net/netfilter/nf_nat_masquerade.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/types.h>
   4 #include <linux/atomic.h>
   5 #include <linux/inetdevice.h>
   6 #include <linux/netfilter.h>
   7 #include <linux/netfilter_ipv4.h>
   8 #include <linux/netfilter_ipv6.h>
   9
  10 #include <net/netfilter/nf_nat_masquerade.h>
  11
  12 static DEFINE_MUTEX(masq_mutex);
  13 static unsigned int masq_refcnt __read_mostly;
  14
  15 unsigned int
  16 nf_nat_masquerade_ipv4(struct sk_buff *skb, unsigned int hooknum,
  17                        const struct nf_nat_range2 *range,
  18                        const struct net_device *out)
  19 {
  20         struct nf_conn *ct;
  21         struct nf_conn_nat *nat;
  22         enum ip_conntrack_info ctinfo;
  23         struct nf_nat_range2 newrange;
  24         const struct rtable *rt;
  25         __be32 newsrc, nh;
  26
  27         WARN_ON(hooknum != NF_INET_POST_ROUTING);
  28
  29         ct = nf_ct_get(skb, &ctinfo);
  30
  31         WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  32                          ctinfo == IP_CT_RELATED_REPLY)));
  33
  34         /* Source address is 0.0.0.0 - locally generated packet that is
  35          * probably not supposed to be masqueraded.
  36          */
  37         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
  38                 return NF_ACCEPT;
  39
  40         rt = skb_rtable(skb);
  41         nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
  42         newsrc = inet_select_addr(out, nh, RT_SCOPE_UNIVERSE);
  43         if (!newsrc) {
  44                 pr_info("%s ate my IP address\n", out->name);
  45                 return NF_DROP;
  46         }
  47
  48         nat = nf_ct_nat_ext_add(ct);
  49         if (nat)
  50                 nat->masq_index = out->ifindex;
  51
  52         /* Transfer from original range. */
  53         memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
  54         memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
  55         newrange.flags       = range->flags | NF_NAT_RANGE_MAP_IPS;
  56         newrange.min_addr.ip = newsrc;
  57         newrange.max_addr.ip = newsrc;
  58         newrange.min_proto   = range->min_proto;
  59         newrange.max_proto   = range->max_proto;
  60
  61         /* Hand modified range to generic setup. */
  62         return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
  63 }
  64 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);
  65
  66 static int device_cmp(struct nf_conn *i, void *ifindex)
  67 {
  68         const struct nf_conn_nat *nat = nfct_nat(i);
  69
  70         if (!nat)
  71                 return 0;
  72         return nat->masq_index == (int)(long)ifindex;
  73 }
  74
  75 static int masq_device_event(struct notifier_block *this,
  76                              unsigned long event,
  77                              void *ptr)
  78 {
  79         const struct net_device *dev = netdev_notifier_info_to_dev(ptr);
  80         struct net *net = dev_net(dev);
  81
  82         if (event == NETDEV_DOWN) {
  83                 /* Device was downed.  Search entire table for
  84                  * conntracks which were associated with that device,
  85                  * and forget them.
  86                  */
  87
  88                 nf_ct_iterate_cleanup_net(net, device_cmp,
  89                                           (void *)(long)dev->ifindex, 0, 0);
  90         }
  91
  92         return NOTIFY_DONE;
  93 }
  94
  95 static int inet_cmp(struct nf_conn *ct, void *ptr)
  96 {
  97         struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
  98         struct net_device *dev = ifa->ifa_dev->dev;
  99         struct nf_conntrack_tuple *tuple;
 100
 101         if (!device_cmp(ct, (void *)(long)dev->ifindex))
 102                 return 0;
 103
 104         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 105
 106         return ifa->ifa_address == tuple->dst.u3.ip;
 107 }
 108
 109 static int masq_inet_event(struct notifier_block *this,
 110                            unsigned long event,
 111                            void *ptr)
 112 {
 113         struct in_device *idev = ((struct in_ifaddr *)ptr)->ifa_dev;
 114         struct net *net = dev_net(idev->dev);
 115
 116         /* The masq_dev_notifier will catch the case of the device going
 117          * down.  So if the inetdev is dead and being destroyed we have
 118          * no work to do.  Otherwise this is an individual address removal
 119          * and we have to perform the flush.
 120          */
 121         if (idev->dead)
 122                 return NOTIFY_DONE;
 123
 124         if (event == NETDEV_DOWN)
 125                 nf_ct_iterate_cleanup_net(net, inet_cmp, ptr, 0, 0);
 126
 127         return NOTIFY_DONE;
 128 }
 129
 130 static struct notifier_block masq_dev_notifier = {
 131         .notifier_call  = masq_device_event,
 132 };
 133
 134 static struct notifier_block masq_inet_notifier = {
 135         .notifier_call  = masq_inet_event,
 136 };
 137
 138 #if IS_ENABLED(CONFIG_IPV6)
 139 static atomic_t v6_worker_count __read_mostly;
 140
 141 static int
 142 nat_ipv6_dev_get_saddr(struct net *net, const struct net_device *dev,
 143                        const struct in6_addr *daddr, unsigned int srcprefs,
 144                        struct in6_addr *saddr)
 145 {
 146 #ifdef CONFIG_IPV6_MODULE
 147         const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
 148
 149         if (!v6_ops)
 150                 return -EHOSTUNREACH;
 151
 152         return v6_ops->dev_get_saddr(net, dev, daddr, srcprefs, saddr);
 153 #else
 154         return ipv6_dev_get_saddr(net, dev, daddr, srcprefs, saddr);
 155 #endif
 156 }
 157
 158 unsigned int
 159 nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
 160                        const struct net_device *out)
 161 {
 162         enum ip_conntrack_info ctinfo;
 163         struct nf_conn_nat *nat;
 164         struct in6_addr src;
 165         struct nf_conn *ct;
 166         struct nf_nat_range2 newrange;
 167
 168         ct = nf_ct_get(skb, &ctinfo);
 169         WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
 170                          ctinfo == IP_CT_RELATED_REPLY)));
 171
 172         if (nat_ipv6_dev_get_saddr(nf_ct_net(ct), out,
 173                                    &ipv6_hdr(skb)->daddr, 0, &src) < 0)
 174                 return NF_DROP;
 175
 176         nat = nf_ct_nat_ext_add(ct);
 177         if (nat)
 178                 nat->masq_index = out->ifindex;
 179
 180         newrange.flags          = range->flags | NF_NAT_RANGE_MAP_IPS;
 181         newrange.min_addr.in6   = src;
 182         newrange.max_addr.in6   = src;
 183         newrange.min_proto      = range->min_proto;
 184         newrange.max_proto      = range->max_proto;
 185
 186         return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
 187 }
 188 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6);
 189
 190 struct masq_dev_work {
 191         struct work_struct work;
 192         struct net *net;
 193         struct in6_addr addr;
 194         int ifindex;
 195 };
 196
 197 static int inet6_cmp(struct nf_conn *ct, void *work)
 198 {
 199         struct masq_dev_work *w = (struct masq_dev_work *)work;
 200         struct nf_conntrack_tuple *tuple;
 201
 202         if (!device_cmp(ct, (void *)(long)w->ifindex))
 203                 return 0;
 204
 205         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 206
 207         return ipv6_addr_equal(&w->addr, &tuple->dst.u3.in6);
 208 }
 209
 210 static void iterate_cleanup_work(struct work_struct *work)
 211 {
 212         struct masq_dev_work *w;
 213
 214         w = container_of(work, struct masq_dev_work, work);
 215
 216         nf_ct_iterate_cleanup_net(w->net, inet6_cmp, (void *)w, 0, 0);
 217
 218         put_net(w->net);
 219         kfree(w);
 220         atomic_dec(&v6_worker_count);
 221         module_put(THIS_MODULE);
 222 }
 223
 224 /* atomic notifier; can't call nf_ct_iterate_cleanup_net (it can sleep).
 225  *
 226  * Defer it to the system workqueue.
 227  *
 228  * As we can have 'a lot' of inet_events (depending on amount of ipv6
 229  * addresses being deleted), we also need to limit work item queue.
 230  */
 231 static int masq_inet6_event(struct notifier_block *this,
 232                             unsigned long event, void *ptr)
 233 {
 234         struct inet6_ifaddr *ifa = ptr;
 235         const struct net_device *dev;
 236         struct masq_dev_work *w;
 237         struct net *net;
 238
 239         if (event != NETDEV_DOWN || atomic_read(&v6_worker_count) >= 16)
 240                 return NOTIFY_DONE;
 241
 242         dev = ifa->idev->dev;
 243         net = maybe_get_net(dev_net(dev));
 244         if (!net)
 245                 return NOTIFY_DONE;
 246
 247         if (!try_module_get(THIS_MODULE))
 248                 goto err_module;
 249
 250         w = kmalloc(sizeof(*w), GFP_ATOMIC);
 251         if (w) {
 252                 atomic_inc(&v6_worker_count);
 253
 254                 INIT_WORK(&w->work, iterate_cleanup_work);
 255                 w->ifindex = dev->ifindex;
 256                 w->net = net;
 257                 w->addr = ifa->addr;
 258                 schedule_work(&w->work);
 259
 260                 return NOTIFY_DONE;
 261         }
 262
 263         module_put(THIS_MODULE);
 264  err_module:
 265         put_net(net);
 266         return NOTIFY_DONE;
 267 }
 268
 269 static struct notifier_block masq_inet6_notifier = {
 270         .notifier_call  = masq_inet6_event,
 271 };
 272
 273 static int nf_nat_masquerade_ipv6_register_notifier(void)
 274 {
 275         return register_inet6addr_notifier(&masq_inet6_notifier);
 276 }
 277 #else
 278 static inline int nf_nat_masquerade_ipv6_register_notifier(void) { return 0; }
 279 #endif
 280
 281 int nf_nat_masquerade_inet_register_notifiers(void)
 282 {
 283         int ret = 0;
 284
 285         mutex_lock(&masq_mutex);
 286         if (WARN_ON_ONCE(masq_refcnt == UINT_MAX)) {
 287                 ret = -EOVERFLOW;
 288                 goto out_unlock;
 289         }
 290
 291         /* check if the notifier was already set */
 292         if (++masq_refcnt > 1)
 293                 goto out_unlock;
 294
 295         /* Register for device down reports */
 296         ret = register_netdevice_notifier(&masq_dev_notifier);
 297         if (ret)
 298                 goto err_dec;
 299         /* Register IP address change reports */
 300         ret = register_inetaddr_notifier(&masq_inet_notifier);
 301         if (ret)
 302                 goto err_unregister;
 303
 304         ret = nf_nat_masquerade_ipv6_register_notifier();
 305         if (ret)
 306                 goto err_unreg_inet;
 307
 308         mutex_unlock(&masq_mutex);
 309         return ret;
 310 err_unreg_inet:
 311         unregister_inetaddr_notifier(&masq_inet_notifier);
 312 err_unregister:
 313         unregister_netdevice_notifier(&masq_dev_notifier);
 314 err_dec:
 315         masq_refcnt--;
 316 out_unlock:
 317         mutex_unlock(&masq_mutex);
 318         return ret;
 319 }
 320 EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_register_notifiers);
 321
 322 void nf_nat_masquerade_inet_unregister_notifiers(void)
 323 {
 324         mutex_lock(&masq_mutex);
 325         /* check if the notifiers still have clients */
 326         if (--masq_refcnt > 0)
 327                 goto out_unlock;
 328
 329         unregister_netdevice_notifier(&masq_dev_notifier);
 330         unregister_inetaddr_notifier(&masq_inet_notifier);
 331 #if IS_ENABLED(CONFIG_IPV6)
 332         unregister_inet6addr_notifier(&masq_inet6_notifier);
 333 #endif
 334 out_unlock:
 335         mutex_unlock(&masq_mutex);
 336 }
 337 EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_unregister_notifiers);