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>
diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index dfbe3ca..8fa8388 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -76,7 +76,7 @@
 };
 
 /* 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 @@
 	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 @@
 			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 @@
 	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 @@
 		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 @@
 	}
 
 	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,