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 uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  50 {
  51     return hash_bytes(mac, ETH_ADDR_LEN, vlan);
  52 }
  53
  54 static struct mac_entry *
  55 mac_entry_from_lru_node(struct list *list)
  56 {
  57     return CONTAINER_OF(list, struct mac_entry, lru_node);
  58 }
  59
  60 /* Returns a tag that represents that 'mac' is on an unknown port in 'vlan'.
  61  * (When we learn where 'mac' is in 'vlan', this allows flows that were
  62  * flooded to be revalidated.) */
  63 static tag_type
  64 make_unknown_mac_tag(const struct mac_learning *ml,
  65                      const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  66 {
  67     uint32_t h = hash_int(ml->secret, mac_table_hash(mac, vlan));
  68     return tag_create_deterministic(h);
  69 }
  70
  71 static struct list *
  72 mac_table_bucket(const struct mac_learning *ml,
  73                  const uint8_t mac[ETH_ADDR_LEN],
  74                  uint16_t vlan)
  75 {
  76     uint32_t hash = mac_table_hash(mac, vlan);
  77     const struct list *list = &ml->table[hash & MAC_HASH_BITS];
  78     return (struct list *) list;
  79 }
  80
  81 static struct mac_entry *
  82 search_bucket(struct list *bucket, const uint8_t mac[ETH_ADDR_LEN],
  83               uint16_t vlan)
  84 {
  85     struct mac_entry *e;
  86     LIST_FOR_EACH (e, hash_node, bucket) {
  87         if (eth_addr_equals(e->mac, mac) && e->vlan == vlan) {
  88             return e;
  89         }
  90     }
  91     return NULL;
  92 }
  93
  94 /* If the LRU list is not empty, stores the least-recently-used entry in '*e'
  95  * and returns true.  Otherwise, if the LRU list is empty, stores NULL in '*e'
  96  * and return false. */
  97 static bool
  98 get_lru(struct mac_learning *ml, struct mac_entry **e)
  99 {
 100     if (!list_is_empty(&ml->lrus)) {
 101         *e = mac_entry_from_lru_node(ml->lrus.next);
 102         return true;
 103     } else {
 104         *e = NULL;
 105         return false;
 106     }
 107 }
 108
 109 /* Creates and returns a new MAC learning table. */
 110 struct mac_learning *
 111 mac_learning_create(void)
 112 {
 113     struct mac_learning *ml;
 114     int i;
 115
 116     ml = xmalloc(sizeof *ml);
 117     list_init(&ml->lrus);
 118     list_init(&ml->free);
 119     for (i = 0; i < MAC_HASH_SIZE; i++) {
 120         list_init(&ml->table[i]);
 121     }
 122     for (i = 0; i < MAC_MAX; i++) {
 123         struct mac_entry *s = &ml->entries[i];
 124         list_push_front(&ml->free, &s->lru_node);
 125     }
 126     ml->secret = random_uint32();
 127     ml->flood_vlans = NULL;
 128     return ml;
 129 }
 130
 131 /* Destroys MAC learning table 'ml'. */
 132 void
 133 mac_learning_destroy(struct mac_learning *ml)
 134 {
 135     if (ml) {
 136         bitmap_free(ml->flood_vlans);
 137         free(ml);
 138     }
 139 }
 140
 141 /* Provides a bitmap of VLANs which have learning disabled, that is, VLANs on
 142  * which all packets are flooded.  Returns true if the set has changed from the
 143  * previous value. */
 144 bool
 145 mac_learning_set_flood_vlans(struct mac_learning *ml,
 146                              const unsigned long *bitmap)
 147 {
 148     if (vlan_bitmap_equal(ml->flood_vlans, bitmap)) {
 149         return false;
 150     } else {
 151         bitmap_free(ml->flood_vlans);
 152         ml->flood_vlans = vlan_bitmap_clone(bitmap);
 153         return true;
 154     }
 155 }
 156
 157 static bool
 158 is_learning_vlan(const struct mac_learning *ml, uint16_t vlan)
 159 {
 160     return vlan_bitmap_contains(ml->flood_vlans, vlan);
 161 }
 162
 163 /* Returns true if 'src_mac' may be learned on 'vlan' for 'ml'.
 164  * Returns false if 'ml' is NULL, if src_mac is not valid for learning, or if
 165  * 'vlan' is configured on 'ml' to flood all packets. */
 166 bool
 167 mac_learning_may_learn(const struct mac_learning *ml,
 168                        const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 169 {
 170     return ml && is_learning_vlan(ml, vlan) && !eth_addr_is_multicast(src_mac);
 171 }
 172
 173 /* Searches 'ml' for and returns a MAC learning entry for 'src_mac' in 'vlan',
 174  * inserting a new entry if necessary.  The caller must have already verified,
 175  * by calling mac_learning_may_learn(), that 'src_mac' and 'vlan' are
 176  * learnable.
 177  *
 178  * If the returned MAC entry is new (as may be determined by calling
 179  * mac_entry_is_new()), then the caller must pass the new entry to
 180  * mac_learning_changed().  The caller must also initialize the new entry's
 181  * 'port' member.  Otherwise calling those functions is at the caller's
 182  * discretion. */
 183 struct mac_entry *
 184 mac_learning_insert(struct mac_learning *ml,
 185                     const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 186 {
 187     struct mac_entry *e;
 188     struct list *bucket;
 189
 190     bucket = mac_table_bucket(ml, src_mac, vlan);
 191     e = search_bucket(bucket, src_mac, vlan);
 192     if (!e) {
 193         if (!list_is_empty(&ml->free)) {
 194             e = mac_entry_from_lru_node(ml->free.next);
 195         } else {
 196             e = mac_entry_from_lru_node(ml->lrus.next);
 197             list_remove(&e->hash_node);
 198         }
 199         list_push_front(bucket, &e->hash_node);
 200         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
 201         e->vlan = vlan;
 202         e->tag = 0;
 203         e->grat_arp_lock = TIME_MIN;
 204     }
 205
 206     /* Mark 'e' as recently used. */
 207     list_remove(&e->lru_node);
 208     list_push_back(&ml->lrus, &e->lru_node);
 209     e->expires = time_now() + MAC_ENTRY_IDLE_TIME;
 210
 211     return e;
 212 }
 213
 214 /* Changes 'e''s tag to a new, randomly selected one, and returns the tag that
 215  * would have been previously used for this entry's MAC and VLAN (either before
 216  * 'e' was inserted, if it is new, or otherwise before its port was updated.)
 217  *
 218  * The client should call this function after obtaining a MAC learning entry
 219  * from mac_learning_insert(), if the entry is either new or if its learned
 220  * port has changed. */
 221 tag_type
 222 mac_learning_changed(struct mac_learning *ml, struct mac_entry *e)
 223 {
 224     tag_type old_tag = e->tag;
 225
 226     COVERAGE_INC(mac_learning_learned);
 227
 228     e->tag = tag_create_random();
 229     return old_tag ? old_tag : make_unknown_mac_tag(ml, e->mac, e->vlan);
 230 }
 231
 232 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml' and returns the associated MAC
 233  * learning entry, if any.  If 'tag' is nonnull, then the tag that associates
 234  * 'dst' and 'vlan' with its currently learned port will be OR'd into
 235  * '*tag'. */
 236 struct mac_entry *
 237 mac_learning_lookup(const struct mac_learning *ml,
 238                     const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan,
 239                     tag_type *tag)
 240 {
 241     if (eth_addr_is_multicast(dst)) {
 242         /* No tag because the treatment of multicast destinations never
 243          * changes. */
 244         return NULL;
 245     } else if (!is_learning_vlan(ml, vlan)) {
 246         /* We don't tag this property.  The set of learning VLANs changes so
 247          * rarely that we revalidate every flow when it changes. */
 248         return NULL;
 249     } else {
 250         struct mac_entry *e = search_bucket(mac_table_bucket(ml, dst, vlan),
 251                                             dst, vlan);
 252         assert(e == NULL || e->tag != 0);
 253         if (tag) {
 254             /* Tag either the learned port or the lack thereof. */
 255             *tag |= e ? e->tag : make_unknown_mac_tag(ml, dst, vlan);
 256         }
 257         return e;
 258     }
 259 }
 260
 261 /* Expires 'e' from the 'ml' hash table.  'e' must not already be on the free
 262  * list. */
 263 void
 264 mac_learning_expire(struct mac_learning *ml, struct mac_entry *e)
 265 {
 266     list_remove(&e->hash_node);
 267     list_remove(&e->lru_node);
 268     list_push_front(&ml->free, &e->lru_node);
 269 }
 270
 271 /* Expires all the mac-learning entries in 'ml'.  The tags in 'ml' are
 272  * discarded, so the client is responsible for revalidating any flows that
 273  * depend on 'ml', if necessary. */
 274 void
 275 mac_learning_flush(struct mac_learning *ml)
 276 {
 277     struct mac_entry *e;
 278     while (get_lru(ml, &e)){
 279         mac_learning_expire(ml, e);
 280     }
 281 }
 282
 283 void
 284 mac_learning_run(struct mac_learning *ml, struct tag_set *set)
 285 {
 286     struct mac_entry *e;
 287     while (get_lru(ml, &e) && time_now() >= e->expires) {
 288         COVERAGE_INC(mac_learning_expired);
 289         if (set) {
 290             tag_set_add(set, e->tag);
 291         }
 292         mac_learning_expire(ml, e);
 293     }
 294 }
 295
 296 void
 297 mac_learning_wait(struct mac_learning *ml)
 298 {
 299     if (!list_is_empty(&ml->lrus)) {
 300         struct mac_entry *e = mac_entry_from_lru_node(ml->lrus.next);
 301         poll_timer_wait_until(e->expires * 1000LL);
 302     }
 303 }