net: arp: Enhance debug prints by printing interface index

Print also network interface index together with the pointer value
in order to get more useful information what is going on in the system.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

subsys/net/l2/ethernet/arp.c

@@ -36,7 +36,7 @@ static struct k_mutex arp_mutex;
 
 static void arp_entry_cleanup(struct arp_entry *entry, bool pending)
 {
-	NET_DBG("%p", entry);
+	NET_DBG("entry %p", entry);
 
 	if (pending) {
 		struct net_pkt *pkt;
@@ -64,8 +64,9 @@ static struct arp_entry *arp_entry_find(sys_slist_t *list,
 	struct arp_entry *entry;
 
 	SYS_SLIST_FOR_EACH_CONTAINER(list, entry, node) {
-		NET_DBG("iface %p dst %s",
-			iface, net_sprint_ipv4_addr(&entry->ip));
+		NET_DBG("iface %d (%p) dst %s",
+			net_if_get_by_iface(iface), iface,
+			net_sprint_ipv4_addr(&entry->ip));
 
 		if (entry->iface == iface &&
 		    net_ipv4_addr_cmp(&entry->ip, dst)) {
@@ -690,10 +691,11 @@ enum net_verdict net_arp_input(struct net_pkt *pkt,
 		 * and the target IP address is our address.
 		 */
 		if (net_eth_is_addr_unspecified(&arp_hdr->dst_hwaddr)) {
-			NET_DBG("Updating ARP cache for %s [%s]",
+			NET_DBG("Updating ARP cache for %s [%s] iface %d",
 				net_sprint_ipv4_addr(&arp_hdr->src_ipaddr),
 				net_sprint_ll_addr((uint8_t *)&arp_hdr->src_hwaddr,
-						   arp_hdr->hwlen));
+						   arp_hdr->hwlen),
+				net_if_get_by_iface(net_pkt_iface(pkt)));
 
 			net_arp_update(net_pkt_iface(pkt),
 				       (struct in_addr *)arp_hdr->src_ipaddr,