net/netfilter/xt_quota2.c

   1 /*
   2  * xt_quota2 - enhanced xt_quota that can count upwards and in packets
   3  * as a minimal accounting match.
   4  * by Jan Engelhardt <jengelh@medozas.de>, 2008
   5  *
   6  * Originally based on xt_quota.c:
   7  *      netfilter module to enforce network quotas
   8  *      Sam Johnston <samj@samj.net>
   9  *
  10  *      This program is free software; you can redistribute it and/or modify
  11  *      it under the terms of the GNU General Public License; either
  12  *      version 2 of the License, as published by the Free Software Foundation.
  13  */
  14 #include <linux/list.h>
  15 #include <linux/module.h>
  16 #include <linux/proc_fs.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/spinlock.h>
  19 #include <asm/atomic.h>
  20 #include <net/netlink.h>
  21
  22 #include <linux/netfilter/x_tables.h>
  23 #include <linux/netfilter/xt_quota2.h>
  24 #ifdef CONFIG_NETFILTER_XT_MATCH_QUOTA2_LOG
  25 #include <linux/netfilter_ipv4/ipt_ULOG.h>
  26 #endif
  27
  28 /**
  29  * @lock:       lock to protect quota writers from each other
  30  */
  31 struct xt_quota_counter {
  32         u_int64_t quota;
  33         spinlock_t lock;
  34         struct list_head list;
  35         atomic_t ref;
  36         char name[sizeof(((struct xt_quota_mtinfo2 *)NULL)->name)];
  37         struct proc_dir_entry *procfs_entry;
  38 };
  39
  40 #ifdef CONFIG_NETFILTER_XT_MATCH_QUOTA2_LOG
  41 /* Harald's favorite number +1 :D From ipt_ULOG.C */
  42 static int qlog_nl_event = 112;
  43 module_param_named(event_num, qlog_nl_event, uint, S_IRUGO | S_IWUSR);
  44 MODULE_PARM_DESC(event_num,
  45                  "Event number for NETLINK_NFLOG message. 0 disables log."
  46                  "111 is what ipt_ULOG uses.");
  47 static struct sock *nflognl;
  48 #endif
  49
  50 static LIST_HEAD(counter_list);
  51 static DEFINE_SPINLOCK(counter_list_lock);
  52
  53 static struct proc_dir_entry *proc_xt_quota;
  54 static unsigned int quota_list_perms = S_IRUGO | S_IWUSR;
  55 static unsigned int quota_list_uid   = 0;
  56 static unsigned int quota_list_gid   = 0;
  57 module_param_named(perms, quota_list_perms, uint, S_IRUGO | S_IWUSR);
  58 module_param_named(uid, quota_list_uid, uint, S_IRUGO | S_IWUSR);
  59 module_param_named(gid, quota_list_gid, uint, S_IRUGO | S_IWUSR);
  60
  61
  62 #ifdef CONFIG_NETFILTER_XT_MATCH_QUOTA2_LOG
  63 static void quota2_log(unsigned int hooknum,
  64                        const struct sk_buff *skb,
  65                        const struct net_device *in,
  66                        const struct net_device *out,
  67                        const char *prefix)
  68 {
  69         ulog_packet_msg_t *pm;
  70         struct sk_buff *log_skb;
  71         size_t size;
  72         struct nlmsghdr *nlh;
  73
  74         if (!qlog_nl_event)
  75                 return;
  76
  77         size = NLMSG_SPACE(sizeof(*pm));
  78         size = max(size, (size_t)NLMSG_GOODSIZE);
  79         log_skb = alloc_skb(size, GFP_ATOMIC);
  80         if (!log_skb) {
  81                 pr_err("xt_quota2: cannot alloc skb for logging\n");
  82                 return;
  83         }
  84
  85         nlh = nlmsg_put(log_skb, /*pid*/0, /*seq*/0, qlog_nl_event,
  86                         sizeof(*pm), 0);
  87         if (!nlh) {
  88                 pr_err("xt_quota2: nlmsg_put failed\n");
  89                 kfree_skb(log_skb);
  90                 return;
  91         }
  92         pm = nlmsg_data(nlh);
  93         if (skb->tstamp.tv64 == 0)
  94                 __net_timestamp((struct sk_buff *)skb);
  95         pm->data_len = 0;
  96         pm->hook = hooknum;
  97         if (prefix != NULL)
  98                 strlcpy(pm->prefix, prefix, sizeof(pm->prefix));
  99         else
 100                 *(pm->prefix) = '\0';
 101         if (in)
 102                 strlcpy(pm->indev_name, in->name, sizeof(pm->indev_name));
 103         else
 104                 pm->indev_name[0] = '\0';
 105
 106         if (out)
 107                 strlcpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
 108         else
 109                 pm->outdev_name[0] = '\0';
 110
 111         NETLINK_CB(log_skb).dst_group = 1;
 112         pr_debug("throwing 1 packets to netlink group 1\n");
 113         netlink_broadcast(nflognl, log_skb, 0, 1, GFP_ATOMIC);
 114 }
 115 #else
 116 static void quota2_log(unsigned int hooknum,
 117                        const struct sk_buff *skb,
 118                        const struct net_device *in,
 119                        const struct net_device *out,
 120                        const char *prefix)
 121 {
 122 }
 123 #endif  /* if+else CONFIG_NETFILTER_XT_MATCH_QUOTA2_LOG */
 124
 125 static ssize_t quota_proc_read(struct file *file, char __user *buf,
 126                            size_t size, loff_t *ppos)
 127 {
 128         struct xt_quota_counter *e = PDE_DATA(file_inode(file));
 129         char tmp[24];
 130         size_t tmp_size;
 131
 132         spin_lock_bh(&e->lock);
 133         tmp_size = scnprintf(tmp, sizeof(tmp), "%llu\n", e->quota);
 134         spin_unlock_bh(&e->lock);
 135         return simple_read_from_buffer(buf, size, ppos, tmp, tmp_size);
 136 }
 137
 138 static ssize_t quota_proc_write(struct file *file, const char __user *input,
 139                             size_t size, loff_t *ppos)
 140 {
 141         struct xt_quota_counter *e = PDE_DATA(file_inode(file));
 142         char buf[sizeof("18446744073709551616")];
 143
 144         if (size > sizeof(buf))
 145                 size = sizeof(buf);
 146         if (copy_from_user(buf, input, size) != 0)
 147                 return -EFAULT;
 148         buf[sizeof(buf)-1] = '\0';
 149
 150         spin_lock_bh(&e->lock);
 151         e->quota = simple_strtoull(buf, NULL, 0);
 152         spin_unlock_bh(&e->lock);
 153         return size;
 154 }
 155
 156 static const struct file_operations q2_counter_fops = {
 157         .read           = quota_proc_read,
 158         .write          = quota_proc_write,
 159         .llseek         = default_llseek,
 160 };
 161
 162 static struct xt_quota_counter *
 163 q2_new_counter(const struct xt_quota_mtinfo2 *q, bool anon)
 164 {
 165         struct xt_quota_counter *e;
 166         unsigned int size;
 167
 168         /* Do not need all the procfs things for anonymous counters. */
 169         size = anon ? offsetof(typeof(*e), list) : sizeof(*e);
 170         e = kmalloc(size, GFP_KERNEL);
 171         if (e == NULL)
 172                 return NULL;
 173
 174         e->quota = q->quota;
 175         spin_lock_init(&e->lock);
 176         if (!anon) {
 177                 INIT_LIST_HEAD(&e->list);
 178                 atomic_set(&e->ref, 1);
 179                 strlcpy(e->name, q->name, sizeof(e->name));
 180         }
 181         return e;
 182 }
 183
 184 /**
 185  * q2_get_counter - get ref to counter or create new
 186  * @name:       name of counter
 187  */
 188 static struct xt_quota_counter *
 189 q2_get_counter(const struct xt_quota_mtinfo2 *q)
 190 {
 191         struct proc_dir_entry *p;
 192         struct xt_quota_counter *e = NULL;
 193         struct xt_quota_counter *new_e;
 194
 195         if (*q->name == '\0')
 196                 return q2_new_counter(q, true);
 197
 198         /* No need to hold a lock while getting a new counter */
 199         new_e = q2_new_counter(q, false);
 200         if (new_e == NULL)
 201                 goto out;
 202
 203         spin_lock_bh(&counter_list_lock);
 204         list_for_each_entry(e, &counter_list, list)
 205                 if (strcmp(e->name, q->name) == 0) {
 206                         atomic_inc(&e->ref);
 207                         spin_unlock_bh(&counter_list_lock);
 208                         kfree(new_e);
 209                         pr_debug("xt_quota2: old counter name=%s", e->name);
 210                         return e;
 211                 }
 212         e = new_e;
 213         pr_debug("xt_quota2: new_counter name=%s", e->name);
 214         list_add_tail(&e->list, &counter_list);
 215         /* The entry having a refcount of 1 is not directly destructible.
 216          * This func has not yet returned the new entry, thus iptables
 217          * has not references for destroying this entry.
 218          * For another rule to try to destroy it, it would 1st need for this
 219          * func* to be re-invoked, acquire a new ref for the same named quota.
 220          * Nobody will access the e->procfs_entry either.
 221          * So release the lock. */
 222         spin_unlock_bh(&counter_list_lock);
 223
 224         /* create_proc_entry() is not spin_lock happy */
 225         p = e->procfs_entry = proc_create_data(e->name, quota_list_perms,
 226                               proc_xt_quota, &q2_counter_fops, e);
 227
 228         if (IS_ERR_OR_NULL(p)) {
 229                 spin_lock_bh(&counter_list_lock);
 230                 list_del(&e->list);
 231                 spin_unlock_bh(&counter_list_lock);
 232                 goto out;
 233         }
 234         proc_set_user(p, quota_list_uid, quota_list_gid);
 235         return e;
 236
 237  out:
 238         kfree(e);
 239         return NULL;
 240 }
 241
 242 static int quota_mt2_check(const struct xt_mtchk_param *par)
 243 {
 244         struct xt_quota_mtinfo2 *q = par->matchinfo;
 245
 246         pr_debug("xt_quota2: check() flags=0x%04x", q->flags);
 247
 248         if (q->flags & ~XT_QUOTA_MASK)
 249                 return -EINVAL;
 250
 251         q->name[sizeof(q->name)-1] = '\0';
 252         if (*q->name == '.' || strchr(q->name, '/') != NULL) {
 253                 printk(KERN_ERR "xt_quota.3: illegal name\n");
 254                 return -EINVAL;
 255         }
 256
 257         q->master = q2_get_counter(q);
 258         if (q->master == NULL) {
 259                 printk(KERN_ERR "xt_quota.3: memory alloc failure\n");
 260                 return -ENOMEM;
 261         }
 262
 263         return 0;
 264 }
 265
 266 static void quota_mt2_destroy(const struct xt_mtdtor_param *par)
 267 {
 268         struct xt_quota_mtinfo2 *q = par->matchinfo;
 269         struct xt_quota_counter *e = q->master;
 270
 271         if (*q->name == '\0') {
 272                 kfree(e);
 273                 return;
 274         }
 275
 276         spin_lock_bh(&counter_list_lock);
 277         if (!atomic_dec_and_test(&e->ref)) {
 278                 spin_unlock_bh(&counter_list_lock);
 279                 return;
 280         }
 281
 282         list_del(&e->list);
 283         remove_proc_entry(e->name, proc_xt_quota);
 284         spin_unlock_bh(&counter_list_lock);
 285         kfree(e);
 286 }
 287
 288 static bool
 289 quota_mt2(const struct sk_buff *skb, struct xt_action_param *par)
 290 {
 291         struct xt_quota_mtinfo2 *q = (void *)par->matchinfo;
 292         struct xt_quota_counter *e = q->master;
 293         bool ret = q->flags & XT_QUOTA_INVERT;
 294
 295         spin_lock_bh(&e->lock);
 296         if (q->flags & XT_QUOTA_GROW) {
 297                 /*
 298                  * While no_change is pointless in "grow" mode, we will
 299                  * implement it here simply to have a consistent behavior.
 300                  */
 301                 if (!(q->flags & XT_QUOTA_NO_CHANGE)) {
 302                         e->quota += (q->flags & XT_QUOTA_PACKET) ? 1 : skb->len;
 303                 }
 304                 ret = true;
 305         } else {
 306                 if (e->quota >= skb->len) {
 307                         if (!(q->flags & XT_QUOTA_NO_CHANGE))
 308                                 e->quota -= (q->flags & XT_QUOTA_PACKET) ? 1 : skb->len;
 309                         ret = !ret;
 310                 } else {
 311                         /* We are transitioning, log that fact. */
 312                         if (e->quota) {
 313                                 quota2_log(par->hooknum,
 314                                            skb,
 315                                            par->in,
 316                                            par->out,
 317                                            q->name);
 318                         }
 319                         /* we do not allow even small packets from now on */
 320                         e->quota = 0;
 321                 }
 322         }
 323         spin_unlock_bh(&e->lock);
 324         return ret;
 325 }
 326
 327 static struct xt_match quota_mt2_reg[] __read_mostly = {
 328         {
 329                 .name       = "quota2",
 330                 .revision   = 3,
 331                 .family     = NFPROTO_IPV4,
 332                 .checkentry = quota_mt2_check,
 333                 .match      = quota_mt2,
 334                 .destroy    = quota_mt2_destroy,
 335                 .matchsize  = sizeof(struct xt_quota_mtinfo2),
 336                 .me         = THIS_MODULE,
 337         },
 338         {
 339                 .name       = "quota2",
 340                 .revision   = 3,
 341                 .family     = NFPROTO_IPV6,
 342                 .checkentry = quota_mt2_check,
 343                 .match      = quota_mt2,
 344                 .destroy    = quota_mt2_destroy,
 345                 .matchsize  = sizeof(struct xt_quota_mtinfo2),
 346                 .me         = THIS_MODULE,
 347         },
 348 };
 349
 350 static int __init quota_mt2_init(void)
 351 {
 352         int ret;
 353         pr_debug("xt_quota2: init()");
 354
 355 #ifdef CONFIG_NETFILTER_XT_MATCH_QUOTA2_LOG
 356         nflognl = netlink_kernel_create(&init_net, NETLINK_NFLOG, NULL);
 357         if (!nflognl)
 358                 return -ENOMEM;
 359 #endif
 360
 361         proc_xt_quota = proc_mkdir("xt_quota", init_net.proc_net);
 362         if (proc_xt_quota == NULL)
 363                 return -EACCES;
 364
 365         ret = xt_register_matches(quota_mt2_reg, ARRAY_SIZE(quota_mt2_reg));
 366         if (ret < 0)
 367                 remove_proc_entry("xt_quota", init_net.proc_net);
 368         pr_debug("xt_quota2: init() %d", ret);
 369         return ret;
 370 }
 371
 372 static void __exit quota_mt2_exit(void)
 373 {
 374         xt_unregister_matches(quota_mt2_reg, ARRAY_SIZE(quota_mt2_reg));
 375         remove_proc_entry("xt_quota", init_net.proc_net);
 376 }
 377
 378 module_init(quota_mt2_init);
 379 module_exit(quota_mt2_exit);
 380 MODULE_DESCRIPTION("Xtables: countdown quota match; up counter");
 381 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
 382 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 383 MODULE_LICENSE("GPL");
 384 MODULE_ALIAS("ipt_quota2");
 385 MODULE_ALIAS("ip6t_quota2");