net/netfilter/xt_recent.c

   1 /*
   2  * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This is a replacement of the old ipt_recent module, which carried the
   9  * following copyright notice:
  10  *
  11  * Author: Stephen Frost <sfrost@snowman.net>
  12  * Copyright 2002-2003, Stephen Frost, 2.5.x port by laforge@netfilter.org
  13  */
  14 #include <linux/init.h>
  15 #include <linux/ip.h>
  16 #include <linux/moduleparam.h>
  17 #include <linux/proc_fs.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/string.h>
  20 #include <linux/ctype.h>
  21 #include <linux/list.h>
  22 #include <linux/random.h>
  23 #include <linux/jhash.h>
  24 #include <linux/bitops.h>
  25 #include <linux/skbuff.h>
  26 #include <linux/inet.h>
  27 #include <net/net_namespace.h>
  28
  29 #include <linux/netfilter/x_tables.h>
  30 #include <linux/netfilter/xt_recent.h>
  31
  32 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  33 MODULE_DESCRIPTION("Xtables: \"recently-seen\" host matching for IPv4");
  34 MODULE_LICENSE("GPL");
  35 MODULE_ALIAS("ipt_recent");
  36
  37 static unsigned int ip_list_tot = 100;
  38 static unsigned int ip_pkt_list_tot = 20;
  39 static unsigned int ip_list_hash_size = 0;
  40 static unsigned int ip_list_perms = 0644;
  41 static unsigned int ip_list_uid = 0;
  42 static unsigned int ip_list_gid = 0;
  43 module_param(ip_list_tot, uint, 0400);
  44 module_param(ip_pkt_list_tot, uint, 0400);
  45 module_param(ip_list_hash_size, uint, 0400);
  46 module_param(ip_list_perms, uint, 0400);
  47 module_param(ip_list_uid, uint, 0400);
  48 module_param(ip_list_gid, uint, 0400);
  49 MODULE_PARM_DESC(ip_list_tot, "number of IPs to remember per list");
  50 MODULE_PARM_DESC(ip_pkt_list_tot, "number of packets per IP to remember (max. 255)");
  51 MODULE_PARM_DESC(ip_list_hash_size, "size of hash table used to look up IPs");
  52 MODULE_PARM_DESC(ip_list_perms, "permissions on /proc/net/ipt_recent/* files");
  53 MODULE_PARM_DESC(ip_list_uid,"owner of /proc/net/ipt_recent/* files");
  54 MODULE_PARM_DESC(ip_list_gid,"owning group of /proc/net/ipt_recent/* files");
  55
  56 struct recent_entry {
  57         struct list_head        list;
  58         struct list_head        lru_list;
  59         __be32                  addr;
  60         u_int8_t                ttl;
  61         u_int8_t                index;
  62         u_int16_t               nstamps;
  63         unsigned long           stamps[0];
  64 };
  65
  66 struct recent_table {
  67         struct list_head        list;
  68         char                    name[XT_RECENT_NAME_LEN];
  69 #ifdef CONFIG_PROC_FS
  70         struct proc_dir_entry   *proc;
  71 #endif
  72         unsigned int            refcnt;
  73         unsigned int            entries;
  74         struct list_head        lru_list;
  75         struct list_head        iphash[0];
  76 };
  77
  78 static LIST_HEAD(tables);
  79 static DEFINE_SPINLOCK(recent_lock);
  80 static DEFINE_MUTEX(recent_mutex);
  81
  82 #ifdef CONFIG_PROC_FS
  83 static struct proc_dir_entry    *proc_dir;
  84 static const struct file_operations     recent_fops;
  85 #endif
  86
  87 static u_int32_t hash_rnd;
  88 static int hash_rnd_initted;
  89
  90 static unsigned int recent_entry_hash(__be32 addr)
  91 {
  92         if (!hash_rnd_initted) {
  93                 get_random_bytes(&hash_rnd, 4);
  94                 hash_rnd_initted = 1;
  95         }
  96         return jhash_1word((__force u32)addr, hash_rnd) & (ip_list_hash_size - 1);
  97 }
  98
  99 static struct recent_entry *
 100 recent_entry_lookup(const struct recent_table *table, __be32 addr, u_int8_t ttl)
 101 {
 102         struct recent_entry *e;
 103         unsigned int h;
 104
 105         h = recent_entry_hash(addr);
 106         list_for_each_entry(e, &table->iphash[h], list)
 107                 if (e->addr == addr && (ttl == e->ttl || !ttl || !e->ttl))
 108                         return e;
 109         return NULL;
 110 }
 111
 112 static void recent_entry_remove(struct recent_table *t, struct recent_entry *e)
 113 {
 114         list_del(&e->list);
 115         list_del(&e->lru_list);
 116         kfree(e);
 117         t->entries--;
 118 }
 119
 120 static struct recent_entry *
 121 recent_entry_init(struct recent_table *t, __be32 addr, u_int8_t ttl)
 122 {
 123         struct recent_entry *e;
 124
 125         if (t->entries >= ip_list_tot) {
 126                 e = list_entry(t->lru_list.next, struct recent_entry, lru_list);
 127                 recent_entry_remove(t, e);
 128         }
 129         e = kmalloc(sizeof(*e) + sizeof(e->stamps[0]) * ip_pkt_list_tot,
 130                     GFP_ATOMIC);
 131         if (e == NULL)
 132                 return NULL;
 133         e->addr      = addr;
 134         e->ttl       = ttl;
 135         e->stamps[0] = jiffies;
 136         e->nstamps   = 1;
 137         e->index     = 1;
 138         list_add_tail(&e->list, &t->iphash[recent_entry_hash(addr)]);
 139         list_add_tail(&e->lru_list, &t->lru_list);
 140         t->entries++;
 141         return e;
 142 }
 143
 144 static void recent_entry_update(struct recent_table *t, struct recent_entry *e)
 145 {
 146         e->stamps[e->index++] = jiffies;
 147         if (e->index > e->nstamps)
 148                 e->nstamps = e->index;
 149         e->index %= ip_pkt_list_tot;
 150         list_move_tail(&e->lru_list, &t->lru_list);
 151 }
 152
 153 static struct recent_table *recent_table_lookup(const char *name)
 154 {
 155         struct recent_table *t;
 156
 157         list_for_each_entry(t, &tables, list)
 158                 if (!strcmp(t->name, name))
 159                         return t;
 160         return NULL;
 161 }
 162
 163 static void recent_table_flush(struct recent_table *t)
 164 {
 165         struct recent_entry *e, *next;
 166         unsigned int i;
 167
 168         for (i = 0; i < ip_list_hash_size; i++)
 169                 list_for_each_entry_safe(e, next, &t->iphash[i], list)
 170                         recent_entry_remove(t, e);
 171 }
 172
 173 static bool
 174 recent_mt(const struct sk_buff *skb, const struct net_device *in,
 175           const struct net_device *out, const struct xt_match *match,
 176           const void *matchinfo, int offset, unsigned int protoff,
 177           bool *hotdrop)
 178 {
 179         const struct xt_recent_mtinfo *info = matchinfo;
 180         struct recent_table *t;
 181         struct recent_entry *e;
 182         __be32 addr;
 183         u_int8_t ttl;
 184         bool ret = info->invert;
 185
 186         if (info->side == XT_RECENT_DEST)
 187                 addr = ip_hdr(skb)->daddr;
 188         else
 189                 addr = ip_hdr(skb)->saddr;
 190
 191         ttl = ip_hdr(skb)->ttl;
 192         /* use TTL as seen before forwarding */
 193         if (out && !skb->sk)
 194                 ttl++;
 195
 196         spin_lock_bh(&recent_lock);
 197         t = recent_table_lookup(info->name);
 198         e = recent_entry_lookup(t, addr,
 199                                 info->check_set & XT_RECENT_TTL ? ttl : 0);
 200         if (e == NULL) {
 201                 if (!(info->check_set & XT_RECENT_SET))
 202                         goto out;
 203                 e = recent_entry_init(t, addr, ttl);
 204                 if (e == NULL)
 205                         *hotdrop = true;
 206                 ret = !ret;
 207                 goto out;
 208         }
 209
 210         if (info->check_set & XT_RECENT_SET)
 211                 ret = !ret;
 212         else if (info->check_set & XT_RECENT_REMOVE) {
 213                 recent_entry_remove(t, e);
 214                 ret = !ret;
 215         } else if (info->check_set & (XT_RECENT_CHECK | XT_RECENT_UPDATE)) {
 216                 unsigned long time = jiffies - info->seconds * HZ;
 217                 unsigned int i, hits = 0;
 218
 219                 for (i = 0; i < e->nstamps; i++) {
 220                         if (info->seconds && time_after(time, e->stamps[i]))
 221                                 continue;
 222                         if (++hits >= info->hit_count) {
 223                                 ret = !ret;
 224                                 break;
 225                         }
 226                 }
 227         }
 228
 229         if (info->check_set & XT_RECENT_SET ||
 230             (info->check_set & XT_RECENT_UPDATE && ret)) {
 231                 recent_entry_update(t, e);
 232                 e->ttl = ttl;
 233         }
 234 out:
 235         spin_unlock_bh(&recent_lock);
 236         return ret;
 237 }
 238
 239 static bool
 240 recent_mt_check(const char *tablename, const void *ip,
 241                 const struct xt_match *match, void *matchinfo,
 242                 unsigned int hook_mask)
 243 {
 244         const struct xt_recent_mtinfo *info = matchinfo;
 245         struct recent_table *t;
 246         unsigned i;
 247         bool ret = false;
 248
 249         if (hweight8(info->check_set &
 250                      (XT_RECENT_SET | XT_RECENT_REMOVE |
 251                       XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1)
 252                 return false;
 253         if ((info->check_set & (XT_RECENT_SET | XT_RECENT_REMOVE)) &&
 254             (info->seconds || info->hit_count))
 255                 return false;
 256         if (info->hit_count > ip_pkt_list_tot)
 257                 return false;
 258         if (info->name[0] == '\0' ||
 259             strnlen(info->name, XT_RECENT_NAME_LEN) == XT_RECENT_NAME_LEN)
 260                 return false;
 261
 262         mutex_lock(&recent_mutex);
 263         t = recent_table_lookup(info->name);
 264         if (t != NULL) {
 265                 t->refcnt++;
 266                 ret = true;
 267                 goto out;
 268         }
 269
 270         t = kzalloc(sizeof(*t) + sizeof(t->iphash[0]) * ip_list_hash_size,
 271                     GFP_KERNEL);
 272         if (t == NULL)
 273                 goto out;
 274         t->refcnt = 1;
 275         strcpy(t->name, info->name);
 276         INIT_LIST_HEAD(&t->lru_list);
 277         for (i = 0; i < ip_list_hash_size; i++)
 278                 INIT_LIST_HEAD(&t->iphash[i]);
 279 #ifdef CONFIG_PROC_FS
 280         t->proc = proc_create(t->name, ip_list_perms, proc_dir, &recent_fops);
 281         if (t->proc == NULL) {
 282                 kfree(t);
 283                 goto out;
 284         }
 285         t->proc->uid       = ip_list_uid;
 286         t->proc->gid       = ip_list_gid;
 287         t->proc->data      = t;
 288 #endif
 289         spin_lock_bh(&recent_lock);
 290         list_add_tail(&t->list, &tables);
 291         spin_unlock_bh(&recent_lock);
 292         ret = true;
 293 out:
 294         mutex_unlock(&recent_mutex);
 295         return ret;
 296 }
 297
 298 static void recent_mt_destroy(const struct xt_match *match, void *matchinfo)
 299 {
 300         const struct xt_recent_mtinfo *info = matchinfo;
 301         struct recent_table *t;
 302
 303         mutex_lock(&recent_mutex);
 304         t = recent_table_lookup(info->name);
 305         if (--t->refcnt == 0) {
 306                 spin_lock_bh(&recent_lock);
 307                 list_del(&t->list);
 308                 spin_unlock_bh(&recent_lock);
 309 #ifdef CONFIG_PROC_FS
 310                 remove_proc_entry(t->name, proc_dir);
 311 #endif
 312                 recent_table_flush(t);
 313                 kfree(t);
 314         }
 315         mutex_unlock(&recent_mutex);
 316 }
 317
 318 #ifdef CONFIG_PROC_FS
 319 struct recent_iter_state {
 320         struct recent_table     *table;
 321         unsigned int            bucket;
 322 };
 323
 324 static void *recent_seq_start(struct seq_file *seq, loff_t *pos)
 325         __acquires(recent_lock)
 326 {
 327         struct recent_iter_state *st = seq->private;
 328         const struct recent_table *t = st->table;
 329         struct recent_entry *e;
 330         loff_t p = *pos;
 331
 332         spin_lock_bh(&recent_lock);
 333
 334         for (st->bucket = 0; st->bucket < ip_list_hash_size; st->bucket++)
 335                 list_for_each_entry(e, &t->iphash[st->bucket], list)
 336                         if (p-- == 0)
 337                                 return e;
 338         return NULL;
 339 }
 340
 341 static void *recent_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 342 {
 343         struct recent_iter_state *st = seq->private;
 344         const struct recent_table *t = st->table;
 345         struct recent_entry *e = v;
 346         struct list_head *head = e->list.next;
 347
 348         while (head == &t->iphash[st->bucket]) {
 349                 if (++st->bucket >= ip_list_hash_size)
 350                         return NULL;
 351                 head = t->iphash[st->bucket].next;
 352         }
 353         (*pos)++;
 354         return list_entry(head, struct recent_entry, list);
 355 }
 356
 357 static void recent_seq_stop(struct seq_file *s, void *v)
 358         __releases(recent_lock)
 359 {
 360         spin_unlock_bh(&recent_lock);
 361 }
 362
 363 static int recent_seq_show(struct seq_file *seq, void *v)
 364 {
 365         const struct recent_entry *e = v;
 366         unsigned int i;
 367
 368         i = (e->index - 1) % ip_pkt_list_tot;
 369         seq_printf(seq, "src=%u.%u.%u.%u ttl: %u last_seen: %lu oldest_pkt: %u",
 370                    NIPQUAD(e->addr), e->ttl, e->stamps[i], e->index);
 371         for (i = 0; i < e->nstamps; i++)
 372                 seq_printf(seq, "%s %lu", i ? "," : "", e->stamps[i]);
 373         seq_printf(seq, "\n");
 374         return 0;
 375 }
 376
 377 static const struct seq_operations recent_seq_ops = {
 378         .start          = recent_seq_start,
 379         .next           = recent_seq_next,
 380         .stop           = recent_seq_stop,
 381         .show           = recent_seq_show,
 382 };
 383
 384 static int recent_seq_open(struct inode *inode, struct file *file)
 385 {
 386         struct proc_dir_entry *pde = PDE(inode);
 387         struct recent_iter_state *st;
 388
 389         st = __seq_open_private(file, &recent_seq_ops, sizeof(*st));
 390         if (st == NULL)
 391                 return -ENOMEM;
 392
 393         st->table    = pde->data;
 394         return 0;
 395 }
 396
 397 static ssize_t recent_proc_write(struct file *file, const char __user *input,
 398                                  size_t size, loff_t *loff)
 399 {
 400         const struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 401         struct recent_table *t = pde->data;
 402         struct recent_entry *e;
 403         char buf[sizeof("+255.255.255.255")], *c = buf;
 404         __be32 addr;
 405         int add;
 406
 407         if (size > sizeof(buf))
 408                 size = sizeof(buf);
 409         if (copy_from_user(buf, input, size))
 410                 return -EFAULT;
 411         while (isspace(*c))
 412                 c++;
 413
 414         if (size - (c - buf) < 5)
 415                 return c - buf;
 416         if (!strncmp(c, "clear", 5)) {
 417                 c += 5;
 418                 spin_lock_bh(&recent_lock);
 419                 recent_table_flush(t);
 420                 spin_unlock_bh(&recent_lock);
 421                 return c - buf;
 422         }
 423
 424         switch (*c) {
 425         case '-':
 426                 add = 0;
 427                 c++;
 428                 break;
 429         case '+':
 430                 c++;
 431         default:
 432                 add = 1;
 433                 break;
 434         }
 435         addr = in_aton(c);
 436
 437         spin_lock_bh(&recent_lock);
 438         e = recent_entry_lookup(t, addr, 0);
 439         if (e == NULL) {
 440                 if (add)
 441                         recent_entry_init(t, addr, 0);
 442         } else {
 443                 if (add)
 444                         recent_entry_update(t, e);
 445                 else
 446                         recent_entry_remove(t, e);
 447         }
 448         spin_unlock_bh(&recent_lock);
 449         return size;
 450 }
 451
 452 static const struct file_operations recent_fops = {
 453         .open           = recent_seq_open,
 454         .read           = seq_read,
 455         .write          = recent_proc_write,
 456         .release        = seq_release_private,
 457         .owner          = THIS_MODULE,
 458 };
 459 #endif /* CONFIG_PROC_FS */
 460
 461 static struct xt_match recent_mt_reg __read_mostly = {
 462         .name           = "recent",
 463         .family         = AF_INET,
 464         .match          = recent_mt,
 465         .matchsize      = sizeof(struct xt_recent_mtinfo),
 466         .checkentry     = recent_mt_check,
 467         .destroy        = recent_mt_destroy,
 468         .me             = THIS_MODULE,
 469 };
 470
 471 static int __init recent_mt_init(void)
 472 {
 473         int err;
 474
 475         if (!ip_list_tot || !ip_pkt_list_tot || ip_pkt_list_tot > 255)
 476                 return -EINVAL;
 477         ip_list_hash_size = 1 << fls(ip_list_tot);
 478
 479         err = xt_register_match(&recent_mt_reg);
 480 #ifdef CONFIG_PROC_FS
 481         if (err)
 482                 return err;
 483         proc_dir = proc_mkdir("ipt_recent", init_net.proc_net);
 484         if (proc_dir == NULL) {
 485                 xt_unregister_match(&recent_mt_reg);
 486                 err = -ENOMEM;
 487         }
 488 #endif
 489         return err;
 490 }
 491
 492 static void __exit recent_mt_exit(void)
 493 {
 494         BUG_ON(!list_empty(&tables));
 495         xt_unregister_match(&recent_mt_reg);
 496 #ifdef CONFIG_PROC_FS
 497         remove_proc_entry("ipt_recent", init_net.proc_net);
 498 #endif
 499 }
 500
 501 module_init(recent_mt_init);
 502 module_exit(recent_mt_exit);