lib/mac-learning.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
   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 <inttypes.h>
  21 #include <stdlib.h>
  22
  23 #include "bitmap.h"
  24 #include "coverage.h"
  25 #include "hash.h"
  26 #include "list.h"
  27 #include "poll-loop.h"
  28 #include "timeval.h"
  29 #include "unaligned.h"
  30 #include "util.h"
  31 #include "vlan-bitmap.h"
  32
  33 COVERAGE_DEFINE(mac_learning_learned);
  34 COVERAGE_DEFINE(mac_learning_expired);
  35
  36 /* Returns the number of seconds since 'e' (within 'ml') was last learned. */
  37 int
  38 mac_entry_age(const struct mac_learning *ml, const struct mac_entry *e)
  39 {
  40     time_t remaining = e->expires - time_now();
  41     return ml->idle_time - remaining;
  42 }
  43
  44 static uint32_t
  45 mac_table_hash(const struct mac_learning *ml, const uint8_t mac[ETH_ADDR_LEN],
  46                uint16_t vlan)
  47 {
  48     return hash_mac(mac, vlan, ml->secret);
  49 }
  50
  51 static struct mac_entry *
  52 mac_entry_from_lru_node(struct ovs_list *list)
  53 {
  54     return CONTAINER_OF(list, struct mac_entry, lru_node);
  55 }
  56
  57 static struct mac_entry *
  58 mac_entry_lookup(const struct mac_learning *ml,
  59                  const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  60 {
  61     struct mac_entry *e;
  62
  63     HMAP_FOR_EACH_WITH_HASH (e, hmap_node, mac_table_hash(ml, mac, vlan),
  64                              &ml->table) {
  65         if (e->vlan == vlan && eth_addr_equals(e->mac, mac)) {
  66             return e;
  67         }
  68     }
  69     return NULL;
  70 }
  71
  72 static struct mac_learning_port *
  73 mac_learning_port_lookup(struct mac_learning *ml, void *port)
  74 {
  75     struct mac_learning_port *mlport;
  76
  77     HMAP_FOR_EACH_IN_BUCKET (mlport, hmap_node, hash_pointer(port, ml->secret),
  78                              &ml->ports_by_ptr) {
  79         if (mlport->port == port) {
  80             return mlport;
  81         }
  82     }
  83     return NULL;
  84 }
  85
  86 /* Changes the client-owned pointer for entry 'e' in 'ml' to 'port'.  The
  87  * pointer can be retrieved with mac_entry_get_port().
  88  *
  89  * The MAC-learning implementation treats the data that 'port' points to as
  90  * opaque and never tries to dereference it.  However, when a MAC learning
  91  * table becomes overfull, so that eviction is required, the implementation
  92  * does first evict MAC entries for the most common 'port's values in 'ml', so
  93  * that there is a degree of fairness, that is, each port is entitled to its
  94  * fair share of MAC entries. */
  95 void
  96 mac_entry_set_port(struct mac_learning *ml, struct mac_entry *e, void *port)
  97     OVS_REQ_WRLOCK(ml->rwlock)
  98 {
  99     if (mac_entry_get_port(ml, e) != port) {
 100         ml->need_revalidate = true;
 101
 102         if (e->mlport) {
 103             struct mac_learning_port *mlport = e->mlport;
 104             list_remove(&e->port_lru_node);
 105
 106             if (list_is_empty(&mlport->port_lrus)) {
 107                 ovs_assert(mlport->heap_node.priority == 1);
 108                 hmap_remove(&ml->ports_by_ptr, &mlport->hmap_node);
 109                 heap_remove(&ml->ports_by_usage, &mlport->heap_node);
 110                 free(mlport);
 111             } else {
 112                 ovs_assert(mlport->heap_node.priority > 1);
 113                 heap_change(&ml->ports_by_usage, &mlport->heap_node,
 114                             mlport->heap_node.priority - 1);
 115             }
 116             e->mlport = NULL;
 117         }
 118
 119         if (port) {
 120             struct mac_learning_port *mlport;
 121
 122             mlport = mac_learning_port_lookup(ml, port);
 123             if (!mlport) {
 124                 mlport = xzalloc(sizeof *mlport);
 125                 hmap_insert(&ml->ports_by_ptr, &mlport->hmap_node,
 126                             hash_pointer(port, ml->secret));
 127                 heap_insert(&ml->ports_by_usage, &mlport->heap_node, 1);
 128                 mlport->port = port;
 129                 list_init(&mlport->port_lrus);
 130             } else {
 131                 heap_change(&ml->ports_by_usage, &mlport->heap_node,
 132                             mlport->heap_node.priority + 1);
 133             }
 134             list_push_back(&mlport->port_lrus, &e->port_lru_node);
 135             e->mlport = mlport;
 136         }
 137     }
 138 }
 139
 140 /* Finds one of the ports with the most MAC entries and evicts its least
 141  * recently used entry. */
 142 static void
 143 evict_mac_entry_fairly(struct mac_learning *ml)
 144     OVS_REQ_WRLOCK(ml->rwlock)
 145 {
 146     struct mac_learning_port *mlport;
 147     struct mac_entry *e;
 148
 149     mlport = CONTAINER_OF(heap_max(&ml->ports_by_usage),
 150                           struct mac_learning_port, heap_node);
 151     e = CONTAINER_OF(list_front(&mlport->port_lrus),
 152                      struct mac_entry, port_lru_node);
 153     mac_learning_expire(ml, e);
 154 }
 155
 156 /* If the LRU list is not empty, stores the least-recently-used entry in '*e'
 157  * and returns true.  Otherwise, if the LRU list is empty, stores NULL in '*e'
 158  * and return false. */
 159 static bool
 160 get_lru(struct mac_learning *ml, struct mac_entry **e)
 161     OVS_REQ_RDLOCK(ml->rwlock)
 162 {
 163     if (!list_is_empty(&ml->lrus)) {
 164         *e = mac_entry_from_lru_node(ml->lrus.next);
 165         return true;
 166     } else {
 167         *e = NULL;
 168         return false;
 169     }
 170 }
 171
 172 static unsigned int
 173 normalize_idle_time(unsigned int idle_time)
 174 {
 175     return (idle_time < 15 ? 15
 176             : idle_time > 3600 ? 3600
 177             : idle_time);
 178 }
 179
 180 /* Creates and returns a new MAC learning table with an initial MAC aging
 181  * timeout of 'idle_time' seconds and an initial maximum of MAC_DEFAULT_MAX
 182  * entries. */
 183 struct mac_learning *
 184 mac_learning_create(unsigned int idle_time)
 185 {
 186     struct mac_learning *ml;
 187
 188     ml = xmalloc(sizeof *ml);
 189     list_init(&ml->lrus);
 190     hmap_init(&ml->table);
 191     ml->secret = random_uint32();
 192     ml->flood_vlans = NULL;
 193     ml->idle_time = normalize_idle_time(idle_time);
 194     ml->max_entries = MAC_DEFAULT_MAX;
 195     ml->need_revalidate = false;
 196     hmap_init(&ml->ports_by_ptr);
 197     heap_init(&ml->ports_by_usage);
 198     ovs_refcount_init(&ml->ref_cnt);
 199     ovs_rwlock_init(&ml->rwlock);
 200     return ml;
 201 }
 202
 203 struct mac_learning *
 204 mac_learning_ref(const struct mac_learning *ml_)
 205 {
 206     struct mac_learning *ml = CONST_CAST(struct mac_learning *, ml_);
 207     if (ml) {
 208         ovs_refcount_ref(&ml->ref_cnt);
 209     }
 210     return ml;
 211 }
 212
 213 /* Unreferences (and possibly destroys) MAC learning table 'ml'. */
 214 void
 215 mac_learning_unref(struct mac_learning *ml)
 216 {
 217     if (ml && ovs_refcount_unref(&ml->ref_cnt) == 1) {
 218         struct mac_entry *e, *next;
 219
 220         ovs_rwlock_wrlock(&ml->rwlock);
 221         HMAP_FOR_EACH_SAFE (e, next, hmap_node, &ml->table) {
 222             mac_learning_expire(ml, e);
 223         }
 224         hmap_destroy(&ml->table);
 225         hmap_destroy(&ml->ports_by_ptr);
 226         heap_destroy(&ml->ports_by_usage);
 227
 228         bitmap_free(ml->flood_vlans);
 229         ovs_rwlock_unlock(&ml->rwlock);
 230         ovs_rwlock_destroy(&ml->rwlock);
 231         free(ml);
 232     }
 233 }
 234
 235 /* Provides a bitmap of VLANs which have learning disabled, that is, VLANs on
 236  * which all packets are flooded.  Returns true if the set has changed from the
 237  * previous value. */
 238 bool
 239 mac_learning_set_flood_vlans(struct mac_learning *ml,
 240                              const unsigned long *bitmap)
 241 {
 242     if (vlan_bitmap_equal(ml->flood_vlans, bitmap)) {
 243         return false;
 244     } else {
 245         bitmap_free(ml->flood_vlans);
 246         ml->flood_vlans = vlan_bitmap_clone(bitmap);
 247         return true;
 248     }
 249 }
 250
 251 /* Changes the MAC aging timeout of 'ml' to 'idle_time' seconds. */
 252 void
 253 mac_learning_set_idle_time(struct mac_learning *ml, unsigned int idle_time)
 254 {
 255     idle_time = normalize_idle_time(idle_time);
 256     if (idle_time != ml->idle_time) {
 257         struct mac_entry *e;
 258         int delta;
 259
 260         delta = (int) idle_time - (int) ml->idle_time;
 261         LIST_FOR_EACH (e, lru_node, &ml->lrus) {
 262             e->expires += delta;
 263         }
 264         ml->idle_time = idle_time;
 265     }
 266 }
 267
 268 /* Sets the maximum number of entries in 'ml' to 'max_entries', adjusting it
 269  * to be within a reasonable range. */
 270 void
 271 mac_learning_set_max_entries(struct mac_learning *ml, size_t max_entries)
 272 {
 273     ml->max_entries = (max_entries < 10 ? 10
 274                        : max_entries > 1000 * 1000 ? 1000 * 1000
 275                        : max_entries);
 276 }
 277
 278 static bool
 279 is_learning_vlan(const struct mac_learning *ml, uint16_t vlan)
 280 {
 281     return !ml->flood_vlans || !bitmap_is_set(ml->flood_vlans, vlan);
 282 }
 283
 284 /* Returns true if 'src_mac' may be learned on 'vlan' for 'ml'.
 285  * Returns false if 'ml' is NULL, if src_mac is not valid for learning, or if
 286  * 'vlan' is configured on 'ml' to flood all packets. */
 287 bool
 288 mac_learning_may_learn(const struct mac_learning *ml,
 289                        const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 290 {
 291     return ml && is_learning_vlan(ml, vlan) && !eth_addr_is_multicast(src_mac);
 292 }
 293
 294 /* Searches 'ml' for and returns a MAC learning entry for 'src_mac' in 'vlan',
 295  * inserting a new entry if necessary.  The caller must have already verified,
 296  * by calling mac_learning_may_learn(), that 'src_mac' and 'vlan' are
 297  * learnable.
 298  *
 299  * If the returned MAC entry is new (that is, if it has a NULL client-provided
 300  * port, as returned by mac_entry_get_port()), then the caller must initialize
 301  * the new entry's port to a nonnull value with mac_entry_set_port(). */
 302 struct mac_entry *
 303 mac_learning_insert(struct mac_learning *ml,
 304                     const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 305 {
 306     struct mac_entry *e;
 307
 308     e = mac_entry_lookup(ml, src_mac, vlan);
 309     if (!e) {
 310         uint32_t hash = mac_table_hash(ml, src_mac, vlan);
 311
 312         if (hmap_count(&ml->table) >= ml->max_entries) {
 313             evict_mac_entry_fairly(ml);
 314         }
 315
 316         e = xmalloc(sizeof *e);
 317         hmap_insert(&ml->table, &e->hmap_node, hash);
 318         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
 319         e->vlan = vlan;
 320         e->grat_arp_lock = TIME_MIN;
 321         e->mlport = NULL;
 322         COVERAGE_INC(mac_learning_learned);
 323     } else {
 324         list_remove(&e->lru_node);
 325     }
 326
 327     /* Mark 'e' as recently used. */
 328     list_push_back(&ml->lrus, &e->lru_node);
 329     if (e->mlport) {
 330         list_remove(&e->port_lru_node);
 331         list_push_back(&e->mlport->port_lrus, &e->port_lru_node);
 332     }
 333     e->expires = time_now() + ml->idle_time;
 334
 335     return e;
 336 }
 337
 338 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml' and returns the associated MAC
 339  * learning entry, if any. */
 340 struct mac_entry *
 341 mac_learning_lookup(const struct mac_learning *ml,
 342                     const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan)
 343 {
 344     if (eth_addr_is_multicast(dst)) {
 345         /* No tag because the treatment of multicast destinations never
 346          * changes. */
 347         return NULL;
 348     } else if (!is_learning_vlan(ml, vlan)) {
 349         /* We don't tag this property.  The set of learning VLANs changes so
 350          * rarely that we revalidate every flow when it changes. */
 351         return NULL;
 352     } else {
 353         struct mac_entry *e = mac_entry_lookup(ml, dst, vlan);
 354
 355         ovs_assert(e == NULL || mac_entry_get_port(ml, e) != NULL);
 356         return e;
 357     }
 358 }
 359
 360 /* Expires 'e' from the 'ml' hash table. */
 361 void
 362 mac_learning_expire(struct mac_learning *ml, struct mac_entry *e)
 363 {
 364     ml->need_revalidate = true;
 365     mac_entry_set_port(ml, e, NULL);
 366     hmap_remove(&ml->table, &e->hmap_node);
 367     list_remove(&e->lru_node);
 368     free(e);
 369 }
 370
 371 /* Expires all the mac-learning entries in 'ml'. */
 372 void
 373 mac_learning_flush(struct mac_learning *ml)
 374 {
 375     struct mac_entry *e;
 376     while (get_lru(ml, &e)){
 377         mac_learning_expire(ml, e);
 378     }
 379     hmap_shrink(&ml->table);
 380 }
 381
 382 /* Does periodic work required by 'ml'.  Returns true if something changed that
 383  * may require flow revalidation. */
 384 bool
 385 mac_learning_run(struct mac_learning *ml)
 386 {
 387     bool need_revalidate;
 388     struct mac_entry *e;
 389
 390     while (get_lru(ml, &e)
 391            && (hmap_count(&ml->table) > ml->max_entries
 392                || time_now() >= e->expires)) {
 393         COVERAGE_INC(mac_learning_expired);
 394         mac_learning_expire(ml, e);
 395     }
 396
 397     need_revalidate = ml->need_revalidate;
 398     ml->need_revalidate = false;
 399     return need_revalidate;
 400 }
 401
 402 void
 403 mac_learning_wait(struct mac_learning *ml)
 404 {
 405     if (hmap_count(&ml->table) > ml->max_entries
 406         || ml->need_revalidate) {
 407         poll_immediate_wake();
 408     } else if (!list_is_empty(&ml->lrus)) {
 409         struct mac_entry *e = mac_entry_from_lru_node(ml->lrus.next);
 410         poll_timer_wait_until(e->expires * 1000LL);
 411     }
 412 }