net: Fix for dst_negative_advice
[linux-2.6.git] / net / core / flow.c
1 /* flow.c: Generic flow cache.
2  *
3  * Copyright (C) 2003 Alexey N. Kuznetsov (kuznet@ms2.inr.ac.ru)
4  * Copyright (C) 2003 David S. Miller (davem@redhat.com)
5  */
6
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/list.h>
10 #include <linux/jhash.h>
11 #include <linux/interrupt.h>
12 #include <linux/mm.h>
13 #include <linux/random.h>
14 #include <linux/init.h>
15 #include <linux/slab.h>
16 #include <linux/smp.h>
17 #include <linux/completion.h>
18 #include <linux/percpu.h>
19 #include <linux/bitops.h>
20 #include <linux/notifier.h>
21 #include <linux/cpu.h>
22 #include <linux/cpumask.h>
23 #include <linux/mutex.h>
24 #include <net/flow.h>
25 #include <asm/atomic.h>
26 #include <linux/security.h>
27
28 struct flow_cache_entry {
29         struct flow_cache_entry *next;
30         u16                     family;
31         u8                      dir;
32         u32                     genid;
33         struct flowi            key;
34         void                    *object;
35         atomic_t                *object_ref;
36 };
37
38 atomic_t flow_cache_genid = ATOMIC_INIT(0);
39
40 static u32 flow_hash_shift;
41 #define flow_hash_size  (1 << flow_hash_shift)
42 static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };
43
44 #define flow_table(cpu) (per_cpu(flow_tables, cpu))
45
46 static struct kmem_cache *flow_cachep __read_mostly;
47
48 static int flow_lwm, flow_hwm;
49
50 struct flow_percpu_info {
51         int hash_rnd_recalc;
52         u32 hash_rnd;
53         int count;
54 };
55 static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };
56
57 #define flow_hash_rnd_recalc(cpu) \
58         (per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
59 #define flow_hash_rnd(cpu) \
60         (per_cpu(flow_hash_info, cpu).hash_rnd)
61 #define flow_count(cpu) \
62         (per_cpu(flow_hash_info, cpu).count)
63
64 static struct timer_list flow_hash_rnd_timer;
65
66 #define FLOW_HASH_RND_PERIOD    (10 * 60 * HZ)
67
68 struct flow_flush_info {
69         atomic_t cpuleft;
70         struct completion completion;
71 };
72 static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };
73
74 #define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))
75
76 static void flow_cache_new_hashrnd(unsigned long arg)
77 {
78         int i;
79
80         for_each_possible_cpu(i)
81                 flow_hash_rnd_recalc(i) = 1;
82
83         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
84         add_timer(&flow_hash_rnd_timer);
85 }
86
87 static void flow_entry_kill(int cpu, struct flow_cache_entry *fle)
88 {
89         if (fle->object)
90                 atomic_dec(fle->object_ref);
91         kmem_cache_free(flow_cachep, fle);
92         flow_count(cpu)--;
93 }
94
95 static void __flow_cache_shrink(int cpu, int shrink_to)
96 {
97         struct flow_cache_entry *fle, **flp;
98         int i;
99
100         for (i = 0; i < flow_hash_size; i++) {
101                 int k = 0;
102
103                 flp = &flow_table(cpu)[i];
104                 while ((fle = *flp) != NULL && k < shrink_to) {
105                         k++;
106                         flp = &fle->next;
107                 }
108                 while ((fle = *flp) != NULL) {
109                         *flp = fle->next;
110                         flow_entry_kill(cpu, fle);
111                 }
112         }
113 }
114
115 static void flow_cache_shrink(int cpu)
116 {
117         int shrink_to = flow_lwm / flow_hash_size;
118
119         __flow_cache_shrink(cpu, shrink_to);
120 }
121
122 static void flow_new_hash_rnd(int cpu)
123 {
124         get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
125         flow_hash_rnd_recalc(cpu) = 0;
126
127         __flow_cache_shrink(cpu, 0);
128 }
129
130 static u32 flow_hash_code(struct flowi *key, int cpu)
131 {
132         u32 *k = (u32 *) key;
133
134         return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
135                 (flow_hash_size - 1));
136 }
137
138 #if (BITS_PER_LONG == 64)
139 typedef u64 flow_compare_t;
140 #else
141 typedef u32 flow_compare_t;
142 #endif
143
144 /* I hear what you're saying, use memcmp.  But memcmp cannot make
145  * important assumptions that we can here, such as alignment and
146  * constant size.
147  */
148 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
149 {
150         flow_compare_t *k1, *k1_lim, *k2;
151         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
152
153         BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));
154
155         k1 = (flow_compare_t *) key1;
156         k1_lim = k1 + n_elem;
157
158         k2 = (flow_compare_t *) key2;
159
160         do {
161                 if (*k1++ != *k2++)
162                         return 1;
163         } while (k1 < k1_lim);
164
165         return 0;
166 }
167
168 void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
169                         flow_resolve_t resolver)
170 {
171         struct flow_cache_entry *fle, **head;
172         unsigned int hash;
173         int cpu;
174
175         local_bh_disable();
176         cpu = smp_processor_id();
177
178         fle = NULL;
179         /* Packet really early in init?  Making flow_cache_init a
180          * pre-smp initcall would solve this.  --RR */
181         if (!flow_table(cpu))
182                 goto nocache;
183
184         if (flow_hash_rnd_recalc(cpu))
185                 flow_new_hash_rnd(cpu);
186         hash = flow_hash_code(key, cpu);
187
188         head = &flow_table(cpu)[hash];
189         for (fle = *head; fle; fle = fle->next) {
190                 if (fle->family == family &&
191                     fle->dir == dir &&
192                     flow_key_compare(key, &fle->key) == 0) {
193                         if (fle->genid == atomic_read(&flow_cache_genid)) {
194                                 void *ret = fle->object;
195
196                                 if (ret)
197                                         atomic_inc(fle->object_ref);
198                                 local_bh_enable();
199
200                                 return ret;
201                         }
202                         break;
203                 }
204         }
205
206         if (!fle) {
207                 if (flow_count(cpu) > flow_hwm)
208                         flow_cache_shrink(cpu);
209
210                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
211                 if (fle) {
212                         fle->next = *head;
213                         *head = fle;
214                         fle->family = family;
215                         fle->dir = dir;
216                         memcpy(&fle->key, key, sizeof(*key));
217                         fle->object = NULL;
218                         flow_count(cpu)++;
219                 }
220         }
221
222 nocache:
223         {
224                 int err;
225                 void *obj;
226                 atomic_t *obj_ref;
227
228                 err = resolver(net, key, family, dir, &obj, &obj_ref);
229
230                 if (fle && !err) {
231                         fle->genid = atomic_read(&flow_cache_genid);
232
233                         if (fle->object)
234                                 atomic_dec(fle->object_ref);
235
236                         fle->object = obj;
237                         fle->object_ref = obj_ref;
238                         if (obj)
239                                 atomic_inc(fle->object_ref);
240                 }
241                 local_bh_enable();
242
243                 if (err)
244                         obj = ERR_PTR(err);
245                 return obj;
246         }
247 }
248
249 static void flow_cache_flush_tasklet(unsigned long data)
250 {
251         struct flow_flush_info *info = (void *)data;
252         int i;
253         int cpu;
254
255         cpu = smp_processor_id();
256         for (i = 0; i < flow_hash_size; i++) {
257                 struct flow_cache_entry *fle;
258
259                 fle = flow_table(cpu)[i];
260                 for (; fle; fle = fle->next) {
261                         unsigned genid = atomic_read(&flow_cache_genid);
262
263                         if (!fle->object || fle->genid == genid)
264                                 continue;
265
266                         fle->object = NULL;
267                         atomic_dec(fle->object_ref);
268                 }
269         }
270
271         if (atomic_dec_and_test(&info->cpuleft))
272                 complete(&info->completion);
273 }
274
275 static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
276 static void flow_cache_flush_per_cpu(void *data)
277 {
278         struct flow_flush_info *info = data;
279         int cpu;
280         struct tasklet_struct *tasklet;
281
282         cpu = smp_processor_id();
283
284         tasklet = flow_flush_tasklet(cpu);
285         tasklet->data = (unsigned long)info;
286         tasklet_schedule(tasklet);
287 }
288
289 void flow_cache_flush(void)
290 {
291         struct flow_flush_info info;
292         static DEFINE_MUTEX(flow_flush_sem);
293
294         /* Don't want cpus going down or up during this. */
295         get_online_cpus();
296         mutex_lock(&flow_flush_sem);
297         atomic_set(&info.cpuleft, num_online_cpus());
298         init_completion(&info.completion);
299
300         local_bh_disable();
301         smp_call_function(flow_cache_flush_per_cpu, &info, 0);
302         flow_cache_flush_tasklet((unsigned long)&info);
303         local_bh_enable();
304
305         wait_for_completion(&info.completion);
306         mutex_unlock(&flow_flush_sem);
307         put_online_cpus();
308 }
309
310 static void __init flow_cache_cpu_prepare(int cpu)
311 {
312         struct tasklet_struct *tasklet;
313         unsigned long order;
314
315         for (order = 0;
316              (PAGE_SIZE << order) <
317                      (sizeof(struct flow_cache_entry *)*flow_hash_size);
318              order++)
319                 /* NOTHING */;
320
321         flow_table(cpu) = (struct flow_cache_entry **)
322                 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
323         if (!flow_table(cpu))
324                 panic("NET: failed to allocate flow cache order %lu\n", order);
325
326         flow_hash_rnd_recalc(cpu) = 1;
327         flow_count(cpu) = 0;
328
329         tasklet = flow_flush_tasklet(cpu);
330         tasklet_init(tasklet, flow_cache_flush_tasklet, 0);
331 }
332
333 static int flow_cache_cpu(struct notifier_block *nfb,
334                           unsigned long action,
335                           void *hcpu)
336 {
337         if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
338                 __flow_cache_shrink((unsigned long)hcpu, 0);
339         return NOTIFY_OK;
340 }
341
342 static int __init flow_cache_init(void)
343 {
344         int i;
345
346         flow_cachep = kmem_cache_create("flow_cache",
347                                         sizeof(struct flow_cache_entry),
348                                         0, SLAB_PANIC,
349                                         NULL);
350         flow_hash_shift = 10;
351         flow_lwm = 2 * flow_hash_size;
352         flow_hwm = 4 * flow_hash_size;
353
354         setup_timer(&flow_hash_rnd_timer, flow_cache_new_hashrnd, 0);
355         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
356         add_timer(&flow_hash_rnd_timer);
357
358         for_each_possible_cpu(i)
359                 flow_cache_cpu_prepare(i);
360
361         hotcpu_notifier(flow_cache_cpu, 0);
362         return 0;
363 }
364
365 module_init(flow_cache_init);
366
367 EXPORT_SYMBOL(flow_cache_genid);
368 EXPORT_SYMBOL(flow_cache_lookup);