Re: Buffer size question

["Gianluca Varenni" <gianluca.varenni () polito it>]

----- Original Message ----- 
From: "Guy Harris" <guy () alum mit edu>
To: <tcpdump-workers () lists tcpdump org>
Sent: Thursday, October 14, 2004 1:45 AM
Subject: Re: [tcpdump-workers] Buffer size question


> Ed Maste wrote:
>
> > 1) Add a new pcap API function pcap_set_bufsize that can be used
> > to set the size used for following pcap_open_live calls (by setting
> > a libpcap global variable).
>
> The global variable is a bit ugly.  If you're going to have API changes...
>
> > 2) Add a new function like pcap_open_live that adds a buffer size
> > argument.  http://www.tcpdump.org/lists/workers/2000/msg01358.html
>
> ...you might as well do that, as there are other reasons for a new API.

...like pcap_setbuff(), as implemented in WinPcap...

http://winpcap.polito.it/docs/docs31beta3/html/group__wpcapfunc.html#a29

Have a nice day
GV


> > 3) Use an environment variable (PCAP_BUFFER_MAX?) to set the
> > initial trial buffer size.  Existing applications could even use a
> > larger size without recompiling.
> >
> > 4) Do a BIOCGBLEN ioctl before trying the initial size.  If the
> > size returned is greater than the initial size, just avoid
> > BIOCSBLEN.  On FreeBSD I've got a sysctl debug.bpf_bufsize that
> > sets the default buffer size, but it has no effect for libpcap.
> > The disadvantage is that the same size gets used for all pcap
> > users, which might be undesirable.
>
> One of those might also be useful.
>
> In fact, libpcap 0.8[.x] already does 4).  Adding 3) might be useful to
> override the default for existing programs.
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