Re: AIX BPF

[Guy Harris <guy () netapp com>]

On Wed, Feb 05, 2003 at 09:55:36AM +1100, Shaun wrote:
> I've been perusing the archives and noticed the (relatively) recent
> discussion and patch applied to the main line regarding AIX BPF reads
> returning EFAULT. The conclusion was the the AIX BPF driver returns an
> EFAULT on the next read after it was forced to drop packets (as an
> indication that packets have been dropped since the last read). I'm not
> sure of this conclusion, we've lately been developing a pcap based
> application that has been receiving EFAULTs but those errors are not
> accompanied by any change to the dropped packet counter. If I
> deliberately slow the program sufficiently to insure dropped packets I get
> the EFAULTs and the dropped packet counter is incremented as expected.

So, so far, it appears that the rule is "an EFAULT is returned if a packet is
dropped", not "an EFAULT is returned iff a packet is dropped" - i.e.,
it appears to be true that an EFAULT is returned if a packet is dropped,
but it does not appear to be true that a packet was dropped if an EFAULT
is returned.

Given that we're currently just ignoring EFAULT and driving on - we're
not doing anything with packet drop statistics if that happens - it
probably doesn't matter why EFAULT is returned, unless there's some
situation where the application (or library) *does* need to do something
with an EFAULT.
-
This is the TCPDUMP workers list. It is archived at
http://www.tcpdump.org/lists/workers/index.html
To unsubscribe use mailto:tcpdump-workers-request () tcpdump org?body=unsubscribe