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

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 *);

 };
 #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;