net/ipv4/netfilter/ipt_ULOG.c

   1 /*
   2  * netfilter module for userspace packet logging daemons
   3  *
   4  * (C) 2000-2004 by Harald Welte <laforge@netfilter.org>
   5  * (C) 1999-2001 Paul `Rusty' Russell
   6  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   7  * (C) 2005-2007 Patrick McHardy <kaber@trash.net>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  * This module accepts two parameters:
  14  *
  15  * nlbufsiz:
  16  *   The parameter specifies how big the buffer for each netlink multicast
  17  * group is. e.g. If you say nlbufsiz=8192, up to eight kb of packets will
  18  * get accumulated in the kernel until they are sent to userspace. It is
  19  * NOT possible to allocate more than 128kB, and it is strongly discouraged,
  20  * because atomically allocating 128kB inside the network rx softirq is not
  21  * reliable. Please also keep in mind that this buffer size is allocated for
  22  * each nlgroup you are using, so the total kernel memory usage increases
  23  * by that factor.
  24  *
  25  * Actually you should use nlbufsiz a bit smaller than PAGE_SIZE, since
  26  * nlbufsiz is used with alloc_skb, which adds another
  27  * sizeof(struct skb_shared_info).  Use NLMSG_GOODSIZE instead.
  28  *
  29  * flushtimeout:
  30  *   Specify, after how many hundredths of a second the queue should be
  31  *   flushed even if it is not full yet.
  32  */
  33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  34 #include <linux/module.h>
  35 #include <linux/spinlock.h>
  36 #include <linux/socket.h>
  37 #include <linux/slab.h>
  38 #include <linux/skbuff.h>
  39 #include <linux/kernel.h>
  40 #include <linux/timer.h>
  41 #include <net/netlink.h>
  42 #include <linux/netdevice.h>
  43 #include <linux/mm.h>
  44 #include <linux/moduleparam.h>
  45 #include <linux/netfilter.h>
  46 #include <linux/netfilter/x_tables.h>
  47 #include <linux/netfilter_ipv4/ipt_ULOG.h>
  48 #include <net/netfilter/nf_log.h>
  49 #include <net/netns/generic.h>
  50 #include <net/sock.h>
  51 #include <linux/bitops.h>
  52 #include <asm/unaligned.h>
  53
  54 MODULE_LICENSE("GPL");
  55 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  56 MODULE_DESCRIPTION("Xtables: packet logging to netlink using ULOG");
  57 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NFLOG);
  58
  59 #define ULOG_NL_EVENT           111             /* Harald's favorite number */
  60 #define ULOG_MAXNLGROUPS        32              /* numer of nlgroups */
  61
  62 static unsigned int nlbufsiz = NLMSG_GOODSIZE;
  63 module_param(nlbufsiz, uint, 0400);
  64 MODULE_PARM_DESC(nlbufsiz, "netlink buffer size");
  65
  66 static unsigned int flushtimeout = 10;
  67 module_param(flushtimeout, uint, 0600);
  68 MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths of a second)");
  69
  70 static bool nflog = true;
  71 module_param(nflog, bool, 0400);
  72 MODULE_PARM_DESC(nflog, "register as internal netfilter logging module");
  73
  74 /* global data structures */
  75
  76 typedef struct {
  77         unsigned int qlen;              /* number of nlmsgs' in the skb */
  78         struct nlmsghdr *lastnlh;       /* netlink header of last msg in skb */
  79         struct sk_buff *skb;            /* the pre-allocated skb */
  80         struct timer_list timer;        /* the timer function */
  81 } ulog_buff_t;
  82
  83 static int ulog_net_id __read_mostly;
  84 struct ulog_net {
  85         unsigned int nlgroup[ULOG_MAXNLGROUPS];
  86         ulog_buff_t ulog_buffers[ULOG_MAXNLGROUPS];
  87         struct sock *nflognl;
  88         spinlock_t lock;
  89 };
  90
  91 static struct ulog_net *ulog_pernet(struct net *net)
  92 {
  93         return net_generic(net, ulog_net_id);
  94 }
  95
  96 /* send one ulog_buff_t to userspace */
  97 static void ulog_send(struct ulog_net *ulog, unsigned int nlgroupnum)
  98 {
  99         ulog_buff_t *ub = &ulog->ulog_buffers[nlgroupnum];
 100
 101         pr_debug("ulog_send: timer is deleting\n");
 102         del_timer(&ub->timer);
 103
 104         if (!ub->skb) {
 105                 pr_debug("ulog_send: nothing to send\n");
 106                 return;
 107         }
 108
 109         /* last nlmsg needs NLMSG_DONE */
 110         if (ub->qlen > 1)
 111                 ub->lastnlh->nlmsg_type = NLMSG_DONE;
 112
 113         NETLINK_CB(ub->skb).dst_group = nlgroupnum + 1;
 114         pr_debug("throwing %d packets to netlink group %u\n",
 115                  ub->qlen, nlgroupnum + 1);
 116         netlink_broadcast(ulog->nflognl, ub->skb, 0, nlgroupnum + 1,
 117                           GFP_ATOMIC);
 118
 119         ub->qlen = 0;
 120         ub->skb = NULL;
 121         ub->lastnlh = NULL;
 122 }
 123
 124
 125 /* timer function to flush queue in flushtimeout time */
 126 static void ulog_timer(unsigned long data)
 127 {
 128         unsigned int groupnum = *((unsigned int *)data);
 129         struct ulog_net *ulog = container_of((void *)data,
 130                                              struct ulog_net,
 131                                              nlgroup[groupnum]);
 132         pr_debug("timer function called, calling ulog_send\n");
 133
 134         /* lock to protect against somebody modifying our structure
 135          * from ipt_ulog_target at the same time */
 136         spin_lock_bh(&ulog->lock);
 137         ulog_send(ulog, groupnum);
 138         spin_unlock_bh(&ulog->lock);
 139 }
 140
 141 static struct sk_buff *ulog_alloc_skb(unsigned int size)
 142 {
 143         struct sk_buff *skb;
 144         unsigned int n;
 145
 146         /* alloc skb which should be big enough for a whole
 147          * multipart message. WARNING: has to be <= 131000
 148          * due to slab allocator restrictions */
 149
 150         n = max(size, nlbufsiz);
 151         skb = alloc_skb(n, GFP_ATOMIC | __GFP_NOWARN);
 152         if (!skb) {
 153                 if (n > size) {
 154                         /* try to allocate only as much as we need for
 155                          * current packet */
 156
 157                         skb = alloc_skb(size, GFP_ATOMIC);
 158                         if (!skb)
 159                                 pr_debug("cannot even allocate %ub\n", size);
 160                 }
 161         }
 162
 163         return skb;
 164 }
 165
 166 static void ipt_ulog_packet(struct net *net,
 167                             unsigned int hooknum,
 168                             const struct sk_buff *skb,
 169                             const struct net_device *in,
 170                             const struct net_device *out,
 171                             const struct ipt_ulog_info *loginfo,
 172                             const char *prefix)
 173 {
 174         ulog_buff_t *ub;
 175         ulog_packet_msg_t *pm;
 176         size_t size, copy_len;
 177         struct nlmsghdr *nlh;
 178         struct timeval tv;
 179         struct ulog_net *ulog = ulog_pernet(net);
 180
 181         /* ffs == find first bit set, necessary because userspace
 182          * is already shifting groupnumber, but we need unshifted.
 183          * ffs() returns [1..32], we need [0..31] */
 184         unsigned int groupnum = ffs(loginfo->nl_group) - 1;
 185
 186         /* calculate the size of the skb needed */
 187         if (loginfo->copy_range == 0 || loginfo->copy_range > skb->len)
 188                 copy_len = skb->len;
 189         else
 190                 copy_len = loginfo->copy_range;
 191
 192         size = nlmsg_total_size(sizeof(*pm) + copy_len);
 193
 194         ub = &ulog->ulog_buffers[groupnum];
 195
 196         spin_lock_bh(&ulog->lock);
 197
 198         if (!ub->skb) {
 199                 if (!(ub->skb = ulog_alloc_skb(size)))
 200                         goto alloc_failure;
 201         } else if (ub->qlen >= loginfo->qthreshold ||
 202                    size > skb_tailroom(ub->skb)) {
 203                 /* either the queue len is too high or we don't have
 204                  * enough room in nlskb left. send it to userspace. */
 205
 206                 ulog_send(ulog, groupnum);
 207
 208                 if (!(ub->skb = ulog_alloc_skb(size)))
 209                         goto alloc_failure;
 210         }
 211
 212         pr_debug("qlen %d, qthreshold %Zu\n", ub->qlen, loginfo->qthreshold);
 213
 214         nlh = nlmsg_put(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
 215                         sizeof(*pm)+copy_len, 0);
 216         if (!nlh) {
 217                 pr_debug("error during nlmsg_put\n");
 218                 goto out_unlock;
 219         }
 220         ub->qlen++;
 221
 222         pm = nlmsg_data(nlh);
 223         memset(pm, 0, sizeof(*pm));
 224
 225         /* We might not have a timestamp, get one */
 226         if (skb->tstamp.tv64 == 0)
 227                 __net_timestamp((struct sk_buff *)skb);
 228
 229         /* copy hook, prefix, timestamp, payload, etc. */
 230         pm->data_len = copy_len;
 231         tv = ktime_to_timeval(skb->tstamp);
 232         put_unaligned(tv.tv_sec, &pm->timestamp_sec);
 233         put_unaligned(tv.tv_usec, &pm->timestamp_usec);
 234         put_unaligned(skb->mark, &pm->mark);
 235         pm->hook = hooknum;
 236         if (prefix != NULL) {
 237                 strncpy(pm->prefix, prefix, sizeof(pm->prefix) - 1);
 238                 pm->prefix[sizeof(pm->prefix) - 1] = '\0';
 239         }
 240         else if (loginfo->prefix[0] != '\0')
 241                 strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
 242
 243         if (in && in->hard_header_len > 0 &&
 244             skb->mac_header != skb->network_header &&
 245             in->hard_header_len <= ULOG_MAC_LEN) {
 246                 memcpy(pm->mac, skb_mac_header(skb), in->hard_header_len);
 247                 pm->mac_len = in->hard_header_len;
 248         } else
 249                 pm->mac_len = 0;
 250
 251         if (in)
 252                 strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
 253
 254         if (out)
 255                 strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
 256
 257         /* copy_len <= skb->len, so can't fail. */
 258         if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
 259                 BUG();
 260
 261         /* check if we are building multi-part messages */
 262         if (ub->qlen > 1)
 263                 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
 264
 265         ub->lastnlh = nlh;
 266
 267         /* if timer isn't already running, start it */
 268         if (!timer_pending(&ub->timer)) {
 269                 ub->timer.expires = jiffies + flushtimeout * HZ / 100;
 270                 add_timer(&ub->timer);
 271         }
 272
 273         /* if threshold is reached, send message to userspace */
 274         if (ub->qlen >= loginfo->qthreshold) {
 275                 if (loginfo->qthreshold > 1)
 276                         nlh->nlmsg_type = NLMSG_DONE;
 277                 ulog_send(ulog, groupnum);
 278         }
 279 out_unlock:
 280         spin_unlock_bh(&ulog->lock);
 281
 282         return;
 283
 284 alloc_failure:
 285         pr_debug("Error building netlink message\n");
 286         spin_unlock_bh(&ulog->lock);
 287 }
 288
 289 static unsigned int
 290 ulog_tg(struct sk_buff *skb, const struct xt_action_param *par)
 291 {
 292         struct net *net = dev_net(par->in ? par->in : par->out);
 293
 294         ipt_ulog_packet(net, par->hooknum, skb, par->in, par->out,
 295                         par->targinfo, NULL);
 296         return XT_CONTINUE;
 297 }
 298
 299 static void ipt_logfn(struct net *net,
 300                       u_int8_t pf,
 301                       unsigned int hooknum,
 302                       const struct sk_buff *skb,
 303                       const struct net_device *in,
 304                       const struct net_device *out,
 305                       const struct nf_loginfo *li,
 306                       const char *prefix)
 307 {
 308         struct ipt_ulog_info loginfo;
 309
 310         if (!li || li->type != NF_LOG_TYPE_ULOG) {
 311                 loginfo.nl_group = ULOG_DEFAULT_NLGROUP;
 312                 loginfo.copy_range = 0;
 313                 loginfo.qthreshold = ULOG_DEFAULT_QTHRESHOLD;
 314                 loginfo.prefix[0] = '\0';
 315         } else {
 316                 loginfo.nl_group = li->u.ulog.group;
 317                 loginfo.copy_range = li->u.ulog.copy_len;
 318                 loginfo.qthreshold = li->u.ulog.qthreshold;
 319                 strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
 320         }
 321
 322         ipt_ulog_packet(net, hooknum, skb, in, out, &loginfo, prefix);
 323 }
 324
 325 static int ulog_tg_check(const struct xt_tgchk_param *par)
 326 {
 327         const struct ipt_ulog_info *loginfo = par->targinfo;
 328
 329         if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
 330                 pr_debug("prefix not null-terminated\n");
 331                 return -EINVAL;
 332         }
 333         if (loginfo->qthreshold > ULOG_MAX_QLEN) {
 334                 pr_debug("queue threshold %Zu > MAX_QLEN\n",
 335                          loginfo->qthreshold);
 336                 return -EINVAL;
 337         }
 338         return 0;
 339 }
 340
 341 #ifdef CONFIG_COMPAT
 342 struct compat_ipt_ulog_info {
 343         compat_uint_t   nl_group;
 344         compat_size_t   copy_range;
 345         compat_size_t   qthreshold;
 346         char            prefix[ULOG_PREFIX_LEN];
 347 };
 348
 349 static void ulog_tg_compat_from_user(void *dst, const void *src)
 350 {
 351         const struct compat_ipt_ulog_info *cl = src;
 352         struct ipt_ulog_info l = {
 353                 .nl_group       = cl->nl_group,
 354                 .copy_range     = cl->copy_range,
 355                 .qthreshold     = cl->qthreshold,
 356         };
 357
 358         memcpy(l.prefix, cl->prefix, sizeof(l.prefix));
 359         memcpy(dst, &l, sizeof(l));
 360 }
 361
 362 static int ulog_tg_compat_to_user(void __user *dst, const void *src)
 363 {
 364         const struct ipt_ulog_info *l = src;
 365         struct compat_ipt_ulog_info cl = {
 366                 .nl_group       = l->nl_group,
 367                 .copy_range     = l->copy_range,
 368                 .qthreshold     = l->qthreshold,
 369         };
 370
 371         memcpy(cl.prefix, l->prefix, sizeof(cl.prefix));
 372         return copy_to_user(dst, &cl, sizeof(cl)) ? -EFAULT : 0;
 373 }
 374 #endif /* CONFIG_COMPAT */
 375
 376 static struct xt_target ulog_tg_reg __read_mostly = {
 377         .name           = "ULOG",
 378         .family         = NFPROTO_IPV4,
 379         .target         = ulog_tg,
 380         .targetsize     = sizeof(struct ipt_ulog_info),
 381         .checkentry     = ulog_tg_check,
 382 #ifdef CONFIG_COMPAT
 383         .compatsize     = sizeof(struct compat_ipt_ulog_info),
 384         .compat_from_user = ulog_tg_compat_from_user,
 385         .compat_to_user = ulog_tg_compat_to_user,
 386 #endif
 387         .me             = THIS_MODULE,
 388 };
 389
 390 static struct nf_logger ipt_ulog_logger __read_mostly = {
 391         .name           = "ipt_ULOG",
 392         .logfn          = ipt_logfn,
 393         .me             = THIS_MODULE,
 394 };
 395
 396 static int __net_init ulog_tg_net_init(struct net *net)
 397 {
 398         int i;
 399         struct ulog_net *ulog = ulog_pernet(net);
 400         struct netlink_kernel_cfg cfg = {
 401                 .groups = ULOG_MAXNLGROUPS,
 402         };
 403
 404         spin_lock_init(&ulog->lock);
 405         /* initialize ulog_buffers */
 406         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 407                 ulog->nlgroup[i] = i;
 408                 setup_timer(&ulog->ulog_buffers[i].timer, ulog_timer,
 409                             (unsigned long)&ulog->nlgroup[i]);
 410         }
 411
 412         ulog->nflognl = netlink_kernel_create(net, NETLINK_NFLOG, &cfg);
 413         if (!ulog->nflognl)
 414                 return -ENOMEM;
 415
 416         if (nflog)
 417                 nf_log_set(net, NFPROTO_IPV4, &ipt_ulog_logger);
 418
 419         return 0;
 420 }
 421
 422 static void __net_exit ulog_tg_net_exit(struct net *net)
 423 {
 424         ulog_buff_t *ub;
 425         int i;
 426         struct ulog_net *ulog = ulog_pernet(net);
 427
 428         if (nflog)
 429                 nf_log_unset(net, &ipt_ulog_logger);
 430
 431         netlink_kernel_release(ulog->nflognl);
 432
 433         /* remove pending timers and free allocated skb's */
 434         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 435                 ub = &ulog->ulog_buffers[i];
 436                 pr_debug("timer is deleting\n");
 437                 del_timer(&ub->timer);
 438
 439                 if (ub->skb) {
 440                         kfree_skb(ub->skb);
 441                         ub->skb = NULL;
 442                 }
 443         }
 444 }
 445
 446 static struct pernet_operations ulog_tg_net_ops = {
 447         .init = ulog_tg_net_init,
 448         .exit = ulog_tg_net_exit,
 449         .id   = &ulog_net_id,
 450         .size = sizeof(struct ulog_net),
 451 };
 452
 453 static int __init ulog_tg_init(void)
 454 {
 455         int ret;
 456         pr_debug("init module\n");
 457
 458         if (nlbufsiz > 128*1024) {
 459                 pr_warn("Netlink buffer has to be <= 128kB\n");
 460                 return -EINVAL;
 461         }
 462
 463         ret = register_pernet_subsys(&ulog_tg_net_ops);
 464         if (ret)
 465                 goto out_pernet;
 466
 467         ret = xt_register_target(&ulog_tg_reg);
 468         if (ret < 0)
 469                 goto out_target;
 470
 471         if (nflog)
 472                 nf_log_register(NFPROTO_IPV4, &ipt_ulog_logger);
 473
 474         return 0;
 475
 476 out_target:
 477         unregister_pernet_subsys(&ulog_tg_net_ops);
 478 out_pernet:
 479         return ret;
 480 }
 481
 482 static void __exit ulog_tg_exit(void)
 483 {
 484         pr_debug("cleanup_module\n");
 485         if (nflog)
 486                 nf_log_unregister(&ipt_ulog_logger);
 487         xt_unregister_target(&ulog_tg_reg);
 488         unregister_pernet_subsys(&ulog_tg_net_ops);
 489 }
 490
 491 module_init(ulog_tg_init);
 492 module_exit(ulog_tg_exit);