lib/mac-learning.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010 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 "vlog.h"
  33
  34 VLOG_DEFINE_THIS_MODULE(mac_learning);
  35
  36 COVERAGE_DEFINE(mac_learning_learned);
  37 COVERAGE_DEFINE(mac_learning_expired);
  38
  39 /* Returns the number of seconds since 'e' was last learned. */
  40 int
  41 mac_entry_age(const struct mac_entry *e)
  42 {
  43     time_t remaining = e->expires - time_now();
  44     return MAC_ENTRY_IDLE_TIME - remaining;
  45 }
  46
  47 static uint32_t
  48 mac_table_hash(const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  49 {
  50     return hash_bytes(mac, ETH_ADDR_LEN, vlan);
  51 }
  52
  53 static struct mac_entry *
  54 mac_entry_from_lru_node(struct list *list)
  55 {
  56     return CONTAINER_OF(list, struct mac_entry, lru_node);
  57 }
  58
  59 /* Returns a tag that represents that 'mac' is on an unknown port in 'vlan'.
  60  * (When we learn where 'mac' is in 'vlan', this allows flows that were
  61  * flooded to be revalidated.) */
  62 static tag_type
  63 make_unknown_mac_tag(const struct mac_learning *ml,
  64                      const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  65 {
  66     uint32_t h = hash_int(ml->secret, mac_table_hash(mac, vlan));
  67     return tag_create_deterministic(h);
  68 }
  69
  70 static struct list *
  71 mac_table_bucket(const struct mac_learning *ml,
  72                  const uint8_t mac[ETH_ADDR_LEN],
  73                  uint16_t vlan)
  74 {
  75     uint32_t hash = mac_table_hash(mac, vlan);
  76     const struct list *list = &ml->table[hash & MAC_HASH_BITS];
  77     return (struct list *) list;
  78 }
  79
  80 static struct mac_entry *
  81 search_bucket(struct list *bucket, const uint8_t mac[ETH_ADDR_LEN],
  82               uint16_t vlan)
  83 {
  84     struct mac_entry *e;
  85     LIST_FOR_EACH (e, hash_node, bucket) {
  86         if (eth_addr_equals(e->mac, mac) && e->vlan == vlan) {
  87             return e;
  88         }
  89     }
  90     return NULL;
  91 }
  92
  93 /* If the LRU list is not empty, stores the least-recently-used entry in '*e'
  94  * and returns true.  Otherwise, if the LRU list is empty, stores NULL in '*e'
  95  * and return false. */
  96 static bool
  97 get_lru(struct mac_learning *ml, struct mac_entry **e)
  98 {
  99     if (!list_is_empty(&ml->lrus)) {
 100         *e = mac_entry_from_lru_node(ml->lrus.next);
 101         return true;
 102     } else {
 103         *e = NULL;
 104         return false;
 105     }
 106 }
 107
 108 /* Removes 'e' from the 'ml' hash table.  'e' must not already be on the free
 109  * list. */
 110 static void
 111 free_mac_entry(struct mac_learning *ml, struct mac_entry *e)
 112 {
 113     list_remove(&e->hash_node);
 114     list_remove(&e->lru_node);
 115     list_push_front(&ml->free, &e->lru_node);
 116 }
 117
 118 /* Creates and returns a new MAC learning table. */
 119 struct mac_learning *
 120 mac_learning_create(void)
 121 {
 122     struct mac_learning *ml;
 123     int i;
 124
 125     ml = xmalloc(sizeof *ml);
 126     list_init(&ml->lrus);
 127     list_init(&ml->free);
 128     for (i = 0; i < MAC_HASH_SIZE; i++) {
 129         list_init(&ml->table[i]);
 130     }
 131     for (i = 0; i < MAC_MAX; i++) {
 132         struct mac_entry *s = &ml->entries[i];
 133         list_push_front(&ml->free, &s->lru_node);
 134     }
 135     ml->secret = random_uint32();
 136     ml->flood_vlans = NULL;
 137     return ml;
 138 }
 139
 140 /* Destroys MAC learning table 'ml'. */
 141 void
 142 mac_learning_destroy(struct mac_learning *ml)
 143 {
 144     if (ml) {
 145         bitmap_free(ml->flood_vlans);
 146     }
 147     free(ml);
 148 }
 149
 150 /* Provides a bitmap of VLANs which have learning disabled, that is, VLANs on
 151  * which all packets are flooded.  It takes ownership of the bitmap.  Returns
 152  * true if the set has changed from the previous value. */
 153 bool
 154 mac_learning_set_flood_vlans(struct mac_learning *ml, unsigned long *bitmap)
 155 {
 156     bool ret = (bitmap == NULL
 157                 ? ml->flood_vlans != NULL
 158                 : (ml->flood_vlans == NULL
 159                    || !bitmap_equal(bitmap, ml->flood_vlans, 4096)));
 160
 161     bitmap_free(ml->flood_vlans);
 162     ml->flood_vlans = bitmap;
 163
 164     return ret;
 165 }
 166
 167 static bool
 168 is_learning_vlan(const struct mac_learning *ml, uint16_t vlan)
 169 {
 170     return !(ml->flood_vlans && bitmap_is_set(ml->flood_vlans, vlan));
 171 }
 172
 173 /* Attempts to make 'ml' learn from the fact that a frame from 'src_mac' was
 174  * just observed arriving from 'src_port' on the given 'vlan'.
 175  *
 176  * Returns nonzero if we actually learned something from this, zero if it just
 177  * confirms what we already knew.  The nonzero return value is the tag of flows
 178  * that now need revalidation.
 179  *
 180  * The 'vlan' parameter is used to maintain separate per-VLAN learning tables.
 181  * Specify 0 if this behavior is undesirable.
 182  *
 183  * 'lock_type' specifies whether the entry should be locked or existing locks
 184  * are check. */
 185 tag_type
 186 mac_learning_learn(struct mac_learning *ml,
 187                    const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan,
 188                    uint16_t src_port, enum grat_arp_lock_type lock_type)
 189 {
 190     struct mac_entry *e;
 191     struct list *bucket;
 192
 193     if (!is_learning_vlan(ml, vlan)) {
 194         return 0;
 195     }
 196
 197     if (eth_addr_is_multicast(src_mac)) {
 198         static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(30, 30);
 199         VLOG_DBG_RL(&rl, "multicast packet source "ETH_ADDR_FMT,
 200                     ETH_ADDR_ARGS(src_mac));
 201         return 0;
 202     }
 203
 204     bucket = mac_table_bucket(ml, src_mac, vlan);
 205     e = search_bucket(bucket, src_mac, vlan);
 206     if (!e) {
 207         if (!list_is_empty(&ml->free)) {
 208             e = mac_entry_from_lru_node(ml->free.next);
 209         } else {
 210             e = mac_entry_from_lru_node(ml->lrus.next);
 211             list_remove(&e->hash_node);
 212         }
 213         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
 214         list_push_front(bucket, &e->hash_node);
 215         e->port = -1;
 216         e->vlan = vlan;
 217         e->tag = make_unknown_mac_tag(ml, src_mac, vlan);
 218         e->grat_arp_lock = TIME_MIN;
 219     }
 220
 221     if (lock_type != GRAT_ARP_LOCK_CHECK || time_now() >= e->grat_arp_lock) {
 222         /* Make the entry most-recently-used. */
 223         list_remove(&e->lru_node);
 224         list_push_back(&ml->lrus, &e->lru_node);
 225         e->expires = time_now() + MAC_ENTRY_IDLE_TIME;
 226         if (lock_type == GRAT_ARP_LOCK_SET) {
 227             e->grat_arp_lock = time_now() + MAC_GRAT_ARP_LOCK_TIME;
 228         }
 229
 230         /* Did we learn something? */
 231         if (e->port != src_port) {
 232             tag_type old_tag = e->tag;
 233             e->port = src_port;
 234             e->tag = tag_create_random();
 235             COVERAGE_INC(mac_learning_learned);
 236             return old_tag;
 237         }
 238     }
 239
 240     return 0;
 241 }
 242
 243 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml'.  Returns the port on which a
 244  * frame destined for 'dst' should be sent, -1 if unknown. 'is_grat_arp_locked'
 245  * is an optional parameter that returns whether the entry is currently
 246  * locked. */
 247 int
 248 mac_learning_lookup(const struct mac_learning *ml,
 249                     const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan,
 250                     bool *is_grat_arp_locked)
 251 {
 252     tag_type tag = 0;
 253     return mac_learning_lookup_tag(ml, dst, vlan, &tag, is_grat_arp_locked);
 254 }
 255
 256 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml'.  Returns the port on which a
 257  * frame destined for 'dst' should be sent, -1 if unknown.
 258  *
 259  * Adds to '*tag' (which the caller must have initialized) the tag that should
 260  * be attached to any flow created based on the return value, if any, to allow
 261  * those flows to be revalidated when the MAC learning entry changes.
 262  *
 263  * 'is_grat_arp_locked' is an optional parameter that returns whether the entry
 264  * is currently locked.*/
 265 int
 266 mac_learning_lookup_tag(const struct mac_learning *ml,
 267                         const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan,
 268                         tag_type *tag, bool *is_grat_arp_locked)
 269 {
 270     if (eth_addr_is_multicast(dst) || !is_learning_vlan(ml, vlan)) {
 271         return -1;
 272     } else {
 273         struct mac_entry *e = search_bucket(mac_table_bucket(ml, dst, vlan),
 274                                             dst, vlan);
 275         if (e) {
 276             *tag |= e->tag;
 277
 278             if (is_grat_arp_locked) {
 279                 *is_grat_arp_locked = time_now() < e->grat_arp_lock;
 280             }
 281
 282             return e->port;
 283         } else {
 284             *tag |= make_unknown_mac_tag(ml, dst, vlan);
 285             return -1;
 286         }
 287     }
 288 }
 289
 290 /* Expires all the mac-learning entries in 'ml'.  The tags in 'ml' are
 291  * discarded, so the client is responsible for revalidating any flows that
 292  * depend on 'ml', if necessary. */
 293 void
 294 mac_learning_flush(struct mac_learning *ml)
 295 {
 296     struct mac_entry *e;
 297     while (get_lru(ml, &e)){
 298         free_mac_entry(ml, e);
 299     }
 300 }
 301
 302 void
 303 mac_learning_run(struct mac_learning *ml, struct tag_set *set)
 304 {
 305     struct mac_entry *e;
 306     while (get_lru(ml, &e) && time_now() >= e->expires) {
 307         COVERAGE_INC(mac_learning_expired);
 308         if (set) {
 309             tag_set_add(set, e->tag);
 310         }
 311         free_mac_entry(ml, e);
 312     }
 313 }
 314
 315 void
 316 mac_learning_wait(struct mac_learning *ml)
 317 {
 318     if (!list_is_empty(&ml->lrus)) {
 319         struct mac_entry *e = mac_entry_from_lru_node(ml->lrus.next);
 320         poll_timer_wait_until(e->expires * 1000LL);
 321     }
 322 }