net/netfilter/core.c

   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
  28 static DEFINE_MUTEX(afinfo_mutex);
  29
  30 const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
  31 EXPORT_SYMBOL(nf_afinfo);
  32
  33 int 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 }
  44 EXPORT_SYMBOL_GPL(nf_register_afinfo);
  45
  46 void 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 }
  53 EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
  54
  55 struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS] __read_mostly;
  56 EXPORT_SYMBOL(nf_hooks);
  57
  58 #if defined(CONFIG_JUMP_LABEL)
  59 struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
  60 EXPORT_SYMBOL(nf_hooks_needed);
  61 #endif
  62
  63 static DEFINE_MUTEX(nf_hook_mutex);
  64
  65 int 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 }
  84 EXPORT_SYMBOL(nf_register_hook);
  85
  86 void 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 }
  96 EXPORT_SYMBOL(nf_unregister_hook);
  97
  98 int 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
 110 err:
 111         if (i > 0)
 112                 nf_unregister_hooks(reg, i);
 113         return err;
 114 }
 115 EXPORT_SYMBOL(nf_register_hooks);
 116
 117 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 118 {
 119         while (n-- > 0)
 120                 nf_unregister_hook(&reg[n]);
 121 }
 122 EXPORT_SYMBOL(nf_unregister_hooks);
 123
 124 unsigned 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 */
 145 repeat:
 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. */
 167 int 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);
 181 next_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 }
 206 EXPORT_SYMBOL(nf_hook_slow);
 207
 208
 209 int 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 }
 228 EXPORT_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. */
 234 void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *) __rcu __read_mostly;
 235 EXPORT_SYMBOL(ip_ct_attach);
 236
 237 void 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 }
 249 EXPORT_SYMBOL(nf_ct_attach);
 250
 251 void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
 252 EXPORT_SYMBOL(nf_ct_destroy);
 253
 254 void 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 }
 264 EXPORT_SYMBOL(nf_conntrack_destroy);
 265
 266 struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
 267 EXPORT_SYMBOL_GPL(nfq_ct_hook);
 268
 269 struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook __read_mostly;
 270 EXPORT_SYMBOL_GPL(nfq_ct_nat_hook);
 271
 272 #endif /* CONFIG_NF_CONNTRACK */
 273
 274 #ifdef CONFIG_NF_NAT_NEEDED
 275 void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
 276 EXPORT_SYMBOL(nf_nat_decode_session_hook);
 277 #endif
 278
 279 #ifdef CONFIG_PROC_FS
 280 struct proc_dir_entry *proc_net_netfilter;
 281 EXPORT_SYMBOL(proc_net_netfilter);
 282 #endif
 283
 284 static int __net_init netfilter_net_init(struct net *net)
 285 {
 286 #ifdef CONFIG_PROC_FS
 287         net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
 288                                                 net->proc_net);
 289         if (net_eq(net, &init_net)) {
 290                 if (!net->nf.proc_netfilter)
 291                         return -ENOMEM;
 292                 else
 293                         proc_net_netfilter = net->nf.proc_netfilter;
 294         } else if (!net->nf.proc_netfilter) {
 295                 pr_err("cannot create netfilter proc entry");
 296                 return -ENOMEM;
 297         }
 298 #endif
 299         return 0;
 300 }
 301
 302 static void __net_exit netfilter_net_exit(struct net *net)
 303 {
 304         remove_proc_entry("netfilter", net->proc_net);
 305 }
 306
 307 static struct pernet_operations netfilter_net_ops = {
 308         .init = netfilter_net_init,
 309         .exit = netfilter_net_exit,
 310 };
 311
 312 void __init netfilter_init(void)
 313 {
 314         int i, h;
 315         for (i = 0; i < ARRAY_SIZE(nf_hooks); i++) {
 316                 for (h = 0; h < NF_MAX_HOOKS; h++)
 317                         INIT_LIST_HEAD(&nf_hooks[i][h]);
 318         }
 319
 320         if (register_pernet_subsys(&netfilter_net_ops) < 0)
 321                 panic("cannot create netfilter proc entry");
 322
 323         if (netfilter_log_init() < 0)
 324                 panic("cannot initialize nf_log");
 325 }