[BRIDGE]: Add support for NETIF_F_HW_CSUM devices

As it is the bridge will only ever declare NETIF_F_IP_CSUM even if all
its constituent devices support NETIF_F_HW_CSUM.  This patch fixes
this by supporting the first one out of NETIF_F_NO_CSUM,
NETIF_F_HW_CSUM, and NETIF_F_IP_CSUM that is supported by all
constituent devices.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 90c95f5..fdec773 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -372,11 +372,17 @@
 	struct net_bridge_port *p;
 	unsigned long features, checksum;
 
-	features = br->feature_mask &~ NETIF_F_IP_CSUM;
-	checksum = br->feature_mask & NETIF_F_IP_CSUM;
+	checksum = br->feature_mask & NETIF_F_ALL_CSUM ? NETIF_F_NO_CSUM : 0;
+	features = br->feature_mask & ~NETIF_F_ALL_CSUM;
 
 	list_for_each_entry(p, &br->port_list, list) {
-		if (!(p->dev->features & NETIF_F_ALL_CSUM))
+		if (checksum & NETIF_F_NO_CSUM &&
+		    !(p->dev->features & NETIF_F_NO_CSUM))
+			checksum ^= NETIF_F_NO_CSUM | NETIF_F_HW_CSUM;
+		if (checksum & NETIF_F_HW_CSUM &&
+		    !(p->dev->features & NETIF_F_HW_CSUM))
+			checksum ^= NETIF_F_HW_CSUM | NETIF_F_IP_CSUM;
+		if (!(p->dev->features & NETIF_F_IP_CSUM))
 			checksum = 0;
 		features &= p->dev->features;
 	}