1 files changed, 245 insertions, 119 deletions

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 9ffa24b9a804..ce616d92cc54 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -63,7 +63,7 @@
  *              refcnt: atomically against modifications on other CPU;
  *                 usually under some other lock to prevent node disappearing
  *              dtime: unused node list lock
- *              v4daddr: unchangeable
+ *              daddr: unchangeable
  *              ip_id_count: atomic value (no lock needed)
  */
 
@@ -72,21 +72,31 @@ static struct kmem_cache *peer_cachep __read_mostly;
 #define node_height(x) x->avl_height
 
 #define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
+#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
 static const struct inet_peer peer_fake_node = {
-        .avl_left       = peer_avl_empty,
-        .avl_right      = peer_avl_empty,
+        .avl_left       = peer_avl_empty_rcu,
+        .avl_right      = peer_avl_empty_rcu,
         .avl_height     = 0
 };
 
-static struct {
-        struct inet_peer *root;
-        spinlock_t      lock;
+struct inet_peer_base {
+        struct inet_peer __rcu *root;
+        seqlock_t       lock;
         int             total;
-} peers = {
-        .root           = peer_avl_empty,
-        .lock           = __SPIN_LOCK_UNLOCKED(peers.lock),
+};
+
+static struct inet_peer_base v4_peers = {
+        .root           = peer_avl_empty_rcu,
+        .lock           = __SEQLOCK_UNLOCKED(v4_peers.lock),
+        .total          = 0,
+};
+
+static struct inet_peer_base v6_peers = {
+        .root           = peer_avl_empty_rcu,
+        .lock           = __SEQLOCK_UNLOCKED(v6_peers.lock),
         .total          = 0,
 };
+
 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
 
 /* Exported for sysctl_net_ipv4.  */
@@ -144,62 +154,99 @@ void __init inet_initpeers(void)
 /* Called with or without local BH being disabled. */
 static void unlink_from_unused(struct inet_peer *p)
 {
-        if (!list_empty(&p->unused)) {
-                spin_lock_bh(&unused_peers.lock);
-                list_del_init(&p->unused);
-                spin_unlock_bh(&unused_peers.lock);
+        spin_lock_bh(&unused_peers.lock);
+        list_del_init(&p->unused);
+        spin_unlock_bh(&unused_peers.lock);
+}
+
+static int addr_compare(const struct inetpeer_addr *a,
+                        const struct inetpeer_addr *b)
+{
+        int i, n = (a->family == AF_INET ? 1 : 4);
+
+        for (i = 0; i < n; i++) {
+                if (a->addr.a6[i] == b->addr.a6[i])
+                        continue;
+                if (a->addr.a6[i] < b->addr.a6[i])
+                        return -1;
+                return 1;
         }
+
+        return 0;
 }
 
+#define rcu_deref_locked(X, BASE)                               \
+        rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
+
 /*
  * Called with local BH disabled and the pool lock held.
  */
-#define lookup(_daddr, _stack)                                  \
+#define lookup(_daddr, _stack, _base)                           \
 ({                                                              \
-        struct inet_peer *u, **v;                               \
+        struct inet_peer *u;                                    \
+        struct inet_peer __rcu **v;                             \
                                                                 \
         stackptr = _stack;                                      \
-        *stackptr++ = &peers.root;                              \
-        for (u = peers.root; u != peer_avl_empty; ) {           \
-                if (_daddr == u->v4daddr)                       \
+        *stackptr++ = &_base->root;                             \
+        for (u = rcu_deref_locked(_base->root, _base);          \
+             u != peer_avl_empty; ) {                           \
+                int cmp = addr_compare(_daddr, &u->daddr);      \
+                if (cmp == 0)                                   \
                         break;                                  \
-                if ((__force __u32)_daddr < (__force __u32)u->v4daddr)  \
+                if (cmp == -1)                                  \
                         v = &u->avl_left;                       \
                 else                                            \
                         v = &u->avl_right;                      \
                 *stackptr++ = v;                                \
-                u = *v;                                         \
+                u = rcu_deref_locked(*v, _base);                \
         }                                                       \
         u;                                                      \
 })
 
+static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv)
+{
+        int cur, old = atomic_read(ptr);
+
+        while (old != u) {
+                *newv = old + a;
+                cur = atomic_cmpxchg(ptr, old, *newv);
+                if (cur == old)
+                        return true;
+                old = cur;
+        }
+        return false;
+}
+
 /*
- * Called with rcu_read_lock_bh()
+ * Called with rcu_read_lock()
  * Because we hold no lock against a writer, its quite possible we fall
  * in an endless loop.
  * But every pointer we follow is guaranteed to be valid thanks to RCU.
  * We exit from this function if number of links exceeds PEER_MAXDEPTH
  */
-static struct inet_peer *lookup_rcu_bh(__be32 daddr)
+static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
+                                    struct inet_peer_base *base,
+                                    int *newrefcnt)
 {
-        struct inet_peer *u = rcu_dereference_bh(peers.root);
+        struct inet_peer *u = rcu_dereference(base->root);
         int count = 0;
 
         while (u != peer_avl_empty) {
-                if (daddr == u->v4daddr) {
+                int cmp = addr_compare(daddr, &u->daddr);
+                if (cmp == 0) {
                         /* Before taking a reference, check if this entry was
                          * deleted, unlink_from_pool() sets refcnt=-1 to make
                          * distinction between an unused entry (refcnt=0) and
                          * a freed one.
                          */
-                        if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1)))
+                        if (!atomic_add_unless_return(&u->refcnt, 1, -1, newrefcnt))
                                 u = NULL;
                         return u;
                 }
-                if ((__force __u32)daddr < (__force __u32)u->v4daddr)
-                        u = rcu_dereference_bh(u->avl_left);
+                if (cmp == -1)
+                        u = rcu_dereference(u->avl_left);
                 else
-                        u = rcu_dereference_bh(u->avl_right);
+                        u = rcu_dereference(u->avl_right);
                 if (unlikely(++count == PEER_MAXDEPTH))
                         break;
         }
@@ -207,15 +254,17 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr)
 }
 
 /* Called with local BH disabled and the pool lock held. */
-#define lookup_rightempty(start)                                \
+#define lookup_rightempty(start, base)                          \
 ({                                                              \
-        struct inet_peer *u, **v;                               \
+        struct inet_peer *u;                                    \
+        struct inet_peer __rcu **v;                             \
         *stackptr++ = &start->avl_left;                         \
         v = &start->avl_left;                                   \
-        for (u = *v; u->avl_right != peer_avl_empty; ) {        \
+        for (u = rcu_deref_locked(*v, base);                    \
+             u->avl_right != peer_avl_empty_rcu; ) {            \
                 v = &u->avl_right;                              \
                 *stackptr++ = v;                                \
-                u = *v;                                         \
+                u = rcu_deref_locked(*v, base);                 \
         }                                                       \
         u;                                                      \
 })
@@ -224,74 +273,76 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr)
  * Variable names are the proof of operation correctness.
  * Look into mm/map_avl.c for more detail description of the ideas.
  */
-static void peer_avl_rebalance(struct inet_peer **stack[],
-                struct inet_peer ***stackend)
+static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
+                               struct inet_peer __rcu ***stackend,
+                               struct inet_peer_base *base)
 {
-        struct inet_peer **nodep, *node, *l, *r;
+        struct inet_peer __rcu **nodep;
+        struct inet_peer *node, *l, *r;
         int lh, rh;
 
         while (stackend > stack) {
                 nodep = *--stackend;
-                node = *nodep;
-                l = node->avl_left;
-                r = node->avl_right;
+                node = rcu_deref_locked(*nodep, base);
+                l = rcu_deref_locked(node->avl_left, base);
+                r = rcu_deref_locked(node->avl_right, base);
                 lh = node_height(l);
                 rh = node_height(r);
                 if (lh > rh + 1) { /* l: RH+2 */
                         struct inet_peer *ll, *lr, *lrl, *lrr;
                         int lrh;
-                        ll = l->avl_left;
-                        lr = l->avl_right;
+                        ll = rcu_deref_locked(l->avl_left, base);
+                        lr = rcu_deref_locked(l->avl_right, base);
                         lrh = node_height(lr);
                         if (lrh <= node_height(ll)) {   /* ll: RH+1 */
-                                node->avl_left = lr;    /* lr: RH or RH+1 */
-                                node->avl_right = r;    /* r: RH */
+                                RCU_INIT_POINTER(node->avl_left, lr);   /* lr: RH or RH+1 */
+                                RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
                                 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
-                                l->avl_left = ll;       /* ll: RH+1 */
-                                l->avl_right = node;    /* node: RH+1 or RH+2 */
+                                RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
+                                RCU_INIT_POINTER(l->avl_right, node);   /* node: RH+1 or RH+2 */
                                 l->avl_height = node->avl_height + 1;
-                                *nodep = l;
+                                RCU_INIT_POINTER(*nodep, l);
                         } else { /* ll: RH, lr: RH+1 */
-                                lrl = lr->avl_left;     /* lrl: RH or RH-1 */
-                                lrr = lr->avl_right;    /* lrr: RH or RH-1 */
-                                node->avl_left = lrr;   /* lrr: RH or RH-1 */
-                                node->avl_right = r;    /* r: RH */
+                                lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
+                                lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
+                                RCU_INIT_POINTER(node->avl_left, lrr);  /* lrr: RH or RH-1 */
+                                RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
                                 node->avl_height = rh + 1; /* node: RH+1 */
-                                l->avl_left = ll;       /* ll: RH */
-                                l->avl_right = lrl;     /* lrl: RH or RH-1 */
+                                RCU_INIT_POINTER(l->avl_left, ll);      /* ll: RH */
+                                RCU_INIT_POINTER(l->avl_right, lrl);    /* lrl: RH or RH-1 */
                                 l->avl_height = rh + 1; /* l: RH+1 */
-                                lr->avl_left = l;       /* l: RH+1 */
-                                lr->avl_right = node;   /* node: RH+1 */
+                                RCU_INIT_POINTER(lr->avl_left, l);      /* l: RH+1 */
+                                RCU_INIT_POINTER(lr->avl_right, node);  /* node: RH+1 */
                                 lr->avl_height = rh + 2;
-                                *nodep = lr;
+                                RCU_INIT_POINTER(*nodep, lr);
                         }
                 } else if (rh > lh + 1) { /* r: LH+2 */
                         struct inet_peer *rr, *rl, *rlr, *rll;
                         int rlh;
-                        rr = r->avl_right;
-                        rl = r->avl_left;
+                        rr = rcu_deref_locked(r->avl_right, base);
+                        rl = rcu_deref_locked(r->avl_left, base);
                         rlh = node_height(rl);
                         if (rlh <= node_height(rr)) {   /* rr: LH+1 */
-                                node->avl_right = rl;   /* rl: LH or LH+1 */
-                                node->avl_left = l;     /* l: LH */
+                                RCU_INIT_POINTER(node->avl_right, rl);  /* rl: LH or LH+1 */
+                                RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
                                 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
-                                r->avl_right = rr;      /* rr: LH+1 */
-                                r->avl_left = node;     /* node: LH+1 or LH+2 */
+                                RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH+1 */
+                                RCU_INIT_POINTER(r->avl_left, node);    /* node: LH+1 or LH+2 */
                                 r->avl_height = node->avl_height + 1;
-                                *nodep = r;
+                                RCU_INIT_POINTER(*nodep, r);
                         } else { /* rr: RH, rl: RH+1 */
-                                rlr = rl->avl_right;    /* rlr: LH or LH-1 */
-                                rll = rl->avl_left;     /* rll: LH or LH-1 */
-                                node->avl_right = rll;  /* rll: LH or LH-1 */
-                                node->avl_left = l;     /* l: LH */
+                                rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
+                                rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
+                                RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
+                                RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
                                 node->avl_height = lh + 1; /* node: LH+1 */
-                                r->avl_right = rr;      /* rr: LH */
-                                r->avl_left = rlr;      /* rlr: LH or LH-1 */
+                                RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH */
+                                RCU_INIT_POINTER(r->avl_left, rlr);     /* rlr: LH or LH-1 */
                                 r->avl_height = lh + 1; /* r: LH+1 */
-                                rl->avl_right = r;      /* r: LH+1 */
-                                rl->avl_left = node;    /* node: LH+1 */
+                                RCU_INIT_POINTER(rl->avl_right, r);     /* r: LH+1 */
+                                RCU_INIT_POINTER(rl->avl_left, node);   /* node: LH+1 */
                                 rl->avl_height = lh + 2;
-                                *nodep = rl;
+                                RCU_INIT_POINTER(*nodep, rl);
                         }
                 } else {
                         node->avl_height = (lh > rh ? lh : rh) + 1;
@@ -300,14 +351,14 @@ static void peer_avl_rebalance(struct inet_peer **stack[],
 }
 
 /* Called with local BH disabled and the pool lock held. */
-#define link_to_pool(n)                                         \
+#define link_to_pool(n, base)                                   \
 do {                                                            \
         n->avl_height = 1;                                      \
-        n->avl_left = peer_avl_empty;                           \
-        n->avl_right = peer_avl_empty;                          \
-        smp_wmb(); /* lockless readers can catch us now */      \
-        **--stackptr = n;                                       \
-        peer_avl_rebalance(stack, stackptr);                    \
+        n->avl_left = peer_avl_empty_rcu;                       \
+        n->avl_right = peer_avl_empty_rcu;                      \
+        /* lockless readers can catch us now */                 \
+        rcu_assign_pointer(**--stackptr, n);                    \
+        peer_avl_rebalance(stack, stackptr, base);              \
 } while (0)
 
 static void inetpeer_free_rcu(struct rcu_head *head)
@@ -316,13 +367,14 @@ static void inetpeer_free_rcu(struct rcu_head *head)
 }
 
 /* May be called with local BH enabled. */
-static void unlink_from_pool(struct inet_peer *p)
+static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
+                             struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 {
         int do_free;
 
         do_free = 0;
 
-        spin_lock_bh(&peers.lock);
+        write_seqlock_bh(&base->lock);
         /* Check the reference counter.  It was artificially incremented by 1
          * in cleanup() function to prevent sudden disappearing.  If we can
          * atomically (because of lockless readers) take this last reference,
@@ -330,38 +382,37 @@ static void unlink_from_pool(struct inet_peer *p)
          * We use refcnt=-1 to alert lockless readers this entry is deleted.
          */
         if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {
-                struct inet_peer **stack[PEER_MAXDEPTH];
-                struct inet_peer ***stackptr, ***delp;
-                if (lookup(p->v4daddr, stack) != p)
+                struct inet_peer __rcu ***stackptr, ***delp;
+                if (lookup(&p->daddr, stack, base) != p)
                         BUG();
                 delp = stackptr - 1; /* *delp[0] == p */
-                if (p->avl_left == peer_avl_empty) {
+                if (p->avl_left == peer_avl_empty_rcu) {
                         *delp[0] = p->avl_right;
                         --stackptr;
                 } else {
                         /* look for a node to insert instead of p */
                         struct inet_peer *t;
-                        t = lookup_rightempty(p);
-                        BUG_ON(*stackptr[-1] != t);
+                        t = lookup_rightempty(p, base);
+                        BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
                         **--stackptr = t->avl_left;
-                        /* t is removed, t->v4daddr > x->v4daddr for any
+                        /* t is removed, t->daddr > x->daddr for any
                          * x in p->avl_left subtree.
                          * Put t in the old place of p. */
-                        *delp[0] = t;
+                        RCU_INIT_POINTER(*delp[0], t);
                         t->avl_left = p->avl_left;
                         t->avl_right = p->avl_right;
                         t->avl_height = p->avl_height;
                         BUG_ON(delp[1] != &p->avl_left);
                         delp[1] = &t->avl_left; /* was &p->avl_left */
                 }
-                peer_avl_rebalance(stack, stackptr);
-                peers.total--;
+                peer_avl_rebalance(stack, stackptr, base);
+                base->total--;
                 do_free = 1;
         }
-        spin_unlock_bh(&peers.lock);
+        write_sequnlock_bh(&base->lock);
 
         if (do_free)
-                call_rcu_bh(&p->rcu, inetpeer_free_rcu);
+                call_rcu(&p->rcu, inetpeer_free_rcu);
         else
                 /* The node is used again.  Decrease the reference counter
                  * back.  The loop "cleanup -> unlink_from_unused
@@ -373,8 +424,18 @@ static void unlink_from_pool(struct inet_peer *p)
                 inet_putpeer(p);
 }
 
+static struct inet_peer_base *family_to_base(int family)
+{
+        return (family == AF_INET ? &v4_peers : &v6_peers);
+}
+
+static struct inet_peer_base *peer_to_base(struct inet_peer *p)
+{
+        return family_to_base(p->daddr.family);
+}
+
 /* May be called with local BH enabled. */
-static int cleanup_once(unsigned long ttl)
+static int cleanup_once(unsigned long ttl, struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 {
         struct inet_peer *p = NULL;
 
@@ -406,79 +467,101 @@ static int cleanup_once(unsigned long ttl)
                  * happen because of entry limits in route cache. */
                 return -1;
 
-        unlink_from_pool(p);
+        unlink_from_pool(p, peer_to_base(p), stack);
         return 0;
 }
 
 /* Called with or without local BH being disabled. */
-struct inet_peer *inet_getpeer(__be32 daddr, int create)
+struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
 {
+        struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
+        struct inet_peer_base *base = family_to_base(daddr->family);
         struct inet_peer *p;
-        struct inet_peer **stack[PEER_MAXDEPTH], ***stackptr;
+        unsigned int sequence;
+        int invalidated, newrefcnt = 0;
 
         /* Look up for the address quickly, lockless.
          * Because of a concurrent writer, we might not find an existing entry.
          */
-        rcu_read_lock_bh();
-        p = lookup_rcu_bh(daddr);
-        rcu_read_unlock_bh();
+        rcu_read_lock();
+        sequence = read_seqbegin(&base->lock);
+        p = lookup_rcu(daddr, base, &newrefcnt);
+        invalidated = read_seqretry(&base->lock, sequence);
+        rcu_read_unlock();
 
         if (p) {
-                /* The existing node has been found.
+found:          /* The existing node has been found.
                  * Remove the entry from unused list if it was there.
                  */
-                unlink_from_unused(p);
+                if (newrefcnt == 1)
+                        unlink_from_unused(p);
                 return p;
         }
 
+        /* If no writer did a change during our lookup, we can return early. */
+        if (!create && !invalidated)
+                return NULL;
+
         /* retry an exact lookup, taking the lock before.
          * At least, nodes should be hot in our cache.
          */
-        spin_lock_bh(&peers.lock);
-        p = lookup(daddr, stack);
+        write_seqlock_bh(&base->lock);
+        p = lookup(daddr, stack, base);
         if (p != peer_avl_empty) {
-                atomic_inc(&p->refcnt);
-                spin_unlock_bh(&peers.lock);
-                /* Remove the entry from unused list if it was there. */
-                unlink_from_unused(p);
-                return p;
+                newrefcnt = atomic_inc_return(&p->refcnt);
+                write_sequnlock_bh(&base->lock);
+                goto found;
         }
         p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
         if (p) {
-                p->v4daddr = daddr;
+                p->daddr = *daddr;
                 atomic_set(&p->refcnt, 1);
                 atomic_set(&p->rid, 0);
-                atomic_set(&p->ip_id_count, secure_ip_id(daddr));
+                atomic_set(&p->ip_id_count, secure_ip_id(daddr->addr.a4));
                 p->tcp_ts_stamp = 0;
+                p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
+                p->rate_tokens = 0;
+                p->rate_last = 0;
+                p->pmtu_expires = 0;
+                p->pmtu_orig = 0;
+                memset(&p->redirect_learned, 0, sizeof(p->redirect_learned));
                 INIT_LIST_HEAD(&p->unused);
 
 
                 /* Link the node. */
-                link_to_pool(p);
-                peers.total++;
+                link_to_pool(p, base);
+                base->total++;
         }
-        spin_unlock_bh(&peers.lock);
+        write_sequnlock_bh(&base->lock);
 
-        if (peers.total >= inet_peer_threshold)
+        if (base->total >= inet_peer_threshold)
                 /* Remove one less-recently-used entry. */
-                cleanup_once(0);
+                cleanup_once(0, stack);
 
         return p;
 }
 
+static int compute_total(void)
+{
+        return v4_peers.total + v6_peers.total;
+}
+EXPORT_SYMBOL_GPL(inet_getpeer);
+
 /* Called with local BH disabled. */
 static void peer_check_expire(unsigned long dummy)
 {
         unsigned long now = jiffies;
-        int ttl;
+        int ttl, total;
+        struct inet_peer __rcu **stack[PEER_MAXDEPTH];
 
-        if (peers.total >= inet_peer_threshold)
+        total = compute_total();
+        if (total >= inet_peer_threshold)
                 ttl = inet_peer_minttl;
         else
                 ttl = inet_peer_maxttl
                                 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
-                                        peers.total / inet_peer_threshold * HZ;
-        while (!cleanup_once(ttl)) {
+                                        total / inet_peer_threshold * HZ;
+        while (!cleanup_once(ttl, stack)) {
                 if (jiffies != now)
                         break;
         }
@@ -486,13 +569,14 @@ static void peer_check_expire(unsigned long dummy)
         /* Trigger the timer after inet_peer_gc_mintime .. inet_peer_gc_maxtime
          * interval depending on the total number of entries (more entries,
          * less interval). */
-        if (peers.total >= inet_peer_threshold)
+        total = compute_total();
+        if (total >= inet_peer_threshold)
                 peer_periodic_timer.expires = jiffies + inet_peer_gc_mintime;
         else
                 peer_periodic_timer.expires = jiffies
                         + inet_peer_gc_maxtime
                         - (inet_peer_gc_maxtime - inet_peer_gc_mintime) / HZ *
-                                peers.total / inet_peer_threshold * HZ;
+                                total / inet_peer_threshold * HZ;
         add_timer(&peer_periodic_timer);
 }
 
@@ -508,3 +592,45 @@ void inet_putpeer(struct inet_peer *p)
 
         local_bh_enable();
 }
+EXPORT_SYMBOL_GPL(inet_putpeer);
+
+/*
+ *      Check transmit rate limitation for given message.
+ *      The rate information is held in the inet_peer entries now.
+ *      This function is generic and could be used for other purposes
+ *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
+ *
+ *      Note that the same inet_peer fields are modified by functions in
+ *      route.c too, but these work for packet destinations while xrlim_allow
+ *      works for icmp destinations. This means the rate limiting information
+ *      for one "ip object" is shared - and these ICMPs are twice limited:
+ *      by source and by destination.
+ *
+ *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
+ *                        SHOULD allow setting of rate limits
+ *
+ *      Shared between ICMPv4 and ICMPv6.
+ */
+#define XRLIM_BURST_FACTOR 6
+bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
+{
+        unsigned long now, token;
+        bool rc = false;
+
+        if (!peer)
+                return true;
+
+        token = peer->rate_tokens;
+        now = jiffies;
+        token += now - peer->rate_last;
+        peer->rate_last = now;
+        if (token > XRLIM_BURST_FACTOR * timeout)
+                token = XRLIM_BURST_FACTOR * timeout;
+        if (token >= timeout) {
+                token -= timeout;
+                rc = true;
+        }
+        peer->rate_tokens = token;
+        return rc;
+}
+EXPORT_SYMBOL(inet_peer_xrlim_allow);