Subject: Re: [PATCH v2] net: Allow ethtool to set interface in loopback mode.

From: Stephen Hemminger <[email-masked]>
Date: Tue, 4 Jan 2011 16:36:45 -0800

On Tue,  4 Jan 2011 16:30:01 -0800
Mahesh Bandewar <[email-masked]> wrote:

> This patch enables ethtool to set the loopback mode on a given interface.
> By configuring the interface in loopback mode in conjunction with a policy
> route / rule, a userland application can stress the egress / ingress path
> exposing the flows of the change in progress and potentially help developer(s)
> understand the impact of those changes without even sending a packet out
> on the network.
> 
> Following set of commands illustrates one such example -
> 	a) ip -4 addr add 192.168.1.1/24 dev eth1
> 	b) ip -4 rule add from all iif eth1 lookup 250
> 	c) ip -4 route add local 0/0 dev lo proto kernel scope host table 250
> 	d) arp -Ds 192.168.1.100 eth1
> 	e) arp -Ds 192.168.1.200 eth1
> 	f) sysctl -w net.ipv4.ip_nonlocal_bind=1
> 	g) sysctl -w net.ipv4.conf.all.accept_local=1
> 	# Assuming that the machine has 8 cores
> 	h) taskset 000f netserver -L 192.168.1.200
> 	i) taskset 00f0 netperf -t TCP_CRR -L 192.168.1.100 -H 192.168.1.200 -l 30
> 
> Signed-off-by: Mahesh Bandewar <[email-masked]>
> Reviewed-by: Ben Hutchings <[email-masked]>

Since this is a boolean it SHOULD go into ethtool_flags rather than
being a high level operation.

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