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