On Thu, 2011-01-06 at 16:47 -0800, Mahesh Bandewar wrote:

On Thu, Jan 6, 2011 at 2:13 PM, Ben Hutchings [off-list ref] wrote:

quoted

On Wed, 2011-01-05 at 11:22 -0500, Jeff Garzik wrote:

quoted

On 01/04/2011 08:21 PM, Ben Hutchings 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 doesn't have to be.  As Stephen guessed, [GS]FLAGS are basically
common flags -- as differentiated from private,
driver-specific/hardware-specific flags.

Well, that would allow the patch to be simplified quite a bit. :-)

Ben, Are you suggesting to use ETH_FLAG_LOOPBACK instead of
ETHTOOL_{G|S}LOOPBACK flags?

[...]

Exactly.

An example implementation (untested):

--- a/drivers/net/sfc/ethtool.c
+++ b/drivers/net/sfc/ethtool.c

@@ -548,11 +548,24 @@ static u32 efx_ethtool_get_rx_csum(struct net_device *net_dev)
 	return efx->rx_checksum_enabled;
 }
 
+static u32 efx_ethtool_get_flags(struct net_device *net_dev)
+{
+	struct efx_nic *efx = netdev_priv(net_dev);
+	u32 flags;
+
+	flags = ethtool_op_get_flags(net_dev);
+	if (efx->loopback_mode != LOOPBACK_NONE)
+		flags |= ETH_FLAG_LOOPBACK;
+	return flags;
+}
+
 static int efx_ethtool_set_flags(struct net_device *net_dev, u32 data)
 {
 	struct efx_nic *efx = netdev_priv(net_dev);
-	u32 supported = (efx->type->offload_features &
-			 (ETH_FLAG_RXHASH | ETH_FLAG_NTUPLE));
+	u32 supported = (ETH_FLAG_LOOPBACK |
+			 (efx->type->offload_features &
+			  (ETH_FLAG_RXHASH | ETH_FLAG_NTUPLE)));
+	enum efx_loopback_mode loopback;
 	int rc;
 
 	rc = ethtool_op_set_flags(net_dev, data, supported);

@@ -562,7 +575,15 @@ static int efx_ethtool_set_flags(struct net_device *net_dev, u32 data)
 	if (!(data & ETH_FLAG_NTUPLE))
 		efx_filter_clear_rx(efx, EFX_FILTER_PRI_MANUAL);
 
-	return 0;
+	loopback = (data & ETH_FLAG_LOOPBACK) ? LOOPBACK_DATA : LOOPBACK_NONE;
+	mutex_lock(&efx->mac_lock);
+	if (efx->loopback_mode != loopback) {
+		efx->loopback_mode = loopback;
+		rc = __efx_reconfigure_port(efx);
+	}
+	mutex_unlock(&efx->mac_lock);
+
+	return rc;
 }
 
 static void efx_ethtool_self_test(struct net_device *net_dev,

@@ -1057,7 +1078,7 @@ const struct ethtool_ops efx_ethtool_ops = {
 	.get_tso		= ethtool_op_get_tso,
 	/* Need to enable/disable TSO-IPv6 too */
 	.set_tso		= efx_ethtool_set_tso,
-	.get_flags		= ethtool_op_get_flags,
+	.get_flags		= efx_ethtool_get_flags,
 	.set_flags		= efx_ethtool_set_flags,
 	.get_sset_count		= efx_ethtool_get_sset_count,
 	.self_test		= efx_ethtool_self_test,
---

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.