net/core/dst.c

   1 /*
   2  * net/dst.c    Protocol independent destination cache.
   3  *
   4  * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
   5  *
   6  */
   7
   8 #include <asm/segment.h>
   9 #include <asm/system.h>
  10 #include <asm/bitops.h>
  11 #include <linux/types.h>
  12 #include <linux/kernel.h>
  13 #include <linux/sched.h>
  14 #include <linux/mm.h>
  15 #include <linux/string.h>
  16 #include <linux/errno.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/init.h>
  20
  21 #include <net/dst.h>
  22
  23 /* Locking strategy:
  24  * 1) Garbage collection state of dead destination cache
  25  *    entries is protected by dst_lock.
  26  * 2) GC is run only from BH context, and is the only remover
  27  *    of entries.
  28  * 3) Entries are added to the garbage list from both BH
  29  *    and non-BH context, so local BH disabling is needed.
  30  * 4) All operations modify state, so a spinlock is used.
  31  */
  32 static struct dst_entry         *dst_garbage_list;
  33 static atomic_t                  dst_total = ATOMIC_INIT(0);
  34 static spinlock_t                dst_lock = SPIN_LOCK_UNLOCKED;
  35
  36 static unsigned long dst_gc_timer_expires;
  37 static unsigned long dst_gc_timer_inc = DST_GC_MAX;
  38 static void dst_run_gc(unsigned long);
  39
  40 static struct timer_list dst_gc_timer =
  41         { NULL, NULL, DST_GC_MIN, 0L, dst_run_gc };
  42
  43
  44 static void dst_run_gc(unsigned long dummy)
  45 {
  46         int    delayed = 0;
  47         struct dst_entry * dst, **dstp;
  48
  49         if (!spin_trylock(&dst_lock)) {
  50                 mod_timer(&dst_gc_timer, jiffies + HZ/10);
  51                 return;
  52         }
  53
  54         del_timer(&dst_gc_timer);
  55         dstp = &dst_garbage_list;
  56         while ((dst = *dstp) != NULL) {
  57                 if (atomic_read(&dst->use)) {
  58                         dstp = &dst->next;
  59                         delayed++;
  60                         continue;
  61                 }
  62                 *dstp = dst->next;
  63                 dst_destroy(dst);
  64         }
  65         if (!dst_garbage_list) {
  66                 dst_gc_timer_inc = DST_GC_MAX;
  67                 goto out;
  68         }
  69         if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
  70                 dst_gc_timer_expires = DST_GC_MAX;
  71         dst_gc_timer_inc += DST_GC_INC;
  72         dst_gc_timer.expires = jiffies + dst_gc_timer_expires;
  73 #if RT_CACHE_DEBUG >= 2
  74         printk("dst_total: %d/%d %ld\n",
  75                atomic_read(&dst_total), delayed,  dst_gc_timer_expires);
  76 #endif
  77         add_timer(&dst_gc_timer);
  78
  79 out:
  80         spin_unlock(&dst_lock);
  81 }
  82
  83 static int dst_discard(struct sk_buff *skb)
  84 {
  85         kfree_skb(skb);
  86         return 0;
  87 }
  88
  89 static int dst_blackhole(struct sk_buff *skb)
  90 {
  91         kfree_skb(skb);
  92         return 0;
  93 }
  94
  95 void * dst_alloc(int size, struct dst_ops * ops)
  96 {
  97         struct dst_entry * dst;
  98
  99         if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
 100                 if (ops->gc())
 101                         return NULL;
 102         }
 103         dst = kmalloc(size, GFP_ATOMIC);
 104         if (!dst)
 105                 return NULL;
 106         memset(dst, 0, size);
 107         dst->ops = ops;
 108         atomic_set(&dst->refcnt, 0);
 109         dst->lastuse = jiffies;
 110         dst->input = dst_discard;
 111         dst->output = dst_blackhole;
 112         atomic_inc(&dst_total);
 113         atomic_inc(&ops->entries);
 114         return dst;
 115 }
 116
 117 void __dst_free(struct dst_entry * dst)
 118 {
 119         spin_lock_bh(&dst_lock);
 120
 121         /* The first case (dev==NULL) is required, when
 122            protocol module is unloaded.
 123          */
 124         if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {
 125                 dst->input = dst_discard;
 126                 dst->output = dst_blackhole;
 127                 dst->dev = &loopback_dev;
 128         }
 129         dst->obsolete = 2;
 130         dst->next = dst_garbage_list;
 131         dst_garbage_list = dst;
 132         if (dst_gc_timer_inc > DST_GC_INC) {
 133                 del_timer(&dst_gc_timer);
 134                 dst_gc_timer_inc = DST_GC_INC;
 135                 dst_gc_timer_expires = DST_GC_MIN;
 136                 dst_gc_timer.expires = jiffies + dst_gc_timer_expires;
 137                 add_timer(&dst_gc_timer);
 138         }
 139
 140         spin_unlock_bh(&dst_lock);
 141 }
 142
 143 void dst_destroy(struct dst_entry * dst)
 144 {
 145         struct neighbour *neigh = dst->neighbour;
 146         struct hh_cache *hh = dst->hh;
 147
 148         dst->hh = NULL;
 149         if (hh && atomic_dec_and_test(&hh->hh_refcnt))
 150                 kfree(hh);
 151
 152         if (neigh) {
 153                 dst->neighbour = NULL;
 154                 neigh_release(neigh);
 155         }
 156
 157         atomic_dec(&dst->ops->entries);
 158
 159         if (dst->ops->destroy)
 160                 dst->ops->destroy(dst);
 161         atomic_dec(&dst_total);
 162         kfree(dst);
 163 }
 164
 165 static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr)
 166 {
 167         struct device *dev = ptr;
 168         struct dst_entry *dst;
 169
 170         switch (event) {
 171         case NETDEV_UNREGISTER:
 172         case NETDEV_DOWN:
 173                 spin_lock_bh(&dst_lock);
 174                 for (dst = dst_garbage_list; dst; dst = dst->next) {
 175                         if (dst->dev == dev) {
 176                                 dst->input = dst_discard;
 177                                 dst->output = dst_blackhole;
 178                                 dst->dev = &loopback_dev;
 179                         }
 180                 }
 181                 spin_unlock_bh(&dst_lock);
 182                 break;
 183         }
 184         return NOTIFY_DONE;
 185 }
 186
 187 struct notifier_block dst_dev_notifier = {
 188         dst_dev_event,
 189         NULL,
 190         0
 191 };
 192
 193 __initfunc(void dst_init(void))
 194 {
 195         register_netdevice_notifier(&dst_dev_notifier);
 196 }