l2t.c

  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
 63static inline unsigned int vlan_prio(const struct l2t_entry *e)
 64{
 65	return e->vlan >> 13;
 66}
 67
 68static 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
 74static 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 */
 87static 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 = __skb_put(skb, sizeof(*req));
100	req->wr.wr_hi = htonl(V_WR_OP(FW_WROPCODE_FORWARD));
101	OPCODE_TID(req) = htonl(MK_OPCODE_TID(CPL_L2T_WRITE_REQ, e->idx));
102	req->params = htonl(V_L2T_W_IDX(e->idx) | V_L2T_W_IFF(e->smt_idx) |
103			    V_L2T_W_VLAN(e->vlan & VLAN_VID_MASK) |
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));
107	skb->priority = CPL_PRIORITY_CONTROL;
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 */
123static inline void arpq_enqueue(struct l2t_entry *e, struct sk_buff *skb)
124{
125	__skb_queue_tail(&e->arpq, skb);
126}
127
128int t3_l2t_send_slow(struct t3cdev *dev, struct sk_buff *skb,
129		     struct l2t_entry *e)
130{
131again:
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		fallthrough;
140	case L2T_STATE_VALID:	/* fast-path, send the packet on */
141		return cxgb3_ofld_send(dev, skb);
142	case L2T_STATE_RESOLVING:
143		spin_lock_bh(&e->lock);
144		if (e->state != L2T_STATE_RESOLVING) {
145			/* ARP already completed */
146			spin_unlock_bh(&e->lock);
147			goto again;
148		}
149		arpq_enqueue(e, skb);
150		spin_unlock_bh(&e->lock);
151
152		/*
153		 * Only the first packet added to the arpq should kick off
154		 * resolution.  However, because the alloc_skb below can fail,
155		 * we allow each packet added to the arpq to retry resolution
156		 * as a way of recovering from transient memory exhaustion.
157		 * A better way would be to use a work request to retry L2T
158		 * entries when there's no memory.
159		 */
160		if (!neigh_event_send(e->neigh, NULL)) {
161			skb = alloc_skb(sizeof(struct cpl_l2t_write_req),
162					GFP_ATOMIC);
163			if (!skb)
164				break;
165
166			spin_lock_bh(&e->lock);
167			if (!skb_queue_empty(&e->arpq))
168				setup_l2e_send_pending(dev, skb, e);
169			else	/* we lost the race */
170				__kfree_skb(skb);
171			spin_unlock_bh(&e->lock);
172		}
173	}
174	return 0;
175}
176
177EXPORT_SYMBOL(t3_l2t_send_slow);
178
179/*
180 * Allocate a free L2T entry.  Must be called with l2t_data.lock held.
181 */
182static struct l2t_entry *alloc_l2e(struct l2t_data *d)
183{
184	struct l2t_entry *end, *e, **p;
185
186	if (!atomic_read(&d->nfree))
187		return NULL;
188
189	/* there's definitely a free entry */
190	for (e = d->rover, end = &d->l2tab[d->nentries]; e != end; ++e)
191		if (atomic_read(&e->refcnt) == 0)
192			goto found;
193
194	for (e = &d->l2tab[1]; atomic_read(&e->refcnt); ++e) ;
195found:
196	d->rover = e + 1;
197	atomic_dec(&d->nfree);
198
199	/*
200	 * The entry we found may be an inactive entry that is
201	 * presently in the hash table.  We need to remove it.
202	 */
203	if (e->state != L2T_STATE_UNUSED) {
204		int hash = arp_hash(e->addr, e->ifindex, d);
205
206		for (p = &d->l2tab[hash].first; *p; p = &(*p)->next)
207			if (*p == e) {
208				*p = e->next;
209				break;
210			}
211		e->state = L2T_STATE_UNUSED;
212	}
213	return e;
214}
215
216/*
217 * Called when an L2T entry has no more users.  The entry is left in the hash
218 * table since it is likely to be reused but we also bump nfree to indicate
219 * that the entry can be reallocated for a different neighbor.  We also drop
220 * the existing neighbor reference in case the neighbor is going away and is
221 * waiting on our reference.
222 *
223 * Because entries can be reallocated to other neighbors once their ref count
224 * drops to 0 we need to take the entry's lock to avoid races with a new
225 * incarnation.
226 */
227void t3_l2e_free(struct l2t_data *d, struct l2t_entry *e)
228{
229	spin_lock_bh(&e->lock);
230	if (atomic_read(&e->refcnt) == 0) {	/* hasn't been recycled */
231		if (e->neigh) {
232			neigh_release(e->neigh);
233			e->neigh = NULL;
234		}
235	}
236	spin_unlock_bh(&e->lock);
237	atomic_inc(&d->nfree);
238}
239
240EXPORT_SYMBOL(t3_l2e_free);
241
242/*
243 * Update an L2T entry that was previously used for the same next hop as neigh.
244 * Must be called with softirqs disabled.
245 */
246static inline void reuse_entry(struct l2t_entry *e, struct neighbour *neigh)
247{
248	unsigned int nud_state;
249
250	spin_lock(&e->lock);	/* avoid race with t3_l2t_free */
251
252	if (neigh != e->neigh)
253		neigh_replace(e, neigh);
254	nud_state = neigh->nud_state;
255	if (memcmp(e->dmac, neigh->ha, sizeof(e->dmac)) ||
256	    !(nud_state & NUD_VALID))
257		e->state = L2T_STATE_RESOLVING;
258	else if (nud_state & NUD_CONNECTED)
259		e->state = L2T_STATE_VALID;
260	else
261		e->state = L2T_STATE_STALE;
262	spin_unlock(&e->lock);
263}
264
265struct l2t_entry *t3_l2t_get(struct t3cdev *cdev, struct dst_entry *dst,
266			     struct net_device *dev, const void *daddr)
267{
268	struct l2t_entry *e = NULL;
269	struct neighbour *neigh;
270	struct port_info *p;
271	struct l2t_data *d;
272	int hash;
273	u32 addr;
274	int ifidx;
275	int smt_idx;
276
277	rcu_read_lock();
278	neigh = dst_neigh_lookup(dst, daddr);
279	if (!neigh)
280		goto done_rcu;
281
282	addr = *(u32 *) neigh->primary_key;
283	ifidx = neigh->dev->ifindex;
284
285	if (!dev)
286		dev = neigh->dev;
287	p = netdev_priv(dev);
288	smt_idx = p->port_id;
289
290	d = L2DATA(cdev);
291	if (!d)
292		goto done_rcu;
293
294	hash = arp_hash(addr, ifidx, d);
295
296	write_lock_bh(&d->lock);
297	for (e = d->l2tab[hash].first; e; e = e->next)
298		if (e->addr == addr && e->ifindex == ifidx &&
299		    e->smt_idx == smt_idx) {
300			l2t_hold(d, e);
301			if (atomic_read(&e->refcnt) == 1)
302				reuse_entry(e, neigh);
303			goto done_unlock;
304		}
305
306	/* Need to allocate a new entry */
307	e = alloc_l2e(d);
308	if (e) {
309		spin_lock(&e->lock);	/* avoid race with t3_l2t_free */
310		e->next = d->l2tab[hash].first;
311		d->l2tab[hash].first = e;
312		e->state = L2T_STATE_RESOLVING;
313		e->addr = addr;
314		e->ifindex = ifidx;
315		e->smt_idx = smt_idx;
316		atomic_set(&e->refcnt, 1);
317		neigh_replace(e, neigh);
318		if (is_vlan_dev(neigh->dev))
319			e->vlan = vlan_dev_vlan_id(neigh->dev);
320		else
321			e->vlan = VLAN_NONE;
322		spin_unlock(&e->lock);
323	}
324done_unlock:
325	write_unlock_bh(&d->lock);
326done_rcu:
327	if (neigh)
328		neigh_release(neigh);
329	rcu_read_unlock();
330	return e;
331}
332
333EXPORT_SYMBOL(t3_l2t_get);
334
335/*
336 * Called when address resolution fails for an L2T entry to handle packets
337 * on the arpq head.  If a packet specifies a failure handler it is invoked,
338 * otherwise the packets is sent to the offload device.
339 *
340 * XXX: maybe we should abandon the latter behavior and just require a failure
341 * handler.
342 */
343static void handle_failed_resolution(struct t3cdev *dev, struct sk_buff_head *arpq)
344{
345	struct sk_buff *skb, *tmp;
346
347	skb_queue_walk_safe(arpq, skb, tmp) {
348		struct l2t_skb_cb *cb = L2T_SKB_CB(skb);
349
350		__skb_unlink(skb, arpq);
351		if (cb->arp_failure_handler)
352			cb->arp_failure_handler(dev, skb);
353		else
354			cxgb3_ofld_send(dev, skb);
355	}
356}
357
358/*
359 * Called when the host's ARP layer makes a change to some entry that is
360 * loaded into the HW L2 table.
361 */
362void t3_l2t_update(struct t3cdev *dev, struct neighbour *neigh)
363{
364	struct sk_buff_head arpq;
365	struct l2t_entry *e;
366	struct l2t_data *d = L2DATA(dev);
367	u32 addr = *(u32 *) neigh->primary_key;
368	int ifidx = neigh->dev->ifindex;
369	int hash = arp_hash(addr, ifidx, d);
370
371	read_lock_bh(&d->lock);
372	for (e = d->l2tab[hash].first; e; e = e->next)
373		if (e->addr == addr && e->ifindex == ifidx) {
374			spin_lock(&e->lock);
375			goto found;
376		}
377	read_unlock_bh(&d->lock);
378	return;
379
380found:
381	__skb_queue_head_init(&arpq);
382
383	read_unlock(&d->lock);
384	if (atomic_read(&e->refcnt)) {
385		if (neigh != e->neigh)
386			neigh_replace(e, neigh);
387
388		if (e->state == L2T_STATE_RESOLVING) {
389			if (neigh->nud_state & NUD_FAILED) {
390				skb_queue_splice_init(&e->arpq, &arpq);
391			} else if (neigh->nud_state & (NUD_CONNECTED|NUD_STALE))
392				setup_l2e_send_pending(dev, NULL, e);
393		} else {
394			e->state = neigh->nud_state & NUD_CONNECTED ?
395			    L2T_STATE_VALID : L2T_STATE_STALE;
396			if (!ether_addr_equal(e->dmac, neigh->ha))
397				setup_l2e_send_pending(dev, NULL, e);
398		}
399	}
400	spin_unlock_bh(&e->lock);
401
402	if (!skb_queue_empty(&arpq))
403		handle_failed_resolution(dev, &arpq);
404}
405
406struct l2t_data *t3_init_l2t(unsigned int l2t_capacity)
407{
408	struct l2t_data *d;
409	int i;
410
411	d = kvzalloc(struct_size(d, l2tab, l2t_capacity), GFP_KERNEL);
412	if (!d)
413		return NULL;
414
415	d->nentries = l2t_capacity;
416	d->rover = &d->l2tab[1];	/* entry 0 is not used */
417	atomic_set(&d->nfree, l2t_capacity - 1);
418	rwlock_init(&d->lock);
419
420	for (i = 0; i < l2t_capacity; ++i) {
421		d->l2tab[i].idx = i;
422		d->l2tab[i].state = L2T_STATE_UNUSED;
423		__skb_queue_head_init(&d->l2tab[i].arpq);
424		spin_lock_init(&d->l2tab[i].lock);
425		atomic_set(&d->l2tab[i].refcnt, 0);
426	}
427	return d;
428}