On Tue,  4 Jan 2011 16:30:01 -0800
Mahesh Bandewar [off-list ref] 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 <redacted>
Reviewed-by: Ben Hutchings <redacted>

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


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