lib/mac-learning.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "mac-learning.h"
  19
  20 #include <assert.h>
  21 #include <inttypes.h>
  22 #include <stdlib.h>
  23
  24 #include "bitmap.h"
  25 #include "coverage.h"
  26 #include "hash.h"
  27 #include "list.h"
  28 #include "poll-loop.h"
  29 #include "tag.h"
  30 #include "timeval.h"
  31 #include "util.h"
  32 #include "vlan-bitmap.h"
  33 #include "vlog.h"
  34
  35 VLOG_DEFINE_THIS_MODULE(mac_learning);
  36
  37 COVERAGE_DEFINE(mac_learning_learned);
  38 COVERAGE_DEFINE(mac_learning_expired);
  39
  40 /* Returns the number of seconds since 'e' was last learned. */
  41 int
  42 mac_entry_age(const struct mac_entry *e)
  43 {
  44     time_t remaining = e->expires - time_now();
  45     return MAC_ENTRY_IDLE_TIME - remaining;
  46 }
  47
  48 static uint32_t
  49 mac_table_hash(const struct mac_learning *ml, const uint8_t mac[ETH_ADDR_LEN],
  50                uint16_t vlan)
  51 {
  52     return hash_bytes(mac, ETH_ADDR_LEN, vlan ^ ml->secret);
  53 }
  54
  55 static struct mac_entry *
  56 mac_entry_from_lru_node(struct list *list)
  57 {
  58     return CONTAINER_OF(list, struct mac_entry, lru_node);
  59 }
  60
  61 /* Returns a tag that represents that 'mac' is on an unknown port in 'vlan'.
  62  * (When we learn where 'mac' is in 'vlan', this allows flows that were
  63  * flooded to be revalidated.) */
  64 static tag_type
  65 make_unknown_mac_tag(const struct mac_learning *ml,
  66                      const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  67 {
  68     return tag_create_deterministic(mac_table_hash(ml, mac, vlan));
  69 }
  70
  71 static struct mac_entry *
  72 mac_entry_lookup(const struct mac_learning *ml,
  73                  const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  74 {
  75     struct mac_entry *e;
  76
  77     HMAP_FOR_EACH_WITH_HASH (e, hmap_node, mac_table_hash(ml, mac, vlan),
  78                              &ml->table) {
  79         if (e->vlan == vlan && eth_addr_equals(e->mac, mac)) {
  80             return e;
  81         }
  82     }
  83     return NULL;
  84 }
  85
  86 /* If the LRU list is not empty, stores the least-recently-used entry in '*e'
  87  * and returns true.  Otherwise, if the LRU list is empty, stores NULL in '*e'
  88  * and return false. */
  89 static bool
  90 get_lru(struct mac_learning *ml, struct mac_entry **e)
  91 {
  92     if (!list_is_empty(&ml->lrus)) {
  93         *e = mac_entry_from_lru_node(ml->lrus.next);
  94         return true;
  95     } else {
  96         *e = NULL;
  97         return false;
  98     }
  99 }
 100
 101 /* Creates and returns a new MAC learning table. */
 102 struct mac_learning *
 103 mac_learning_create(void)
 104 {
 105     struct mac_learning *ml;
 106
 107     ml = xmalloc(sizeof *ml);
 108     list_init(&ml->lrus);
 109     hmap_init(&ml->table);
 110     ml->secret = random_uint32();
 111     ml->flood_vlans = NULL;
 112     return ml;
 113 }
 114
 115 /* Destroys MAC learning table 'ml'. */
 116 void
 117 mac_learning_destroy(struct mac_learning *ml)
 118 {
 119     if (ml) {
 120         struct mac_entry *e, *next;
 121
 122         HMAP_FOR_EACH_SAFE (e, next, hmap_node, &ml->table) {
 123             hmap_remove(&ml->table, &e->hmap_node);
 124             free(e);
 125         }
 126         hmap_destroy(&ml->table);
 127
 128         bitmap_free(ml->flood_vlans);
 129         free(ml);
 130     }
 131 }
 132
 133 /* Provides a bitmap of VLANs which have learning disabled, that is, VLANs on
 134  * which all packets are flooded.  Returns true if the set has changed from the
 135  * previous value. */
 136 bool
 137 mac_learning_set_flood_vlans(struct mac_learning *ml,
 138                              const unsigned long *bitmap)
 139 {
 140     if (vlan_bitmap_equal(ml->flood_vlans, bitmap)) {
 141         return false;
 142     } else {
 143         bitmap_free(ml->flood_vlans);
 144         ml->flood_vlans = vlan_bitmap_clone(bitmap);
 145         return true;
 146     }
 147 }
 148
 149 static bool
 150 is_learning_vlan(const struct mac_learning *ml, uint16_t vlan)
 151 {
 152     return !ml->flood_vlans || !bitmap_is_set(ml->flood_vlans, vlan);
 153 }
 154
 155 /* Returns true if 'src_mac' may be learned on 'vlan' for 'ml'.
 156  * Returns false if 'ml' is NULL, if src_mac is not valid for learning, or if
 157  * 'vlan' is configured on 'ml' to flood all packets. */
 158 bool
 159 mac_learning_may_learn(const struct mac_learning *ml,
 160                        const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 161 {
 162     return ml && is_learning_vlan(ml, vlan) && !eth_addr_is_multicast(src_mac);
 163 }
 164
 165 /* Searches 'ml' for and returns a MAC learning entry for 'src_mac' in 'vlan',
 166  * inserting a new entry if necessary.  The caller must have already verified,
 167  * by calling mac_learning_may_learn(), that 'src_mac' and 'vlan' are
 168  * learnable.
 169  *
 170  * If the returned MAC entry is new (as may be determined by calling
 171  * mac_entry_is_new()), then the caller must pass the new entry to
 172  * mac_learning_changed().  The caller must also initialize the new entry's
 173  * 'port' member.  Otherwise calling those functions is at the caller's
 174  * discretion. */
 175 struct mac_entry *
 176 mac_learning_insert(struct mac_learning *ml,
 177                     const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 178 {
 179     struct mac_entry *e;
 180
 181     e = mac_entry_lookup(ml, src_mac, vlan);
 182     if (!e) {
 183         uint32_t hash = mac_table_hash(ml, src_mac, vlan);
 184
 185         if (hmap_count(&ml->table) >= MAC_MAX) {
 186             get_lru(ml, &e);
 187             mac_learning_expire(ml, e);
 188         }
 189
 190         e = xmalloc(sizeof *e);
 191         hmap_insert(&ml->table, &e->hmap_node, hash);
 192         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
 193         e->vlan = vlan;
 194         e->tag = 0;
 195         e->grat_arp_lock = TIME_MIN;
 196     } else {
 197         list_remove(&e->lru_node);
 198     }
 199
 200     /* Mark 'e' as recently used. */
 201     list_push_back(&ml->lrus, &e->lru_node);
 202     e->expires = time_now() + MAC_ENTRY_IDLE_TIME;
 203
 204     return e;
 205 }
 206
 207 /* Changes 'e''s tag to a new, randomly selected one, and returns the tag that
 208  * would have been previously used for this entry's MAC and VLAN (either before
 209  * 'e' was inserted, if it is new, or otherwise before its port was updated.)
 210  *
 211  * The client should call this function after obtaining a MAC learning entry
 212  * from mac_learning_insert(), if the entry is either new or if its learned
 213  * port has changed. */
 214 tag_type
 215 mac_learning_changed(struct mac_learning *ml, struct mac_entry *e)
 216 {
 217     tag_type old_tag = e->tag;
 218
 219     COVERAGE_INC(mac_learning_learned);
 220
 221     e->tag = tag_create_random();
 222     return old_tag ? old_tag : make_unknown_mac_tag(ml, e->mac, e->vlan);
 223 }
 224
 225 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml' and returns the associated MAC
 226  * learning entry, if any.  If 'tag' is nonnull, then the tag that associates
 227  * 'dst' and 'vlan' with its currently learned port will be OR'd into
 228  * '*tag'. */
 229 struct mac_entry *
 230 mac_learning_lookup(const struct mac_learning *ml,
 231                     const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan,
 232                     tag_type *tag)
 233 {
 234     if (eth_addr_is_multicast(dst)) {
 235         /* No tag because the treatment of multicast destinations never
 236          * changes. */
 237         return NULL;
 238     } else if (!is_learning_vlan(ml, vlan)) {
 239         /* We don't tag this property.  The set of learning VLANs changes so
 240          * rarely that we revalidate every flow when it changes. */
 241         return NULL;
 242     } else {
 243         struct mac_entry *e = mac_entry_lookup(ml, dst, vlan);
 244
 245         assert(e == NULL || e->tag != 0);
 246         if (tag) {
 247             /* Tag either the learned port or the lack thereof. */
 248             *tag |= e ? e->tag : make_unknown_mac_tag(ml, dst, vlan);
 249         }
 250         return e;
 251     }
 252 }
 253
 254 /* Expires 'e' from the 'ml' hash table. */
 255 void
 256 mac_learning_expire(struct mac_learning *ml, struct mac_entry *e)
 257 {
 258     hmap_remove(&ml->table, &e->hmap_node);
 259     list_remove(&e->lru_node);
 260     free(e);
 261 }
 262
 263 /* Expires all the mac-learning entries in 'ml'.  The tags in 'ml' are
 264  * discarded, so the client is responsible for revalidating any flows that
 265  * depend on 'ml', if necessary. */
 266 void
 267 mac_learning_flush(struct mac_learning *ml)
 268 {
 269     struct mac_entry *e;
 270     while (get_lru(ml, &e)){
 271         mac_learning_expire(ml, e);
 272     }
 273     hmap_shrink(&ml->table);
 274 }
 275
 276 void
 277 mac_learning_run(struct mac_learning *ml, struct tag_set *set)
 278 {
 279     struct mac_entry *e;
 280     while (get_lru(ml, &e) && time_now() >= e->expires) {
 281         COVERAGE_INC(mac_learning_expired);
 282         if (set) {
 283             tag_set_add(set, e->tag);
 284         }
 285         mac_learning_expire(ml, e);
 286     }
 287 }
 288
 289 void
 290 mac_learning_wait(struct mac_learning *ml)
 291 {
 292     if (!list_is_empty(&ml->lrus)) {
 293         struct mac_entry *e = mac_entry_from_lru_node(ml->lrus.next);
 294         poll_timer_wait_until(e->expires * 1000LL);
 295     }
 296 }