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/*
* inet fragments management
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Authors: Pavel Emelyanov <xemul@openvz.org>
* Started as consolidation of ipv4/ip_fragment.c,
* ipv6/reassembly. and ipv6 nf conntrack reassembly
*/
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/inet_frag.h>
#include <net/inet_ecn.h>
#define INETFRAGS_EVICT_BUCKETS 128
#define INETFRAGS_EVICT_MAX 512
/* don't rebuild inetfrag table with new secret more often than this */
#define INETFRAGS_MIN_REBUILD_INTERVAL (5 * HZ)
/* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
* Value : 0xff if frame should be dropped.
* 0 or INET_ECN_CE value, to be ORed in to final iph->tos field
*/
const u8 ip_frag_ecn_table[16] = {
/* at least one fragment had CE, and others ECT_0 or ECT_1 */
[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE,
[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
/* invalid combinations : drop frame */
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
};
EXPORT_SYMBOL(ip_frag_ecn_table);
static unsigned int
inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q)
{
return f->hashfn(q) & (INETFRAGS_HASHSZ - 1);
}
static bool inet_frag_may_rebuild(struct inet_frags *f)
{
return time_after(jiffies,
f->last_rebuild_jiffies + INETFRAGS_MIN_REBUILD_INTERVAL);
}
static void inet_frag_secret_rebuild(struct inet_frags *f)
{
int i;
write_seqlock_bh(&f->rnd_seqlock);
if (!inet_frag_may_rebuild(f))
goto out;
get_random_bytes(&f->rnd, sizeof(u32));
for (i = 0; i < INETFRAGS_HASHSZ; i++) {
struct inet_frag_bucket *hb;
struct inet_frag_queue *q;
struct hlist_node *n;
hb = &f->hash[i];
spin_lock(&hb->chain_lock);
hlist_for_each_entry_safe(q, n, &hb->chain, list) {
unsigned int hval = inet_frag_hashfn(f, q);
if (hval != i) {
struct inet_frag_bucket *hb_dest;
hlist_del(&q->list);
/* Relink to new hash chain. */
hb_dest = &f->hash[hval];
/* This is the only place where we take
* another chain_lock while already holding
* one. As this will not run concurrently,
* we cannot deadlock on hb_dest lock below, if its
* already locked it will be released soon since
* other caller cannot be waiting for hb lock
* that we've taken above.
*/
spin_lock_nested(&hb_dest->chain_lock,
SINGLE_DEPTH_NESTING);
hlist_add_head(&q->list, &hb_dest->chain);
spin_unlock(&hb_dest->chain_lock);
}
}
spin_unlock(&hb->chain_lock);
}
f->rebuild = false;
f->last_rebuild_jiffies = jiffies;
out:
write_sequnlock_bh(&f->rnd_seqlock);
}
static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
{
return q->net->low_thresh == 0 ||
frag_mem_limit(q->net) >= q->net->low_thresh;
}
static unsigned int
inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb)
{
struct inet_frag_queue *fq;
struct hlist_node *n;
unsigned int evicted = 0;
HLIST_HEAD(expired);
evict_again:
spin_lock(&hb->chain_lock);
hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
if (!inet_fragq_should_evict(fq))
continue;
if (!del_timer(&fq->timer)) {
/* q expiring right now thus increment its refcount so
* it won't be freed under us and wait until the timer
* has finished executing then destroy it
*/
atomic_inc(&fq->refcnt);
spin_unlock(&hb->chain_lock);
del_timer_sync(&fq->timer);
WARN_ON(atomic_read(&fq->refcnt) != 1);
inet_frag_put(fq, f);
goto evict_again;
}
fq->flags |= INET_FRAG_EVICTED;
hlist_del(&fq->list);
hlist_add_head(&fq->list, &expired);
++evicted;
}
spin_unlock(&hb->chain_lock);
hlist_for_each_entry_safe(fq, n, &expired, list)
f->frag_expire((unsigned long) fq);
return evicted;
}
static void inet_frag_worker(struct work_struct *work)
{
unsigned int budget = INETFRAGS_EVICT_BUCKETS;
unsigned int i, evicted = 0;
struct inet_frags *f;
f = container_of(work, struct inet_frags, frags_work);
BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
local_bh_disable();
for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
evicted += inet_evict_bucket(f, &f->hash[i]);
i = (i + 1) & (INETFRAGS_HASHSZ - 1);
if (evicted > INETFRAGS_EVICT_MAX)
break;
}
f->next_bucket = i;
local_bh_enable();
if (f->rebuild && inet_frag_may_rebuild(f))
inet_frag_secret_rebuild(f);
}
static void inet_frag_schedule_worker(struct inet_frags *f)
{
if (unlikely(!work_pending(&f->frags_work)))
schedule_work(&f->frags_work);
}
int inet_frags_init(struct inet_frags *f)
{
int i;
INIT_WORK(&f->frags_work, inet_frag_worker);
for (i = 0; i < INETFRAGS_HASHSZ; i++) {
struct inet_frag_bucket *hb = &f->hash[i];
spin_lock_init(&hb->chain_lock);
INIT_HLIST_HEAD(&hb->chain);
}
seqlock_init(&f->rnd_seqlock);
f->last_rebuild_jiffies = 0;
f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
NULL);
if (!f->frags_cachep)
return -ENOMEM;
return 0;
}
EXPORT_SYMBOL(inet_frags_init);
void inet_frags_init_net(struct netns_frags *nf)
{
init_frag_mem_limit(nf);
}
EXPORT_SYMBOL(inet_frags_init_net);
void inet_frags_fini(struct inet_frags *f)
{
cancel_work_sync(&f->frags_work);
kmem_cache_destroy(f->frags_cachep);
}
EXPORT_SYMBOL(inet_frags_fini);
void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
{
unsigned int seq;
int i;
nf->low_thresh = 0;
local_bh_disable();
evict_again:
seq = read_seqbegin(&f->rnd_seqlock);
for (i = 0; i < INETFRAGS_HASHSZ ; i++)
inet_evict_bucket(f, &f->hash[i]);
if (read_seqretry(&f->rnd_seqlock, seq))
goto evict_again;
local_bh_enable();
percpu_counter_destroy(&nf->mem);
}
EXPORT_SYMBOL(inet_frags_exit_net);
static struct inet_frag_bucket *
get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
__acquires(hb->chain_lock)
{
struct
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