Re: [PATCH] Add ioctl to disable bpf timestamping

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

On Sep 8, 2004, at 2:26 AM, Bruce M Simpson wrote:

> Here's a patch against 5.3 to add a per-instance switch which allows
> the user to specify if captured packets should be timestamped (and,
> if so, whether microtime() or the faster but less accurate
> getmicrotime() call should be used).

This is probably a pointless optimization, as you probably relatively 
rarely have multiple BPF devices bound to the same interface receiving 
the bulk of the packets (as opposed to some daemon with a filter that 
passes only the packets it's interested in), but would there be any 
advantage to having "bpf_tap()" and "bpf_mtap()" fetch the time stamp 
and pass that to "catchpacket()", so that in the case where there *is* 
more than one tap, the time stamp is only fetched once?

That has the "disadvantage" that a tap might get a more accurate time 
stamp than it needs (the most accurate time stamp requested by a BPF 
device would be the one used).

> Comments/flames/etc to the usual...

If this is generally accepted as a good idea, it might be worth 
mentioning it to the other BSDs.

-
This is the tcpdump-workers list.
Visit https://lists.sandelman.ca/ to unsubscribe.