[NET]: Store skb->timestamp as offset to a base timestamp

Reduces skb size by 8 bytes on 64-bit.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 7ae72d4..a7eae30 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -812,7 +812,7 @@
 		if (ipv6_chk_acast_addr(dev, &msg->target) ||
 		    (idev->cnf.forwarding && 
 		     pneigh_lookup(&nd_tbl, &msg->target, dev, 0))) {
-			if (skb->stamp.tv_sec != LOCALLY_ENQUEUED &&
+			if (!(NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED) &&
 			    skb->pkt_type != PACKET_HOST &&
 			    inc != 0 &&
 			    idev->nd_parms->proxy_delay != 0) {
@@ -1487,6 +1487,8 @@
 		return 0;
 	}
 
+	memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
+
 	switch (msg->icmph.icmp6_type) {
 	case NDISC_NEIGHBOUR_SOLICITATION:
 		ndisc_recv_ns(skb);