Re: [PATCH v2] net: Allow ethtool to set interface in loopback mode.
From: Mahesh Bandewar <hidden>
Date: 2011-01-05 01:39:26
On Tue, Jan 4, 2011 at 5:29 PM, Stephen Hemminger [off-list ref] wrote:
On Wed, 05 Jan 2011 01:21:44 +0000 Ben Hutchings [off-list ref] wrote:quoted
On Tue, 2011-01-04 at 16:36 -0800, Stephen Hemminger wrote:quoted
On Tue, 4 Jan 2011 16:30:01 -0800 Mahesh Bandewar [off-list ref] wrote:quoted
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.It could do, but I though ETHTOOL_{G,S}FLAGS were intended for controlling offload features.It just seems the number of hooks keeps growing which takes more space and increases complexity. There was some talk about changing GRO/TSO/UFO .. to be bits in FLAGS but not sure how far along that is. --
This is not merely getting / setting flags but involves invoking a method from the driver(s). If done this way; the code in ethtool_op_set_flags() will have to be special-cased to handle this flag which (I think) would not be clean.