[Oisf-users] Percentage of dropped packets

[Peter Bates]

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Hello all

On 29/05/2012 17:12, Chris Wakelin wrote:
> What's the NIC? Which version of ethtool are you using? For my
> Intel 10GB cards (ixgbe)  I get:
> 
> Offload parameters for eth1: rx-checksumming: on tx-checksumming:
> on scatter-gather: on tcp-segmentation-offload: on 
> udp-fragmentation-offload: off generic-segmentation-offload: on 
> generic-receive-offload: on large-receive-offload: on
> 
> and for me tcp.invalid_checksum is always 0.

Interesting. I'm using the same NIC (ixgbe), and was following Doug
Burk's advice:
http://securityonion.blogspot.co.uk/2011/10/when-is-full-packet-capture-not-full.html

When I first had the 10Gb NIC up I was seeing (in ifconfig) rx dropped
increasing and no rx packets received - and subsequently nothing to
capture in tcpdump/etc - however as the advice above changes all the
settings to 'off' I was unsure which one actually solved my problem.

I've turned the checksumming back on:
Offload parameters for eth6:
rx-checksumming: on
tx-checksumming: on
scatter-gather: off
tcp-segmentation-offload: off
udp-fragmentation-offload: off
generic-segmentation-offload: off
generic-receive-offload: off
large-receive-offload: off
rx-vlan-offload: off
tx-vlan-offload: off
ntuple-filters: off
receive-hashing: off

although seeing as I'm only rx'ing then the tx-checksumming presumably
has nothing to do with the situation.

My ethtool version is 2.6.39 and the NIC driver is
driver: ixgbe
version: 2.0.62-k2
firmware-version: 0.9-3

I'll fiddle some more but my next step might be to upgrade Linux
version to get a 3.x kernel so that the AF_PACKET driver will support
FANOUT.

- -- 
Peter Bates
Senior Computer Security Officer    Phone: +44(0)2076792049
Information Services Division	    Internal Ext: 32049
University College London
London WC1E 6BT
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