Re: [PATCH] enable memory mapped access toethernet

["Gianluca Varenni" <gianluca.varenni () cacetech com>]

I agree with you.

Consider that under windows, for example, we have a windows-only function to 
set the kernel buffer size 
(http://www.winpcap.org/docs/docs_40_2/html/group__wpcapfunc.html#g124bde25ccd9e39017ff2abec2dda623)
and the kernel buffer in WinPcap is actually a ring buffer (although we do 
not use memory mapped access).

Have a nice day
GV




----- Original Message ----- 
From: "Gregor Maier" <gregor () net in tum de>
To: <tcpdump-workers () lists tcpdump org>
Sent: Wednesday, December 05, 2007 10:27 AM
Subject: Re: [tcpdump-workers] [PATCH] enable memory mapped access 
toethernet


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>
> > The idea behind the snaplen [miss-]use is to permit legacy application
> > to take advantage of the memory mapped access and permit new ones to
> > control the ring behaviur. Such goal could be obtained even with other
> > solution, but I was a bit 'scared' to add a 'Linux only' API to pcap.h.
>
> IMHO that's not an issue. Furthermore we have a student working on an
> MMAP-pcap for FreeBSD as his master thesis. So it won't be a Linux only
> API for long ;-)
>
>
> > Undoubtedly my implementation is not the most clean one; I can rework
> > the patch adding a function to control the ring size [something like
> > 'pcap_set_ring_size(handle, ring_size)'] and using some default values
> > for the memory mapped ring during pcap_open_live, if there is some
> > consensus in this direction.
>
> Using a function to set the ring buffer size sounds like the best choice
> to me, as long as these parameters can still be changed after the open
> or after packets have been read. If you can't change these parameters
> during the capture I would introduce a new pcap_open_live_mmap()
> function and make the "old" pcap_open_live() call pcap_open_live_mmap()
>
>
> just my 2ct
>
> Gregor
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