v4.19.13 snapshot.
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
new file mode 100644
index 0000000..d757b96
--- /dev/null
+++ b/net/ipv4/inetpeer.c
@@ -0,0 +1,302 @@
+/*
+ * INETPEER - A storage for permanent information about peers
+ *
+ * This source is covered by the GNU GPL, the same as all kernel sources.
+ *
+ * Authors: Andrey V. Savochkin <saw@msu.ru>
+ */
+
+#include <linux/cache.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/random.h>
+#include <linux/timer.h>
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/net.h>
+#include <linux/workqueue.h>
+#include <net/ip.h>
+#include <net/inetpeer.h>
+#include <net/secure_seq.h>
+
+/*
+ * Theory of operations.
+ * We keep one entry for each peer IP address. The nodes contains long-living
+ * information about the peer which doesn't depend on routes.
+ *
+ * Nodes are removed only when reference counter goes to 0.
+ * When it's happened the node may be removed when a sufficient amount of
+ * time has been passed since its last use. The less-recently-used entry can
+ * also be removed if the pool is overloaded i.e. if the total amount of
+ * entries is greater-or-equal than the threshold.
+ *
+ * Node pool is organised as an RB tree.
+ * Such an implementation has been chosen not just for fun. It's a way to
+ * prevent easy and efficient DoS attacks by creating hash collisions. A huge
+ * amount of long living nodes in a single hash slot would significantly delay
+ * lookups performed with disabled BHs.
+ *
+ * Serialisation issues.
+ * 1. Nodes may appear in the tree only with the pool lock held.
+ * 2. Nodes may disappear from the tree only with the pool lock held
+ * AND reference count being 0.
+ * 3. Global variable peer_total is modified under the pool lock.
+ * 4. struct inet_peer fields modification:
+ * rb_node: pool lock
+ * refcnt: atomically against modifications on other CPU;
+ * usually under some other lock to prevent node disappearing
+ * daddr: unchangeable
+ */
+
+static struct kmem_cache *peer_cachep __ro_after_init;
+
+void inet_peer_base_init(struct inet_peer_base *bp)
+{
+ bp->rb_root = RB_ROOT;
+ seqlock_init(&bp->lock);
+ bp->total = 0;
+}
+EXPORT_SYMBOL_GPL(inet_peer_base_init);
+
+#define PEER_MAX_GC 32
+
+/* Exported for sysctl_net_ipv4. */
+int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
+ * aggressively at this stage */
+int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
+int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
+
+/* Called from ip_output.c:ip_init */
+void __init inet_initpeers(void)
+{
+ struct sysinfo si;
+
+ /* Use the straight interface to information about memory. */
+ si_meminfo(&si);
+ /* The values below were suggested by Alexey Kuznetsov
+ * <kuznet@ms2.inr.ac.ru>. I don't have any opinion about the values
+ * myself. --SAW
+ */
+ if (si.totalram <= (32768*1024)/PAGE_SIZE)
+ inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
+ if (si.totalram <= (16384*1024)/PAGE_SIZE)
+ inet_peer_threshold >>= 1; /* about 512KB */
+ if (si.totalram <= (8192*1024)/PAGE_SIZE)
+ inet_peer_threshold >>= 2; /* about 128KB */
+
+ peer_cachep = kmem_cache_create("inet_peer_cache",
+ sizeof(struct inet_peer),
+ 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
+ NULL);
+}
+
+/* Called with rcu_read_lock() or base->lock held */
+static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
+ struct inet_peer_base *base,
+ unsigned int seq,
+ struct inet_peer *gc_stack[],
+ unsigned int *gc_cnt,
+ struct rb_node **parent_p,
+ struct rb_node ***pp_p)
+{
+ struct rb_node **pp, *parent, *next;
+ struct inet_peer *p;
+
+ pp = &base->rb_root.rb_node;
+ parent = NULL;
+ while (1) {
+ int cmp;
+
+ next = rcu_dereference_raw(*pp);
+ if (!next)
+ break;
+ parent = next;
+ p = rb_entry(parent, struct inet_peer, rb_node);
+ cmp = inetpeer_addr_cmp(daddr, &p->daddr);
+ if (cmp == 0) {
+ if (!refcount_inc_not_zero(&p->refcnt))
+ break;
+ return p;
+ }
+ if (gc_stack) {
+ if (*gc_cnt < PEER_MAX_GC)
+ gc_stack[(*gc_cnt)++] = p;
+ } else if (unlikely(read_seqretry(&base->lock, seq))) {
+ break;
+ }
+ if (cmp == -1)
+ pp = &next->rb_left;
+ else
+ pp = &next->rb_right;
+ }
+ *parent_p = parent;
+ *pp_p = pp;
+ return NULL;
+}
+
+static void inetpeer_free_rcu(struct rcu_head *head)
+{
+ kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
+}
+
+/* perform garbage collect on all items stacked during a lookup */
+static void inet_peer_gc(struct inet_peer_base *base,
+ struct inet_peer *gc_stack[],
+ unsigned int gc_cnt)
+{
+ struct inet_peer *p;
+ __u32 delta, ttl;
+ int i;
+
+ if (base->total >= inet_peer_threshold)
+ ttl = 0; /* be aggressive */
+ else
+ ttl = inet_peer_maxttl
+ - (inet_peer_maxttl - inet_peer_minttl) / HZ *
+ base->total / inet_peer_threshold * HZ;
+ for (i = 0; i < gc_cnt; i++) {
+ p = gc_stack[i];
+ delta = (__u32)jiffies - p->dtime;
+ if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
+ gc_stack[i] = NULL;
+ }
+ for (i = 0; i < gc_cnt; i++) {
+ p = gc_stack[i];
+ if (p) {
+ rb_erase(&p->rb_node, &base->rb_root);
+ base->total--;
+ call_rcu(&p->rcu, inetpeer_free_rcu);
+ }
+ }
+}
+
+struct inet_peer *inet_getpeer(struct inet_peer_base *base,
+ const struct inetpeer_addr *daddr,
+ int create)
+{
+ struct inet_peer *p, *gc_stack[PEER_MAX_GC];
+ struct rb_node **pp, *parent;
+ unsigned int gc_cnt, seq;
+ int invalidated;
+
+ /* Attempt a lockless lookup first.
+ * Because of a concurrent writer, we might not find an existing entry.
+ */
+ rcu_read_lock();
+ seq = read_seqbegin(&base->lock);
+ p = lookup(daddr, base, seq, NULL, &gc_cnt, &parent, &pp);
+ invalidated = read_seqretry(&base->lock, seq);
+ rcu_read_unlock();
+
+ if (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.
+ */
+ parent = NULL;
+ write_seqlock_bh(&base->lock);
+
+ gc_cnt = 0;
+ p = lookup(daddr, base, seq, gc_stack, &gc_cnt, &parent, &pp);
+ if (!p && create) {
+ p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
+ if (p) {
+ p->daddr = *daddr;
+ p->dtime = (__u32)jiffies;
+ refcount_set(&p->refcnt, 2);
+ atomic_set(&p->rid, 0);
+ p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
+ p->rate_tokens = 0;
+ /* 60*HZ is arbitrary, but chosen enough high so that the first
+ * calculation of tokens is at its maximum.
+ */
+ p->rate_last = jiffies - 60*HZ;
+
+ rb_link_node(&p->rb_node, parent, pp);
+ rb_insert_color(&p->rb_node, &base->rb_root);
+ base->total++;
+ }
+ }
+ if (gc_cnt)
+ inet_peer_gc(base, gc_stack, gc_cnt);
+ write_sequnlock_bh(&base->lock);
+
+ return p;
+}
+EXPORT_SYMBOL_GPL(inet_getpeer);
+
+void inet_putpeer(struct inet_peer *p)
+{
+ p->dtime = (__u32)jiffies;
+
+ if (refcount_dec_and_test(&p->refcnt))
+ call_rcu(&p->rcu, inetpeer_free_rcu);
+}
+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);
+
+void inetpeer_invalidate_tree(struct inet_peer_base *base)
+{
+ struct rb_node *p = rb_first(&base->rb_root);
+
+ while (p) {
+ struct inet_peer *peer = rb_entry(p, struct inet_peer, rb_node);
+
+ p = rb_next(p);
+ rb_erase(&peer->rb_node, &base->rb_root);
+ inet_putpeer(peer);
+ cond_resched();
+ }
+
+ base->total = 0;
+}
+EXPORT_SYMBOL(inetpeer_invalidate_tree);