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/sock.h>
  23
  24 #include "nf_internals.h"
  25
  26 static DEFINE_MUTEX(afinfo_mutex);
  27
  28 struct nf_afinfo *nf_afinfo[NPROTO] __read_mostly;
  29 EXPORT_SYMBOL(nf_afinfo);
  30
  31 int nf_register_afinfo(struct nf_afinfo *afinfo)
  32 {
  33         int err;
  34
  35         err = mutex_lock_interruptible(&afinfo_mutex);
  36         if (err < 0)
  37                 return err;
  38         rcu_assign_pointer(nf_afinfo[afinfo->family], afinfo);
  39         mutex_unlock(&afinfo_mutex);
  40         return 0;
  41 }
  42 EXPORT_SYMBOL_GPL(nf_register_afinfo);
  43
  44 void nf_unregister_afinfo(struct nf_afinfo *afinfo)
  45 {
  46         mutex_lock(&afinfo_mutex);
  47         rcu_assign_pointer(nf_afinfo[afinfo->family], NULL);
  48         mutex_unlock(&afinfo_mutex);
  49         synchronize_rcu();
  50 }
  51 EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
  52
  53 /* In this code, we can be waiting indefinitely for userspace to
  54  * service a packet if a hook returns NF_QUEUE.  We could keep a count
  55  * of skbuffs queued for userspace, and not deregister a hook unless
  56  * this is zero, but that sucks.  Now, we simply check when the
  57  * packets come back: if the hook is gone, the packet is discarded. */
  58 struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS] __read_mostly;
  59 EXPORT_SYMBOL(nf_hooks);
  60 static DEFINE_MUTEX(nf_hook_mutex);
  61
  62 int nf_register_hook(struct nf_hook_ops *reg)
  63 {
  64         struct list_head *i;
  65         int err;
  66
  67         err = mutex_lock_interruptible(&nf_hook_mutex);
  68         if (err < 0)
  69                 return err;
  70         list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) {
  71                 if (reg->priority < ((struct nf_hook_ops *)i)->priority)
  72                         break;
  73         }
  74         list_add_rcu(&reg->list, i->prev);
  75         mutex_unlock(&nf_hook_mutex);
  76         return 0;
  77 }
  78 EXPORT_SYMBOL(nf_register_hook);
  79
  80 void nf_unregister_hook(struct nf_hook_ops *reg)
  81 {
  82         mutex_lock(&nf_hook_mutex);
  83         list_del_rcu(&reg->list);
  84         mutex_unlock(&nf_hook_mutex);
  85
  86         synchronize_net();
  87 }
  88 EXPORT_SYMBOL(nf_unregister_hook);
  89
  90 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
  91 {
  92         unsigned int i;
  93         int err = 0;
  94
  95         for (i = 0; i < n; i++) {
  96                 err = nf_register_hook(&reg[i]);
  97                 if (err)
  98                         goto err;
  99         }
 100         return err;
 101
 102 err:
 103         if (i > 0)
 104                 nf_unregister_hooks(reg, i);
 105         return err;
 106 }
 107 EXPORT_SYMBOL(nf_register_hooks);
 108
 109 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 110 {
 111         unsigned int i;
 112
 113         for (i = 0; i < n; i++)
 114                 nf_unregister_hook(&reg[i]);
 115 }
 116 EXPORT_SYMBOL(nf_unregister_hooks);
 117
 118 unsigned int nf_iterate(struct list_head *head,
 119                         struct sk_buff **skb,
 120                         int hook,
 121                         const struct net_device *indev,
 122                         const struct net_device *outdev,
 123                         struct list_head **i,
 124                         int (*okfn)(struct sk_buff *),
 125                         int hook_thresh)
 126 {
 127         unsigned int verdict;
 128
 129         /*
 130          * The caller must not block between calls to this
 131          * function because of risk of continuing from deleted element.
 132          */
 133         list_for_each_continue_rcu(*i, head) {
 134                 struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
 135
 136                 if (hook_thresh > elem->priority)
 137                         continue;
 138
 139                 /* Optimization: we don't need to hold module
 140                    reference here, since function can't sleep. --RR */
 141                 verdict = elem->hook(hook, skb, indev, outdev, okfn);
 142                 if (verdict != NF_ACCEPT) {
 143 #ifdef CONFIG_NETFILTER_DEBUG
 144                         if (unlikely((verdict & NF_VERDICT_MASK)
 145                                                         > NF_MAX_VERDICT)) {
 146                                 NFDEBUG("Evil return from %p(%u).\n",
 147                                         elem->hook, hook);
 148                                 continue;
 149                         }
 150 #endif
 151                         if (verdict != NF_REPEAT)
 152                                 return verdict;
 153                         *i = (*i)->prev;
 154                 }
 155         }
 156         return NF_ACCEPT;
 157 }
 158
 159
 160 /* Returns 1 if okfn() needs to be executed by the caller,
 161  * -EPERM for NF_DROP, 0 otherwise. */
 162 int nf_hook_slow(int pf, unsigned int hook, struct sk_buff **pskb,
 163                  struct net_device *indev,
 164                  struct net_device *outdev,
 165                  int (*okfn)(struct sk_buff *),
 166                  int hook_thresh)
 167 {
 168         struct list_head *elem;
 169         unsigned int verdict;
 170         int ret = 0;
 171
 172         /* We may already have this, but read-locks nest anyway */
 173         rcu_read_lock();
 174
 175         elem = &nf_hooks[pf][hook];
 176 next_hook:
 177         verdict = nf_iterate(&nf_hooks[pf][hook], pskb, hook, indev,
 178                              outdev, &elem, okfn, hook_thresh);
 179         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 180                 ret = 1;
 181                 goto unlock;
 182         } else if (verdict == NF_DROP) {
 183                 kfree_skb(*pskb);
 184                 ret = -EPERM;
 185         } else if ((verdict & NF_VERDICT_MASK)  == NF_QUEUE) {
 186                 NFDEBUG("nf_hook: Verdict = QUEUE.\n");
 187                 if (!nf_queue(*pskb, elem, pf, hook, indev, outdev, okfn,
 188                               verdict >> NF_VERDICT_BITS))
 189                         goto next_hook;
 190         }
 191 unlock:
 192         rcu_read_unlock();
 193         return ret;
 194 }
 195 EXPORT_SYMBOL(nf_hook_slow);
 196
 197
 198 int skb_make_writable(struct sk_buff **pskb, unsigned int writable_len)
 199 {
 200         struct sk_buff *nskb;
 201
 202         if (writable_len > (*pskb)->len)
 203                 return 0;
 204
 205         /* Not exclusive use of packet?  Must copy. */
 206         if (skb_shared(*pskb) || skb_cloned(*pskb))
 207                 goto copy_skb;
 208
 209         return pskb_may_pull(*pskb, writable_len);
 210
 211 copy_skb:
 212         nskb = skb_copy(*pskb, GFP_ATOMIC);
 213         if (!nskb)
 214                 return 0;
 215         BUG_ON(skb_is_nonlinear(nskb));
 216
 217         /* Rest of kernel will get very unhappy if we pass it a
 218            suddenly-orphaned skbuff */
 219         if ((*pskb)->sk)
 220                 skb_set_owner_w(nskb, (*pskb)->sk);
 221         kfree_skb(*pskb);
 222         *pskb = nskb;
 223         return 1;
 224 }
 225 EXPORT_SYMBOL(skb_make_writable);
 226
 227 void nf_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 228                             __be32 from, __be32 to, int pseudohdr)
 229 {
 230         __be32 diff[] = { ~from, to };
 231         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 232                 *sum = csum_fold(csum_partial((char *)diff, sizeof(diff),
 233                                 ~csum_unfold(*sum)));
 234                 if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
 235                         skb->csum = ~csum_partial((char *)diff, sizeof(diff),
 236                                                 ~skb->csum);
 237         } else if (pseudohdr)
 238                 *sum = ~csum_fold(csum_partial((char *)diff, sizeof(diff),
 239                                 csum_unfold(*sum)));
 240 }
 241 EXPORT_SYMBOL(nf_proto_csum_replace4);
 242
 243 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 244 /* This does not belong here, but locally generated errors need it if connection
 245    tracking in use: without this, connection may not be in hash table, and hence
 246    manufactured ICMP or RST packets will not be associated with it. */
 247 void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *);
 248 EXPORT_SYMBOL(ip_ct_attach);
 249
 250 void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
 251 {
 252         void (*attach)(struct sk_buff *, struct sk_buff *);
 253
 254         if (skb->nfct) {
 255                 rcu_read_lock();
 256                 attach = rcu_dereference(ip_ct_attach);
 257                 if (attach)
 258                         attach(new, skb);
 259                 rcu_read_unlock();
 260         }
 261 }
 262 EXPORT_SYMBOL(nf_ct_attach);
 263
 264 void (*nf_ct_destroy)(struct nf_conntrack *);
 265 EXPORT_SYMBOL(nf_ct_destroy);
 266
 267 void nf_conntrack_destroy(struct nf_conntrack *nfct)
 268 {
 269         void (*destroy)(struct nf_conntrack *);
 270
 271         rcu_read_lock();
 272         destroy = rcu_dereference(nf_ct_destroy);
 273         BUG_ON(destroy == NULL);
 274         destroy(nfct);
 275         rcu_read_unlock();
 276 }
 277 EXPORT_SYMBOL(nf_conntrack_destroy);
 278 #endif /* CONFIG_NF_CONNTRACK */
 279
 280 #ifdef CONFIG_PROC_FS
 281 struct proc_dir_entry *proc_net_netfilter;
 282 EXPORT_SYMBOL(proc_net_netfilter);
 283 #endif
 284
 285 void __init netfilter_init(void)
 286 {
 287         int i, h;
 288         for (i = 0; i < NPROTO; i++) {
 289                 for (h = 0; h < NF_MAX_HOOKS; h++)
 290                         INIT_LIST_HEAD(&nf_hooks[i][h]);
 291         }
 292
 293 #ifdef CONFIG_PROC_FS
 294         proc_net_netfilter = proc_mkdir("netfilter", proc_net);
 295         if (!proc_net_netfilter)
 296                 panic("cannot create netfilter proc entry");
 297 #endif
 298
 299         if (netfilter_queue_init() < 0)
 300                 panic("cannot initialize nf_queue");
 301         if (netfilter_log_init() < 0)
 302                 panic("cannot initialize nf_log");
 303 }