linux/net/netfilter/nf_conntrack_ecache.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/* Event cache for netfilter. */
   3
   4/*
   5 * (C) 2005 Harald Welte <laforge@gnumonks.org>
   6 * (C) 2005 Patrick McHardy <kaber@trash.net>
   7 * (C) 2005-2006 Netfilter Core Team <coreteam@netfilter.org>
   8 * (C) 2005 USAGI/WIDE Project <http://www.linux-ipv6.org>
   9 */
  10
  11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13#include <linux/types.h>
  14#include <linux/netfilter.h>
  15#include <linux/skbuff.h>
  16#include <linux/vmalloc.h>
  17#include <linux/stddef.h>
  18#include <linux/err.h>
  19#include <linux/percpu.h>
  20#include <linux/kernel.h>
  21#include <linux/netdevice.h>
  22#include <linux/slab.h>
  23#include <linux/export.h>
  24
  25#include <net/netfilter/nf_conntrack.h>
  26#include <net/netfilter/nf_conntrack_core.h>
  27#include <net/netfilter/nf_conntrack_ecache.h>
  28#include <net/netfilter/nf_conntrack_extend.h>
  29
  30static DEFINE_MUTEX(nf_ct_ecache_mutex);
  31
  32#define ECACHE_RETRY_WAIT (HZ/10)
  33#define ECACHE_STACK_ALLOC (256 / sizeof(void *))
  34
  35enum retry_state {
  36        STATE_CONGESTED,
  37        STATE_RESTART,
  38        STATE_DONE,
  39};
  40
  41static enum retry_state ecache_work_evict_list(struct ct_pcpu *pcpu)
  42{
  43        struct nf_conn *refs[ECACHE_STACK_ALLOC];
  44        enum retry_state ret = STATE_DONE;
  45        struct nf_conntrack_tuple_hash *h;
  46        struct hlist_nulls_node *n;
  47        unsigned int evicted = 0;
  48
  49        spin_lock(&pcpu->lock);
  50
  51        hlist_nulls_for_each_entry(h, n, &pcpu->dying, hnnode) {
  52                struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
  53                struct nf_conntrack_ecache *e;
  54
  55                if (!nf_ct_is_confirmed(ct))
  56                        continue;
  57
  58                /* This ecache access is safe because the ct is on the
  59                 * pcpu dying list and we hold the spinlock -- the entry
  60                 * cannot be free'd until after the lock is released.
  61                 *
  62                 * This is true even if ct has a refcount of 0: the
  63                 * cpu that is about to free the entry must remove it
  64                 * from the dying list and needs the lock to do so.
  65                 */
  66                e = nf_ct_ecache_find(ct);
  67                if (!e || e->state != NFCT_ECACHE_DESTROY_FAIL)
  68                        continue;
  69
  70                /* ct is in NFCT_ECACHE_DESTROY_FAIL state, this means
  71                 * the worker owns this entry: the ct will remain valid
  72                 * until the worker puts its ct reference.
  73                 */
  74                if (nf_conntrack_event(IPCT_DESTROY, ct)) {
  75                        ret = STATE_CONGESTED;
  76                        break;
  77                }
  78
  79                e->state = NFCT_ECACHE_DESTROY_SENT;
  80                refs[evicted] = ct;
  81
  82                if (++evicted >= ARRAY_SIZE(refs)) {
  83                        ret = STATE_RESTART;
  84                        break;
  85                }
  86        }
  87
  88        spin_unlock(&pcpu->lock);
  89
  90        /* can't _put while holding lock */
  91        while (evicted)
  92                nf_ct_put(refs[--evicted]);
  93
  94        return ret;
  95}
  96
  97static void ecache_work(struct work_struct *work)
  98{
  99        struct nf_conntrack_net *cnet = container_of(work, struct nf_conntrack_net, ecache_dwork.work);
 100        struct netns_ct *ctnet = cnet->ct_net;
 101        int cpu, delay = -1;
 102        struct ct_pcpu *pcpu;
 103
 104        local_bh_disable();
 105
 106        for_each_possible_cpu(cpu) {
 107                enum retry_state ret;
 108
 109                pcpu = per_cpu_ptr(ctnet->pcpu_lists, cpu);
 110
 111                ret = ecache_work_evict_list(pcpu);
 112
 113                switch (ret) {
 114                case STATE_CONGESTED:
 115                        delay = ECACHE_RETRY_WAIT;
 116                        goto out;
 117                case STATE_RESTART:
 118                        delay = 0;
 119                        break;
 120                case STATE_DONE:
 121                        break;
 122                }
 123        }
 124
 125 out:
 126        local_bh_enable();
 127
 128        ctnet->ecache_dwork_pending = delay > 0;
 129        if (delay >= 0)
 130                schedule_delayed_work(&cnet->ecache_dwork, delay);
 131}
 132
 133int nf_conntrack_eventmask_report(unsigned int eventmask, struct nf_conn *ct,
 134                                  u32 portid, int report)
 135{
 136        int ret = 0;
 137        struct net *net = nf_ct_net(ct);
 138        struct nf_ct_event_notifier *notify;
 139        struct nf_conntrack_ecache *e;
 140
 141        rcu_read_lock();
 142        notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
 143        if (!notify)
 144                goto out_unlock;
 145
 146        e = nf_ct_ecache_find(ct);
 147        if (!e)
 148                goto out_unlock;
 149
 150        if (nf_ct_is_confirmed(ct)) {
 151                struct nf_ct_event item = {
 152                        .ct     = ct,
 153                        .portid = e->portid ? e->portid : portid,
 154                        .report = report
 155                };
 156                /* This is a resent of a destroy event? If so, skip missed */
 157                unsigned long missed = e->portid ? 0 : e->missed;
 158
 159                if (!((eventmask | missed) & e->ctmask))
 160                        goto out_unlock;
 161
 162                ret = notify->fcn(eventmask | missed, &item);
 163                if (unlikely(ret < 0 || missed)) {
 164                        spin_lock_bh(&ct->lock);
 165                        if (ret < 0) {
 166                                /* This is a destroy event that has been
 167                                 * triggered by a process, we store the PORTID
 168                                 * to include it in the retransmission.
 169                                 */
 170                                if (eventmask & (1 << IPCT_DESTROY)) {
 171                                        if (e->portid == 0 && portid != 0)
 172                                                e->portid = portid;
 173                                        e->state = NFCT_ECACHE_DESTROY_FAIL;
 174                                } else {
 175                                        e->missed |= eventmask;
 176                                }
 177                        } else {
 178                                e->missed &= ~missed;
 179                        }
 180                        spin_unlock_bh(&ct->lock);
 181                }
 182        }
 183out_unlock:
 184        rcu_read_unlock();
 185        return ret;
 186}
 187EXPORT_SYMBOL_GPL(nf_conntrack_eventmask_report);
 188
 189/* deliver cached events and clear cache entry - must be called with locally
 190 * disabled softirqs */
 191void nf_ct_deliver_cached_events(struct nf_conn *ct)
 192{
 193        struct net *net = nf_ct_net(ct);
 194        unsigned long events, missed;
 195        struct nf_ct_event_notifier *notify;
 196        struct nf_conntrack_ecache *e;
 197        struct nf_ct_event item;
 198        int ret;
 199
 200        rcu_read_lock();
 201        notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
 202        if (notify == NULL)
 203                goto out_unlock;
 204
 205        if (!nf_ct_is_confirmed(ct) || nf_ct_is_dying(ct))
 206                goto out_unlock;
 207
 208        e = nf_ct_ecache_find(ct);
 209        if (e == NULL)
 210                goto out_unlock;
 211
 212        events = xchg(&e->cache, 0);
 213
 214        /* We make a copy of the missed event cache without taking
 215         * the lock, thus we may send missed events twice. However,
 216         * this does not harm and it happens very rarely. */
 217        missed = e->missed;
 218
 219        if (!((events | missed) & e->ctmask))
 220                goto out_unlock;
 221
 222        item.ct = ct;
 223        item.portid = 0;
 224        item.report = 0;
 225
 226        ret = notify->fcn(events | missed, &item);
 227
 228        if (likely(ret == 0 && !missed))
 229                goto out_unlock;
 230
 231        spin_lock_bh(&ct->lock);
 232        if (ret < 0)
 233                e->missed |= events;
 234        else
 235                e->missed &= ~missed;
 236        spin_unlock_bh(&ct->lock);
 237
 238out_unlock:
 239        rcu_read_unlock();
 240}
 241EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
 242
 243void nf_ct_expect_event_report(enum ip_conntrack_expect_events event,
 244                               struct nf_conntrack_expect *exp,
 245                               u32 portid, int report)
 246
 247{
 248        struct net *net = nf_ct_exp_net(exp);
 249        struct nf_exp_event_notifier *notify;
 250        struct nf_conntrack_ecache *e;
 251
 252        rcu_read_lock();
 253        notify = rcu_dereference(net->ct.nf_expect_event_cb);
 254        if (!notify)
 255                goto out_unlock;
 256
 257        e = nf_ct_ecache_find(exp->master);
 258        if (!e)
 259                goto out_unlock;
 260
 261        if (e->expmask & (1 << event)) {
 262                struct nf_exp_event item = {
 263                        .exp    = exp,
 264                        .portid = portid,
 265                        .report = report
 266                };
 267                notify->fcn(1 << event, &item);
 268        }
 269out_unlock:
 270        rcu_read_unlock();
 271}
 272
 273int nf_conntrack_register_notifier(struct net *net,
 274                                   struct nf_ct_event_notifier *new)
 275{
 276        int ret;
 277        struct nf_ct_event_notifier *notify;
 278
 279        mutex_lock(&nf_ct_ecache_mutex);
 280        notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
 281                                           lockdep_is_held(&nf_ct_ecache_mutex));
 282        if (notify != NULL) {
 283                ret = -EBUSY;
 284                goto out_unlock;
 285        }
 286        rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
 287        ret = 0;
 288
 289out_unlock:
 290        mutex_unlock(&nf_ct_ecache_mutex);
 291        return ret;
 292}
 293EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);
 294
 295void nf_conntrack_unregister_notifier(struct net *net,
 296                                      struct nf_ct_event_notifier *new)
 297{
 298        struct nf_ct_event_notifier *notify;
 299
 300        mutex_lock(&nf_ct_ecache_mutex);
 301        notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
 302                                           lockdep_is_held(&nf_ct_ecache_mutex));
 303        BUG_ON(notify != new);
 304        RCU_INIT_POINTER(net->ct.nf_conntrack_event_cb, NULL);
 305        mutex_unlock(&nf_ct_ecache_mutex);
 306        /* synchronize_rcu() is called from ctnetlink_exit. */
 307}
 308EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);
 309
 310int nf_ct_expect_register_notifier(struct net *net,
 311                                   struct nf_exp_event_notifier *new)
 312{
 313        int ret;
 314        struct nf_exp_event_notifier *notify;
 315
 316        mutex_lock(&nf_ct_ecache_mutex);
 317        notify = rcu_dereference_protected(net->ct.nf_expect_event_cb,
 318                                           lockdep_is_held(&nf_ct_ecache_mutex));
 319        if (notify != NULL) {
 320                ret = -EBUSY;
 321                goto out_unlock;
 322        }
 323        rcu_assign_pointer(net->ct.nf_expect_event_cb, new);
 324        ret = 0;
 325
 326out_unlock:
 327        mutex_unlock(&nf_ct_ecache_mutex);
 328        return ret;
 329}
 330EXPORT_SYMBOL_GPL(nf_ct_expect_register_notifier);
 331
 332void nf_ct_expect_unregister_notifier(struct net *net,
 333                                      struct nf_exp_event_notifier *new)
 334{
 335        struct nf_exp_event_notifier *notify;
 336
 337        mutex_lock(&nf_ct_ecache_mutex);
 338        notify = rcu_dereference_protected(net->ct.nf_expect_event_cb,
 339                                           lockdep_is_held(&nf_ct_ecache_mutex));
 340        BUG_ON(notify != new);
 341        RCU_INIT_POINTER(net->ct.nf_expect_event_cb, NULL);
 342        mutex_unlock(&nf_ct_ecache_mutex);
 343        /* synchronize_rcu() is called from ctnetlink_exit. */
 344}
 345EXPORT_SYMBOL_GPL(nf_ct_expect_unregister_notifier);
 346
 347void nf_conntrack_ecache_work(struct net *net, enum nf_ct_ecache_state state)
 348{
 349        struct nf_conntrack_net *cnet = nf_ct_pernet(net);
 350
 351        if (state == NFCT_ECACHE_DESTROY_FAIL &&
 352            !delayed_work_pending(&cnet->ecache_dwork)) {
 353                schedule_delayed_work(&cnet->ecache_dwork, HZ);
 354                net->ct.ecache_dwork_pending = true;
 355        } else if (state == NFCT_ECACHE_DESTROY_SENT) {
 356                net->ct.ecache_dwork_pending = false;
 357                mod_delayed_work(system_wq, &cnet->ecache_dwork, 0);
 358        }
 359}
 360
 361#define NF_CT_EVENTS_DEFAULT 1
 362static int nf_ct_events __read_mostly = NF_CT_EVENTS_DEFAULT;
 363
 364static const struct nf_ct_ext_type event_extend = {
 365        .len    = sizeof(struct nf_conntrack_ecache),
 366        .align  = __alignof__(struct nf_conntrack_ecache),
 367        .id     = NF_CT_EXT_ECACHE,
 368};
 369
 370void nf_conntrack_ecache_pernet_init(struct net *net)
 371{
 372        struct nf_conntrack_net *cnet = nf_ct_pernet(net);
 373
 374        net->ct.sysctl_events = nf_ct_events;
 375        cnet->ct_net = &net->ct;
 376        INIT_DELAYED_WORK(&cnet->ecache_dwork, ecache_work);
 377}
 378
 379void nf_conntrack_ecache_pernet_fini(struct net *net)
 380{
 381        struct nf_conntrack_net *cnet = nf_ct_pernet(net);
 382
 383        cancel_delayed_work_sync(&cnet->ecache_dwork);
 384}
 385
 386int nf_conntrack_ecache_init(void)
 387{
 388        int ret = nf_ct_extend_register(&event_extend);
 389        if (ret < 0)
 390                pr_err("Unable to register event extension\n");
 391
 392        BUILD_BUG_ON(__IPCT_MAX >= 16); /* ctmask, missed use u16 */
 393
 394        return ret;
 395}
 396
 397void nf_conntrack_ecache_fini(void)
 398{
 399        nf_ct_extend_unregister(&event_extend);
 400}
 401