// SPDX-License-Identifier: GPL-2.0/* *		INETPEER - A storage for permanent information about peers * *  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>#include <linux/siphash.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;static siphash_aligned_key_t inetpeer_hash_key __read_mostly; static u64 inetpeer_addr_hash(const struct inetpeer_addr *a){	net_get_random_once(&inetpeer_hash_key, sizeof(inetpeer_hash_key)); 	if (a->family == AF_INET)		return siphash_2u32((__force u32)a->a4.addr, a->a4.vif,				    &inetpeer_hash_key); 	return siphash_4u32((__force u32)a->a6.s6_addr32[0],			    (__force u32)a->a6.s6_addr32[1],			    (__force u32)a->a6.s6_addr32[2],			    (__force u32)a->a6.s6_addr32[3],			    &inetpeer_hash_key);} static int inetpeer_entry_cmp(u64 dhash,			      const struct inetpeer_addr *daddr,			      const struct inet_peer *p){	if (dhash < p->hash)		return -1;	if (dhash > p->hash)		return 1; 	return inetpeer_addr_cmp(daddr, &p->daddr);} void inet_peer_base_init(struct inet_peer_base *bp){	bp->rb_root = RB_ROOT;	seqlock_init(&bp->lock);	bp->total = 0;} #define PEER_MAX_GC 32 /* Exported for sysctl_net_ipv4.  */int inet_peer_threshold __read_mostly;	/* 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){	u64 nr_entries; 	 /* 1% of physical memory */	nr_entries = div64_ul((u64)totalram_pages() << PAGE_SHIFT,			      100 * L1_CACHE_ALIGN(sizeof(struct inet_peer))); 	inet_peer_threshold = clamp_val(nr_entries, 4096, 65536 + 128); 	peer_cachep = KMEM_CACHE(inet_peer, SLAB_HWCACHE_ALIGN | SLAB_PANIC);} /* Called with rcu_read_lock() or base->lock held */static struct inet_peer *lookup(const struct inetpeer_addr *daddr,				u64 dhash,				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;	u32 now; 	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_entry_cmp(dhash, daddr, p);		if (cmp == 0) {			now = jiffies;			if (READ_ONCE(p->dtime) != now)				WRITE_ONCE(p->dtime, now);			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;} /* 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){	int peer_threshold, peer_maxttl, peer_minttl;	struct inet_peer *p;	__u32 delta, ttl;	int i; 	peer_threshold = READ_ONCE(inet_peer_threshold);	peer_maxttl = READ_ONCE(inet_peer_maxttl);	peer_minttl = READ_ONCE(inet_peer_minttl); 	if (base->total >= peer_threshold)		ttl = 0; /* be aggressive */	else		ttl = peer_maxttl - (peer_maxttl - peer_minttl) / HZ *			base->total / peer_threshold * HZ;	for (i = 0; i < gc_cnt; i++) {		p = gc_stack[i]; 		delta = (__u32)jiffies - READ_ONCE(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--;			kfree_rcu(p, rcu);		}	}} /* Must be called under RCU : No refcount change is done here. */struct inet_peer *inet_getpeer(struct inet_peer_base *base,			       const struct inetpeer_addr *daddr){	struct inet_peer *p, *gc_stack[PEER_MAX_GC];	u64 dhash = inetpeer_addr_hash(daddr);	struct rb_node **pp, *parent;	unsigned int gc_cnt, seq; 	/* Attempt a lockless lookup first.	 * Because of a concurrent writer, we might not find an existing entry.	 */	seq = read_seqbegin(&base->lock);	p = lookup(daddr, dhash, base, seq, NULL, &gc_cnt, &parent, &pp); 	/* Make sure tree was not modified during our lookup. */	if (p && !read_seqretry(&base->lock, seq))		return p; 	/* 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, dhash, base, seq, gc_stack, &gc_cnt, &parent, &pp);	if (!p) {		p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);		if (p) {			p->daddr = *daddr;			p->hash = dhash;			p->dtime = (__u32)jiffies;			refcount_set(&p->refcnt, 1);			atomic_set(&p->rid, 0);			p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;			p->rate_tokens = 0;			p->n_redirects = 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;} void inet_putpeer(struct inet_peer *p){	if (refcount_dec_and_test(&p->refcnt))		kfree_rcu(p, rcu);} /* *	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 6bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout){	unsigned long now, token, otoken, delta;	bool rc = false; 	if (!peer)		return true; 	token = otoken = READ_ONCE(peer->rate_tokens);	now = jiffies;	delta = now - READ_ONCE(peer->rate_last);	if (delta) {		WRITE_ONCE(peer->rate_last, now);		token += delta;		if (token > XRLIM_BURST_FACTOR * timeout)			token = XRLIM_BURST_FACTOR * timeout;	}	if (token >= timeout) {		token -= timeout;		rc = true;	}	if (token != otoken)		WRITE_ONCE(peer->rate_tokens, token);	return rc;} 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;}