mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 16:29:59 +00:00
![Lorenzo Bianconi](/assets/img/avatar_default.png)
According to the algorithm described in the comment block at the
beginning of ip_rt_send_redirect, the host should try to send
'ip_rt_redirect_number' ICMP redirect packets with an exponential
backoff and then stop sending them at all assuming that the destination
ignores redirects.
If the device has previously sent some ICMP error packets that are
rate-limited (e.g TTL expired) and continues to receive traffic,
the redirect packets will never be transmitted. This happens since
peer->rate_tokens will be typically greater than 'ip_rt_redirect_number'
and so it will never be reset even if the redirect silence timeout
(ip_rt_redirect_silence) has elapsed without receiving any packet
requiring redirects.
Fix it by using a dedicated counter for the number of ICMP redirect
packets that has been sent by the host
I have not been able to identify a given commit that introduced the
issue since ip_rt_send_redirect implements the same rate-limiting
algorithm from commit 1da177e4c3
("Linux-2.6.12-rc2")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
303 lines
8.3 KiB
C
303 lines
8.3 KiB
C
/*
|
|
* 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;
|
|
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;
|
|
}
|
|
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);
|