1 /* 2 * net/core/dst.c Protocol independent destination cache. 3 * 4 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> 5 * 6 */ 7 8 #include <linux/bitops.h> 9 #include <linux/errno.h> 10 #include <linux/init.h> 11 #include <linux/kernel.h> 12 #include <linux/mm.h> 13 #include <linux/module.h> 14 #include <linux/netdevice.h> 15 #include <linux/skbuff.h> 16 #include <linux/string.h> 17 #include <linux/types.h> 18 #include <net/net_namespace.h> 19 20 #include <net/dst.h> 21 22 /* Locking strategy: 23 * 1) Garbage collection state of dead destination cache 24 * entries is protected by dst_lock. 25 * 2) GC is run only from BH context, and is the only remover 26 * of entries. 27 * 3) Entries are added to the garbage list from both BH 28 * and non-BH context, so local BH disabling is needed. 29 * 4) All operations modify state, so a spinlock is used. 30 */ 31 static struct dst_entry *dst_garbage_list; 32 #if RT_CACHE_DEBUG >= 2 33 static atomic_t dst_total = ATOMIC_INIT(0); 34 #endif 35 static DEFINE_SPINLOCK(dst_lock); 36 37 static unsigned long dst_gc_timer_expires; 38 static unsigned long dst_gc_timer_inc = DST_GC_MAX; 39 static void dst_run_gc(unsigned long); 40 static void ___dst_free(struct dst_entry * dst); 41 42 static DEFINE_TIMER(dst_gc_timer, dst_run_gc, DST_GC_MIN, 0); 43 44 static void dst_run_gc(unsigned long dummy) 45 { 46 int delayed = 0; 47 int work_performed; 48 struct dst_entry * dst, **dstp; 49 50 if (!spin_trylock(&dst_lock)) { 51 mod_timer(&dst_gc_timer, jiffies + HZ/10); 52 return; 53 } 54 55 del_timer(&dst_gc_timer); 56 dstp = &dst_garbage_list; 57 work_performed = 0; 58 while ((dst = *dstp) != NULL) { 59 if (atomic_read(&dst->__refcnt)) { 60 dstp = &dst->next; 61 delayed++; 62 continue; 63 } 64 *dstp = dst->next; 65 work_performed = 1; 66 67 dst = dst_destroy(dst); 68 if (dst) { 69 /* NOHASH and still referenced. Unless it is already 70 * on gc list, invalidate it and add to gc list. 71 * 72 * Note: this is temporary. Actually, NOHASH dst's 73 * must be obsoleted when parent is obsoleted. 74 * But we do not have state "obsoleted, but 75 * referenced by parent", so it is right. 76 */ 77 if (dst->obsolete > 1) 78 continue; 79 80 ___dst_free(dst); 81 dst->next = *dstp; 82 *dstp = dst; 83 dstp = &dst->next; 84 } 85 } 86 if (!dst_garbage_list) { 87 dst_gc_timer_inc = DST_GC_MAX; 88 goto out; 89 } 90 if (!work_performed) { 91 if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX) 92 dst_gc_timer_expires = DST_GC_MAX; 93 dst_gc_timer_inc += DST_GC_INC; 94 } else { 95 dst_gc_timer_inc = DST_GC_INC; 96 dst_gc_timer_expires = DST_GC_MIN; 97 } 98 #if RT_CACHE_DEBUG >= 2 99 printk("dst_total: %d/%d %ld\n", 100 atomic_read(&dst_total), delayed, dst_gc_timer_expires); 101 #endif 102 /* if the next desired timer is more than 4 seconds in the future 103 * then round the timer to whole seconds 104 */ 105 if (dst_gc_timer_expires > 4*HZ) 106 mod_timer(&dst_gc_timer, 107 round_jiffies(jiffies + dst_gc_timer_expires)); 108 else 109 mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); 110 111 out: 112 spin_unlock(&dst_lock); 113 } 114 115 static int dst_discard(struct sk_buff *skb) 116 { 117 kfree_skb(skb); 118 return 0; 119 } 120 121 void * dst_alloc(struct dst_ops * ops) 122 { 123 struct dst_entry * dst; 124 125 if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) { 126 if (ops->gc()) 127 return NULL; 128 } 129 dst = kmem_cache_zalloc(ops->kmem_cachep, GFP_ATOMIC); 130 if (!dst) 131 return NULL; 132 atomic_set(&dst->__refcnt, 0); 133 dst->ops = ops; 134 dst->lastuse = jiffies; 135 dst->path = dst; 136 dst->input = dst->output = dst_discard; 137 #if RT_CACHE_DEBUG >= 2 138 atomic_inc(&dst_total); 139 #endif 140 atomic_inc(&ops->entries); 141 return dst; 142 } 143 144 static void ___dst_free(struct dst_entry * dst) 145 { 146 /* The first case (dev==NULL) is required, when 147 protocol module is unloaded. 148 */ 149 if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) { 150 dst->input = dst->output = dst_discard; 151 } 152 dst->obsolete = 2; 153 } 154 155 void __dst_free(struct dst_entry * dst) 156 { 157 spin_lock_bh(&dst_lock); 158 ___dst_free(dst); 159 dst->next = dst_garbage_list; 160 dst_garbage_list = dst; 161 if (dst_gc_timer_inc > DST_GC_INC) { 162 dst_gc_timer_inc = DST_GC_INC; 163 dst_gc_timer_expires = DST_GC_MIN; 164 mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); 165 } 166 spin_unlock_bh(&dst_lock); 167 } 168 169 struct dst_entry *dst_destroy(struct dst_entry * dst) 170 { 171 struct dst_entry *child; 172 struct neighbour *neigh; 173 struct hh_cache *hh; 174 175 smp_rmb(); 176 177 again: 178 neigh = dst->neighbour; 179 hh = dst->hh; 180 child = dst->child; 181 182 dst->hh = NULL; 183 if (hh && atomic_dec_and_test(&hh->hh_refcnt)) 184 kfree(hh); 185 186 if (neigh) { 187 dst->neighbour = NULL; 188 neigh_release(neigh); 189 } 190 191 atomic_dec(&dst->ops->entries); 192 193 if (dst->ops->destroy) 194 dst->ops->destroy(dst); 195 if (dst->dev) 196 dev_put(dst->dev); 197 #if RT_CACHE_DEBUG >= 2 198 atomic_dec(&dst_total); 199 #endif 200 kmem_cache_free(dst->ops->kmem_cachep, dst); 201 202 dst = child; 203 if (dst) { 204 int nohash = dst->flags & DST_NOHASH; 205 206 if (atomic_dec_and_test(&dst->__refcnt)) { 207 /* We were real parent of this dst, so kill child. */ 208 if (nohash) 209 goto again; 210 } else { 211 /* Child is still referenced, return it for freeing. */ 212 if (nohash) 213 return dst; 214 /* Child is still in his hash table */ 215 } 216 } 217 return NULL; 218 } 219 220 /* Dirty hack. We did it in 2.2 (in __dst_free), 221 * we have _very_ good reasons not to repeat 222 * this mistake in 2.3, but we have no choice 223 * now. _It_ _is_ _explicit_ _deliberate_ 224 * _race_ _condition_. 225 * 226 * Commented and originally written by Alexey. 227 */ 228 static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev, 229 int unregister) 230 { 231 if (dst->ops->ifdown) 232 dst->ops->ifdown(dst, dev, unregister); 233 234 if (dev != dst->dev) 235 return; 236 237 if (!unregister) { 238 dst->input = dst->output = dst_discard; 239 } else { 240 dst->dev = &loopback_dev; 241 dev_hold(&loopback_dev); 242 dev_put(dev); 243 if (dst->neighbour && dst->neighbour->dev == dev) { 244 dst->neighbour->dev = &loopback_dev; 245 dev_put(dev); 246 dev_hold(&loopback_dev); 247 } 248 } 249 } 250 251 static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr) 252 { 253 struct net_device *dev = ptr; 254 struct dst_entry *dst; 255 256 if (dev->nd_net != &init_net) 257 return NOTIFY_DONE; 258 259 switch (event) { 260 case NETDEV_UNREGISTER: 261 case NETDEV_DOWN: 262 spin_lock_bh(&dst_lock); 263 for (dst = dst_garbage_list; dst; dst = dst->next) { 264 dst_ifdown(dst, dev, event != NETDEV_DOWN); 265 } 266 spin_unlock_bh(&dst_lock); 267 break; 268 } 269 return NOTIFY_DONE; 270 } 271 272 static struct notifier_block dst_dev_notifier = { 273 .notifier_call = dst_dev_event, 274 }; 275 276 void __init dst_init(void) 277 { 278 register_netdevice_notifier(&dst_dev_notifier); 279 } 280 281 EXPORT_SYMBOL(__dst_free); 282 EXPORT_SYMBOL(dst_alloc); 283 EXPORT_SYMBOL(dst_destroy); 284