[Winpcap-users] How to ensure all packets are captured

Denis Kourktchan dennis.kg at gmail.com
Tue Aug 11 11:27:36 PDT 2009

Dear Mr. Varenni,


Thanks for your reply. I just wanted to clarify a few points you have made.
(Note: I am using a multicore machine so the multithread is a natural choice
and my processing code is definitely not as optimized as your pcap code, but
this is a solo project so I don't need to satisfy anyone else)


1.       You mention, that I should pre-allocate and reuse buffer space
where to store packets and not allocate new buffer. Do you mean something

PCAPDATANODE myPacketBuffer[amountOfNeededPackets];   // store in a specific
memory location predetermined 

Is PCAPDATANODE packetNode = new PCAPDATANODE(); not a good way to go?


2.       To prevent overloading, I need to pause capture (not extraction)
for a some amounts time according to SYSTEM time settings, is there a
command that can facilitate that? Or should I simply stop the adapter,
release it, and then reacquire when the time comes to capture (also would
this automatically flush the buffer)? At the moment, I merely stopped the
extraction but as you might have predicted the capture continued and I
simply continued processing where I last left it off.


Thanks again for you time,


-          Dennis


From: Gianluca Varenni [mailto:gianluca.varenni at cacetech.com] 
Sent: Monday, August 10, 2009 2:50 PM
To: dennis.kg at gmail.com; winpcap-users at winpcap.org
Subject: Re: [Winpcap-users] How to ensure all packets are captured


Moving the processing code in a separate thread may or might not help. If
you move the processing on a different thread and use a FIFO/linked list to
pass the packets among the threads, you will need to copy the packets in
your own allocated buffer. Copying a packet is extremely fast, but it makes
sense only if your packet processing code is much more CPU intensive than
copying the packet itself. Also, using a different thread makes sense if you
run on a multicore machine, where basically you can use both the CPUs.

If you go this way, remember to preallocate and reuse the buffers in which
you copy the packets, do not allocate a new buffer whenever you receive a


Hope this helps


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

From: Denis Kourktchan <mailto:dennis.kg at gmail.com>  

To: winpcap-users at winpcap.org 

Sent: Sunday, August 09, 2009 1:05 PM

Subject: [Winpcap-users] How to ensure all packets are captured


Hi Everybody,


I am writing an application that is intercepting packets from a network and
after reading a whole lot of posts regarding lost messages I figured the
fault is usually in application taking too long to process a batch of
packets which causes the overfilled buffer to replace oldest messages. So I
decided that the following setup is the best possible way to ensure that my
messages are not lost.


1.       Put capture (using pcap_next_ex()) into a different thread then the

2.       Store packets immediately upon extraction into a custom written
linked list, adding to the end and processing from the front (in different
threads) ensuring no mutex controls are necessary and no idle time.


Now here is the problem for which I need your expert advice, since the
pcap_next_ex() returns pointers to data, I still need to extract them (I use
for loop) before I can store which still preoccupies the capture thread and
slows down extraction process. So is there a better way to extract packets
without this delay?


I would appreciate any and all advice regarding the optimal solution
architecture wise.




-          Dennis 

















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