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