mpls: Add MPLS entropy label in flow_keys

Hello Tom Herbert,

The patch b3baa0fbd02a: "mpls: Add MPLS entropy label in flow_keys" from Jun 4, 2015, leads to the following static checker warning:

	net/core/flow_dissector.c:303 __skb_flow_dissect()
	warn: masked condition '(() & 4294963200) = 7' is always false.

net/core/flow_dissector.c
299 if (!hdr)
300 return false;
301
302 if ((ntohl(hdr[0].entry) & MPLS_LS_LABEL_MASK) =
303 MPLS_LABEL_ENTROPY) {

#define MPLS_LS_LABEL_MASK 0xFFFFF000
#define MPLS_LABEL_ENTROPY 7 /* RFC6790 */

This can never be true. Not sure what was intended.

   304                          if (skb_flow_dissector_uses_key(flow_dissector,
   305                                                          FLOW_DISSECTOR_KEY_MPLS_ENTROPY)) {
   306                                  key_keyid = skb_flow_dissector_target(flow_dissector,
   307                                                                        FLOW_DISSECTOR_KEY_MPLS_ENTROPY,
   308                                                                        target_container);
   309                                  key_keyid->keyid = hdr[1].entry &
   310                                          htonl(MPLS_LS_LABEL_MASK);
   311                          }
   312  
   313                          key_basic->n_proto = proto;
   314                          key_basic->ip_proto = ip_proto;
   315                          key_control->thoff = (u16)nhoff;
   316  
   317                          return true;
   318                  }
   319  
   320                  return true;
   321          }

regards,
dan carpenter