GENEVE: Support outer IPv4 Tx checksums by default

This change makes it so that if UDP CSUM is not specified we will default
to enabling it.  The main motivation behind this is the fact that with the
use of outer checksum we can greatly improve the performance for GENEVE
tunnels on hardware that doesn't know how to parse them.
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/geneve.c

@@ -76,7 +76,7 @@ struct geneve_dev {
 };
 
 /* Geneve device flags */
-#define GENEVE_F_UDP_CSUM		BIT(0)
+#define GENEVE_F_UDP_ZERO_CSUM_TX	BIT(0)
 #define GENEVE_F_UDP_ZERO_CSUM6_TX	BIT(1)
 #define GENEVE_F_UDP_ZERO_CSUM6_RX	BIT(2)
 
@@ -703,7 +703,7 @@ static int geneve_build_skb(struct rtable *rt, struct sk_buff *skb,
 	struct genevehdr *gnvh;
 	int min_headroom;
 	int err;
-	bool udp_sum = !!(flags & GENEVE_F_UDP_CSUM);
+	bool udp_sum = !(flags & GENEVE_F_UDP_ZERO_CSUM_TX);
 
 	skb_scrub_packet(skb, xnet);
 
@@ -944,9 +944,9 @@ static netdev_tx_t geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 			opts = ip_tunnel_info_opts(info);
 
 		if (key->tun_flags & TUNNEL_CSUM)
-			flags |= GENEVE_F_UDP_CSUM;
+			flags &= ~GENEVE_F_UDP_ZERO_CSUM_TX;
 		else
-			flags &= ~GENEVE_F_UDP_CSUM;
+			flags |= GENEVE_F_UDP_ZERO_CSUM_TX;
 
 		err = geneve_build_skb(rt, skb, key->tun_flags, vni,
 				       info->options_len, opts, flags, xnet);
@@ -972,7 +972,7 @@ static netdev_tx_t geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 	udp_tunnel_xmit_skb(rt, gs4->sock->sk, skb, fl4.saddr, fl4.daddr,
 			    tos, ttl, df, sport, geneve->dst_port,
 			    !net_eq(geneve->net, dev_net(geneve->dev)),
-			    !(flags & GENEVE_F_UDP_CSUM));
+			    !!(flags & GENEVE_F_UDP_ZERO_CSUM_TX));
 
 	return NETDEV_TX_OK;
 
@@ -1383,8 +1383,8 @@ static int geneve_newlink(struct net *net, struct net_device *dev,
 		metadata = true;
 
 	if (data[IFLA_GENEVE_UDP_CSUM] &&
-	    nla_get_u8(data[IFLA_GENEVE_UDP_CSUM]))
-		flags |= GENEVE_F_UDP_CSUM;
+	    !nla_get_u8(data[IFLA_GENEVE_UDP_CSUM]))
+		flags |= GENEVE_F_UDP_ZERO_CSUM_TX;
 
 	if (data[IFLA_GENEVE_UDP_ZERO_CSUM6_TX] &&
 	    nla_get_u8(data[IFLA_GENEVE_UDP_ZERO_CSUM6_TX]))
@@ -1454,7 +1454,7 @@ static int geneve_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	}
 
 	if (nla_put_u8(skb, IFLA_GENEVE_UDP_CSUM,
-		       !!(geneve->flags & GENEVE_F_UDP_CSUM)) ||
+		       !(geneve->flags & GENEVE_F_UDP_ZERO_CSUM_TX)) ||
 	    nla_put_u8(skb, IFLA_GENEVE_UDP_ZERO_CSUM6_TX,
 		       !!(geneve->flags & GENEVE_F_UDP_ZERO_CSUM6_TX)) ||
 	    nla_put_u8(skb, IFLA_GENEVE_UDP_ZERO_CSUM6_RX,