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 list_head **i,
 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_continue_rcu(*i, head) {
 140                struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
 141
 142                if (hook_thresh > elem->priority)
 143                        continue;
 144
 145                /* Optimization: we don't need to hold module
 146                   reference here, since function can't sleep. --RR */
 147repeat:
 148                verdict = elem->hook(hook, skb, indev, outdev, okfn);
 149                if (verdict != NF_ACCEPT) {
 150#ifdef CONFIG_NETFILTER_DEBUG
 151                        if (unlikely((verdict & NF_VERDICT_MASK)
 152                                                        > NF_MAX_VERDICT)) {
 153                                NFDEBUG("Evil return from %p(%u).\n",
 154                                        elem->hook, hook);
 155                                continue;
 156                        }
 157#endif
 158                        if (verdict != NF_REPEAT)
 159                                return verdict;
 160                        goto repeat;
 161                }
 162        }
 163        return NF_ACCEPT;
 164}
 165
 166
 167/* Returns 1 if okfn() needs to be executed by the caller,
 168 * -EPERM for NF_DROP, 0 otherwise. */
 169int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
 170                 struct net_device *indev,
 171                 struct net_device *outdev,
 172                 int (*okfn)(struct sk_buff *),
 173                 int hook_thresh)
 174{
 175        struct list_head *elem;
 176        unsigned int verdict;
 177        int ret = 0;
 178
 179        /* We may already have this, but read-locks nest anyway */
 180        rcu_read_lock();
 181
 182        elem = &nf_hooks[pf][hook];
 183next_hook:
 184        verdict = nf_iterate(&nf_hooks[pf][hook], skb, hook, indev,
 185                             outdev, &elem, okfn, hook_thresh);
 186        if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 187                ret = 1;
 188        } else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
 189                kfree_skb(skb);
 190                ret = NF_DROP_GETERR(verdict);
 191                if (ret == 0)
 192                        ret = -EPERM;
 193        } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
 194                int err = nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
 195                                                verdict >> NF_VERDICT_QBITS);
 196                if (err < 0) {
 197                        if (err == -ECANCELED)
 198                                goto next_hook;
 199                        if (err == -ESRCH &&
 200                           (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 201                                goto next_hook;
 202                        kfree_skb(skb);
 203                }
 204        }
 205        rcu_read_unlock();
 206        return ret;
 207}
 208EXPORT_SYMBOL(nf_hook_slow);
 209
 210
 211int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
 212{
 213        if (writable_len > skb->len)
 214                return 0;
 215
 216        /* Not exclusive use of packet?  Must copy. */
 217        if (!skb_cloned(skb)) {
 218                if (writable_len <= skb_headlen(skb))
 219                        return 1;
 220        } else if (skb_clone_writable(skb, writable_len))
 221                return 1;
 222
 223        if (writable_len <= skb_headlen(skb))
 224                writable_len = 0;
 225        else
 226                writable_len -= skb_headlen(skb);
 227
 228        return !!__pskb_pull_tail(skb, writable_len);
 229}
 230EXPORT_SYMBOL(skb_make_writable);
 231
 232#if IS_ENABLED(CONFIG_NF_CONNTRACK)
 233/* This does not belong here, but locally generated errors need it if connection
 234   tracking in use: without this, connection may not be in hash table, and hence
 235   manufactured ICMP or RST packets will not be associated with it. */
 236void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *) __rcu __read_mostly;
 237EXPORT_SYMBOL(ip_ct_attach);
 238
 239void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
 240{
 241        void (*attach)(struct sk_buff *, struct sk_buff *);
 242
 243        if (skb->nfct) {
 244                rcu_read_lock();
 245                attach = rcu_dereference(ip_ct_attach);
 246                if (attach)
 247                        attach(new, skb);
 248                rcu_read_unlock();
 249        }
 250}
 251EXPORT_SYMBOL(nf_ct_attach);
 252
 253void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
 254EXPORT_SYMBOL(nf_ct_destroy);
 255
 256void nf_conntrack_destroy(struct nf_conntrack *nfct)
 257{
 258        void (*destroy)(struct nf_conntrack *);
 259
 260        rcu_read_lock();
 261        destroy = rcu_dereference(nf_ct_destroy);
 262        BUG_ON(destroy == NULL);
 263        destroy(nfct);
 264        rcu_read_unlock();
 265}
 266EXPORT_SYMBOL(nf_conntrack_destroy);
 267
 268struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
 269EXPORT_SYMBOL_GPL(nfq_ct_hook);
 270
 271struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook __read_mostly;
 272EXPORT_SYMBOL_GPL(nfq_ct_nat_hook);
 273
 274#endif /* CONFIG_NF_CONNTRACK */
 275
 276#ifdef CONFIG_PROC_FS
 277struct proc_dir_entry *proc_net_netfilter;
 278EXPORT_SYMBOL(proc_net_netfilter);
 279#endif
 280
 281void __init netfilter_init(void)
 282{
 283        int i, h;
 284        for (i = 0; i < ARRAY_SIZE(nf_hooks); i++) {
 285                for (h = 0; h < NF_MAX_HOOKS; h++)
 286                        INIT_LIST_HEAD(&nf_hooks[i][h]);
 287        }
 288
 289#ifdef CONFIG_PROC_FS
 290        proc_net_netfilter = proc_mkdir("netfilter", init_net.proc_net);
 291        if (!proc_net_netfilter)
 292                panic("cannot create netfilter proc entry");
 293#endif
 294
 295        if (netfilter_queue_init() < 0)
 296                panic("cannot initialize nf_queue");
 297        if (netfilter_log_init() < 0)
 298                panic("cannot initialize nf_log");
 299}
 300
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