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l2t.c
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1 /*
2  * Copyright (c) 2003-2008 Chelsio, Inc. All rights reserved.
3  *
4  * This software is available to you under a choice of one of two
5  * licenses. You may choose to be licensed under the terms of the GNU
6  * General Public License (GPL) Version 2, available from the file
7  * COPYING in the main directory of this source tree, or the
8  * OpenIB.org BSD license below:
9  *
10  * Redistribution and use in source and binary forms, with or
11  * without modification, are permitted provided that the following
12  * conditions are met:
13  *
14  * - Redistributions of source code must retain the above
15  * copyright notice, this list of conditions and the following
16  * disclaimer.
17  *
18  * - Redistributions in binary form must reproduce the above
19  * copyright notice, this list of conditions and the following
20  * disclaimer in the documentation and/or other materials
21  * provided with the distribution.
22  *
23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
30  * SOFTWARE.
31  */
32 #include <linux/skbuff.h>
33 #include <linux/netdevice.h>
34 #include <linux/if.h>
35 #include <linux/if_vlan.h>
36 #include <linux/jhash.h>
37 #include <linux/slab.h>
38 #include <linux/export.h>
39 #include <net/neighbour.h>
40 #include "common.h"
41 #include "t3cdev.h"
42 #include "cxgb3_defs.h"
43 #include "l2t.h"
44 #include "t3_cpl.h"
45 #include "firmware_exports.h"
46 
47 #define VLAN_NONE 0xfff
48 
49 /*
50  * Module locking notes: There is a RW lock protecting the L2 table as a
51  * whole plus a spinlock per L2T entry. Entry lookups and allocations happen
52  * under the protection of the table lock, individual entry changes happen
53  * while holding that entry's spinlock. The table lock nests outside the
54  * entry locks. Allocations of new entries take the table lock as writers so
55  * no other lookups can happen while allocating new entries. Entry updates
56  * take the table lock as readers so multiple entries can be updated in
57  * parallel. An L2T entry can be dropped by decrementing its reference count
58  * and therefore can happen in parallel with entry allocation but no entry
59  * can change state or increment its ref count during allocation as both of
60  * these perform lookups.
61  */
62 
63 static inline unsigned int vlan_prio(const struct l2t_entry *e)
64 {
65  return e->vlan >> 13;
66 }
67 
68 static inline unsigned int arp_hash(u32 key, int ifindex,
69  const struct l2t_data *d)
70 {
71  return jhash_2words(key, ifindex, 0) & (d->nentries - 1);
72 }
73 
74 static inline void neigh_replace(struct l2t_entry *e, struct neighbour *n)
75 {
76  neigh_hold(n);
77  if (e->neigh)
78  neigh_release(e->neigh);
79  e->neigh = n;
80 }
81 
82 /*
83  * Set up an L2T entry and send any packets waiting in the arp queue. The
84  * supplied skb is used for the CPL_L2T_WRITE_REQ. Must be called with the
85  * entry locked.
86  */
87 static int setup_l2e_send_pending(struct t3cdev *dev, struct sk_buff *skb,
88  struct l2t_entry *e)
89 {
90  struct cpl_l2t_write_req *req;
91  struct sk_buff *tmp;
92 
93  if (!skb) {
94  skb = alloc_skb(sizeof(*req), GFP_ATOMIC);
95  if (!skb)
96  return -ENOMEM;
97  }
98 
99  req = (struct cpl_l2t_write_req *)__skb_put(skb, sizeof(*req));
100  req->wr.wr_hi = htonl(V_WR_OP(FW_WROPCODE_FORWARD));
102  req->params = htonl(V_L2T_W_IDX(e->idx) | V_L2T_W_IFF(e->smt_idx) |
104  V_L2T_W_PRIO(vlan_prio(e)));
105  memcpy(e->dmac, e->neigh->ha, sizeof(e->dmac));
106  memcpy(req->dst_mac, e->dmac, sizeof(req->dst_mac));
108  cxgb3_ofld_send(dev, skb);
109 
110  skb_queue_walk_safe(&e->arpq, skb, tmp) {
111  __skb_unlink(skb, &e->arpq);
112  cxgb3_ofld_send(dev, skb);
113  }
114  e->state = L2T_STATE_VALID;
115 
116  return 0;
117 }
118 
119 /*
120  * Add a packet to the an L2T entry's queue of packets awaiting resolution.
121  * Must be called with the entry's lock held.
122  */
123 static inline void arpq_enqueue(struct l2t_entry *e, struct sk_buff *skb)
124 {
125  __skb_queue_tail(&e->arpq, skb);
126 }
127 
128 int t3_l2t_send_slow(struct t3cdev *dev, struct sk_buff *skb,
129  struct l2t_entry *e)
130 {
131 again:
132  switch (e->state) {
133  case L2T_STATE_STALE: /* entry is stale, kick off revalidation */
134  neigh_event_send(e->neigh, NULL);
135  spin_lock_bh(&e->lock);
136  if (e->state == L2T_STATE_STALE)
137  e->state = L2T_STATE_VALID;
138  spin_unlock_bh(&e->lock);
139  case L2T_STATE_VALID: /* fast-path, send the packet on */
140  return cxgb3_ofld_send(dev, skb);
141  case L2T_STATE_RESOLVING:
142  spin_lock_bh(&e->lock);
143  if (e->state != L2T_STATE_RESOLVING) {
144  /* ARP already completed */
145  spin_unlock_bh(&e->lock);
146  goto again;
147  }
148  arpq_enqueue(e, skb);
149  spin_unlock_bh(&e->lock);
150 
151  /*
152  * Only the first packet added to the arpq should kick off
153  * resolution. However, because the alloc_skb below can fail,
154  * we allow each packet added to the arpq to retry resolution
155  * as a way of recovering from transient memory exhaustion.
156  * A better way would be to use a work request to retry L2T
157  * entries when there's no memory.
158  */
159  if (!neigh_event_send(e->neigh, NULL)) {
160  skb = alloc_skb(sizeof(struct cpl_l2t_write_req),
161  GFP_ATOMIC);
162  if (!skb)
163  break;
164 
165  spin_lock_bh(&e->lock);
166  if (!skb_queue_empty(&e->arpq))
167  setup_l2e_send_pending(dev, skb, e);
168  else /* we lost the race */
169  __kfree_skb(skb);
170  spin_unlock_bh(&e->lock);
171  }
172  }
173  return 0;
174 }
175 
177 
178 void t3_l2t_send_event(struct t3cdev *dev, struct l2t_entry *e)
179 {
180 again:
181  switch (e->state) {
182  case L2T_STATE_STALE: /* entry is stale, kick off revalidation */
183  neigh_event_send(e->neigh, NULL);
184  spin_lock_bh(&e->lock);
185  if (e->state == L2T_STATE_STALE) {
186  e->state = L2T_STATE_VALID;
187  }
188  spin_unlock_bh(&e->lock);
189  return;
190  case L2T_STATE_VALID: /* fast-path, send the packet on */
191  return;
192  case L2T_STATE_RESOLVING:
193  spin_lock_bh(&e->lock);
194  if (e->state != L2T_STATE_RESOLVING) {
195  /* ARP already completed */
196  spin_unlock_bh(&e->lock);
197  goto again;
198  }
199  spin_unlock_bh(&e->lock);
200 
201  /*
202  * Only the first packet added to the arpq should kick off
203  * resolution. However, because the alloc_skb below can fail,
204  * we allow each packet added to the arpq to retry resolution
205  * as a way of recovering from transient memory exhaustion.
206  * A better way would be to use a work request to retry L2T
207  * entries when there's no memory.
208  */
209  neigh_event_send(e->neigh, NULL);
210  }
211 }
212 
214 
215 /*
216  * Allocate a free L2T entry. Must be called with l2t_data.lock held.
217  */
218 static struct l2t_entry *alloc_l2e(struct l2t_data *d)
219 {
220  struct l2t_entry *end, *e, **p;
221 
222  if (!atomic_read(&d->nfree))
223  return NULL;
224 
225  /* there's definitely a free entry */
226  for (e = d->rover, end = &d->l2tab[d->nentries]; e != end; ++e)
227  if (atomic_read(&e->refcnt) == 0)
228  goto found;
229 
230  for (e = &d->l2tab[1]; atomic_read(&e->refcnt); ++e) ;
231 found:
232  d->rover = e + 1;
233  atomic_dec(&d->nfree);
234 
235  /*
236  * The entry we found may be an inactive entry that is
237  * presently in the hash table. We need to remove it.
238  */
239  if (e->state != L2T_STATE_UNUSED) {
240  int hash = arp_hash(e->addr, e->ifindex, d);
241 
242  for (p = &d->l2tab[hash].first; *p; p = &(*p)->next)
243  if (*p == e) {
244  *p = e->next;
245  break;
246  }
247  e->state = L2T_STATE_UNUSED;
248  }
249  return e;
250 }
251 
252 /*
253  * Called when an L2T entry has no more users. The entry is left in the hash
254  * table since it is likely to be reused but we also bump nfree to indicate
255  * that the entry can be reallocated for a different neighbor. We also drop
256  * the existing neighbor reference in case the neighbor is going away and is
257  * waiting on our reference.
258  *
259  * Because entries can be reallocated to other neighbors once their ref count
260  * drops to 0 we need to take the entry's lock to avoid races with a new
261  * incarnation.
262  */
263 void t3_l2e_free(struct l2t_data *d, struct l2t_entry *e)
264 {
265  spin_lock_bh(&e->lock);
266  if (atomic_read(&e->refcnt) == 0) { /* hasn't been recycled */
267  if (e->neigh) {
268  neigh_release(e->neigh);
269  e->neigh = NULL;
270  }
271  }
272  spin_unlock_bh(&e->lock);
273  atomic_inc(&d->nfree);
274 }
275 
277 
278 /*
279  * Update an L2T entry that was previously used for the same next hop as neigh.
280  * Must be called with softirqs disabled.
281  */
282 static inline void reuse_entry(struct l2t_entry *e, struct neighbour *neigh)
283 {
284  unsigned int nud_state;
285 
286  spin_lock(&e->lock); /* avoid race with t3_l2t_free */
287 
288  if (neigh != e->neigh)
289  neigh_replace(e, neigh);
290  nud_state = neigh->nud_state;
291  if (memcmp(e->dmac, neigh->ha, sizeof(e->dmac)) ||
292  !(nud_state & NUD_VALID))
294  else if (nud_state & NUD_CONNECTED)
295  e->state = L2T_STATE_VALID;
296  else
297  e->state = L2T_STATE_STALE;
298  spin_unlock(&e->lock);
299 }
300 
301 struct l2t_entry *t3_l2t_get(struct t3cdev *cdev, struct dst_entry *dst,
302  struct net_device *dev, const void *daddr)
303 {
304  struct l2t_entry *e = NULL;
305  struct neighbour *neigh;
306  struct port_info *p;
307  struct l2t_data *d;
308  int hash;
309  u32 addr;
310  int ifidx;
311  int smt_idx;
312 
313  rcu_read_lock();
314  neigh = dst_neigh_lookup(dst, daddr);
315  if (!neigh)
316  goto done_rcu;
317 
318  addr = *(u32 *) neigh->primary_key;
319  ifidx = neigh->dev->ifindex;
320 
321  if (!dev)
322  dev = neigh->dev;
323  p = netdev_priv(dev);
324  smt_idx = p->port_id;
325 
326  d = L2DATA(cdev);
327  if (!d)
328  goto done_rcu;
329 
330  hash = arp_hash(addr, ifidx, d);
331 
332  write_lock_bh(&d->lock);
333  for (e = d->l2tab[hash].first; e; e = e->next)
334  if (e->addr == addr && e->ifindex == ifidx &&
335  e->smt_idx == smt_idx) {
336  l2t_hold(d, e);
337  if (atomic_read(&e->refcnt) == 1)
338  reuse_entry(e, neigh);
339  goto done_unlock;
340  }
341 
342  /* Need to allocate a new entry */
343  e = alloc_l2e(d);
344  if (e) {
345  spin_lock(&e->lock); /* avoid race with t3_l2t_free */
346  e->next = d->l2tab[hash].first;
347  d->l2tab[hash].first = e;
349  e->addr = addr;
350  e->ifindex = ifidx;
351  e->smt_idx = smt_idx;
352  atomic_set(&e->refcnt, 1);
353  neigh_replace(e, neigh);
354  if (neigh->dev->priv_flags & IFF_802_1Q_VLAN)
355  e->vlan = vlan_dev_vlan_id(neigh->dev);
356  else
357  e->vlan = VLAN_NONE;
358  spin_unlock(&e->lock);
359  }
360 done_unlock:
361  write_unlock_bh(&d->lock);
362 done_rcu:
363  if (neigh)
364  neigh_release(neigh);
365  rcu_read_unlock();
366  return e;
367 }
368 
370 
371 /*
372  * Called when address resolution fails for an L2T entry to handle packets
373  * on the arpq head. If a packet specifies a failure handler it is invoked,
374  * otherwise the packets is sent to the offload device.
375  *
376  * XXX: maybe we should abandon the latter behavior and just require a failure
377  * handler.
378  */
379 static void handle_failed_resolution(struct t3cdev *dev, struct sk_buff_head *arpq)
380 {
381  struct sk_buff *skb, *tmp;
382 
383  skb_queue_walk_safe(arpq, skb, tmp) {
384  struct l2t_skb_cb *cb = L2T_SKB_CB(skb);
385 
386  __skb_unlink(skb, arpq);
387  if (cb->arp_failure_handler)
388  cb->arp_failure_handler(dev, skb);
389  else
390  cxgb3_ofld_send(dev, skb);
391  }
392 }
393 
394 /*
395  * Called when the host's ARP layer makes a change to some entry that is
396  * loaded into the HW L2 table.
397  */
398 void t3_l2t_update(struct t3cdev *dev, struct neighbour *neigh)
399 {
400  struct sk_buff_head arpq;
401  struct l2t_entry *e;
402  struct l2t_data *d = L2DATA(dev);
403  u32 addr = *(u32 *) neigh->primary_key;
404  int ifidx = neigh->dev->ifindex;
405  int hash = arp_hash(addr, ifidx, d);
406 
407  read_lock_bh(&d->lock);
408  for (e = d->l2tab[hash].first; e; e = e->next)
409  if (e->addr == addr && e->ifindex == ifidx) {
410  spin_lock(&e->lock);
411  goto found;
412  }
413  read_unlock_bh(&d->lock);
414  return;
415 
416 found:
417  __skb_queue_head_init(&arpq);
418 
419  read_unlock(&d->lock);
420  if (atomic_read(&e->refcnt)) {
421  if (neigh != e->neigh)
422  neigh_replace(e, neigh);
423 
424  if (e->state == L2T_STATE_RESOLVING) {
425  if (neigh->nud_state & NUD_FAILED) {
426  skb_queue_splice_init(&e->arpq, &arpq);
427  } else if (neigh->nud_state & (NUD_CONNECTED|NUD_STALE))
428  setup_l2e_send_pending(dev, NULL, e);
429  } else {
430  e->state = neigh->nud_state & NUD_CONNECTED ?
432  if (memcmp(e->dmac, neigh->ha, 6))
433  setup_l2e_send_pending(dev, NULL, e);
434  }
435  }
436  spin_unlock_bh(&e->lock);
437 
438  if (!skb_queue_empty(&arpq))
439  handle_failed_resolution(dev, &arpq);
440 }
441 
442 struct l2t_data *t3_init_l2t(unsigned int l2t_capacity)
443 {
444  struct l2t_data *d;
445  int i, size = sizeof(*d) + l2t_capacity * sizeof(struct l2t_entry);
446 
447  d = cxgb_alloc_mem(size);
448  if (!d)
449  return NULL;
450 
451  d->nentries = l2t_capacity;
452  d->rover = &d->l2tab[1]; /* entry 0 is not used */
453  atomic_set(&d->nfree, l2t_capacity - 1);
454  rwlock_init(&d->lock);
455 
456  for (i = 0; i < l2t_capacity; ++i) {
457  d->l2tab[i].idx = i;
458  d->l2tab[i].state = L2T_STATE_UNUSED;
459  __skb_queue_head_init(&d->l2tab[i].arpq);
460  spin_lock_init(&d->l2tab[i].lock);
461  atomic_set(&d->l2tab[i].refcnt, 0);
462  }
463  return d;
464 }
465 
466 void t3_free_l2t(struct l2t_data *d)
467 {
468  cxgb_free_mem(d);
469 }
470