flow_dissector: Move MPLS dissection into a separate function

Make the main flow_dissect function a bit smaller and move the MPLS
dissection into a separate function. Along with that, do the MPLS header
processing only in case the flow dissection user requires it.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/flow_dissector.c

@@ -118,6 +118,33 @@ enum flow_dissect_ret {
 	FLOW_DISSECT_RET_OUT_BAD,
 };
 
+static enum flow_dissect_ret
+__skb_flow_dissect_mpls(const struct sk_buff *skb,
+			struct flow_dissector *flow_dissector,
+			void *target_container, void *data, int nhoff, int hlen)
+{
+	struct flow_dissector_key_keyid *key_keyid;
+	struct mpls_label *hdr, _hdr[2];
+
+	if (!dissector_uses_key(flow_dissector,
+				FLOW_DISSECTOR_KEY_MPLS_ENTROPY))
+		return FLOW_DISSECT_RET_OUT_GOOD;
+
+	hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data,
+				   hlen, &_hdr);
+	if (!hdr)
+		return FLOW_DISSECT_RET_OUT_BAD;
+
+	if ((ntohl(hdr[0].entry) & MPLS_LS_LABEL_MASK) >>
+	    MPLS_LS_LABEL_SHIFT == MPLS_LABEL_ENTROPY) {
+		key_keyid = skb_flow_dissector_target(flow_dissector,
+						      FLOW_DISSECTOR_KEY_MPLS_ENTROPY,
+						      target_container);
+		key_keyid->keyid = hdr[1].entry & htonl(MPLS_LS_LABEL_MASK);
+	}
+	return FLOW_DISSECT_RET_OUT_GOOD;
+}
+
 static enum flow_dissect_ret
 __skb_flow_dissect_arp(const struct sk_buff *skb,
 		       struct flow_dissector *flow_dissector,
@@ -408,31 +435,16 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 	}
 
 	case htons(ETH_P_MPLS_UC):
-	case htons(ETH_P_MPLS_MC): {
-		struct mpls_label *hdr, _hdr[2];
+	case htons(ETH_P_MPLS_MC):
 mpls:
-		hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data,
-					   hlen, &_hdr);
-		if (!hdr)
-			goto out_bad;
-
-		if ((ntohl(hdr[0].entry) & MPLS_LS_LABEL_MASK) >>
-		     MPLS_LS_LABEL_SHIFT == MPLS_LABEL_ENTROPY) {
-			if (dissector_uses_key(flow_dissector,
-					       FLOW_DISSECTOR_KEY_MPLS_ENTROPY)) {
-				key_keyid = skb_flow_dissector_target(flow_dissector,
-								      FLOW_DISSECTOR_KEY_MPLS_ENTROPY,
-								      target_container);
-				key_keyid->keyid = hdr[1].entry &
-					htonl(MPLS_LS_LABEL_MASK);
-			}
-
+		switch (__skb_flow_dissect_mpls(skb, flow_dissector,
+						target_container, data,
+						nhoff, hlen)) {
+		case FLOW_DISSECT_RET_OUT_GOOD:
 			goto out_good;
+		case FLOW_DISSECT_RET_OUT_BAD:
+			goto out_bad;
 		}
-
-		goto out_good;
-	}
-
 	case htons(ETH_P_FCOE):
 		if ((hlen - nhoff) < FCOE_HEADER_LEN)
 			goto out_bad;