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