenni
Sent: Tuesday, May 26, 2009 1:22 PM
To: winpcap-users at winpcap.org
Subject: Re: [Winpcap-users] How
canigetthenew-estpacketfrombuffer?HELPPLEASE~!

 

Sorry for jumping in this conversation late.

 

Please be aware that WinPcap does *not* overwrite older packets with new
ones. If the kernel buffer (or the user buffer) is full, newer packets are
simply dropped.

 

Have a nice day

GV

----- Original Message ----- 

From: Alan Jay Weiner <mailto:a.weiner at valid8.com>  

To: winpcap-users at winpcap.org 

Sent: Tuesday, May 26, 2009 9:27 AM

Subject: Re: [Winpcap-users] How can
igetthenew-estpacketfrombuffer?HELPPLEASE~!

 

I presume the packets contain some kind of status conditions and you're
doing something based on the latest status.

 

What about using small buffers?  The older data is overwritten by newer data
- if the buffer is only large enough for 1 or 2 packets, you'll get the 1 or
2 most-recent packets.  All the other packets will be lost, but that seems
ok in your situation.

 

How many of the most-recent packets do you need?   Is it sufficient to have
only the most-recent packet?

 

 

- Al Weiner -

 

 

----------------------------------------------------------------------------
Alan Jay Weiner / Valid8.com, Inc. - Conform, Perform & Excel(tm)
500 W Cummings Park, Suite #2700, Woburn, MA 01801, USA
a.weiner at valid8.com / Tel:+1-781-938-1221 x112, Fax +1-781-207-0550
http://www.VALID8.com 

 


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From: winpcap-users-bounces at winpcap.org
[mailto:winpcap-users-bounces at winpcap.org] On Behalf Of rst
Sent: Tuesday, May 26, 2009 5:19 AM
To: winpcap-users at winpcap.org
Subject: Re: [Winpcap-users] How can i
getthenew-estpacketfrombuffer?HELPPLEASE~!

 

The machine always sending packets , never stop.

and my computer only connected with the machine (using a crossover network
cable).

so every packets I get are what I wanted, but only the newest packet I need.

 

Machine ----(Sending packets)---> My Computer
.........................every 0.000005 second

 

My Application ----(Get the newest packet)---> Get information to do
control...................every 0.0001 second

 

if the buffer can contrain 10000 packets,

0.000005 * 10000 = 0.05 second,

so I can only get the information before 0.05 second,

but in my realtime control, i must get the information less than 0.0001
second.

 

so have any ideas?

 

Really thank you!!

 

If the other machine is sending a constant 200,000 packets per second and
won't slow down, you may be out of luck.  However, if the other machine
sends 200,000 packet per second for a short burst (say 10 seconds), then you
should be able to store those 2M packets into your own memory space.  After
you store the packets, you can do your analysis.

 

For a quick test, just change your control loop to do...

 

static int counter;

 

pcap_next_ex(...);

counter++;

 

That is, don't do anything with the packet (other than advance the buffer
and count how many you receive).  This will tell you how fast your machine
can move through the buffer.

 

If this works well, then you need to do a memcpy() of the packet into
pre-allocated space (i.e. malloc your own circular queue).  This will slow
down the loop, but should be much faster than 0.1ms.

 

Last question:  Most packet capturing applications need to decode EVERY
packet, are you saying that you do NOT need to decode every packet?  If not,
how do you know which packets you need to decode and which ones you don't?

 

DC


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