mac-learning: Simplify memory management.

The mac-learning implementation used a free list to keep track of
statically allocated table entries.  This made the code slightly
more difficult to understand than the more straightforward heap
based strategy implemented by this patch.

diff --git a/lib/mac-learning.c b/lib/mac-learning.c
index 5e05885..bb84cfc 100644 (file)
--- a/lib/mac-learning.c
+++ b/lib/mac-learning.c
@@ -103,16 +103,10 @@ struct mac_learning *
 mac_learning_create(void)
 {
     struct mac_learning *ml;
-    int i;
 
     ml = xmalloc(sizeof *ml);
     list_init(&ml->lrus);
-    list_init(&ml->free);
     hmap_init(&ml->table);
-    for (i = 0; i < MAC_MAX; i++) {
-        struct mac_entry *s = &ml->entries[i];
-        list_push_front(&ml->free, &s->lru_node);
-    }
     ml->secret = random_uint32();
     ml->flood_vlans = NULL;
     return ml;
@@ -123,7 +117,14 @@ void
 mac_learning_destroy(struct mac_learning *ml)
 {
     if (ml) {
+        struct mac_entry *e, *next;
+
+        HMAP_FOR_EACH_SAFE (e, next, hmap_node, &ml->table) {
+            hmap_remove(&ml->table, &e->hmap_node);
+            free(e);
+        }
         hmap_destroy(&ml->table);
+
         bitmap_free(ml->flood_vlans);
         free(ml);
     }
@@ -181,22 +182,22 @@ mac_learning_insert(struct mac_learning *ml,
     if (!e) {
         uint32_t hash = mac_table_hash(ml, src_mac, vlan);
 
-        if (!list_is_empty(&ml->free)) {
-            e = mac_entry_from_lru_node(ml->free.next);
-        } else {
-            e = mac_entry_from_lru_node(ml->lrus.next);
-            hmap_remove(&ml->table, &e->hmap_node);
+        if (hmap_count(&ml->table) >= MAC_MAX) {
+            get_lru(ml, &e);
+            mac_learning_expire(ml, e);
         }
 
+        e = xmalloc(sizeof *e);
         hmap_insert(&ml->table, &e->hmap_node, hash);
         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
         e->vlan = vlan;
         e->tag = 0;
         e->grat_arp_lock = TIME_MIN;
+    } else {
+        list_remove(&e->lru_node);
     }
 
     /* Mark 'e' as recently used. */
-    list_remove(&e->lru_node);
     list_push_back(&ml->lrus, &e->lru_node);
     e->expires = time_now() + MAC_ENTRY_IDLE_TIME;
 
@@ -250,14 +251,13 @@ mac_learning_lookup(const struct mac_learning *ml,
     }
 }
 
-/* Expires 'e' from the 'ml' hash table.  'e' must not already be on the free
- * list. */
+/* Expires 'e' from the 'ml' hash table. */
 void
 mac_learning_expire(struct mac_learning *ml, struct mac_entry *e)
 {
     hmap_remove(&ml->table, &e->hmap_node);
     list_remove(&e->lru_node);
-    list_push_front(&ml->free, &e->lru_node);
+    free(e);
 }
 
 /* Expires all the mac-learning entries in 'ml'.  The tags in 'ml' are
@@ -270,6 +270,7 @@ mac_learning_flush(struct mac_learning *ml)
     while (get_lru(ml, &e)){
         mac_learning_expire(ml, e);
     }
+    hmap_shrink(&ml->table);
 }
 
 void

diff --git a/lib/mac-learning.h b/lib/mac-learning.h
index d2f2874..0263e49 100644 (file)
--- a/lib/mac-learning.h
+++ b/lib/mac-learning.h
@@ -36,7 +36,7 @@
 /* A MAC learning table entry. */
 struct mac_entry {
     struct hmap_node hmap_node; /* Node in a mac_learning hmap. */
-    struct list lru_node;       /* Element in 'lrus' or 'free' list. */
+    struct list lru_node;       /* Element in 'lrus' list. */
     time_t expires;             /* Expiration time. */
     time_t grat_arp_lock;       /* Gratuitous ARP lock expiration time. */
     uint8_t mac[ETH_ADDR_LEN];  /* Known MAC address. */
@@ -76,10 +76,8 @@ static inline bool mac_entry_is_grat_arp_locked(const struct mac_entry *mac)
 /* MAC learning table. */
 struct mac_learning {
     struct hmap table;          /* Learning table. */
-    struct list free;           /* Not-in-use entries. */
     struct list lrus;           /* In-use entries, least recently used at the
                                    front, most recently used at the back. */
-    struct mac_entry entries[MAC_MAX]; /* All entries. */
     uint32_t secret;            /* Secret for randomizing hash table. */
     unsigned long *flood_vlans; /* Bitmap of learning disabled VLANs. */
 };