macsec: add some of the lower device's features when offloading

This commit extends the set of netdevice features supported by macsec
devices when offload is enabled, which increases performance
significantly (for a single TCP stream: 17.5Gbps to 38.5Gbps on my
test machines).

Commit c850240b6c41 ("net: macsec: report real_dev features when HW
offloading is enabled") previously attempted something similar, but
had to be reverted (commit 8bcd560ae878 ("Revert "net: macsec: report
real_dev features when HW offloading is enabled"")) because the set of
features it exposed was too large.

During initialization, all features are set, and they're then removed
via ndo_fix_features (macsec_fix_features). This allows the
offloadable features to be automatically enabled if offloading is
turned on after device creation.

Signed-off-by: Sabrina Dubroca <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/macsec.c

···
 	macsec_set_head_tail_room(dev);
 	macsec->insert_tx_tag = macsec_needs_tx_tag(macsec, ops);
 
+	netdev_update_features(dev);
+
 	return ret;
 }
 
···
 #define MACSEC_FEATURES \
 	(NETIF_F_SG | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST)
 
+#define MACSEC_OFFLOAD_FEATURES \
+	(MACSEC_FEATURES | NETIF_F_GSO_SOFTWARE | NETIF_F_SOFT_FEATURES | \
+	 NETIF_F_LRO | NETIF_F_RXHASH | NETIF_F_CSUM_MASK | NETIF_F_RXCSUM)
+
 static int macsec_dev_init(struct net_device *dev)
 {
 	struct macsec_dev *macsec = macsec_priv(dev);
···
 	if (err)
 		return err;
 
-	dev->features = real_dev->features & MACSEC_FEATURES;
+	dev->hw_features = real_dev->hw_features & MACSEC_OFFLOAD_FEATURES;
+	dev->hw_features |= NETIF_F_GSO_SOFTWARE;
+
+	dev->features = real_dev->features & MACSEC_OFFLOAD_FEATURES;
 	dev->features |= NETIF_F_GSO_SOFTWARE;
 	dev->lltx = true;
 	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
···
 {
 	struct macsec_dev *macsec = macsec_priv(dev);
 	struct net_device *real_dev = macsec->real_dev;
+	netdev_features_t mask;
 
-	features &= (real_dev->features & MACSEC_FEATURES) |
+	mask = macsec_is_offloaded(macsec) ? MACSEC_OFFLOAD_FEATURES
+					   : MACSEC_FEATURES;
+
+	features &= (real_dev->features & mask) |
 		    NETIF_F_GSO_SOFTWARE | NETIF_F_SOFT_FEATURES;
 
 	return features;