net: Kill link between CSUM and SG features.

Earlier SG was unset if CSUM was not available for given device to
force skb copy to avoid sending inconsistent csum.
Commit c9af6db4c11c (net: Fix possible wrong checksum generation)
added explicit flag to force copy to fix this issue.  Therefore
there is no need to link SG and CSUM, following patch kills this
link between there two features.

This patch is also required following patch in series.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -2683,6 +2683,19 @@ struct sk_buff *skb_gso_segment(struct sk_buff *skb, netdev_features_t features)
 {
 	return __skb_gso_segment(skb, features, true);
 }
+__be16 skb_network_protocol(struct sk_buff *skb);
+
+static inline bool can_checksum_protocol(netdev_features_t features,
+					 __be16 protocol)
+{
+	return ((features & NETIF_F_GEN_CSUM) ||
+		((features & NETIF_F_V4_CSUM) &&
+		 protocol == htons(ETH_P_IP)) ||
+		((features & NETIF_F_V6_CSUM) &&
+		 protocol == htons(ETH_P_IPV6)) ||
+		((features & NETIF_F_FCOE_CRC) &&
+		 protocol == htons(ETH_P_FCOE)));
+}
 
 #ifdef CONFIG_BUG
 extern void netdev_rx_csum_fault(struct net_device *dev);

net/core/dev.c

@@ -2208,16 +2208,8 @@ out:
 }
 EXPORT_SYMBOL(skb_checksum_help);
 
-/**
- *	skb_mac_gso_segment - mac layer segmentation handler.
- *	@skb: buffer to segment
- *	@features: features for the output path (see dev->features)
- */
-struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
-				    netdev_features_t features)
+__be16 skb_network_protocol(struct sk_buff *skb)
 {
-	struct sk_buff *segs = ERR_PTR(-EPROTONOSUPPORT);
-	struct packet_offload *ptype;
 	__be16 type = skb->protocol;
 
 	while (type == htons(ETH_P_8021Q)) {
@@ -2225,13 +2217,31 @@ struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
 		struct vlan_hdr *vh;
 
 		if (unlikely(!pskb_may_pull(skb, vlan_depth + VLAN_HLEN)))
-			return ERR_PTR(-EINVAL);
+			return 0;
 
 		vh = (struct vlan_hdr *)(skb->data + vlan_depth);
 		type = vh->h_vlan_encapsulated_proto;
 		vlan_depth += VLAN_HLEN;
 	}
 
+	return type;
+}
+
+/**
+ *	skb_mac_gso_segment - mac layer segmentation handler.
+ *	@skb: buffer to segment
+ *	@features: features for the output path (see dev->features)
+ */
+struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
+				    netdev_features_t features)
+{
+	struct sk_buff *segs = ERR_PTR(-EPROTONOSUPPORT);
+	struct packet_offload *ptype;
+	__be16 type = skb_network_protocol(skb);
+
+	if (unlikely(!type))
+		return ERR_PTR(-EINVAL);
+
 	__skb_pull(skb, skb->mac_len);
 
 	rcu_read_lock();
@@ -2398,24 +2408,12 @@ static int dev_gso_segment(struct sk_buff *skb, netdev_features_t features)
 	return 0;
 }
 
-static bool can_checksum_protocol(netdev_features_t features, __be16 protocol)
-{
-	return ((features & NETIF_F_GEN_CSUM) ||
-		((features & NETIF_F_V4_CSUM) &&
-		 protocol == htons(ETH_P_IP)) ||
-		((features & NETIF_F_V6_CSUM) &&
-		 protocol == htons(ETH_P_IPV6)) ||
-		((features & NETIF_F_FCOE_CRC) &&
-		 protocol == htons(ETH_P_FCOE)));
-}
-
 static netdev_features_t harmonize_features(struct sk_buff *skb,
 	__be16 protocol, netdev_features_t features)
 {
 	if (skb->ip_summed != CHECKSUM_NONE &&
 	    !can_checksum_protocol(features, protocol)) {
 		features &= ~NETIF_F_ALL_CSUM;
-		features &= ~NETIF_F_SG;
 	} else if (illegal_highdma(skb->dev, skb)) {
 		features &= ~NETIF_F_SG;
 	}
@@ -4921,20 +4919,25 @@ static netdev_features_t netdev_fix_features(struct net_device *dev,
 		features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
 	}
 
-	/* Fix illegal SG+CSUM combinations. */
-	if ((features & NETIF_F_SG) &&
-	    !(features & NETIF_F_ALL_CSUM)) {
-		netdev_dbg(dev,
-			"Dropping NETIF_F_SG since no checksum feature.\n");
-		features &= ~NETIF_F_SG;
-	}
-
 	/* TSO requires that SG is present as well. */
 	if ((features & NETIF_F_ALL_TSO) && !(features & NETIF_F_SG)) {
 		netdev_dbg(dev, "Dropping TSO features since no SG feature.\n");
 		features &= ~NETIF_F_ALL_TSO;
 	}
 
+	if ((features & NETIF_F_TSO) && !(features & NETIF_F_HW_CSUM) &&
+					!(features & NETIF_F_IP_CSUM)) {
+		netdev_dbg(dev, "Dropping TSO features since no CSUM feature.\n");
+		features &= ~NETIF_F_TSO;
+		features &= ~NETIF_F_TSO_ECN;
+	}
+
+	if ((features & NETIF_F_TSO6) && !(features & NETIF_F_HW_CSUM) &&
+					 !(features & NETIF_F_IPV6_CSUM)) {
+		netdev_dbg(dev, "Dropping TSO6 features since no CSUM feature.\n");
+		features &= ~NETIF_F_TSO6;
+	}
+
 	/* TSO ECN requires that TSO is present as well. */
 	if ((features & NETIF_F_ALL_TSO) == NETIF_F_TSO_ECN)
 		features &= ~NETIF_F_TSO_ECN;

net/core/skbuff.c

@@ -2741,12 +2741,19 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
 	unsigned int tnl_hlen = skb_tnl_header_len(skb);
 	unsigned int headroom;
 	unsigned int len;
+	__be16 proto;
+	bool csum;
 	int sg = !!(features & NETIF_F_SG);
 	int nfrags = skb_shinfo(skb)->nr_frags;
 	int err = -ENOMEM;
 	int i = 0;
 	int pos;
 
+	proto = skb_network_protocol(skb);
+	if (unlikely(!proto))
+		return ERR_PTR(-EINVAL);
+
+	csum = !!can_checksum_protocol(features, proto);
 	__skb_push(skb, doffset);
 	headroom = skb_headroom(skb);
 	pos = skb_headlen(skb);
@@ -2884,6 +2891,12 @@ skip_fraglist:
 		nskb->data_len = len - hsize;
 		nskb->len += nskb->data_len;
 		nskb->truesize += nskb->data_len;
+
+		if (!csum) {
+			nskb->csum = skb_checksum(nskb, doffset,
+						  nskb->len - doffset, 0);
+			nskb->ip_summed = CHECKSUM_NONE;
+		}
 	} while ((offset += len) < skb->len);
 
 	return segs;

net/ipv4/af_inet.c

@@ -1284,9 +1284,6 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 	int id;
 	unsigned int offset = 0;
 
-	if (!(features & NETIF_F_V4_CSUM))
-		features &= ~NETIF_F_SG;
-
 	if (unlikely(skb_shinfo(skb)->gso_type &
 		     ~(SKB_GSO_TCPV4 |
 		       SKB_GSO_UDP |

net/ipv6/ip6_offload.c

@@ -92,9 +92,6 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	u8 *prevhdr;
 	int offset = 0;
 
-	if (!(features & NETIF_F_V6_CSUM))
-		features &= ~NETIF_F_SG;
-
 	if (unlikely(skb_shinfo(skb)->gso_type &
 		     ~(SKB_GSO_UDP |
 		       SKB_GSO_DODGY |