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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  33 #include <linux/module.h>
  34 #include <linux/spinlock.h>
  35 #include <linux/socket.h>
  36 #include <linux/slab.h>
  37 #include <linux/skbuff.h>
  38 #include <linux/kernel.h>
  39 #include <linux/timer.h>
  40 #include <linux/netlink.h>
  41 #include <linux/netdevice.h>
  42 #include <linux/mm.h>
  43 #include <linux/moduleparam.h>
  44 #include <linux/netfilter.h>
  45 #include <linux/netfilter/x_tables.h>
  46 #include <linux/netfilter_ipv4/ipt_ULOG.h>
  47 #include <net/netfilter/nf_log.h>
  48 #include <net/sock.h>
  49 #include <linux/bitops.h>
  50 #include <asm/unaligned.h>
  51
  52 MODULE_LICENSE("GPL");
  53 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  54 MODULE_DESCRIPTION("Xtables: packet logging to netlink using ULOG");
  55 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NFLOG);
  56
  57 #define ULOG_NL_EVENT           111             /* Harald's favorite number */
  58 #define ULOG_MAXNLGROUPS        32              /* numer of nlgroups */
  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 bool nflog = true;
  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("ulog_send: timer was pending, deleting\n");
  93                 del_timer(&ub->timer);
  94         }
  95
  96         if (!ub->skb) {
  97                 pr_debug("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("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("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 | __GFP_NOWARN);
 139         if (!skb) {
 140                 if (n > size) {
 141                         /* try to allocate only as much as we need for
 142                          * current packet */
 143
 144                         skb = alloc_skb(size, GFP_ATOMIC);
 145                         if (!skb)
 146                                 pr_debug("cannot even allocate %ub\n", size);
 147                 }
 148         }
 149
 150         return skb;
 151 }
 152
 153 static void ipt_ulog_packet(unsigned int hooknum,
 154                             const struct sk_buff *skb,
 155                             const struct net_device *in,
 156                             const struct net_device *out,
 157                             const struct ipt_ulog_info *loginfo,
 158                             const char *prefix)
 159 {
 160         ulog_buff_t *ub;
 161         ulog_packet_msg_t *pm;
 162         size_t size, copy_len;
 163         struct nlmsghdr *nlh;
 164         struct timeval tv;
 165
 166         /* ffs == find first bit set, necessary because userspace
 167          * is already shifting groupnumber, but we need unshifted.
 168          * ffs() returns [1..32], we need [0..31] */
 169         unsigned int groupnum = ffs(loginfo->nl_group) - 1;
 170
 171         /* calculate the size of the skb needed */
 172         if (loginfo->copy_range == 0 || loginfo->copy_range > skb->len)
 173                 copy_len = skb->len;
 174         else
 175                 copy_len = loginfo->copy_range;
 176
 177         size = NLMSG_SPACE(sizeof(*pm) + copy_len);
 178
 179         ub = &ulog_buffers[groupnum];
 180
 181         spin_lock_bh(&ulog_lock);
 182
 183         if (!ub->skb) {
 184                 if (!(ub->skb = ulog_alloc_skb(size)))
 185                         goto alloc_failure;
 186         } else if (ub->qlen >= loginfo->qthreshold ||
 187                    size > skb_tailroom(ub->skb)) {
 188                 /* either the queue len is too high or we don't have
 189                  * enough room in nlskb left. send it to userspace. */
 190
 191                 ulog_send(groupnum);
 192
 193                 if (!(ub->skb = ulog_alloc_skb(size)))
 194                         goto alloc_failure;
 195         }
 196
 197         pr_debug("qlen %d, qthreshold %Zu\n", ub->qlen, loginfo->qthreshold);
 198
 199         /* NLMSG_PUT contains a hidden goto nlmsg_failure !!! */
 200         nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
 201                         sizeof(*pm)+copy_len);
 202         ub->qlen++;
 203
 204         pm = NLMSG_DATA(nlh);
 205
 206         /* We might not have a timestamp, get one */
 207         if (skb->tstamp.tv64 == 0)
 208                 __net_timestamp((struct sk_buff *)skb);
 209
 210         /* copy hook, prefix, timestamp, payload, etc. */
 211         pm->data_len = copy_len;
 212         tv = ktime_to_timeval(skb->tstamp);
 213         put_unaligned(tv.tv_sec, &pm->timestamp_sec);
 214         put_unaligned(tv.tv_usec, &pm->timestamp_usec);
 215         put_unaligned(skb->mark, &pm->mark);
 216         pm->hook = hooknum;
 217         if (prefix != NULL)
 218                 strncpy(pm->prefix, prefix, sizeof(pm->prefix));
 219         else if (loginfo->prefix[0] != '\0')
 220                 strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
 221         else
 222                 *(pm->prefix) = '\0';
 223
 224         if (in && in->hard_header_len > 0 &&
 225             skb->mac_header != skb->network_header &&
 226             in->hard_header_len <= ULOG_MAC_LEN) {
 227                 memcpy(pm->mac, skb_mac_header(skb), in->hard_header_len);
 228                 pm->mac_len = in->hard_header_len;
 229         } else
 230                 pm->mac_len = 0;
 231
 232         if (in)
 233                 strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
 234         else
 235                 pm->indev_name[0] = '\0';
 236
 237         if (out)
 238                 strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
 239         else
 240                 pm->outdev_name[0] = '\0';
 241
 242         /* copy_len <= skb->len, so can't fail. */
 243         if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
 244                 BUG();
 245
 246         /* check if we are building multi-part messages */
 247         if (ub->qlen > 1)
 248                 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
 249
 250         ub->lastnlh = nlh;
 251
 252         /* if timer isn't already running, start it */
 253         if (!timer_pending(&ub->timer)) {
 254                 ub->timer.expires = jiffies + flushtimeout * HZ / 100;
 255                 add_timer(&ub->timer);
 256         }
 257
 258         /* if threshold is reached, send message to userspace */
 259         if (ub->qlen >= loginfo->qthreshold) {
 260                 if (loginfo->qthreshold > 1)
 261                         nlh->nlmsg_type = NLMSG_DONE;
 262                 ulog_send(groupnum);
 263         }
 264
 265         spin_unlock_bh(&ulog_lock);
 266
 267         return;
 268
 269 nlmsg_failure:
 270         pr_debug("error during NLMSG_PUT\n");
 271 alloc_failure:
 272         pr_debug("Error building netlink message\n");
 273         spin_unlock_bh(&ulog_lock);
 274 }
 275
 276 static unsigned int
 277 ulog_tg(struct sk_buff *skb, const struct xt_action_param *par)
 278 {
 279         ipt_ulog_packet(par->hooknum, skb, par->in, par->out,
 280                         par->targinfo, NULL);
 281         return XT_CONTINUE;
 282 }
 283
 284 static void ipt_logfn(u_int8_t pf,
 285                       unsigned int hooknum,
 286                       const struct sk_buff *skb,
 287                       const struct net_device *in,
 288                       const struct net_device *out,
 289                       const struct nf_loginfo *li,
 290                       const char *prefix)
 291 {
 292         struct ipt_ulog_info loginfo;
 293
 294         if (!li || li->type != NF_LOG_TYPE_ULOG) {
 295                 loginfo.nl_group = ULOG_DEFAULT_NLGROUP;
 296                 loginfo.copy_range = 0;
 297                 loginfo.qthreshold = ULOG_DEFAULT_QTHRESHOLD;
 298                 loginfo.prefix[0] = '\0';
 299         } else {
 300                 loginfo.nl_group = li->u.ulog.group;
 301                 loginfo.copy_range = li->u.ulog.copy_len;
 302                 loginfo.qthreshold = li->u.ulog.qthreshold;
 303                 strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
 304         }
 305
 306         ipt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
 307 }
 308
 309 static int ulog_tg_check(const struct xt_tgchk_param *par)
 310 {
 311         const struct ipt_ulog_info *loginfo = par->targinfo;
 312
 313         if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
 314                 pr_debug("prefix not null-terminated\n");
 315                 return -EINVAL;
 316         }
 317         if (loginfo->qthreshold > ULOG_MAX_QLEN) {
 318                 pr_debug("queue threshold %Zu > MAX_QLEN\n",
 319                          loginfo->qthreshold);
 320                 return -EINVAL;
 321         }
 322         return 0;
 323 }
 324
 325 #ifdef CONFIG_COMPAT
 326 struct compat_ipt_ulog_info {
 327         compat_uint_t   nl_group;
 328         compat_size_t   copy_range;
 329         compat_size_t   qthreshold;
 330         char            prefix[ULOG_PREFIX_LEN];
 331 };
 332
 333 static void ulog_tg_compat_from_user(void *dst, const void *src)
 334 {
 335         const struct compat_ipt_ulog_info *cl = src;
 336         struct ipt_ulog_info l = {
 337                 .nl_group       = cl->nl_group,
 338                 .copy_range     = cl->copy_range,
 339                 .qthreshold     = cl->qthreshold,
 340         };
 341
 342         memcpy(l.prefix, cl->prefix, sizeof(l.prefix));
 343         memcpy(dst, &l, sizeof(l));
 344 }
 345
 346 static int ulog_tg_compat_to_user(void __user *dst, const void *src)
 347 {
 348         const struct ipt_ulog_info *l = src;
 349         struct compat_ipt_ulog_info cl = {
 350                 .nl_group       = l->nl_group,
 351                 .copy_range     = l->copy_range,
 352                 .qthreshold     = l->qthreshold,
 353         };
 354
 355         memcpy(cl.prefix, l->prefix, sizeof(cl.prefix));
 356         return copy_to_user(dst, &cl, sizeof(cl)) ? -EFAULT : 0;
 357 }
 358 #endif /* CONFIG_COMPAT */
 359
 360 static struct xt_target ulog_tg_reg __read_mostly = {
 361         .name           = "ULOG",
 362         .family         = NFPROTO_IPV4,
 363         .target         = ulog_tg,
 364         .targetsize     = sizeof(struct ipt_ulog_info),
 365         .checkentry     = ulog_tg_check,
 366 #ifdef CONFIG_COMPAT
 367         .compatsize     = sizeof(struct compat_ipt_ulog_info),
 368         .compat_from_user = ulog_tg_compat_from_user,
 369         .compat_to_user = ulog_tg_compat_to_user,
 370 #endif
 371         .me             = THIS_MODULE,
 372 };
 373
 374 static struct nf_logger ipt_ulog_logger __read_mostly = {
 375         .name           = "ipt_ULOG",
 376         .logfn          = ipt_logfn,
 377         .me             = THIS_MODULE,
 378 };
 379
 380 static int __init ulog_tg_init(void)
 381 {
 382         int ret, i;
 383
 384         pr_debug("init module\n");
 385
 386         if (nlbufsiz > 128*1024) {
 387                 pr_warning("Netlink buffer has to be <= 128kB\n");
 388                 return -EINVAL;
 389         }
 390
 391         /* initialize ulog_buffers */
 392         for (i = 0; i < ULOG_MAXNLGROUPS; i++)
 393                 setup_timer(&ulog_buffers[i].timer, ulog_timer, i);
 394
 395         nflognl = netlink_kernel_create(&init_net,
 396                                         NETLINK_NFLOG, ULOG_MAXNLGROUPS, NULL,
 397                                         NULL, THIS_MODULE);
 398         if (!nflognl)
 399                 return -ENOMEM;
 400
 401         ret = xt_register_target(&ulog_tg_reg);
 402         if (ret < 0) {
 403                 netlink_kernel_release(nflognl);
 404                 return ret;
 405         }
 406         if (nflog)
 407                 nf_log_register(NFPROTO_IPV4, &ipt_ulog_logger);
 408
 409         return 0;
 410 }
 411
 412 static void __exit ulog_tg_exit(void)
 413 {
 414         ulog_buff_t *ub;
 415         int i;
 416
 417         pr_debug("cleanup_module\n");
 418
 419         if (nflog)
 420                 nf_log_unregister(&ipt_ulog_logger);
 421         xt_unregister_target(&ulog_tg_reg);
 422         netlink_kernel_release(nflognl);
 423
 424         /* remove pending timers and free allocated skb's */
 425         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 426                 ub = &ulog_buffers[i];
 427                 if (timer_pending(&ub->timer)) {
 428                         pr_debug("timer was pending, deleting\n");
 429                         del_timer(&ub->timer);
 430                 }
 431
 432                 if (ub->skb) {
 433                         kfree_skb(ub->skb);
 434                         ub->skb = NULL;
 435                 }
 436         }
 437 }
 438
 439 module_init(ulog_tg_init);
 440 module_exit(ulog_tg_exit);