gnrc_ipv6_nib: Force unspecified next hop addresses

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

@@ -84,8 +84,11 @@ void _nib_release(void)
 static inline bool _addr_equals(const ipv6_addr_t *addr,
                                 const _nib_onl_entry_t *node)
 {
-    return (addr == NULL) || ipv6_addr_is_unspecified(&node->ipv6) ||
-           (ipv6_addr_equal(addr, &node->ipv6));
+    if (addr == NULL) {
+        return ipv6_addr_is_unspecified(&node->ipv6);
+    } else {
+        return ipv6_addr_equal(addr, &node->ipv6);
+    }
 }
 
 _nib_onl_entry_t *_nib_onl_alloc(const ipv6_addr_t *addr, unsigned iface)
@@ -501,28 +504,34 @@ _nib_offl_entry_t *_nib_offl_alloc(const ipv6_addr_t *next_hop, unsigned iface,
         _nib_offl_entry_t *tmp = &_dsts[i];
         _nib_onl_entry_t *tmp_node = tmp->next_hop;
 
-        if ((tmp->pfx_len == pfx_len) &&                /* prefix length matches and */
-            (tmp_node != NULL) &&                       /* there is a next hop that */
-            (_nib_onl_get_if(tmp_node) == iface) &&     /* has a matching interface and */
-            _addr_equals(next_hop, tmp_node) &&         /* equal address to next_hop, also */
-            (ipv6_addr_match_prefix(&tmp->pfx, pfx) >= pfx_len)) {  /* the prefix matches */
-            /* exact match (or next hop address was previously unset) */
-            DEBUG("  %p is an exact match\n", (void *)tmp);
-            if (next_hop != NULL) {
-                memcpy(&tmp_node->ipv6, next_hop, sizeof(tmp_node->ipv6));
+        if (tmp->mode == _EMPTY) {
+            if (dst == NULL) {
+                dst = tmp;
+            }
+            continue;
+        }
+
+        /* else: offlink entry not empty, potential match */
+        if (tmp->pfx_len == pfx_len && ipv6_addr_match_prefix(&tmp->pfx, pfx) >= pfx_len) {
+            /* prefix matches */
+            assert(tmp_node);
+            if (_nib_onl_get_if(tmp_node) == iface && (ipv6_addr_is_unspecified(&tmp_node->ipv6)
+                                                       || _addr_equals(next_hop, tmp_node))) {
+                /* next hop matches or is unspecified */
+                DEBUG("  %p is an exact match\n", (void *)tmp);
+                if (next_hop != NULL) {
+                    /* sets next_hop if it was previously unspecified */
+                    memcpy(&tmp_node->ipv6, next_hop, sizeof(tmp_node->ipv6));
+                }
+                /*mark that this NCE is used by an offl_entry*/
+                tmp->next_hop->mode |= _DST;
+                return tmp;
             }
-            tmp->next_hop->mode |= _DST;
-            return tmp;
-        }
-        if ((dst == NULL) && (tmp_node == NULL)) {
-            dst = tmp;
         }
     }
     if (dst != NULL) {
         DEBUG("  using %p\n", (void *)dst);
-        dst->next_hop = _nib_onl_alloc(next_hop, iface);
-
-        if (dst->next_hop == NULL) {
+        if (!dst->next_hop && !(dst->next_hop = _nib_onl_alloc(next_hop, iface))) {
             memset(dst, 0, sizeof(_nib_offl_entry_t));
             return NULL;
         }

tests/unittests/tests-gnrc_ipv6_nib/tests-gnrc_ipv6_nib-internal.c

@@ -1449,6 +1449,60 @@
     TEST_ASSERT(ipv6_addr_equal(&next_hop, &dst1->next_hop->ipv6));
 }
 
+/*
+ * Creates an off-link entry (to a next hop) and an on-link entry on the same interface.
+ * Then proceeds to delete the off-link entries to this next hop
+ * by only comparing the next hop, not checking the _PFX_ON_LINK flag.
+ *
+ * Expected results: Only off-link entries are deleted.
+ * On-link entries on the same interface are unaffected by the deletion.
+ */
+static void test_nib_offl_alloc__next_hop_indicates_whether_onl(void)
+{
+    static const ipv6_addr_t next_hop = { .u64 = { { .u8 = LINK_LOCAL_PREFIX },
+                                                 { .u64 = TEST_UINT64 } } };
+    static const ipv6_addr_t pfx = { .u64 = { { .u8 = GLOBAL_PREFIX } } };
+
+    /*are in practice different prefixes actually*/
+    static const ipv6_addr_t *onl_pfx = &pfx;
+    static const ipv6_addr_t *offl_pfx = &pfx;
+
+    /* Add off-link entry */
+    _nib_offl_entry_t *dst1;
+    TEST_ASSERT_NOT_NULL((dst1 = _nib_ft_add(&next_hop, IFACE, offl_pfx, GLOBAL_PREFIX_LEN)));
+
+    /* Add on-link entry */
+    const unsigned pfx_len = GLOBAL_PREFIX_LEN; /* arbitrary */
+
+    /* (calls _nib_offl_alloc) */
+    _nib_offl_entry_t *dst;
+    TEST_ASSERT_NOT_NULL((dst = _nib_pl_add(IFACE, onl_pfx, pfx_len, UINT32_MAX, UINT32_MAX)));
+    TEST_ASSERT(ipv6_addr_is_unspecified(&dst->next_hop->ipv6));
+    /* would normally be set by PIO flags in Router Advertisement */
+    dst->flags |= _PFX_ON_LINK;
+
+    /* Delete all off-link entries to next_hop */
+    _nib_offl_entry_t *route = NULL;
+    while ((route = _nib_offl_iter(route))) {
+        if ((_nib_onl_get_if(route->next_hop) == IFACE) &&
+            (route->next_hop != NULL) &&
+            ipv6_addr_equal(&route->next_hop->ipv6, &next_hop) /*off-link, to this next hop*/
+            /*should not need to be checked for when next hop is already checked:*/
+            /*&& !(route->flags & _PFX_ON_LINK)*/
+            ) {
+            _nib_ft_remove(route);
+            }
+    }
+
+    /* Expected result: On-link entries remain unaffected */
+    gnrc_ipv6_nib_pl_t prefix;
+    void *state = NULL;
+    TEST_ASSERT_MESSAGE(gnrc_ipv6_nib_pl_iter(IFACE, &state, &prefix),
+                        "No prefix list entry found");
+    TEST_ASSERT_MESSAGE(ipv6_addr_match_prefix(onl_pfx, &prefix.pfx) >= pfx_len,
+                        "Unexpected prefix configured");
+}
+
 /*
  * Creates an off-link entry.
  * Expected result: new entry should contain the given prefix, address and
@@ -2069,6 +2123,7 @@
         new_TestFixture(test_nib_offl_alloc__no_space_left_diff_next_hop_iface_pfx_pfx_len),
         new_TestFixture(test_nib_offl_alloc__success_duplicate),
         new_TestFixture(test_nib_offl_alloc__success_overwrite_unspecified),
+        new_TestFixture(test_nib_offl_alloc__next_hop_indicates_whether_onl),
         new_TestFixture(test_nib_offl_alloc__success),
         new_TestFixture(test_nib_offl_clear__uncleared),
         new_TestFixture(test_nib_offl_clear__same_next_hop),
@@ -2106,4 +2161,4 @@
                         fixtures);
 
     return (Test *)&tests;
 }