bonding: Correctly support GSO ESP offload

The referenced fix is incomplete. It correctly computes
bond_dev->gso_partial_features across slaves, but unfortunately
netdev_fix_features discards gso_partial_features from the feature set
if NETIF_F_GSO_PARTIAL isn't set in bond_dev->features.

This is visible with ethtool -k bond0 | grep esp:
tx-esp-segmentation: off [requested on]
esp-hw-offload: on
esp-tx-csum-hw-offload: on

This patch reworks the bonding GSO offload support by:
- making aggregating gso_partial_features across slaves similar to the
  other feature sets (this part is a no-op).
- advertising the default partial gso features on empty bond devs, same
  as with other feature sets (also a no-op).
- adding NETIF_F_GSO_PARTIAL to hw_enc_features filtered across slaves.
- adding NETIF_F_GSO_PARTIAL to features in bond_setup()

With all of these, 'ethtool -k bond0 | grep esp' now reports:
tx-esp-segmentation: on
esp-hw-offload: on
esp-tx-csum-hw-offload: on

Fixes: 4861333 ("bonding: add ESP offload features when slaves support")
Signed-off-by: Hangbin Liu <[email protected]>
Signed-off-by: Cosmin Ratiu <[email protected]>
Acked-by: Jay Vosburgh <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: Cosmin Ratiu

drivers/net/bonding/bond_main.c

@@ -1538,17 +1538,20 @@ static netdev_features_t bond_fix_features(struct net_device *dev,
 				 NETIF_F_HIGHDMA | NETIF_F_LRO)
 
 #define BOND_ENC_FEATURES	(NETIF_F_HW_CSUM | NETIF_F_SG | \
-				 NETIF_F_RXCSUM | NETIF_F_GSO_SOFTWARE)
+				 NETIF_F_RXCSUM | NETIF_F_GSO_SOFTWARE | \
+				 NETIF_F_GSO_PARTIAL)
 
 #define BOND_MPLS_FEATURES	(NETIF_F_HW_CSUM | NETIF_F_SG | \
 				 NETIF_F_GSO_SOFTWARE)
 
+#define BOND_GSO_PARTIAL_FEATURES (NETIF_F_GSO_ESP)
+
 
 static void bond_compute_features(struct bonding *bond)
 {
+	netdev_features_t gso_partial_features = BOND_GSO_PARTIAL_FEATURES;
 	unsigned int dst_release_flag = IFF_XMIT_DST_RELEASE |
 					IFF_XMIT_DST_RELEASE_PERM;
-	netdev_features_t gso_partial_features = NETIF_F_GSO_ESP;
 	netdev_features_t vlan_features = BOND_VLAN_FEATURES;
 	netdev_features_t enc_features  = BOND_ENC_FEATURES;
 #ifdef CONFIG_XFRM_OFFLOAD
@@ -1582,8 +1585,9 @@ static void bond_compute_features(struct bonding *bond)
 							  BOND_XFRM_FEATURES);
 #endif /* CONFIG_XFRM_OFFLOAD */
 
-		if (slave->dev->hw_enc_features & NETIF_F_GSO_PARTIAL)
-			gso_partial_features &= slave->dev->gso_partial_features;
+		gso_partial_features = netdev_increment_features(gso_partial_features,
+								 slave->dev->gso_partial_features,
+								 BOND_GSO_PARTIAL_FEATURES);
 
 		mpls_features = netdev_increment_features(mpls_features,
 							  slave->dev->mpls_features,
@@ -1598,12 +1602,8 @@ static void bond_compute_features(struct bonding *bond)
 	}
 	bond_dev->hard_header_len = max_hard_header_len;
 
-	if (gso_partial_features & NETIF_F_GSO_ESP)
-		bond_dev->gso_partial_features |= NETIF_F_GSO_ESP;
-	else
-		bond_dev->gso_partial_features &= ~NETIF_F_GSO_ESP;
-
 done:
+	bond_dev->gso_partial_features = gso_partial_features;
 	bond_dev->vlan_features = vlan_features;
 	bond_dev->hw_enc_features = enc_features | NETIF_F_GSO_ENCAP_ALL |
 				    NETIF_F_HW_VLAN_CTAG_TX |
@@ -6046,6 +6046,7 @@ void bond_setup(struct net_device *bond_dev)
 	bond_dev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
 	bond_dev->features |= bond_dev->hw_features;
 	bond_dev->features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_STAG_TX;
+	bond_dev->features |= NETIF_F_GSO_PARTIAL;
 #ifdef CONFIG_XFRM_OFFLOAD
 	bond_dev->hw_features |= BOND_XFRM_FEATURES;
 	/* Only enable XFRM features if this is an active-backup config */