[BRIDGE]: Disable SG/GSO if TX checksum is off

When the bridge recomputes features, it does not maintain the
constraint that SG/GSO must be off if TX checksum is off.
This patch adds that constraint.

On a completely unrelated note, I've also added TSO6 and TSO_ECN
feature bits if GSO is enabled on the underlying device through
the new NETIF_F_GSO_SOFTWARE macro.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -320,6 +320,9 @@ struct net_device
 #define NETIF_F_TSO_ECN		(SKB_GSO_TCP_ECN << NETIF_F_GSO_SHIFT)
 #define NETIF_F_TSO6		(SKB_GSO_TCPV6 << NETIF_F_GSO_SHIFT)
 
+	/* List of features with software fallbacks. */
+#define NETIF_F_GSO_SOFTWARE	(NETIF_F_TSO | NETIF_F_TSO_ECN | NETIF_F_TSO6)
+
 #define NETIF_F_GEN_CSUM	(NETIF_F_NO_CSUM | NETIF_F_HW_CSUM)
 #define NETIF_F_ALL_CSUM	(NETIF_F_IP_CSUM | NETIF_F_GEN_CSUM)
 

net/bridge/br_if.c

@@ -386,12 +386,17 @@ void br_features_recompute(struct net_bridge *br)
 			checksum = 0;
 
 		if (feature & NETIF_F_GSO)
-			feature |= NETIF_F_TSO;
+			feature |= NETIF_F_GSO_SOFTWARE;
 		feature |= NETIF_F_GSO;
 
 		features &= feature;
 	}
 
+	if (!(checksum & NETIF_F_ALL_CSUM))
+		features &= ~NETIF_F_SG;
+	if (!(features & NETIF_F_SG))
+		features &= ~NETIF_F_GSO_MASK;
+
 	br->dev->features = features | checksum | NETIF_F_LLTX |
 			    NETIF_F_GSO_ROBUST;
 }