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 struct nf_afinfo *nf_afinfo[NPROTO] __read_mostly;
  30 EXPORT_SYMBOL(nf_afinfo);
  31
  32 int nf_register_afinfo(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(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 /* In this code, we can be waiting indefinitely for userspace to
  55  * service a packet if a hook returns NF_QUEUE.  We could keep a count
  56  * of skbuffs queued for userspace, and not deregister a hook unless
  57  * this is zero, but that sucks.  Now, we simply check when the
  58  * packets come back: if the hook is gone, the packet is discarded. */
  59 struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS] __read_mostly;
  60 EXPORT_SYMBOL(nf_hooks);
  61 static DEFINE_MUTEX(nf_hook_mutex);
  62
  63 int nf_register_hook(struct nf_hook_ops *reg)
  64 {
  65         struct list_head *i;
  66         int err;
  67
  68         err = mutex_lock_interruptible(&nf_hook_mutex);
  69         if (err < 0)
  70                 return err;
  71         list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) {
  72                 if (reg->priority < ((struct nf_hook_ops *)i)->priority)
  73                         break;
  74         }
  75         list_add_rcu(&reg->list, i->prev);
  76         mutex_unlock(&nf_hook_mutex);
  77         return 0;
  78 }
  79 EXPORT_SYMBOL(nf_register_hook);
  80
  81 void nf_unregister_hook(struct nf_hook_ops *reg)
  82 {
  83         mutex_lock(&nf_hook_mutex);
  84         list_del_rcu(&reg->list);
  85         mutex_unlock(&nf_hook_mutex);
  86
  87         synchronize_net();
  88 }
  89 EXPORT_SYMBOL(nf_unregister_hook);
  90
  91 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
  92 {
  93         unsigned int i;
  94         int err = 0;
  95
  96         for (i = 0; i < n; i++) {
  97                 err = nf_register_hook(&reg[i]);
  98                 if (err)
  99                         goto err;
 100         }
 101         return err;
 102
 103 err:
 104         if (i > 0)
 105                 nf_unregister_hooks(reg, i);
 106         return err;
 107 }
 108 EXPORT_SYMBOL(nf_register_hooks);
 109
 110 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 111 {
 112         unsigned int i;
 113
 114         for (i = 0; i < n; i++)
 115                 nf_unregister_hook(&reg[i]);
 116 }
 117 EXPORT_SYMBOL(nf_unregister_hooks);
 118
 119 unsigned int nf_iterate(struct list_head *head,
 120                         struct sk_buff **skb,
 121                         int hook,
 122                         const struct net_device *indev,
 123                         const struct net_device *outdev,
 124                         struct list_head **i,
 125                         int (*okfn)(struct sk_buff *),
 126                         int hook_thresh)
 127 {
 128         unsigned int verdict;
 129
 130         /*
 131          * The caller must not block between calls to this
 132          * function because of risk of continuing from deleted element.
 133          */
 134         list_for_each_continue_rcu(*i, head) {
 135                 struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
 136
 137                 if (hook_thresh > elem->priority)
 138                         continue;
 139
 140                 /* Optimization: we don't need to hold module
 141                    reference here, since function can't sleep. --RR */
 142                 verdict = elem->hook(hook, skb, indev, outdev, okfn);
 143                 if (verdict != NF_ACCEPT) {
 144 #ifdef CONFIG_NETFILTER_DEBUG
 145                         if (unlikely((verdict & NF_VERDICT_MASK)
 146                                                         > NF_MAX_VERDICT)) {
 147                                 NFDEBUG("Evil return from %p(%u).\n",
 148                                         elem->hook, hook);
 149                                 continue;
 150                         }
 151 #endif
 152                         if (verdict != NF_REPEAT)
 153                                 return verdict;
 154                         *i = (*i)->prev;
 155                 }
 156         }
 157         return NF_ACCEPT;
 158 }
 159
 160
 161 /* Returns 1 if okfn() needs to be executed by the caller,
 162  * -EPERM for NF_DROP, 0 otherwise. */
 163 int nf_hook_slow(int pf, unsigned int hook, struct sk_buff **pskb,
 164                  struct net_device *indev,
 165                  struct net_device *outdev,
 166                  int (*okfn)(struct sk_buff *),
 167                  int hook_thresh)
 168 {
 169         struct list_head *elem;
 170         unsigned int verdict;
 171         int ret = 0;
 172
 173         /* We may already have this, but read-locks nest anyway */
 174         rcu_read_lock();
 175
 176         elem = &nf_hooks[pf][hook];
 177 next_hook:
 178         verdict = nf_iterate(&nf_hooks[pf][hook], pskb, hook, indev,
 179                              outdev, &elem, okfn, hook_thresh);
 180         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 181                 ret = 1;
 182                 goto unlock;
 183         } else if (verdict == NF_DROP) {
 184                 kfree_skb(*pskb);
 185                 ret = -EPERM;
 186         } else if ((verdict & NF_VERDICT_MASK)  == NF_QUEUE) {
 187                 NFDEBUG("nf_hook: Verdict = QUEUE.\n");
 188                 if (!nf_queue(*pskb, elem, pf, hook, indev, outdev, okfn,
 189                               verdict >> NF_VERDICT_BITS))
 190                         goto next_hook;
 191         }
 192 unlock:
 193         rcu_read_unlock();
 194         return ret;
 195 }
 196 EXPORT_SYMBOL(nf_hook_slow);
 197
 198
 199 int skb_make_writable(struct sk_buff **pskb, unsigned int writable_len)
 200 {
 201         struct sk_buff *nskb;
 202
 203         if (writable_len > (*pskb)->len)
 204                 return 0;
 205
 206         /* Not exclusive use of packet?  Must copy. */
 207         if (skb_cloned(*pskb) && !skb_clone_writable(*pskb, writable_len))
 208                 goto copy_skb;
 209         if (skb_shared(*pskb))
 210                 goto copy_skb;
 211
 212         return pskb_may_pull(*pskb, writable_len);
 213
 214 copy_skb:
 215         nskb = skb_copy(*pskb, GFP_ATOMIC);
 216         if (!nskb)
 217                 return 0;
 218         BUG_ON(skb_is_nonlinear(nskb));
 219
 220         /* Rest of kernel will get very unhappy if we pass it a
 221            suddenly-orphaned skbuff */
 222         if ((*pskb)->sk)
 223                 skb_set_owner_w(nskb, (*pskb)->sk);
 224         kfree_skb(*pskb);
 225         *pskb = nskb;
 226         return 1;
 227 }
 228 EXPORT_SYMBOL(skb_make_writable);
 229
 230 void nf_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 231                             __be32 from, __be32 to, int pseudohdr)
 232 {
 233         __be32 diff[] = { ~from, to };
 234         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 235                 *sum = csum_fold(csum_partial(diff, sizeof(diff),
 236                                 ~csum_unfold(*sum)));
 237                 if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
 238                         skb->csum = ~csum_partial(diff, sizeof(diff),
 239                                                 ~skb->csum);
 240         } else if (pseudohdr)
 241                 *sum = ~csum_fold(csum_partial(diff, sizeof(diff),
 242                                 csum_unfold(*sum)));
 243 }
 244 EXPORT_SYMBOL(nf_proto_csum_replace4);
 245
 246 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 247 /* This does not belong here, but locally generated errors need it if connection
 248    tracking in use: without this, connection may not be in hash table, and hence
 249    manufactured ICMP or RST packets will not be associated with it. */
 250 void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *);
 251 EXPORT_SYMBOL(ip_ct_attach);
 252
 253 void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
 254 {
 255         void (*attach)(struct sk_buff *, struct sk_buff *);
 256
 257         if (skb->nfct) {
 258                 rcu_read_lock();
 259                 attach = rcu_dereference(ip_ct_attach);
 260                 if (attach)
 261                         attach(new, skb);
 262                 rcu_read_unlock();
 263         }
 264 }
 265 EXPORT_SYMBOL(nf_ct_attach);
 266
 267 void (*nf_ct_destroy)(struct nf_conntrack *);
 268 EXPORT_SYMBOL(nf_ct_destroy);
 269
 270 void nf_conntrack_destroy(struct nf_conntrack *nfct)
 271 {
 272         void (*destroy)(struct nf_conntrack *);
 273
 274         rcu_read_lock();
 275         destroy = rcu_dereference(nf_ct_destroy);
 276         BUG_ON(destroy == NULL);
 277         destroy(nfct);
 278         rcu_read_unlock();
 279 }
 280 EXPORT_SYMBOL(nf_conntrack_destroy);
 281 #endif /* CONFIG_NF_CONNTRACK */
 282
 283 #ifdef CONFIG_PROC_FS
 284 struct proc_dir_entry *proc_net_netfilter;
 285 EXPORT_SYMBOL(proc_net_netfilter);
 286 #endif
 287
 288 void __init netfilter_init(void)
 289 {
 290         int i, h;
 291         for (i = 0; i < NPROTO; i++) {
 292                 for (h = 0; h < NF_MAX_HOOKS; h++)
 293                         INIT_LIST_HEAD(&nf_hooks[i][h]);
 294         }
 295
 296 #ifdef CONFIG_PROC_FS
 297         proc_net_netfilter = proc_mkdir("netfilter", init_net.proc_net);
 298         if (!proc_net_netfilter)
 299                 panic("cannot create netfilter proc entry");
 300 #endif
 301
 302         if (netfilter_queue_init() < 0)
 303                 panic("cannot initialize nf_queue");
 304         if (netfilter_log_init() < 0)
 305                 panic("cannot initialize nf_log");
 306 }