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  * February 2000: Modified by James Morris to have 1 queue per protocol.
  10  * 15-Mar-2000:   Added NF_REPEAT --RR.
  11  * 08-May-2003:   Internal logging interface added by Jozsef Kadlecsik.
  12  */
  13 #include <linux/config.h>
  14 #include <linux/kernel.h>
  15 #include <linux/netfilter.h>
  16 #include <net/protocol.h>
  17 #include <linux/init.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/wait.h>
  20 #include <linux/module.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/if.h>
  23 #include <linux/netdevice.h>
  24 #include <linux/inetdevice.h>
  25 #include <linux/proc_fs.h>
  26 #include <net/sock.h>
  27
  28 #include "nf_internals.h"
  29
  30 static DEFINE_SPINLOCK(afinfo_lock);
  31
  32 struct nf_afinfo *nf_afinfo[NPROTO];
  33 EXPORT_SYMBOL(nf_afinfo);
  34
  35 int nf_register_afinfo(struct nf_afinfo *afinfo)
  36 {
  37         spin_lock(&afinfo_lock);
  38         rcu_assign_pointer(nf_afinfo[afinfo->family], afinfo);
  39         spin_unlock(&afinfo_lock);
  40         return 0;
  41 }
  42 EXPORT_SYMBOL_GPL(nf_register_afinfo);
  43
  44 void nf_unregister_afinfo(struct nf_afinfo *afinfo)
  45 {
  46         spin_lock(&afinfo_lock);
  47         rcu_assign_pointer(nf_afinfo[afinfo->family], NULL);
  48         spin_unlock(&afinfo_lock);
  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];
  59 EXPORT_SYMBOL(nf_hooks);
  60 static DEFINE_SPINLOCK(nf_hook_lock);
  61
  62 int nf_register_hook(struct nf_hook_ops *reg)
  63 {
  64         struct list_head *i;
  65
  66         spin_lock_bh(&nf_hook_lock);
  67         list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) {
  68                 if (reg->priority < ((struct nf_hook_ops *)i)->priority)
  69                         break;
  70         }
  71         list_add_rcu(&reg->list, i->prev);
  72         spin_unlock_bh(&nf_hook_lock);
  73
  74         synchronize_net();
  75         return 0;
  76 }
  77 EXPORT_SYMBOL(nf_register_hook);
  78
  79 void nf_unregister_hook(struct nf_hook_ops *reg)
  80 {
  81         spin_lock_bh(&nf_hook_lock);
  82         list_del_rcu(&reg->list);
  83         spin_unlock_bh(&nf_hook_lock);
  84
  85         synchronize_net();
  86 }
  87 EXPORT_SYMBOL(nf_unregister_hook);
  88
  89 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
  90 {
  91         unsigned int i;
  92         int err = 0;
  93
  94         for (i = 0; i < n; i++) {
  95                 err = nf_register_hook(&reg[i]);
  96                 if (err)
  97                         goto err;
  98         }
  99         return err;
 100
 101 err:
 102         if (i > 0)
 103                 nf_unregister_hooks(reg, i);
 104         return err;
 105 }
 106 EXPORT_SYMBOL(nf_register_hooks);
 107
 108 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 109 {
 110         unsigned int i;
 111
 112         for (i = 0; i < n; i++)
 113                 nf_unregister_hook(&reg[i]);
 114 }
 115 EXPORT_SYMBOL(nf_unregister_hooks);
 116
 117 unsigned int nf_iterate(struct list_head *head,
 118                         struct sk_buff **skb,
 119                         int hook,
 120                         const struct net_device *indev,
 121                         const struct net_device *outdev,
 122                         struct list_head **i,
 123                         int (*okfn)(struct sk_buff *),
 124                         int hook_thresh)
 125 {
 126         unsigned int verdict;
 127
 128         /*
 129          * The caller must not block between calls to this
 130          * function because of risk of continuing from deleted element.
 131          */
 132         list_for_each_continue_rcu(*i, head) {
 133                 struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
 134
 135                 if (hook_thresh > elem->priority)
 136                         continue;
 137
 138                 /* Optimization: we don't need to hold module
 139                    reference here, since function can't sleep. --RR */
 140                 verdict = elem->hook(hook, skb, indev, outdev, okfn);
 141                 if (verdict != NF_ACCEPT) {
 142 #ifdef CONFIG_NETFILTER_DEBUG
 143                         if (unlikely((verdict & NF_VERDICT_MASK)
 144                                                         > NF_MAX_VERDICT)) {
 145                                 NFDEBUG("Evil return from %p(%u).\n",
 146                                         elem->hook, hook);
 147                                 continue;
 148                         }
 149 #endif
 150                         if (verdict != NF_REPEAT)
 151                                 return verdict;
 152                         *i = (*i)->prev;
 153                 }
 154         }
 155         return NF_ACCEPT;
 156 }
 157
 158
 159 /* Returns 1 if okfn() needs to be executed by the caller,
 160  * -EPERM for NF_DROP, 0 otherwise. */
 161 int nf_hook_slow(int pf, unsigned int hook, struct sk_buff **pskb,
 162                  struct net_device *indev,
 163                  struct net_device *outdev,
 164                  int (*okfn)(struct sk_buff *),
 165                  int hook_thresh)
 166 {
 167         struct list_head *elem;
 168         unsigned int verdict;
 169         int ret = 0;
 170
 171         /* We may already have this, but read-locks nest anyway */
 172         rcu_read_lock();
 173
 174         elem = &nf_hooks[pf][hook];
 175 next_hook:
 176         verdict = nf_iterate(&nf_hooks[pf][hook], pskb, hook, indev,
 177                              outdev, &elem, okfn, hook_thresh);
 178         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 179                 ret = 1;
 180                 goto unlock;
 181         } else if (verdict == NF_DROP) {
 182                 kfree_skb(*pskb);
 183                 ret = -EPERM;
 184         } else if ((verdict & NF_VERDICT_MASK)  == NF_QUEUE) {
 185                 NFDEBUG("nf_hook: Verdict = QUEUE.\n");
 186                 if (!nf_queue(pskb, elem, pf, hook, indev, outdev, okfn,
 187                               verdict >> NF_VERDICT_BITS))
 188                         goto next_hook;
 189         }
 190 unlock:
 191         rcu_read_unlock();
 192         return ret;
 193 }
 194 EXPORT_SYMBOL(nf_hook_slow);
 195
 196
 197 int skb_make_writable(struct sk_buff **pskb, unsigned int writable_len)
 198 {
 199         struct sk_buff *nskb;
 200
 201         if (writable_len > (*pskb)->len)
 202                 return 0;
 203
 204         /* Not exclusive use of packet?  Must copy. */
 205         if (skb_shared(*pskb) || skb_cloned(*pskb))
 206                 goto copy_skb;
 207
 208         return pskb_may_pull(*pskb, writable_len);
 209
 210 copy_skb:
 211         nskb = skb_copy(*pskb, GFP_ATOMIC);
 212         if (!nskb)
 213                 return 0;
 214         BUG_ON(skb_is_nonlinear(nskb));
 215
 216         /* Rest of kernel will get very unhappy if we pass it a
 217            suddenly-orphaned skbuff */
 218         if ((*pskb)->sk)
 219                 skb_set_owner_w(nskb, (*pskb)->sk);
 220         kfree_skb(*pskb);
 221         *pskb = nskb;
 222         return 1;
 223 }
 224 EXPORT_SYMBOL(skb_make_writable);
 225
 226
 227 /* This does not belong here, but locally generated errors need it if connection
 228    tracking in use: without this, connection may not be in hash table, and hence
 229    manufactured ICMP or RST packets will not be associated with it. */
 230 void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *);
 231 EXPORT_SYMBOL(ip_ct_attach);
 232
 233 void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
 234 {
 235         void (*attach)(struct sk_buff *, struct sk_buff *);
 236
 237         if (skb->nfct && (attach = ip_ct_attach) != NULL) {
 238                 mb(); /* Just to be sure: must be read before executing this */
 239                 attach(new, skb);
 240         }
 241 }
 242 EXPORT_SYMBOL(nf_ct_attach);
 243
 244 #ifdef CONFIG_PROC_FS
 245 struct proc_dir_entry *proc_net_netfilter;
 246 EXPORT_SYMBOL(proc_net_netfilter);
 247 #endif
 248
 249 void __init netfilter_init(void)
 250 {
 251         int i, h;
 252         for (i = 0; i < NPROTO; i++) {
 253                 for (h = 0; h < NF_MAX_HOOKS; h++)
 254                         INIT_LIST_HEAD(&nf_hooks[i][h]);
 255         }
 256
 257 #ifdef CONFIG_PROC_FS
 258         proc_net_netfilter = proc_mkdir("netfilter", proc_net);
 259         if (!proc_net_netfilter)
 260                 panic("cannot create netfilter proc entry");
 261 #endif
 262
 263         if (netfilter_queue_init() < 0)
 264                 panic("cannot initialize nf_queue");
 265         if (netfilter_log_init() < 0)
 266                 panic("cannot initialize nf_log");
 267 }