gre: fix TUNNEL_SEQ bit check on sequence numbering

The current logic of flags | TUNNEL_SEQ is always non-zero and hence
sequence numbers are always incremented no matter the setting of the
TUNNEL_SEQ bit.  Fix this by using & instead of |.

Detected by CoverityScan, CID#1466039 ("Operands don't affect result")

Fixes: 77a5196 ("gre: add sequence number for collect md mode.")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: William Tu <u9012063@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -550,7 +550,7 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev,
 		(TUNNEL_CSUM | TUNNEL_KEY | TUNNEL_SEQ);
 	gre_build_header(skb, tunnel_hlen, flags, proto,
 			 tunnel_id_to_key32(tun_info->key.tun_id),
-			 (flags | TUNNEL_SEQ) ? htonl(tunnel->o_seqno++) : 0);
+			 (flags & TUNNEL_SEQ) ? htonl(tunnel->o_seqno++) : 0);
 
 	df = key->tun_flags & TUNNEL_DONT_FRAGMENT ?  htons(IP_DF) : 0;
 

net/ipv6/ip6_gre.c

@@ -724,7 +724,7 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
 		gre_build_header(skb, tunnel->tun_hlen,
 				 flags, protocol,
 				 tunnel_id_to_key32(tun_info->key.tun_id),
-				 (flags | TUNNEL_SEQ) ? htonl(tunnel->o_seqno++)
+				 (flags & TUNNEL_SEQ) ? htonl(tunnel->o_seqno++)
 						      : 0);
 
 	} else {