LCOV - code coverage report
Current view: top level - net/ipv4 - inetpeer.c (source / functions) Hit Total Coverage
Test: gcov_data_raspi2_real_modules_combined.info Lines: 58 99 58.6 %
Date: 2020-09-30 20:25:40 Functions: 6 9 66.7 %
Branches: 18 52 34.6 %

           Branch data     Line data    Source code
       1                 :            : /*
       2                 :            :  *              INETPEER - A storage for permanent information about peers
       3                 :            :  *
       4                 :            :  *  This source is covered by the GNU GPL, the same as all kernel sources.
       5                 :            :  *
       6                 :            :  *  Authors:    Andrey V. Savochkin <saw@msu.ru>
       7                 :            :  */
       8                 :            : 
       9                 :            : #include <linux/cache.h>
      10                 :            : #include <linux/module.h>
      11                 :            : #include <linux/types.h>
      12                 :            : #include <linux/slab.h>
      13                 :            : #include <linux/interrupt.h>
      14                 :            : #include <linux/spinlock.h>
      15                 :            : #include <linux/random.h>
      16                 :            : #include <linux/timer.h>
      17                 :            : #include <linux/time.h>
      18                 :            : #include <linux/kernel.h>
      19                 :            : #include <linux/mm.h>
      20                 :            : #include <linux/net.h>
      21                 :            : #include <linux/workqueue.h>
      22                 :            : #include <net/ip.h>
      23                 :            : #include <net/inetpeer.h>
      24                 :            : #include <net/secure_seq.h>
      25                 :            : 
      26                 :            : /*
      27                 :            :  *  Theory of operations.
      28                 :            :  *  We keep one entry for each peer IP address.  The nodes contains long-living
      29                 :            :  *  information about the peer which doesn't depend on routes.
      30                 :            :  *
      31                 :            :  *  Nodes are removed only when reference counter goes to 0.
      32                 :            :  *  When it's happened the node may be removed when a sufficient amount of
      33                 :            :  *  time has been passed since its last use.  The less-recently-used entry can
      34                 :            :  *  also be removed if the pool is overloaded i.e. if the total amount of
      35                 :            :  *  entries is greater-or-equal than the threshold.
      36                 :            :  *
      37                 :            :  *  Node pool is organised as an RB tree.
      38                 :            :  *  Such an implementation has been chosen not just for fun.  It's a way to
      39                 :            :  *  prevent easy and efficient DoS attacks by creating hash collisions.  A huge
      40                 :            :  *  amount of long living nodes in a single hash slot would significantly delay
      41                 :            :  *  lookups performed with disabled BHs.
      42                 :            :  *
      43                 :            :  *  Serialisation issues.
      44                 :            :  *  1.  Nodes may appear in the tree only with the pool lock held.
      45                 :            :  *  2.  Nodes may disappear from the tree only with the pool lock held
      46                 :            :  *      AND reference count being 0.
      47                 :            :  *  3.  Global variable peer_total is modified under the pool lock.
      48                 :            :  *  4.  struct inet_peer fields modification:
      49                 :            :  *              rb_node: pool lock
      50                 :            :  *              refcnt: atomically against modifications on other CPU;
      51                 :            :  *                 usually under some other lock to prevent node disappearing
      52                 :            :  *              daddr: unchangeable
      53                 :            :  */
      54                 :            : 
      55                 :            : static struct kmem_cache *peer_cachep __ro_after_init;
      56                 :            : 
      57                 :        828 : void inet_peer_base_init(struct inet_peer_base *bp)
      58                 :            : {
      59                 :        828 :         bp->rb_root = RB_ROOT;
      60                 :        828 :         seqlock_init(&bp->lock);
      61                 :        828 :         bp->total = 0;
      62                 :        828 : }
      63                 :            : EXPORT_SYMBOL_GPL(inet_peer_base_init);
      64                 :            : 
      65                 :            : #define PEER_MAX_GC 32
      66                 :            : 
      67                 :            : /* Exported for sysctl_net_ipv4.  */
      68                 :            : int inet_peer_threshold __read_mostly = 65536 + 128;    /* start to throw entries more
      69                 :            :                                          * aggressively at this stage */
      70                 :            : int inet_peer_minttl __read_mostly = 120 * HZ;  /* TTL under high load: 120 sec */
      71                 :            : int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;      /* usual time to live: 10 min */
      72                 :            : 
      73                 :            : /* Called from ip_output.c:ip_init  */
      74                 :        207 : void __init inet_initpeers(void)
      75                 :            : {
      76                 :            :         struct sysinfo si;
      77                 :            : 
      78                 :            :         /* Use the straight interface to information about memory. */
      79                 :        207 :         si_meminfo(&si);
      80                 :            :         /* The values below were suggested by Alexey Kuznetsov
      81                 :            :          * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
      82                 :            :          * myself.  --SAW
      83                 :            :          */
      84         [ -  + ]:        207 :         if (si.totalram <= (32768*1024)/PAGE_SIZE)
      85                 :          0 :                 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
      86         [ -  + ]:        207 :         if (si.totalram <= (16384*1024)/PAGE_SIZE)
      87                 :          0 :                 inet_peer_threshold >>= 1; /* about 512KB */
      88         [ -  + ]:        207 :         if (si.totalram <= (8192*1024)/PAGE_SIZE)
      89                 :          0 :                 inet_peer_threshold >>= 2; /* about 128KB */
      90                 :            : 
      91                 :        207 :         peer_cachep = kmem_cache_create("inet_peer_cache",
      92                 :            :                         sizeof(struct inet_peer),
      93                 :            :                         0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
      94                 :            :                         NULL);
      95                 :        207 : }
      96                 :            : 
      97                 :            : /* Called with rcu_read_lock() or base->lock held */
      98                 :       1035 : static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
      99                 :            :                                 struct inet_peer_base *base,
     100                 :            :                                 unsigned int seq,
     101                 :            :                                 struct inet_peer *gc_stack[],
     102                 :            :                                 unsigned int *gc_cnt,
     103                 :            :                                 struct rb_node **parent_p,
     104                 :            :                                 struct rb_node ***pp_p)
     105                 :            : {
     106                 :            :         struct rb_node **pp, *parent, *next;
     107                 :            :         struct inet_peer *p;
     108                 :            : 
     109                 :       1035 :         pp = &base->rb_root.rb_node;
     110                 :            :         parent = NULL;
     111                 :            :         while (1) {
     112                 :            :                 int cmp;
     113                 :            : 
     114                 :       1035 :                 next = rcu_dereference_raw(*pp);
     115         [ +  + ]:       1035 :                 if (!next)
     116                 :            :                         break;
     117                 :            :                 parent = next;
     118                 :            :                 p = rb_entry(parent, struct inet_peer, rb_node);
     119                 :            :                 cmp = inetpeer_addr_cmp(daddr, &p->daddr);
     120         [ +  - ]:        621 :                 if (cmp == 0) {
     121         [ +  - ]:        621 :                         if (!refcount_inc_not_zero(&p->refcnt))
     122                 :            :                                 break;
     123                 :        621 :                         return p;
     124                 :            :                 }
     125         [ #  # ]:          0 :                 if (gc_stack) {
     126         [ #  # ]:          0 :                         if (*gc_cnt < PEER_MAX_GC)
     127                 :          0 :                                 gc_stack[(*gc_cnt)++] = p;
     128         [ #  # ]:          0 :                 } else if (unlikely(read_seqretry(&base->lock, seq))) {
     129                 :            :                         break;
     130                 :            :                 }
     131         [ #  # ]:          0 :                 if (cmp == -1)
     132                 :          0 :                         pp = &next->rb_left;
     133                 :            :                 else
     134                 :          0 :                         pp = &next->rb_right;
     135                 :            :         }
     136                 :        414 :         *parent_p = parent;
     137                 :        414 :         *pp_p = pp;
     138                 :        414 :         return NULL;
     139                 :            : }
     140                 :            : 
     141                 :          0 : static void inetpeer_free_rcu(struct rcu_head *head)
     142                 :            : {
     143                 :          0 :         kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
     144                 :          0 : }
     145                 :            : 
     146                 :            : /* perform garbage collect on all items stacked during a lookup */
     147                 :          0 : static void inet_peer_gc(struct inet_peer_base *base,
     148                 :            :                          struct inet_peer *gc_stack[],
     149                 :            :                          unsigned int gc_cnt)
     150                 :            : {
     151                 :            :         struct inet_peer *p;
     152                 :            :         __u32 delta, ttl;
     153                 :            :         int i;
     154                 :            : 
     155         [ #  # ]:          0 :         if (base->total >= inet_peer_threshold)
     156                 :            :                 ttl = 0; /* be aggressive */
     157                 :            :         else
     158                 :          0 :                 ttl = inet_peer_maxttl
     159                 :          0 :                                 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
     160                 :          0 :                                         base->total / inet_peer_threshold * HZ;
     161         [ #  # ]:          0 :         for (i = 0; i < gc_cnt; i++) {
     162                 :          0 :                 p = gc_stack[i];
     163                 :            : 
     164                 :            :                 /* The READ_ONCE() pairs with the WRITE_ONCE()
     165                 :            :                  * in inet_putpeer()
     166                 :            :                  */
     167                 :          0 :                 delta = (__u32)jiffies - READ_ONCE(p->dtime);
     168                 :            : 
     169   [ #  #  #  # ]:          0 :                 if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
     170                 :          0 :                         gc_stack[i] = NULL;
     171                 :            :         }
     172         [ #  # ]:          0 :         for (i = 0; i < gc_cnt; i++) {
     173                 :          0 :                 p = gc_stack[i];
     174         [ #  # ]:          0 :                 if (p) {
     175                 :          0 :                         rb_erase(&p->rb_node, &base->rb_root);
     176                 :          0 :                         base->total--;
     177                 :          0 :                         call_rcu(&p->rcu, inetpeer_free_rcu);
     178                 :            :                 }
     179                 :            :         }
     180                 :          0 : }
     181                 :            : 
     182                 :        828 : struct inet_peer *inet_getpeer(struct inet_peer_base *base,
     183                 :            :                                const struct inetpeer_addr *daddr,
     184                 :            :                                int create)
     185                 :            : {
     186                 :            :         struct inet_peer *p, *gc_stack[PEER_MAX_GC];
     187                 :            :         struct rb_node **pp, *parent;
     188                 :            :         unsigned int gc_cnt, seq;
     189                 :            :         int invalidated;
     190                 :            : 
     191                 :            :         /* Attempt a lockless lookup first.
     192                 :            :          * Because of a concurrent writer, we might not find an existing entry.
     193                 :            :          */
     194                 :            :         rcu_read_lock();
     195                 :            :         seq = read_seqbegin(&base->lock);
     196                 :        828 :         p = lookup(daddr, base, seq, NULL, &gc_cnt, &parent, &pp);
     197                 :            :         invalidated = read_seqretry(&base->lock, seq);
     198                 :            :         rcu_read_unlock();
     199                 :            : 
     200         [ +  + ]:        828 :         if (p)
     201                 :            :                 return p;
     202                 :            : 
     203                 :            :         /* If no writer did a change during our lookup, we can return early. */
     204         [ +  - ]:        207 :         if (!create && !invalidated)
     205                 :            :                 return NULL;
     206                 :            : 
     207                 :            :         /* retry an exact lookup, taking the lock before.
     208                 :            :          * At least, nodes should be hot in our cache.
     209                 :            :          */
     210                 :        207 :         parent = NULL;
     211                 :            :         write_seqlock_bh(&base->lock);
     212                 :            : 
     213                 :        207 :         gc_cnt = 0;
     214                 :        207 :         p = lookup(daddr, base, seq, gc_stack, &gc_cnt, &parent, &pp);
     215         [ +  - ]:        207 :         if (!p && create) {
     216                 :        207 :                 p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
     217         [ +  - ]:        207 :                 if (p) {
     218                 :        207 :                         p->daddr = *daddr;
     219                 :        207 :                         p->dtime = (__u32)jiffies;
     220                 :            :                         refcount_set(&p->refcnt, 2);
     221                 :            :                         atomic_set(&p->rid, 0);
     222                 :        207 :                         p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
     223                 :        207 :                         p->rate_tokens = 0;
     224                 :        207 :                         p->n_redirects = 0;
     225                 :            :                         /* 60*HZ is arbitrary, but chosen enough high so that the first
     226                 :            :                          * calculation of tokens is at its maximum.
     227                 :            :                          */
     228                 :        207 :                         p->rate_last = jiffies - 60*HZ;
     229                 :            : 
     230                 :        207 :                         rb_link_node(&p->rb_node, parent, pp);
     231                 :        207 :                         rb_insert_color(&p->rb_node, &base->rb_root);
     232                 :        207 :                         base->total++;
     233                 :            :                 }
     234                 :            :         }
     235         [ -  + ]:        207 :         if (gc_cnt)
     236                 :          0 :                 inet_peer_gc(base, gc_stack, gc_cnt);
     237                 :            :         write_sequnlock_bh(&base->lock);
     238                 :            : 
     239                 :        207 :         return p;
     240                 :            : }
     241                 :            : EXPORT_SYMBOL_GPL(inet_getpeer);
     242                 :            : 
     243                 :        828 : void inet_putpeer(struct inet_peer *p)
     244                 :            : {
     245                 :            :         /* The WRITE_ONCE() pairs with itself (we run lockless)
     246                 :            :          * and the READ_ONCE() in inet_peer_gc()
     247                 :            :          */
     248                 :        828 :         WRITE_ONCE(p->dtime, (__u32)jiffies);
     249                 :            : 
     250         [ -  + ]:        828 :         if (refcount_dec_and_test(&p->refcnt))
     251                 :          0 :                 call_rcu(&p->rcu, inetpeer_free_rcu);
     252                 :        828 : }
     253                 :            : EXPORT_SYMBOL_GPL(inet_putpeer);
     254                 :            : 
     255                 :            : /*
     256                 :            :  *      Check transmit rate limitation for given message.
     257                 :            :  *      The rate information is held in the inet_peer entries now.
     258                 :            :  *      This function is generic and could be used for other purposes
     259                 :            :  *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
     260                 :            :  *
     261                 :            :  *      Note that the same inet_peer fields are modified by functions in
     262                 :            :  *      route.c too, but these work for packet destinations while xrlim_allow
     263                 :            :  *      works for icmp destinations. This means the rate limiting information
     264                 :            :  *      for one "ip object" is shared - and these ICMPs are twice limited:
     265                 :            :  *      by source and by destination.
     266                 :            :  *
     267                 :            :  *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
     268                 :            :  *                        SHOULD allow setting of rate limits
     269                 :            :  *
     270                 :            :  *      Shared between ICMPv4 and ICMPv6.
     271                 :            :  */
     272                 :            : #define XRLIM_BURST_FACTOR 6
     273                 :        828 : bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
     274                 :            : {
     275                 :            :         unsigned long now, token;
     276                 :            :         bool rc = false;
     277                 :            : 
     278         [ +  - ]:        828 :         if (!peer)
     279                 :            :                 return true;
     280                 :            : 
     281                 :        828 :         token = peer->rate_tokens;
     282                 :        828 :         now = jiffies;
     283                 :        828 :         token += now - peer->rate_last;
     284                 :        828 :         peer->rate_last = now;
     285         [ +  + ]:        828 :         if (token > XRLIM_BURST_FACTOR * timeout)
     286                 :            :                 token = XRLIM_BURST_FACTOR * timeout;
     287         [ +  - ]:        828 :         if (token >= timeout) {
     288                 :        828 :                 token -= timeout;
     289                 :            :                 rc = true;
     290                 :            :         }
     291                 :        828 :         peer->rate_tokens = token;
     292                 :        828 :         return rc;
     293                 :            : }
     294                 :            : EXPORT_SYMBOL(inet_peer_xrlim_allow);
     295                 :            : 
     296                 :          0 : void inetpeer_invalidate_tree(struct inet_peer_base *base)
     297                 :            : {
     298                 :          0 :         struct rb_node *p = rb_first(&base->rb_root);
     299                 :            : 
     300         [ #  # ]:          0 :         while (p) {
     301                 :            :                 struct inet_peer *peer = rb_entry(p, struct inet_peer, rb_node);
     302                 :            : 
     303                 :          0 :                 p = rb_next(p);
     304                 :          0 :                 rb_erase(&peer->rb_node, &base->rb_root);
     305                 :          0 :                 inet_putpeer(peer);
     306                 :          0 :                 cond_resched();
     307                 :            :         }
     308                 :            : 
     309                 :          0 :         base->total = 0;
     310                 :          0 : }
     311                 :            : EXPORT_SYMBOL(inetpeer_invalidate_tree);

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