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/kernel.h>
  14 #include <linux/netfilter.h>
  15 #include <net/protocol.h>
  16 #include <linux/init.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/wait.h>
  19 #include <linux/module.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/if.h>
  22 #include <linux/netdevice.h>
  23 #include <linux/inetdevice.h>
  24 #include <linux/proc_fs.h>
  25 #include <linux/mutex.h>
  26 #include <net/sock.h>
  27
  28 #include "nf_internals.h"
  29
  30 static DEFINE_MUTEX(afinfo_mutex);
  31
  32 struct nf_afinfo *nf_afinfo[NPROTO] __read_mostly;
  33 EXPORT_SYMBOL(nf_afinfo);
  34
  35 int nf_register_afinfo(struct nf_afinfo *afinfo)
  36 {
  37         int err;
  38
  39         err = mutex_lock_interruptible(&afinfo_mutex);
  40         if (err < 0)
  41                 return err;
  42         rcu_assign_pointer(nf_afinfo[afinfo->family], afinfo);
  43         mutex_unlock(&afinfo_mutex);
  44         return 0;
  45 }
  46 EXPORT_SYMBOL_GPL(nf_register_afinfo);
  47
  48 void nf_unregister_afinfo(struct nf_afinfo *afinfo)
  49 {
  50         mutex_lock(&afinfo_mutex);
  51         rcu_assign_pointer(nf_afinfo[afinfo->family], NULL);
  52         mutex_unlock(&afinfo_mutex);
  53         synchronize_rcu();
  54 }
  55 EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
  56
  57 /* In this code, we can be waiting indefinitely for userspace to
  58  * service a packet if a hook returns NF_QUEUE.  We could keep a count
  59  * of skbuffs queued for userspace, and not deregister a hook unless
  60  * this is zero, but that sucks.  Now, we simply check when the
  61  * packets come back: if the hook is gone, the packet is discarded. */
  62 struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS] __read_mostly;
  63 EXPORT_SYMBOL(nf_hooks);
  64 static DEFINE_MUTEX(nf_hook_mutex);
  65
  66 int nf_register_hook(struct nf_hook_ops *reg)
  67 {
  68         struct list_head *i;
  69         int err;
  70
  71         err = mutex_lock_interruptible(&nf_hook_mutex);
  72         if (err < 0)
  73                 return err;
  74         list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) {
  75                 if (reg->priority < ((struct nf_hook_ops *)i)->priority)
  76                         break;
  77         }
  78         list_add_rcu(&reg->list, i->prev);
  79         mutex_unlock(&nf_hook_mutex);
  80         return 0;
  81 }
  82 EXPORT_SYMBOL(nf_register_hook);
  83
  84 void nf_unregister_hook(struct nf_hook_ops *reg)
  85 {
  86         mutex_lock(&nf_hook_mutex);
  87         list_del_rcu(&reg->list);
  88         mutex_unlock(&nf_hook_mutex);
  89
  90         synchronize_net();
  91 }
  92 EXPORT_SYMBOL(nf_unregister_hook);
  93
  94 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
  95 {
  96         unsigned int i;
  97         int err = 0;
  98
  99         for (i = 0; i < n; i++) {
 100                 err = nf_register_hook(&reg[i]);
 101                 if (err)
 102                         goto err;
 103         }
 104         return err;
 105
 106 err:
 107         if (i > 0)
 108                 nf_unregister_hooks(reg, i);
 109         return err;
 110 }
 111 EXPORT_SYMBOL(nf_register_hooks);
 112
 113 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 114 {
 115         unsigned int i;
 116
 117         for (i = 0; i < n; i++)
 118                 nf_unregister_hook(&reg[i]);
 119 }
 120 EXPORT_SYMBOL(nf_unregister_hooks);
 121
 122 unsigned int nf_iterate(struct list_head *head,
 123                         struct sk_buff **skb,
 124                         int hook,
 125                         const struct net_device *indev,
 126                         const struct net_device *outdev,
 127                         struct list_head **i,
 128                         int (*okfn)(struct sk_buff *),
 129                         int hook_thresh)
 130 {
 131         unsigned int verdict;
 132
 133         /*
 134          * The caller must not block between calls to this
 135          * function because of risk of continuing from deleted element.
 136          */
 137         list_for_each_continue_rcu(*i, head) {
 138                 struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
 139
 140                 if (hook_thresh > elem->priority)
 141                         continue;
 142
 143                 /* Optimization: we don't need to hold module
 144                    reference here, since function can't sleep. --RR */
 145                 verdict = elem->hook(hook, skb, indev, outdev, okfn);
 146                 if (verdict != NF_ACCEPT) {
 147 #ifdef CONFIG_NETFILTER_DEBUG
 148                         if (unlikely((verdict & NF_VERDICT_MASK)
 149                                                         > NF_MAX_VERDICT)) {
 150                                 NFDEBUG("Evil return from %p(%u).\n",
 151                                         elem->hook, hook);
 152                                 continue;
 153                         }
 154 #endif
 155                         if (verdict != NF_REPEAT)
 156                                 return verdict;
 157                         *i = (*i)->prev;
 158                 }
 159         }
 160         return NF_ACCEPT;
 161 }
 162
 163
 164 /* Returns 1 if okfn() needs to be executed by the caller,
 165  * -EPERM for NF_DROP, 0 otherwise. */
 166 int nf_hook_slow(int pf, unsigned int hook, struct sk_buff **pskb,
 167                  struct net_device *indev,
 168                  struct net_device *outdev,
 169                  int (*okfn)(struct sk_buff *),
 170                  int hook_thresh)
 171 {
 172         struct list_head *elem;
 173         unsigned int verdict;
 174         int ret = 0;
 175
 176         /* We may already have this, but read-locks nest anyway */
 177         rcu_read_lock();
 178
 179         elem = &nf_hooks[pf][hook];
 180 next_hook:
 181         verdict = nf_iterate(&nf_hooks[pf][hook], pskb, hook, indev,
 182                              outdev, &elem, okfn, hook_thresh);
 183         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 184                 ret = 1;
 185                 goto unlock;
 186         } else if (verdict == NF_DROP) {
 187                 kfree_skb(*pskb);
 188                 ret = -EPERM;
 189         } else if ((verdict & NF_VERDICT_MASK)  == NF_QUEUE) {
 190                 NFDEBUG("nf_hook: Verdict = QUEUE.\n");
 191                 if (!nf_queue(*pskb, elem, pf, hook, indev, outdev, okfn,
 192                               verdict >> NF_VERDICT_BITS))
 193                         goto next_hook;
 194         }
 195 unlock:
 196         rcu_read_unlock();
 197         return ret;
 198 }
 199 EXPORT_SYMBOL(nf_hook_slow);
 200
 201
 202 int skb_make_writable(struct sk_buff **pskb, unsigned int writable_len)
 203 {
 204         struct sk_buff *nskb;
 205
 206         if (writable_len > (*pskb)->len)
 207                 return 0;
 208
 209         /* Not exclusive use of packet?  Must copy. */
 210         if (skb_shared(*pskb) || skb_cloned(*pskb))
 211                 goto copy_skb;
 212
 213         return pskb_may_pull(*pskb, writable_len);
 214
 215 copy_skb:
 216         nskb = skb_copy(*pskb, GFP_ATOMIC);
 217         if (!nskb)
 218                 return 0;
 219         BUG_ON(skb_is_nonlinear(nskb));
 220
 221         /* Rest of kernel will get very unhappy if we pass it a
 222            suddenly-orphaned skbuff */
 223         if ((*pskb)->sk)
 224                 skb_set_owner_w(nskb, (*pskb)->sk);
 225         kfree_skb(*pskb);
 226         *pskb = nskb;
 227         return 1;
 228 }
 229 EXPORT_SYMBOL(skb_make_writable);
 230
 231 void nf_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 232                             __be32 from, __be32 to, int pseudohdr)
 233 {
 234         __be32 diff[] = { ~from, to };
 235         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 236                 *sum = csum_fold(csum_partial((char *)diff, sizeof(diff),
 237                                 ~csum_unfold(*sum)));
 238                 if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
 239                         skb->csum = ~csum_partial((char *)diff, sizeof(diff),
 240                                                 ~skb->csum);
 241         } else if (pseudohdr)
 242                 *sum = ~csum_fold(csum_partial((char *)diff, sizeof(diff),
 243                                 csum_unfold(*sum)));
 244 }
 245 EXPORT_SYMBOL(nf_proto_csum_replace4);
 246
 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 #ifdef CONFIG_PROC_FS
 268 struct proc_dir_entry *proc_net_netfilter;
 269 EXPORT_SYMBOL(proc_net_netfilter);
 270 #endif
 271
 272 void __init netfilter_init(void)
 273 {
 274         int i, h;
 275         for (i = 0; i < NPROTO; i++) {
 276                 for (h = 0; h < NF_MAX_HOOKS; h++)
 277                         INIT_LIST_HEAD(&nf_hooks[i][h]);
 278         }
 279
 280 #ifdef CONFIG_PROC_FS
 281         proc_net_netfilter = proc_mkdir("netfilter", proc_net);
 282         if (!proc_net_netfilter)
 283                 panic("cannot create netfilter proc entry");
 284 #endif
 285
 286         if (netfilter_queue_init() < 0)
 287                 panic("cannot initialize nf_queue");
 288         if (netfilter_log_init() < 0)
 289                 panic("cannot initialize nf_log");
 290 }