466 lines
14 KiB
C
466 lines
14 KiB
C
/*
|
|
* INETPEER - A storage for permanent information about peers
|
|
*
|
|
* This source is covered by the GNU GPL, the same as all kernel sources.
|
|
*
|
|
* Version: $Id: inetpeer.c,v 1.7 2001/09/20 21:22:50 davem Exp $
|
|
*
|
|
* Authors: Andrey V. Savochkin <saw@msu.ru>
|
|
*/
|
|
|
|
#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 <net/ip.h>
|
|
#include <net/inetpeer.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.
|
|
* At this moment this information consists only of ID field for the next
|
|
* outgoing IP packet. This field is incremented with each packet as encoded
|
|
* in inet_getid() function (include/net/inetpeer.h).
|
|
* At the moment of writing this notes identifier of IP packets is generated
|
|
* to be unpredictable using this code only for packets subjected
|
|
* (actually or potentially) to defragmentation. I.e. DF packets less than
|
|
* PMTU in size uses a constant ID and do not use this code (see
|
|
* ip_select_ident() in include/net/ip.h).
|
|
*
|
|
* Route cache entries hold references to our nodes.
|
|
* New cache entries get references via lookup by destination IP address in
|
|
* the avl tree. The reference is grabbed only when it's needed i.e. only
|
|
* when we try to output IP packet which needs an unpredictable ID (see
|
|
* __ip_select_ident() in net/ipv4/route.c).
|
|
* 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 AVL 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 write lock held.
|
|
* 2. Nodes may disappear from the tree only with the pool write lock held
|
|
* AND reference count being 0.
|
|
* 3. Nodes appears and disappears from unused node list only under
|
|
* "inet_peer_unused_lock".
|
|
* 4. Global variable peer_total is modified under the pool lock.
|
|
* 5. struct inet_peer fields modification:
|
|
* avl_left, avl_right, avl_parent, avl_height: pool lock
|
|
* unused: unused node list lock
|
|
* refcnt: atomically against modifications on other CPU;
|
|
* usually under some other lock to prevent node disappearing
|
|
* dtime: unused node list lock
|
|
* v4daddr: unchangeable
|
|
* ip_id_count: idlock
|
|
*/
|
|
|
|
/* Exported for inet_getid inline function. */
|
|
DEFINE_SPINLOCK(inet_peer_idlock);
|
|
|
|
static struct kmem_cache *peer_cachep __read_mostly;
|
|
|
|
#define node_height(x) x->avl_height
|
|
static struct inet_peer peer_fake_node = {
|
|
.avl_left = &peer_fake_node,
|
|
.avl_right = &peer_fake_node,
|
|
.avl_height = 0
|
|
};
|
|
#define peer_avl_empty (&peer_fake_node)
|
|
static struct inet_peer *peer_root = peer_avl_empty;
|
|
static DEFINE_RWLOCK(peer_pool_lock);
|
|
#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
|
|
|
|
static int peer_total;
|
|
/* 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 */
|
|
int inet_peer_gc_mintime __read_mostly = 10 * HZ;
|
|
int inet_peer_gc_maxtime __read_mostly = 120 * HZ;
|
|
|
|
static LIST_HEAD(unused_peers);
|
|
static DEFINE_SPINLOCK(inet_peer_unused_lock);
|
|
|
|
static void peer_check_expire(unsigned long dummy);
|
|
static DEFINE_TIMER(peer_periodic_timer, peer_check_expire, 0, 0);
|
|
|
|
|
|
/* 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);
|
|
|
|
/* All the timers, started at system startup tend
|
|
to synchronize. Perturb it a bit.
|
|
*/
|
|
peer_periodic_timer.expires = jiffies
|
|
+ net_random() % inet_peer_gc_maxtime
|
|
+ inet_peer_gc_maxtime;
|
|
add_timer(&peer_periodic_timer);
|
|
}
|
|
|
|
/* Called with or without local BH being disabled. */
|
|
static void unlink_from_unused(struct inet_peer *p)
|
|
{
|
|
spin_lock_bh(&inet_peer_unused_lock);
|
|
list_del_init(&p->unused);
|
|
spin_unlock_bh(&inet_peer_unused_lock);
|
|
}
|
|
|
|
/*
|
|
* Called with local BH disabled and the pool lock held.
|
|
* _stack is known to be NULL or not at compile time,
|
|
* so compiler will optimize the if (_stack) tests.
|
|
*/
|
|
#define lookup(_daddr,_stack) \
|
|
({ \
|
|
struct inet_peer *u, **v; \
|
|
if (_stack != NULL) { \
|
|
stackptr = _stack; \
|
|
*stackptr++ = &peer_root; \
|
|
} \
|
|
for (u = peer_root; u != peer_avl_empty; ) { \
|
|
if (_daddr == u->v4daddr) \
|
|
break; \
|
|
if ((__force __u32)_daddr < (__force __u32)u->v4daddr) \
|
|
v = &u->avl_left; \
|
|
else \
|
|
v = &u->avl_right; \
|
|
if (_stack != NULL) \
|
|
*stackptr++ = v; \
|
|
u = *v; \
|
|
} \
|
|
u; \
|
|
})
|
|
|
|
/* Called with local BH disabled and the pool write lock held. */
|
|
#define lookup_rightempty(start) \
|
|
({ \
|
|
struct inet_peer *u, **v; \
|
|
*stackptr++ = &start->avl_left; \
|
|
v = &start->avl_left; \
|
|
for (u = *v; u->avl_right != peer_avl_empty; ) { \
|
|
v = &u->avl_right; \
|
|
*stackptr++ = v; \
|
|
u = *v; \
|
|
} \
|
|
u; \
|
|
})
|
|
|
|
/* Called with local BH disabled and the pool write lock held.
|
|
* 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)
|
|
{
|
|
struct inet_peer **nodep, *node, *l, *r;
|
|
int lh, rh;
|
|
|
|
while (stackend > stack) {
|
|
nodep = *--stackend;
|
|
node = *nodep;
|
|
l = node->avl_left;
|
|
r = node->avl_right;
|
|
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;
|
|
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 */
|
|
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 */
|
|
l->avl_height = node->avl_height + 1;
|
|
*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 */
|
|
node->avl_height = rh + 1; /* node: RH+1 */
|
|
l->avl_left = ll; /* ll: RH */
|
|
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 */
|
|
lr->avl_height = rh + 2;
|
|
*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;
|
|
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 */
|
|
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 */
|
|
r->avl_height = node->avl_height + 1;
|
|
*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 */
|
|
node->avl_height = lh + 1; /* node: LH+1 */
|
|
r->avl_right = rr; /* rr: LH */
|
|
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 */
|
|
rl->avl_height = lh + 2;
|
|
*nodep = rl;
|
|
}
|
|
} else {
|
|
node->avl_height = (lh > rh ? lh : rh) + 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Called with local BH disabled and the pool write lock held. */
|
|
#define link_to_pool(n) \
|
|
do { \
|
|
n->avl_height = 1; \
|
|
n->avl_left = peer_avl_empty; \
|
|
n->avl_right = peer_avl_empty; \
|
|
**--stackptr = n; \
|
|
peer_avl_rebalance(stack, stackptr); \
|
|
} while(0)
|
|
|
|
/* May be called with local BH enabled. */
|
|
static void unlink_from_pool(struct inet_peer *p)
|
|
{
|
|
int do_free;
|
|
|
|
do_free = 0;
|
|
|
|
write_lock_bh(&peer_pool_lock);
|
|
/* Check the reference counter. It was artificially incremented by 1
|
|
* in cleanup() function to prevent sudden disappearing. If the
|
|
* reference count is still 1 then the node is referenced only as `p'
|
|
* here and from the pool. So under the exclusive pool lock it's safe
|
|
* to remove the node and free it later. */
|
|
if (atomic_read(&p->refcnt) == 1) {
|
|
struct inet_peer **stack[PEER_MAXDEPTH];
|
|
struct inet_peer ***stackptr, ***delp;
|
|
if (lookup(p->v4daddr, stack) != p)
|
|
BUG();
|
|
delp = stackptr - 1; /* *delp[0] == p */
|
|
if (p->avl_left == peer_avl_empty) {
|
|
*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);
|
|
**--stackptr = t->avl_left;
|
|
/* t is removed, t->v4daddr > x->v4daddr for any
|
|
* x in p->avl_left subtree.
|
|
* Put t in the old place of p. */
|
|
*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);
|
|
peer_total--;
|
|
do_free = 1;
|
|
}
|
|
write_unlock_bh(&peer_pool_lock);
|
|
|
|
if (do_free)
|
|
kmem_cache_free(peer_cachep, p);
|
|
else
|
|
/* The node is used again. Decrease the reference counter
|
|
* back. The loop "cleanup -> unlink_from_unused
|
|
* -> unlink_from_pool -> putpeer -> link_to_unused
|
|
* -> cleanup (for the same node)"
|
|
* doesn't really exist because the entry will have a
|
|
* recent deletion time and will not be cleaned again soon. */
|
|
inet_putpeer(p);
|
|
}
|
|
|
|
/* May be called with local BH enabled. */
|
|
static int cleanup_once(unsigned long ttl)
|
|
{
|
|
struct inet_peer *p = NULL;
|
|
|
|
/* Remove the first entry from the list of unused nodes. */
|
|
spin_lock_bh(&inet_peer_unused_lock);
|
|
if (!list_empty(&unused_peers)) {
|
|
__u32 delta;
|
|
|
|
p = list_first_entry(&unused_peers, struct inet_peer, unused);
|
|
delta = (__u32)jiffies - p->dtime;
|
|
|
|
if (delta < ttl) {
|
|
/* Do not prune fresh entries. */
|
|
spin_unlock_bh(&inet_peer_unused_lock);
|
|
return -1;
|
|
}
|
|
|
|
list_del_init(&p->unused);
|
|
|
|
/* Grab an extra reference to prevent node disappearing
|
|
* before unlink_from_pool() call. */
|
|
atomic_inc(&p->refcnt);
|
|
}
|
|
spin_unlock_bh(&inet_peer_unused_lock);
|
|
|
|
if (p == NULL)
|
|
/* It means that the total number of USED entries has
|
|
* grown over inet_peer_threshold. It shouldn't really
|
|
* happen because of entry limits in route cache. */
|
|
return -1;
|
|
|
|
unlink_from_pool(p);
|
|
return 0;
|
|
}
|
|
|
|
/* Called with or without local BH being disabled. */
|
|
struct inet_peer *inet_getpeer(__be32 daddr, int create)
|
|
{
|
|
struct inet_peer *p, *n;
|
|
struct inet_peer **stack[PEER_MAXDEPTH], ***stackptr;
|
|
|
|
/* Look up for the address quickly. */
|
|
read_lock_bh(&peer_pool_lock);
|
|
p = lookup(daddr, NULL);
|
|
if (p != peer_avl_empty)
|
|
atomic_inc(&p->refcnt);
|
|
read_unlock_bh(&peer_pool_lock);
|
|
|
|
if (p != peer_avl_empty) {
|
|
/* The existing node has been found. */
|
|
/* Remove the entry from unused list if it was there. */
|
|
unlink_from_unused(p);
|
|
return p;
|
|
}
|
|
|
|
if (!create)
|
|
return NULL;
|
|
|
|
/* Allocate the space outside the locked region. */
|
|
n = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
|
|
if (n == NULL)
|
|
return NULL;
|
|
n->v4daddr = daddr;
|
|
atomic_set(&n->refcnt, 1);
|
|
atomic_set(&n->rid, 0);
|
|
n->ip_id_count = secure_ip_id(daddr);
|
|
n->tcp_ts_stamp = 0;
|
|
|
|
write_lock_bh(&peer_pool_lock);
|
|
/* Check if an entry has suddenly appeared. */
|
|
p = lookup(daddr, stack);
|
|
if (p != peer_avl_empty)
|
|
goto out_free;
|
|
|
|
/* Link the node. */
|
|
link_to_pool(n);
|
|
INIT_LIST_HEAD(&n->unused);
|
|
peer_total++;
|
|
write_unlock_bh(&peer_pool_lock);
|
|
|
|
if (peer_total >= inet_peer_threshold)
|
|
/* Remove one less-recently-used entry. */
|
|
cleanup_once(0);
|
|
|
|
return n;
|
|
|
|
out_free:
|
|
/* The appropriate node is already in the pool. */
|
|
atomic_inc(&p->refcnt);
|
|
write_unlock_bh(&peer_pool_lock);
|
|
/* Remove the entry from unused list if it was there. */
|
|
unlink_from_unused(p);
|
|
/* Free preallocated the preallocated node. */
|
|
kmem_cache_free(peer_cachep, n);
|
|
return p;
|
|
}
|
|
|
|
/* Called with local BH disabled. */
|
|
static void peer_check_expire(unsigned long dummy)
|
|
{
|
|
unsigned long now = jiffies;
|
|
int ttl;
|
|
|
|
if (peer_total >= inet_peer_threshold)
|
|
ttl = inet_peer_minttl;
|
|
else
|
|
ttl = inet_peer_maxttl
|
|
- (inet_peer_maxttl - inet_peer_minttl) / HZ *
|
|
peer_total / inet_peer_threshold * HZ;
|
|
while (!cleanup_once(ttl)) {
|
|
if (jiffies != now)
|
|
break;
|
|
}
|
|
|
|
/* 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 (peer_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 *
|
|
peer_total / inet_peer_threshold * HZ;
|
|
add_timer(&peer_periodic_timer);
|
|
}
|
|
|
|
void inet_putpeer(struct inet_peer *p)
|
|
{
|
|
spin_lock_bh(&inet_peer_unused_lock);
|
|
if (atomic_dec_and_test(&p->refcnt)) {
|
|
list_add_tail(&p->unused, &unused_peers);
|
|
p->dtime = (__u32)jiffies;
|
|
}
|
|
spin_unlock_bh(&inet_peer_unused_lock);
|
|
}
|