lib/mac-learning.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012 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 <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 "unaligned.h"
  32 #include "util.h"
  33 #include "vlan-bitmap.h"
  34 #include "vlog.h"
  35
  36 VLOG_DEFINE_THIS_MODULE(mac_learning);
  37
  38 COVERAGE_DEFINE(mac_learning_learned);
  39 COVERAGE_DEFINE(mac_learning_expired);
  40
  41 /* Returns the number of seconds since 'e' (within 'ml') was last learned. */
  42 int
  43 mac_entry_age(const struct mac_learning *ml, const struct mac_entry *e)
  44 {
  45     time_t remaining = e->expires - time_now();
  46     return ml->idle_time - remaining;
  47 }
  48
  49 static uint32_t
  50 mac_table_hash(const struct mac_learning *ml, const uint8_t mac[ETH_ADDR_LEN],
  51                uint16_t vlan)
  52 {
  53     unsigned int mac1 = get_unaligned_u32((uint32_t *) mac);
  54     unsigned int mac2 = get_unaligned_u16((uint16_t *) (mac + 4));
  55     return hash_3words(mac1, mac2 | (vlan << 16), ml->secret);
  56 }
  57
  58 static struct mac_entry *
  59 mac_entry_from_lru_node(struct list *list)
  60 {
  61     return CONTAINER_OF(list, struct mac_entry, lru_node);
  62 }
  63
  64 /* Returns a tag that represents that 'mac' is on an unknown port in 'vlan'.
  65  * (When we learn where 'mac' is in 'vlan', this allows flows that were
  66  * flooded to be revalidated.) */
  67 static tag_type
  68 make_unknown_mac_tag(const struct mac_learning *ml,
  69                      const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  70 {
  71     return tag_create_deterministic(mac_table_hash(ml, mac, vlan));
  72 }
  73
  74 static struct mac_entry *
  75 mac_entry_lookup(const struct mac_learning *ml,
  76                  const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  77 {
  78     struct mac_entry *e;
  79
  80     HMAP_FOR_EACH_WITH_HASH (e, hmap_node, mac_table_hash(ml, mac, vlan),
  81                              &ml->table) {
  82         if (e->vlan == vlan && eth_addr_equals(e->mac, mac)) {
  83             return e;
  84         }
  85     }
  86     return NULL;
  87 }
  88
  89 /* If the LRU list is not empty, stores the least-recently-used entry in '*e'
  90  * and returns true.  Otherwise, if the LRU list is empty, stores NULL in '*e'
  91  * and return false. */
  92 static bool
  93 get_lru(struct mac_learning *ml, struct mac_entry **e)
  94 {
  95     if (!list_is_empty(&ml->lrus)) {
  96         *e = mac_entry_from_lru_node(ml->lrus.next);
  97         return true;
  98     } else {
  99         *e = NULL;
 100         return false;
 101     }
 102 }
 103
 104 static unsigned int
 105 normalize_idle_time(unsigned int idle_time)
 106 {
 107     return (idle_time < 15 ? 15
 108             : idle_time > 3600 ? 3600
 109             : idle_time);
 110 }
 111
 112 /* Creates and returns a new MAC learning table with an initial MAC aging
 113  * timeout of 'idle_time' seconds. */
 114 struct mac_learning *
 115 mac_learning_create(unsigned int idle_time)
 116 {
 117     struct mac_learning *ml;
 118
 119     ml = xmalloc(sizeof *ml);
 120     list_init(&ml->lrus);
 121     hmap_init(&ml->table);
 122     ml->secret = random_uint32();
 123     ml->flood_vlans = NULL;
 124     ml->idle_time = normalize_idle_time(idle_time);
 125     return ml;
 126 }
 127
 128 /* Destroys MAC learning table 'ml'. */
 129 void
 130 mac_learning_destroy(struct mac_learning *ml)
 131 {
 132     if (ml) {
 133         struct mac_entry *e, *next;
 134
 135         HMAP_FOR_EACH_SAFE (e, next, hmap_node, &ml->table) {
 136             hmap_remove(&ml->table, &e->hmap_node);
 137             free(e);
 138         }
 139         hmap_destroy(&ml->table);
 140
 141         bitmap_free(ml->flood_vlans);
 142         free(ml);
 143     }
 144 }
 145
 146 /* Provides a bitmap of VLANs which have learning disabled, that is, VLANs on
 147  * which all packets are flooded.  Returns true if the set has changed from the
 148  * previous value. */
 149 bool
 150 mac_learning_set_flood_vlans(struct mac_learning *ml,
 151                              const unsigned long *bitmap)
 152 {
 153     if (vlan_bitmap_equal(ml->flood_vlans, bitmap)) {
 154         return false;
 155     } else {
 156         bitmap_free(ml->flood_vlans);
 157         ml->flood_vlans = vlan_bitmap_clone(bitmap);
 158         return true;
 159     }
 160 }
 161
 162 /* Changes the MAC aging timeout of 'ml' to 'idle_time' seconds. */
 163 void
 164 mac_learning_set_idle_time(struct mac_learning *ml, unsigned int idle_time)
 165 {
 166     idle_time = normalize_idle_time(idle_time);
 167     if (idle_time != ml->idle_time) {
 168         struct mac_entry *e;
 169         int delta;
 170
 171         delta = (int) idle_time - (int) ml->idle_time;
 172         LIST_FOR_EACH (e, lru_node, &ml->lrus) {
 173             e->expires += delta;
 174         }
 175         ml->idle_time = idle_time;
 176     }
 177 }
 178
 179 static bool
 180 is_learning_vlan(const struct mac_learning *ml, uint16_t vlan)
 181 {
 182     return !ml->flood_vlans || !bitmap_is_set(ml->flood_vlans, vlan);
 183 }
 184
 185 /* Returns true if 'src_mac' may be learned on 'vlan' for 'ml'.
 186  * Returns false if 'ml' is NULL, if src_mac is not valid for learning, or if
 187  * 'vlan' is configured on 'ml' to flood all packets. */
 188 bool
 189 mac_learning_may_learn(const struct mac_learning *ml,
 190                        const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 191 {
 192     return ml && is_learning_vlan(ml, vlan) && !eth_addr_is_multicast(src_mac);
 193 }
 194
 195 /* Searches 'ml' for and returns a MAC learning entry for 'src_mac' in 'vlan',
 196  * inserting a new entry if necessary.  The caller must have already verified,
 197  * by calling mac_learning_may_learn(), that 'src_mac' and 'vlan' are
 198  * learnable.
 199  *
 200  * If the returned MAC entry is new (as may be determined by calling
 201  * mac_entry_is_new()), then the caller must pass the new entry to
 202  * mac_learning_changed().  The caller must also initialize the new entry's
 203  * 'port' member.  Otherwise calling those functions is at the caller's
 204  * discretion. */
 205 struct mac_entry *
 206 mac_learning_insert(struct mac_learning *ml,
 207                     const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 208 {
 209     struct mac_entry *e;
 210
 211     e = mac_entry_lookup(ml, src_mac, vlan);
 212     if (!e) {
 213         uint32_t hash = mac_table_hash(ml, src_mac, vlan);
 214
 215         if (hmap_count(&ml->table) >= MAC_MAX) {
 216             get_lru(ml, &e);
 217             mac_learning_expire(ml, e);
 218         }
 219
 220         e = xmalloc(sizeof *e);
 221         hmap_insert(&ml->table, &e->hmap_node, hash);
 222         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
 223         e->vlan = vlan;
 224         e->tag = 0;
 225         e->grat_arp_lock = TIME_MIN;
 226     } else {
 227         list_remove(&e->lru_node);
 228     }
 229
 230     /* Mark 'e' as recently used. */
 231     list_push_back(&ml->lrus, &e->lru_node);
 232     e->expires = time_now() + ml->idle_time;
 233
 234     return e;
 235 }
 236
 237 /* Changes 'e''s tag to a new, randomly selected one, and returns the tag that
 238  * would have been previously used for this entry's MAC and VLAN (either before
 239  * 'e' was inserted, if it is new, or otherwise before its port was updated.)
 240  *
 241  * The client should call this function after obtaining a MAC learning entry
 242  * from mac_learning_insert(), if the entry is either new or if its learned
 243  * port has changed. */
 244 tag_type
 245 mac_learning_changed(struct mac_learning *ml, struct mac_entry *e)
 246 {
 247     tag_type old_tag = e->tag;
 248
 249     COVERAGE_INC(mac_learning_learned);
 250
 251     e->tag = tag_create_random();
 252     return old_tag ? old_tag : make_unknown_mac_tag(ml, e->mac, e->vlan);
 253 }
 254
 255 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml' and returns the associated MAC
 256  * learning entry, if any.  If 'tag' is nonnull, then the tag that associates
 257  * 'dst' and 'vlan' with its currently learned port will be OR'd into
 258  * '*tag'. */
 259 struct mac_entry *
 260 mac_learning_lookup(const struct mac_learning *ml,
 261                     const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan,
 262                     tag_type *tag)
 263 {
 264     if (eth_addr_is_multicast(dst)) {
 265         /* No tag because the treatment of multicast destinations never
 266          * changes. */
 267         return NULL;
 268     } else if (!is_learning_vlan(ml, vlan)) {
 269         /* We don't tag this property.  The set of learning VLANs changes so
 270          * rarely that we revalidate every flow when it changes. */
 271         return NULL;
 272     } else {
 273         struct mac_entry *e = mac_entry_lookup(ml, dst, vlan);
 274
 275         assert(e == NULL || e->tag != 0);
 276         if (tag) {
 277             /* Tag either the learned port or the lack thereof. */
 278             *tag |= e ? e->tag : make_unknown_mac_tag(ml, dst, vlan);
 279         }
 280         return e;
 281     }
 282 }
 283
 284 /* Expires 'e' from the 'ml' hash table. */
 285 void
 286 mac_learning_expire(struct mac_learning *ml, struct mac_entry *e)
 287 {
 288     hmap_remove(&ml->table, &e->hmap_node);
 289     list_remove(&e->lru_node);
 290     free(e);
 291 }
 292
 293 /* Expires all the mac-learning entries in 'ml'.  If not NULL, the tags in 'ml'
 294  * are added to 'tags'.  Otherwise the tags in 'ml' are discarded.  The client
 295  * is responsible for revalidating any flows that depend on 'ml', if
 296  * necessary. */
 297 void
 298 mac_learning_flush(struct mac_learning *ml, struct tag_set *tags)
 299 {
 300     struct mac_entry *e;
 301     while (get_lru(ml, &e)){
 302         if (tags) {
 303             tag_set_add(tags, e->tag);
 304         }
 305         mac_learning_expire(ml, e);
 306     }
 307     hmap_shrink(&ml->table);
 308 }
 309
 310 void
 311 mac_learning_run(struct mac_learning *ml, struct tag_set *set)
 312 {
 313     struct mac_entry *e;
 314     while (get_lru(ml, &e) && time_now() >= e->expires) {
 315         COVERAGE_INC(mac_learning_expired);
 316         if (set) {
 317             tag_set_add(set, e->tag);
 318         }
 319         mac_learning_expire(ml, e);
 320     }
 321 }
 322
 323 void
 324 mac_learning_wait(struct mac_learning *ml)
 325 {
 326     if (!list_is_empty(&ml->lrus)) {
 327         struct mac_entry *e = mac_entry_from_lru_node(ml->lrus.next);
 328         poll_timer_wait_until(e->expires * 1000LL);
 329     }
 330 }