Re: [RFC 1/2] net: Support getting/setting RX-FCS in drivers.

On 06/17/2011 05:20 AM, Ben Hutchings wrote:

On Thu, 2011-06-16 at 21:30 -0700, greearb@candelatech.com wrote:

quoted

From: Ben Greear<redacted>

This will allow us to enable/disable having the Ethernet
frame checksum appended to the skb.  Enabling this is
useful when sniffing packets.

In particular, this can be used to test logic that allows
a NIC to receive all frames, even ones with bad checksums.

Signed-off-by: Ben Greear<redacted>
---
:100644 100644 439b173... e5e8747... M	include/linux/ethtool.h
:100644 100644 fd14116... b36bac7... M	net/core/ethtool.c
  include/linux/ethtool.h |    5 +++++
  net/core/ethtool.c      |   38 ++++++++++++++++++++++++++++++++++++++
  2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 439b173..e5e8747 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h

@@ -955,6 +955,8 @@ struct ethtool_ops {
  	int	(*get_dump_data)(struct net_device *,
  				 struct ethtool_dump *, void *);
  	int	(*set_dump)(struct net_device *, struct ethtool_dump *);
+	int	(*set_save_fcs)(struct net_device *, u32);
+	int	(*get_save_fcs)(struct net_device *, u32 *);

These need to be described in the kernel-doc.

Why do these function names use 'save_fcs' whereas the command names use
'RXFCS'?

quoted

  };
  #endif /* __KERNEL__ */

@@ -1029,6 +1031,9 @@ struct ethtool_ops {
  #define ETHTOOL_SET_DUMP	0x0000003e /* Set dump settings */
  #define ETHTOOL_GET_DUMP_FLAG	0x0000003f /* Get dump settings */
  #define ETHTOOL_GET_DUMP_DATA	0x00000040 /* Get dump data */
+#define ETHTOOL_GETRXFCS	0x00000041 /* Get RX Save Frame Checksum */
+#define ETHTOOL_SETRXFCS	0x00000042 /* Set RX Save Frame Checksum */
+

  /* compatibility with older code */
  #define SPARC_ETH_GSET		ETHTOOL_GSET

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index fd14116..b36bac7 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c

@@ -1927,6 +1927,38 @@ out:
  	return ret;
  }

+static int ethtool_get_rx_fcs(struct net_device *dev, void __user *useraddr)
+{
+	struct ethtool_value edata;
+	int rv = 0;
+
+	if (!dev->ethtool_ops->get_save_fcs)
+		return -EOPNOTSUPP;
+
+	rv = dev->ethtool_ops->get_save_fcs(dev,&edata.data);
+	if (rv<  0)
+		return rv;
+
+	if (copy_to_user(useraddr,&edata, sizeof(edata)))
+		return -EFAULT;
+	return 0;
+}
+
+
+static int ethtool_set_rx_fcs(struct net_device *dev, void __user *useraddr)
+{
+	struct ethtool_value id;
+
+	if (!dev->ethtool_ops->set_save_fcs)
+		return -EOPNOTSUPP;
+
+	if (copy_from_user(&id, useraddr, sizeof(id)))
+		return -EFAULT;
+
+	return dev->ethtool_ops->set_save_fcs(dev, id.data);
+}
+
+
  /* The main entry point in this file.  Called from net/core/dev.c */

  int dev_ethtool(struct net *net, struct ifreq *ifr)

@@ -2152,6 +2184,12 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
  	case ETHTOOL_GET_DUMP_DATA:
  		rc = ethtool_get_dump_data(dev, useraddr);
  		break;
+	case ETHTOOL_SETRXFCS:
+		rc = ethtool_set_rx_fcs(dev, useraddr);
+		break;
+	case ETHTOOL_GETRXFCS:
+		rc = ethtool_get_rx_fcs(dev, useraddr);
+		break;

You can use ethtool_{get,set}_value() rather than adding new trivial
functions.

I'll look at that.

And as Michal says, this could reasonably be a feature not an entirely
separate flag.  I'm not sure it's that important to have debugging flags
in features, but I also don't want to have 2 commands per flag...

I'm not sure it really counts as a feature, and I've no desire to tangle
with the effort to extend features beyond 32 bits.  Maybe we could have a new
ethtool command that took a struct with two args, so we can "set flag-foo val"
instead of 'enable-flag-foo' and 'disable-flag-foo'?

That should be only one additional method for the drivers to implement, and
can be used for the other patches I have planned as well.

Thanks,
Ben

-- 
Ben Greear [off-list ref]
Candela Technologies Inc  http://www.candelatech.com