net: remove NETIF_F_NO_CSUM feature bit

Only distinct use is checking if NETIF_F_NOCACHE_COPY should be
enabled by default. The check heuristics is altered a bit here,
so it hits other people than before. The default shouldn't be
trusted for performance-critical cases anyway.

For all other uses NETIF_F_NO_CSUM is equivalent to NETIF_F_HW_CSUM.

Signed-off-by: Michał Mirosław <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/ieee802154/fakehard.c

···
 {
 	dev->addr_len		= IEEE802154_ADDR_LEN;
 	memset(dev->broadcast, 0xff, IEEE802154_ADDR_LEN);
-	dev->features		= NETIF_F_NO_CSUM;
+	dev->features		= NETIF_F_HW_CSUM;
 	dev->needed_tailroom	= 2; /* FCS */
 	dev->mtu		= 127;
 	dev->tx_queue_len	= 10;

drivers/misc/sgi-xp/xpnet.c

···
 	 * report an error if the data is not retrievable and the
 	 * packet will be dropped.
 	 */
-	xpnet_device->features = NETIF_F_NO_CSUM;
+	xpnet_device->features = NETIF_F_HW_CSUM;
 
 	result = register_netdev(xpnet_device);
 	if (result != 0) {

drivers/net/bonding/bond_main.c

···
 				NETIF_F_HW_VLAN_RX |
 				NETIF_F_HW_VLAN_FILTER;
 
-	bond_dev->hw_features &= ~(NETIF_F_ALL_CSUM & ~NETIF_F_NO_CSUM);
+	bond_dev->hw_features &= ~(NETIF_F_ALL_CSUM & ~NETIF_F_HW_CSUM);
 	bond_dev->features |= bond_dev->hw_features;
 }
 

drivers/net/can/dev.c

···
 
 	/* New-style flags. */
 	dev->flags = IFF_NOARP;
-	dev->features = NETIF_F_NO_CSUM;
+	dev->features = NETIF_F_HW_CSUM;
 }
 
 struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)

drivers/net/can/slcan.c

···
 
 	/* New-style flags. */
 	dev->flags		= IFF_NOARP;
-	dev->features           = NETIF_F_NO_CSUM;
+	dev->features           = NETIF_F_HW_CSUM;
 }
 
 /******************************************

drivers/net/dummy.c

···
 	dev->flags |= IFF_NOARP;
 	dev->flags &= ~IFF_MULTICAST;
 	dev->features	|= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
-	dev->features	|= NETIF_F_NO_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
+	dev->features	|= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
 	random_ether_addr(dev->dev_addr);
 }
 

drivers/net/ifb.c

···
 	.ndo_validate_addr = eth_validate_addr,
 };
 
-#define IFB_FEATURES (NETIF_F_NO_CSUM | NETIF_F_SG  | NETIF_F_FRAGLIST	| \
+#define IFB_FEATURES (NETIF_F_HW_CSUM | NETIF_F_SG  | NETIF_F_FRAGLIST	| \
 		      NETIF_F_TSO_ECN | NETIF_F_TSO | NETIF_F_TSO6	| \
 		      NETIF_F_HIGHDMA | NETIF_F_HW_VLAN_TX)
 

drivers/net/loopback.c

···
 	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
 		| NETIF_F_ALL_TSO
 		| NETIF_F_UFO
-		| NETIF_F_NO_CSUM
+		| NETIF_F_HW_CSUM
 		| NETIF_F_RXCSUM
 		| NETIF_F_HIGHDMA
 		| NETIF_F_LLTX

drivers/net/veth.c

···
 	dev->features |= NETIF_F_LLTX;
 	dev->destructor = veth_dev_free;
 
-	dev->hw_features = NETIF_F_NO_CSUM | NETIF_F_SG | NETIF_F_RXCSUM;
+	dev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG | NETIF_F_RXCSUM;
 }
 
 /*

include/linux/netdev_features.h

···
 enum {
 	NETIF_F_SG_BIT,			/* Scatter/gather IO. */
 	NETIF_F_IP_CSUM_BIT,		/* Can checksum TCP/UDP over IPv4. */
-	NETIF_F_NO_CSUM_BIT,		/* Does not require checksum. F.e. loopack. */
+	__UNUSED_NETIF_F_1,
 	NETIF_F_HW_CSUM_BIT,		/* Can checksum all the packets. */
 	NETIF_F_IPV6_CSUM_BIT,		/* Can checksum TCP/UDP over IPV6 */
 	NETIF_F_HIGHDMA_BIT,		/* Can DMA to high memory. */
···
 #define NETIF_F_LRO		__NETIF_F(LRO)
 #define NETIF_F_NETNS_LOCAL	__NETIF_F(NETNS_LOCAL)
 #define NETIF_F_NOCACHE_COPY	__NETIF_F(NOCACHE_COPY)
-#define NETIF_F_NO_CSUM		__NETIF_F(NO_CSUM)
 #define NETIF_F_NTUPLE		__NETIF_F(NTUPLE)
 #define NETIF_F_RXCSUM		__NETIF_F(RXCSUM)
 #define NETIF_F_RXHASH		__NETIF_F(RXHASH)
···
 #define NETIF_F_GSO_SOFTWARE	(NETIF_F_TSO | NETIF_F_TSO_ECN | \
 				 NETIF_F_TSO6 | NETIF_F_UFO)
 
-#define NETIF_F_GEN_CSUM	(NETIF_F_HW_CSUM | NETIF_F_NO_CSUM)
+#define NETIF_F_GEN_CSUM	NETIF_F_HW_CSUM
 #define NETIF_F_V4_CSUM		(NETIF_F_GEN_CSUM | NETIF_F_IP_CSUM)
 #define NETIF_F_V6_CSUM		(NETIF_F_GEN_CSUM | NETIF_F_IPV6_CSUM)
 #define NETIF_F_ALL_CSUM	(NETIF_F_V4_CSUM | NETIF_F_V6_CSUM)

include/linux/skbuff.h

···
  *	at device setup time.
  *	NETIF_F_HW_CSUM	- it is clever device, it is able to checksum
  *			  everything.
- *	NETIF_F_NO_CSUM - loopback or reliable single hop media.
  *	NETIF_F_IP_CSUM - device is dumb. It is able to csum only
  *			  TCP/UDP over IPv4. Sigh. Vendors like this
  *			  way by an unknown reason. Though, see comment above

net/bridge/br_device.c

···
 	dev->priv_flags = IFF_EBRIDGE;
 
 	dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA |
-			NETIF_F_GSO_MASK | NETIF_F_NO_CSUM | NETIF_F_LLTX |
+			NETIF_F_GSO_MASK | NETIF_F_HW_CSUM | NETIF_F_LLTX |
 			NETIF_F_NETNS_LOCAL | NETIF_F_HW_VLAN_TX;
 	dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA |
-			   NETIF_F_GSO_MASK | NETIF_F_NO_CSUM |
+			   NETIF_F_GSO_MASK | NETIF_F_HW_CSUM |
 			   NETIF_F_HW_VLAN_TX;
 
 	br->dev = dev;

net/core/dev.c

···
 		features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
 	}
 
-	if ((features & NETIF_F_NO_CSUM) &&
-	    (features & (NETIF_F_HW_CSUM|NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
-		netdev_warn(dev, "mixed no checksumming and other settings.\n");
-		features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM|NETIF_F_HW_CSUM);
-	}
-
 	/* Fix illegal SG+CSUM combinations. */
 	if ((features & NETIF_F_SG) &&
 	    !(features & NETIF_F_ALL_CSUM)) {
···
 	dev->wanted_features = dev->features & dev->hw_features;
 
 	/* Turn on no cache copy if HW is doing checksum */
-	dev->hw_features |= NETIF_F_NOCACHE_COPY;
-	if ((dev->features & NETIF_F_ALL_CSUM) &&
-	    !(dev->features & NETIF_F_NO_CSUM)) {
-		dev->wanted_features |= NETIF_F_NOCACHE_COPY;
-		dev->features |= NETIF_F_NOCACHE_COPY;
+	if (!(dev->flags & IFF_LOOPBACK)) {
+		dev->hw_features |= NETIF_F_NOCACHE_COPY;
+		if (dev->features & NETIF_F_ALL_CSUM) {
+			dev->wanted_features |= NETIF_F_NOCACHE_COPY;
+			dev->features |= NETIF_F_NOCACHE_COPY;
+		}
 	}
 
 	/* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
···
 
 	all |= one & (NETIF_F_ONE_FOR_ALL|NETIF_F_ALL_CSUM) & mask;
 	all &= one | ~NETIF_F_ALL_FOR_ALL;
-
-	/* If device needs checksumming, downgrade to it. */
-	if (all & (NETIF_F_ALL_CSUM & ~NETIF_F_NO_CSUM))
-		all &= ~NETIF_F_NO_CSUM;
 
 	/* If one device supports hw checksumming, set for all. */
 	if (all & NETIF_F_GEN_CSUM)

net/core/ethtool.c

···
 static const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_SG_BIT] =               "tx-scatter-gather",
 	[NETIF_F_IP_CSUM_BIT] =          "tx-checksum-ipv4",
-	[NETIF_F_NO_CSUM_BIT] =          "tx-checksum-unneeded",
 	[NETIF_F_HW_CSUM_BIT] =          "tx-checksum-ip-generic",
 	[NETIF_F_IPV6_CSUM_BIT] =        "tx-checksum-ipv6",
 	[NETIF_F_HIGHDMA_BIT] =          "highdma",