net: l2: ethernet: arp: Simplify ACD case

In case of ACD Probe/Announcement, all we need is to generate ARP
packet, we don't really want any cache entries to be created or searched
for. There was a bug, that a cache entry was created for the
Announcement sent, resulting in skipped ARP packet generation and
malformed packet being sent by the ACD module.

Therefore, simplify all this, by simply returning early in case of
conflict detection packets.

Signed-off-by: Robert Lubos <[email protected]>

subsys/net/l2/ethernet/arp.c

@@ -355,6 +355,11 @@ struct net_pkt *net_arp_prepare(struct net_pkt *pkt,
 		return NULL;
 	}
 
+	if (net_pkt_ipv4_acd(pkt)) {
+		return arp_prepare(net_pkt_iface(pkt), request_ip, NULL,
+				   pkt, current_ip);
+	}
+
 	if (IS_ENABLED(CONFIG_NET_IPV4_AUTO)) {
 		is_ipv4_ll_used = net_ipv4_is_ll_addr((struct in_addr *)
 						&NET_IPV4_HDR(pkt)->src) ||
@@ -406,8 +411,7 @@ struct net_pkt *net_arp_prepare(struct net_pkt *pkt,
 			 * in the pending list and if so, resend the request, otherwise just
 			 * append the packet to the request fifo list.
 			 */
-			if (!net_pkt_ipv4_acd(pkt) &&
-			    k_queue_unique_append(&entry->pending_queue._queue,
+			if (k_queue_unique_append(&entry->pending_queue._queue,
 						  net_pkt_ref(pkt))) {
 				NET_DBG("Pending ARP request for %s, queuing pkt %p",
 					net_sprint_ipv4_addr(addr), pkt);