openvswitch: Widen TCP flags handling.

Widen TCP flags handling from 7 bits (uint8_t) to 12 bits (uint16_t).
The kernel interface remains at 8 bits, which makes no functional
difference now, as none of the higher bits is currently of interest
to the userspace.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 617810f..b73c768 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -58,19 +58,17 @@
 	return cur_ms - idle_ms;
 }
 
-#define TCP_FLAGS_OFFSET 13
-#define TCP_FLAG_MASK 0x3f
+#define TCP_FLAGS_BE16(tp) (*(__be16 *)&tcp_flag_word(tp) & htons(0x0FFF))
 
 void ovs_flow_used(struct sw_flow *flow, struct sk_buff *skb)
 {
-	u8 tcp_flags = 0;
+	__be16 tcp_flags = 0;
 
 	if ((flow->key.eth.type == htons(ETH_P_IP) ||
 	     flow->key.eth.type == htons(ETH_P_IPV6)) &&
 	    flow->key.ip.proto == IPPROTO_TCP &&
 	    likely(skb->len >= skb_transport_offset(skb) + sizeof(struct tcphdr))) {
-		u8 *tcp = (u8 *)tcp_hdr(skb);
-		tcp_flags = *(tcp + TCP_FLAGS_OFFSET) & TCP_FLAG_MASK;
+		tcp_flags = TCP_FLAGS_BE16(tcp_hdr(skb));
 	}
 
 	spin_lock(&flow->lock);