linux/net/netfilter/core.c
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   1/* netfilter.c: look after the filters for various protocols.
   2 * Heavily influenced by the old firewall.c by David Bonn and Alan Cox.
   3 *
   4 * Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
   5 * way.
   6 *
   7 * Rusty Russell (C)2000 -- This code is GPL.
   8 */
   9#include <linux/kernel.h>
  10#include <linux/netfilter.h>
  11#include <net/protocol.h>
  12#include <linux/init.h>
  13#include <linux/skbuff.h>
  14#include <linux/wait.h>
  15#include <linux/module.h>
  16#include <linux/interrupt.h>
  17#include <linux/if.h>
  18#include <linux/netdevice.h>
  19#include <linux/inetdevice.h>
  20#include <linux/proc_fs.h>
  21#include <linux/mutex.h>
  22#include <linux/slab.h>
  23#include <net/net_namespace.h>
  24#include <net/sock.h>
  25
  26#include "nf_internals.h"
  27
  28static DEFINE_MUTEX(afinfo_mutex);
  29
  30const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
  31EXPORT_SYMBOL(nf_afinfo);
  32
  33int nf_register_afinfo(const struct nf_afinfo *afinfo)
  34{
  35        int err;
  36
  37        err = mutex_lock_interruptible(&afinfo_mutex);
  38        if (err < 0)
  39                return err;
  40        RCU_INIT_POINTER(nf_afinfo[afinfo->family], afinfo);
  41        mutex_unlock(&afinfo_mutex);
  42        return 0;
  43}
  44EXPORT_SYMBOL_GPL(nf_register_afinfo);
  45
  46void nf_unregister_afinfo(const struct nf_afinfo *afinfo)
  47{
  48        mutex_lock(&afinfo_mutex);
  49        RCU_INIT_POINTER(nf_afinfo[afinfo->family], NULL);
  50        mutex_unlock(&afinfo_mutex);
  51        synchronize_rcu();
  52}
  53EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
  54
  55struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS] __read_mostly;
  56EXPORT_SYMBOL(nf_hooks);
  57
  58#if defined(CONFIG_JUMP_LABEL)
  59struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
  60EXPORT_SYMBOL(nf_hooks_needed);
  61#endif
  62
  63static DEFINE_MUTEX(nf_hook_mutex);
  64
  65int nf_register_hook(struct nf_hook_ops *reg)
  66{
  67        struct nf_hook_ops *elem;
  68        int err;
  69
  70        err = mutex_lock_interruptible(&nf_hook_mutex);
  71        if (err < 0)
  72                return err;
  73        list_for_each_entry(elem, &nf_hooks[reg->pf][reg->hooknum], list) {
  74                if (reg->priority < elem->priority)
  75                        break;
  76        }
  77        list_add_rcu(&reg->list, elem->list.prev);
  78        mutex_unlock(&nf_hook_mutex);
  79#if defined(CONFIG_JUMP_LABEL)
  80        static_key_slow_inc(&nf_hooks_needed[reg->pf][reg->hooknum]);
  81#endif
  82        return 0;
  83}
  84EXPORT_SYMBOL(nf_register_hook);
  85
  86void nf_unregister_hook(struct nf_hook_ops *reg)
  87{
  88        mutex_lock(&nf_hook_mutex);
  89        list_del_rcu(&reg->list);
  90        mutex_unlock(&nf_hook_mutex);
  91#if defined(CONFIG_JUMP_LABEL)
  92        static_key_slow_dec(&nf_hooks_needed[reg->pf][reg->hooknum]);
  93#endif
  94        synchronize_net();
  95}
  96EXPORT_SYMBOL(nf_unregister_hook);
  97
  98int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
  99{
 100        unsigned int i;
 101        int err = 0;
 102
 103        for (i = 0; i < n; i++) {
 104                err = nf_register_hook(&reg[i]);
 105                if (err)
 106                        goto err;
 107        }
 108        return err;
 109
 110err:
 111        if (i > 0)
 112                nf_unregister_hooks(reg, i);
 113        return err;
 114}
 115EXPORT_SYMBOL(nf_register_hooks);
 116
 117void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 118{
 119        while (n-- > 0)
 120                nf_unregister_hook(&reg[n]);
 121}
 122EXPORT_SYMBOL(nf_unregister_hooks);
 123
 124unsigned int nf_iterate(struct list_head *head,
 125                        struct sk_buff *skb,
 126                        unsigned int hook,
 127                        const struct net_device *indev,
 128                        const struct net_device *outdev,
 129                        struct nf_hook_ops **elemp,
 130                        int (*okfn)(struct sk_buff *),
 131                        int hook_thresh)
 132{
 133        unsigned int verdict;
 134
 135        /*
 136         * The caller must not block between calls to this
 137         * function because of risk of continuing from deleted element.
 138         */
 139        list_for_each_entry_continue_rcu((*elemp), head, list) {
 140                if (hook_thresh > (*elemp)->priority)
 141                        continue;
 142
 143                /* Optimization: we don't need to hold module
 144                   reference here, since function can't sleep. --RR */
 145repeat:
 146                verdict = (*elemp)->hook(hook, skb, indev, outdev, okfn);
 147                if (verdict != NF_ACCEPT) {
 148#ifdef CONFIG_NETFILTER_DEBUG
 149                        if (unlikely((verdict & NF_VERDICT_MASK)
 150                                                        > NF_MAX_VERDICT)) {
 151                                NFDEBUG("Evil return from %p(%u).\n",
 152                                        (*elemp)->hook, hook);
 153                                continue;
 154                        }
 155#endif
 156                        if (verdict != NF_REPEAT)
 157                                return verdict;
 158                        goto repeat;
 159                }
 160        }
 161        return NF_ACCEPT;
 162}
 163
 164
 165/* Returns 1 if okfn() needs to be executed by the caller,
 166 * -EPERM for NF_DROP, 0 otherwise. */
 167int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
 168                 struct net_device *indev,
 169                 struct net_device *outdev,
 170                 int (*okfn)(struct sk_buff *),
 171                 int hook_thresh)
 172{
 173        struct nf_hook_ops *elem;
 174        unsigned int verdict;
 175        int ret = 0;
 176
 177        /* We may already have this, but read-locks nest anyway */
 178        rcu_read_lock();
 179
 180        elem = list_entry_rcu(&nf_hooks[pf][hook], struct nf_hook_ops, list);
 181next_hook:
 182        verdict = nf_iterate(&nf_hooks[pf][hook], skb, hook, indev,
 183                             outdev, &elem, okfn, hook_thresh);
 184        if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 185                ret = 1;
 186        } else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
 187                kfree_skb(skb);
 188                ret = NF_DROP_GETERR(verdict);
 189                if (ret == 0)
 190                        ret = -EPERM;
 191        } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
 192                int err = nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
 193                                                verdict >> NF_VERDICT_QBITS);
 194                if (err < 0) {
 195                        if (err == -ECANCELED)
 196                                goto next_hook;
 197                        if (err == -ESRCH &&
 198                           (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 199                                goto next_hook;
 200                        kfree_skb(skb);
 201                }
 202        }
 203        rcu_read_unlock();
 204        return ret;
 205}
 206EXPORT_SYMBOL(nf_hook_slow);
 207
 208
 209int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
 210{
 211        if (writable_len > skb->len)
 212                return 0;
 213
 214        /* Not exclusive use of packet?  Must copy. */
 215        if (!skb_cloned(skb)) {
 216                if (writable_len <= skb_headlen(skb))
 217                        return 1;
 218        } else if (skb_clone_writable(skb, writable_len))
 219                return 1;
 220
 221        if (writable_len <= skb_headlen(skb))
 222                writable_len = 0;
 223        else
 224                writable_len -= skb_headlen(skb);
 225
 226        return !!__pskb_pull_tail(skb, writable_len);
 227}
 228EXPORT_SYMBOL(skb_make_writable);
 229
 230#if IS_ENABLED(CONFIG_NF_CONNTRACK)
 231/* This does not belong here, but locally generated errors need it if connection
 232   tracking in use: without this, connection may not be in hash table, and hence
 233   manufactured ICMP or RST packets will not be associated with it. */
 234void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *) __rcu __read_mostly;
 235EXPORT_SYMBOL(ip_ct_attach);
 236
 237void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
 238{
 239        void (*attach)(struct sk_buff *, struct sk_buff *);
 240
 241        if (skb->nfct) {
 242                rcu_read_lock();
 243                attach = rcu_dereference(ip_ct_attach);
 244                if (attach)
 245                        attach(new, skb);
 246                rcu_read_unlock();
 247        }
 248}
 249EXPORT_SYMBOL(nf_ct_attach);
 250
 251void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
 252EXPORT_SYMBOL(nf_ct_destroy);
 253
 254void nf_conntrack_destroy(struct nf_conntrack *nfct)
 255{
 256        void (*destroy)(struct nf_conntrack *);
 257
 258        rcu_read_lock();
 259        destroy = rcu_dereference(nf_ct_destroy);
 260        BUG_ON(destroy == NULL);
 261        destroy(nfct);
 262        rcu_read_unlock();
 263}
 264EXPORT_SYMBOL(nf_conntrack_destroy);
 265
 266struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
 267EXPORT_SYMBOL_GPL(nfq_ct_hook);
 268
 269struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook __read_mostly;
 270EXPORT_SYMBOL_GPL(nfq_ct_nat_hook);
 271
 272#endif /* CONFIG_NF_CONNTRACK */
 273
 274#ifdef CONFIG_NF_NAT_NEEDED
 275void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
 276EXPORT_SYMBOL(nf_nat_decode_session_hook);
 277#endif
 278
 279#ifdef CONFIG_PROC_FS
 280struct proc_dir_entry *proc_net_netfilter;
 281EXPORT_SYMBOL(proc_net_netfilter);
 282#endif
 283
 284void __init netfilter_init(void)
 285{
 286        int i, h;
 287        for (i = 0; i < ARRAY_SIZE(nf_hooks); i++) {
 288                for (h = 0; h < NF_MAX_HOOKS; h++)
 289                        INIT_LIST_HEAD(&nf_hooks[i][h]);
 290        }
 291
 292#ifdef CONFIG_PROC_FS
 293        proc_net_netfilter = proc_mkdir("netfilter", init_net.proc_net);
 294        if (!proc_net_netfilter)
 295                panic("cannot create netfilter proc entry");
 296#endif
 297
 298        if (netfilter_queue_init() < 0)
 299                panic("cannot initialize nf_queue");
 300        if (netfilter_log_init() < 0)
 301                panic("cannot initialize nf_log");
 302}
 303
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