Re: [tcpdump-workers] [libpcap] High latency on i7 vs. Core 2 Duo systems (#304)

[Michael Richardson]

> "sbourland" == sbourland   writes:
sbourland> I have a very simple program that watches for packets on
sbourland> an interface and then sends a reply packet.  On all the
sbourland> Core 2 Duo systems I have tested, the response time is on
sbourland> the order of <20 usec (measured using a separate machine
sbourland> running tcpdump fed packets from a mirrored port).  When
sbourland> attempting to upgrade to i7 based systems, the response
sbourland> time is now over 100 usec.  Obviously Intel has been less
sbourland> than interested in helping figure out what has happened.
sbourland> Have tested with multiple Core 2 Duo and i7 systems with
sbourland> consistent results.  I am hoping someone on here as

Identical kernels?
Identical network interface cards?

I would suspect that the difference of 80us is the result of different
mechanisms being used by the NIC card to either signal arrival of the
packet (interrupt mitigation mechanisms, for instance), and/or the same
thing on the transmit side.

-- 
]   Never tell me the odds! | ipv6 mesh networks [ 
]   Michael Richardson, Sandelman Software Works| network architect  [ 
] m...@sandelman.ca  http://www.sandelman.ca/|   ruby on rails[ 


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[tcpdump-workers] Same packet on different interfaces

[Asier Martínez]

Hi to all,
I'm trying to sniff from several wifi cards at the same time with pcap
library,
if the wifi interfaces are set for example to channel 1 and 3, there is a
chance
for both of them to read the same packet.
Anyone have an idea how I can discard duplicated packets and only process
them once?

Thank you very much,
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