tcpdump mailing list archives

Re: capturing on both interfaces simultaneously


From: Guy Harris <guy () alum mit edu>
Date: Mon, 12 Dec 2011 14:05:07 -0800


On Dec 12, 2011, at 1:41 PM, Guy Harris wrote:

On Dec 12, 2011, at 3:59 AM, David Laight wrote:

I also think that interface could defer freeing the last
rx buffer until the request to read another packet.
That would avoid the necessity of a buffer copy
for applications that don't want to use callbacks.

Actually, that *might* be doable, with some additional complexity, although it does leave one less buffer slot 
available to the kernel, and, given how difficult it is to get an appropriate buffer slot size in the 
fixed-length-packet-slot TPACKET_V1/TPACKET_V2 architecture, that might be significant.  I forget why I decided not to 
go with that strategy.

The more I deal with TPACKET_V1/TPACKET_V2 the more annoying it is.  Hopefully I'll have time to look at TPACKET_V3 at 
some point; it looks less troublesome (and a bit more like BPF, at least at first glance :-)).
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