gnrc/ipv6/nib: don't queue packets on 6lo neighbors and drop/flush if…

… UNREACHABLE

sys/include/net/gnrc/ipv6/nib/conf.h

@@ -176,6 +176,17 @@ extern "C" {
 #define CONFIG_GNRC_IPV6_NIB_QUEUE_PKT                1
 #endif
 
+#if CONFIG_GNRC_IPV6_NIB_QUEUE_PKT
+/**
+ * @brief    queue capacity for the packets waiting for address resolution,
+ *           per neighbor. SHOULD always be smaller than @ref CONFIG_GNRC_IPV6_NIB_NUMOF
+ */
+#ifndef CONFIG_GNRC_IPV6_NIB_QUEUE_PKT_CAP
+#define CONFIG_GNRC_IPV6_NIB_QUEUE_PKT_CAP  (CONFIG_GNRC_IPV6_NIB_NUMOF > 16 ? 16 : 1)
+#endif
+
+#endif /* CONFIG_GNRC_IPV6_NIB_QUEUE_PKT */
+
 /**
  * @brief   handle NDP messages according for stateless address
  *          auto-configuration (if activated on interface)

sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c

@@ -228,9 +228,7 @@ void _handle_snd_ns(_nib_onl_entry_t *nbr)
         case GNRC_IPV6_NIB_NC_INFO_NUD_STATE_PROBE:
             if (nbr->ns_sent >= NDP_MAX_UC_SOL_NUMOF) {
                 gnrc_netif_t *netif = gnrc_netif_get_by_pid(_nib_onl_get_if(nbr));
-
-                _set_nud_state(netif, nbr,
-                               GNRC_IPV6_NIB_NC_INFO_NUD_STATE_UNREACHABLE);
+                _set_unreachable(netif, nbr);
             }
             /* intentionally falls through */
         case GNRC_IPV6_NIB_NC_INFO_NUD_STATE_UNREACHABLE:
@@ -391,7 +389,7 @@ void _handle_adv_l2(gnrc_netif_t *netif, _nib_onl_entry_t *nce,
         /* send queued packets */
         gnrc_pktqueue_t *ptr;
         DEBUG("nib: Sending queued packets\n");
-        while ((ptr = gnrc_pktqueue_remove_head(&nce->pktqueue)) != NULL) {
+        while ((ptr = _nbr_pop_pkt(nce)) != NULL) {
             if (!gnrc_netapi_dispatch_send(GNRC_NETTYPE_IPV6,
                                            GNRC_NETREG_DEMUX_CTX_ALL,
                                            ptr->pkt)) {
@@ -439,6 +437,15 @@ void _set_reachable(gnrc_netif_t *netif, _nib_onl_entry_t *nce)
                  netif->ipv6.reach_time);
 }
 
+void _set_unreachable(gnrc_netif_t *netif, _nib_onl_entry_t *nce)
+{
+    DEBUG("nib: set %s to UNREACHABLE\n",
+          ipv6_addr_to_str(addr_str, &nce->ipv6, sizeof(addr_str)));
+
+    _nbr_flush_pktqueue(nce);
+    _set_nud_state(netif, nce, GNRC_IPV6_NIB_NC_INFO_NUD_STATE_UNREACHABLE);
+}
+
 void _set_nud_state(gnrc_netif_t *netif, _nib_onl_entry_t *nce,
                     uint16_t state)
 {

sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.h

@@ -174,14 +174,22 @@ void _handle_adv_l2(gnrc_netif_t *netif, _nib_onl_entry_t *nce,
 void _recalc_reach_time(gnrc_netif_ipv6_t *netif);
 
 /**
- * @brief   Sets a neighbor cache entry reachable and starts the required
+ * @brief   Sets a neighbor cache entry REACHABLE and starts the required
  *          event timers
  *
  * @param[in] netif Interface to the NCE
- * @param[in] nce   The neighbor cache entry to set reachable
+ * @param[in] nce   The neighbor cache entry to set REACHABLE
  */
 void _set_reachable(gnrc_netif_t *netif, _nib_onl_entry_t *nce);
 
+/**
+ * @brief   Sets a neighbor cache entry UNREACHABLE and flushes its packet queue
+ *
+ * @param[in] netif Interface to the NCE
+ * @param[in] nce   The neighbor cache entry to set UNREACHABLE
+ */
+void _set_unreachable(gnrc_netif_t *netif, _nib_onl_entry_t *nce);
+
 /**
  * @brief   Initializes interface for address registration state machine
  *

sys/net/gnrc/network_layer/ipv6/nib/_nib-internal.c

@@ -277,16 +277,7 @@ void _nib_nc_remove(_nib_onl_entry_t *node)
     evtimer_del((evtimer_t *)&_nib_evtimer, &node->addr_reg_timeout.event);
 #endif  /* CONFIG_GNRC_IPV6_NIB_6LR */
 #if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_QUEUE_PKT)
-    gnrc_pktqueue_t *tmp;
-    for (gnrc_pktqueue_t *ptr = node->pktqueue;
-         (ptr != NULL) && (tmp = (ptr->next), 1);
-         ptr = tmp) {
-        gnrc_pktqueue_t *entry = gnrc_pktqueue_remove(&node->pktqueue, ptr);
-        gnrc_icmpv6_error_dst_unr_send(ICMPV6_ERROR_DST_UNR_ADDR,
-                                       entry->pkt);
-        gnrc_pktbuf_release_error(entry->pkt, EHOSTUNREACH);
-        entry->pkt = NULL;
-    }
+    _nbr_flush_pktqueue(node);
 #endif  /* CONFIG_GNRC_IPV6_NIB_QUEUE_PKT */
     /* remove from cache-out procedure */
     clist_remove(&_next_removable, (clist_node_t *)node);

sys/net/gnrc/network_layer/ipv6/nib/_nib-internal.h

@@ -100,6 +100,7 @@ typedef struct _nib_onl_entry {
      * @note    Only available if @ref CONFIG_GNRC_IPV6_NIB_QUEUE_PKT != 0.
      */
     gnrc_pktqueue_t *pktqueue;
+    size_t pktqueue_len;                       /**< Number of queued packets */
 #endif
     /**
      * @brief Neighbors IPv6 address
@@ -872,6 +873,38 @@ void _nib_ft_get(const _nib_offl_entry_t *dst, gnrc_ipv6_nib_ft_t *fte);
 int _nib_get_route(const ipv6_addr_t *dst, gnrc_pktsnip_t *ctx,
                    gnrc_ipv6_nib_ft_t *entry);
 
+#if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_QUEUE_PKT)
+/**
+ * @brief Flush the packet queue of a on-link neighbor.
+ *
+ * @param node neighbor entry to be flushed
+ */
+void _nbr_flush_pktqueue(_nib_onl_entry_t *node);
+
+/**
+ * @brief Remove oldest packet from a on-link neighbor's packet queue.
+ *
+ * @param node neighbor entry
+ *
+ * @retval pointer to the packet entry or NULL if the queue is empty
+ */
+gnrc_pktqueue_t *_nbr_pop_pkt(_nib_onl_entry_t *node);
+
+/**
+ * @brief Push packet to a on-link neighbor's packet queue.
+ *
+ * @note If the neighbor is UNREACHABLE, the packet will be dropped.
+ *
+ * @note If the queue size is @ref CONFIG_GNRC_IPV6_NIB_QUEUE_PKT_CAP,
+ *       this will @ref _nbr_pop_pkt() the oldest packet and release it.
+ *
+ * @param node neighbor entry
+ * @param pkt packet to be pushed
+ */
+void _nbr_push_pkt(_nib_onl_entry_t *node, gnrc_pktqueue_t *pkt);
+
+#endif
+
 #ifdef __cplusplus
 }
 #endif

sys/net/gnrc/network_layer/ipv6/nib/nib.c

@@ -1338,7 +1338,7 @@ static bool _enqueue_for_resolve(gnrc_netif_t *netif, gnrc_pktsnip_t *pkt,
     }
 
 #if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_QUEUE_PKT)
-    gnrc_pktqueue_add(&entry->pktqueue, queue_entry);
+    _nbr_push_pkt(entry, queue_entry);
 #else
     (void)entry;
 #endif
@@ -1399,15 +1399,25 @@ static bool _resolve_addr(const ipv6_addr_t *dst, gnrc_netif_t *netif,
     }
 #endif
 
+    /* don't do multicast address resolution on 6lo */
+    if (gnrc_netif_is_6ln(netif)) {
+        if (pkt != NULL) {
+            /* https://www.rfc-editor.org/rfc/rfc6775.html#section-5.6
+             * A LoWPAN node is not required to maintain a minimum of one buffer
+             * per neighbor as specified in [RFC4861], since packets are never
+             * queued while waiting for address resolution. */
+            gnrc_pktbuf_release(pkt);
+        }
+
+        return false;
+    }
+
     /* queue packet as we have to do address resolution first */
     if (pkt != NULL && !_enqueue_for_resolve(netif, pkt, entry)) {
         return false;
     }
 
-    /* don't do multicast address resolution on 6lo */
-    if (!gnrc_netif_is_6ln(netif)) {
-        _probe_nbr(entry, reset);
-    }
+    _probe_nbr(entry, reset);
 
     return false;
 }
@@ -1733,4 +1743,54 @@ static uint32_t _handle_rio(gnrc_netif_t *netif, const ipv6_hdr_t *ipv6,
 
     return route_ltime;
 }
+
+#if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_QUEUE_PKT)
+gnrc_pktqueue_t *_nbr_pop_pkt(_nib_onl_entry_t *node)
+{
+    if (node->pktqueue_len == 0) {
+        assert(node->pktqueue == NULL);
+        return NULL;
+    }
+    assert(node->pktqueue != NULL);
+
+    node->pktqueue_len--;
+
+    return gnrc_pktqueue_remove_head(&node->pktqueue);
+}
+
+void _nbr_push_pkt(_nib_onl_entry_t *node, gnrc_pktqueue_t *pkt)
+{
+    if (_get_nud_state(node) == GNRC_IPV6_NIB_NC_INFO_NUD_STATE_UNREACHABLE) {
+        assert(node->pktqueue_len == 0);
+
+        gnrc_icmpv6_error_dst_unr_send(ICMPV6_ERROR_DST_UNR_ADDR, pkt->pkt);
+        gnrc_pktbuf_release_error(pkt->pkt, EHOSTUNREACH);
+        pkt->pkt = NULL;
+
+        return;
+    }
+
+    assert(node->pktqueue_len <= CONFIG_GNRC_IPV6_NIB_QUEUE_PKT_CAP);
+    if (node->pktqueue_len == CONFIG_GNRC_IPV6_NIB_QUEUE_PKT_CAP) {
+        gnrc_pktqueue_t *oldest = _nbr_pop_pkt(node);
+        assert(oldest != NULL);
+        gnrc_icmpv6_error_dst_unr_send(ICMPV6_ERROR_DST_UNR_ADDR, oldest->pkt);
+        gnrc_pktbuf_release_error(oldest->pkt, ENOBUFS);
+        oldest->pkt = NULL;
+    }
+
+    gnrc_pktqueue_add(&node->pktqueue, pkt);
+    node->pktqueue_len++;
+}
+
+void _nbr_flush_pktqueue(_nib_onl_entry_t *node)
+{
+    gnrc_pktqueue_t *entry;
+    while ((entry = _nbr_pop_pkt(node))) {
+        gnrc_icmpv6_error_dst_unr_send(ICMPV6_ERROR_DST_UNR_ADDR, entry->pkt);
+        gnrc_pktbuf_release_error(entry->pkt, EHOSTUNREACH);
+        entry->pkt = NULL;
+    }
+}
+#endif  /* CONFIG_GNRC_IPV6_NIB_QUEUE_PKT */
 /** @} */