[Winpcap-users] Re: breaking out of a pcap_next_ex() loop

Guy Harris guy at alum.mit.edu
Mon May 15 18:23:11 GMT 2006

Gianluca Varenni wrote:

> The most important problem is that it doesn't actually stop the capture 
> immediately: if simply exits the capture loop *when* the read timeout 
> occurs or at the first reception of a packet (whatever comes first). If 
> you put a long timeout (say 10 seconds) and you don't receive packets, 
> pcap_next_ex/pcap_loop/pcap_dispatch will return after up to 10 seconds.

It was originally added for use in signal handler routines on UNIX; if a 
signal occurs while libpcap is blocked waiting for packets to arrive, 
the system call on which it's blocked with return an EINTR error, which 
will break out of the packet read/receive.


	1) that doesn't happen on Windows;

	2) that doesn't, as far as I know, help on UNIX if the signal is 
delivered to a thread other than the one blocked in libpcap.

1) could be handled if there were a packet.dll call that poked the 
driver (with a new ioctl or something such as that) to cause any blocked 
read on a particular open device to return immediately with an error 
indication.  2) might require a similar facility in the packet capture 
mechanisms in various UN*Xes.

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