Re: pcap_loop() not returning after pcap_breakloop() until another packet arrives

[Guy Harris <guy () alum mit edu>]

On Jun 24, 2006, at 10:50 PM, Richard Hansen wrote:

> I have one thread that sits in pcap_loop() and another thread that  
> calls pcap_breakloop() when it is time to shut down.  My code works  
> well on Windows (WinPcap 3.1).

Well, sort of.  I suspect that pcap_breakloop() doesn't *immediately*  
break you out of the loop - it's probably delayed until a packet  
arrives *or* the timeout expires.

>   On Linux (libpcap 0.9.4, kernel 2.6.16) the pcap_loop() doesn't  
> return after calling pcap_breakloop() until another packet  
> arrives.  Is this expected or proper behavior?

Expected, yes.  Linux's packet capture mechanism doesn't have the  
timeouts that the WinPcap driver, BPF, etc. do.

>   How can I tell Linux to return from that readfrom() call that  
> it's blocking on?

You *might* be able to do it with pthread_cancel(), although that  
will, ultimately, terminate the thread (unless a cleanup handler  
never returns).
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