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  *
   6  * 2000/09/22 ulog-cprange feature added
   7  * 2001/01/04 in-kernel queue as proposed by Sebastian Zander
   8  *                                              <zander@fokus.gmd.de>
   9  * 2001/01/30 per-rule nlgroup conflicts with global queue.
  10  *            nlgroup now global (sysctl)
  11  * 2001/04/19 ulog-queue reworked, now fixed buffer size specified at
  12  *            module loadtime -HW
  13  * 2002/07/07 remove broken nflog_rcv() function -HW
  14  * 2002/08/29 fix shifted/unshifted nlgroup bug -HW
  15  * 2002/10/30 fix uninitialized mac_len field - <Anders K. Pedersen>
  16  * 2004/10/25 fix erroneous calculation of 'len' parameter to NLMSG_PUT
  17  *            resulting in bogus 'error during NLMSG_PUT' messages.
  18  *
  19  * (C) 1999-2001 Paul `Rusty' Russell
  20  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
  21  *
  22  * This program is free software; you can redistribute it and/or modify
  23  * it under the terms of the GNU General Public License version 2 as
  24  * published by the Free Software Foundation.
  25  *
  26  * This module accepts two parameters:
  27  *
  28  * nlbufsiz:
  29  *   The parameter specifies how big the buffer for each netlink multicast
  30  * group is. e.g. If you say nlbufsiz=8192, up to eight kb of packets will
  31  * get accumulated in the kernel until they are sent to userspace. It is
  32  * NOT possible to allocate more than 128kB, and it is strongly discouraged,
  33  * because atomically allocating 128kB inside the network rx softirq is not
  34  * reliable. Please also keep in mind that this buffer size is allocated for
  35  * each nlgroup you are using, so the total kernel memory usage increases
  36  * by that factor.
  37  *
  38  * Actually you should use nlbufsiz a bit smaller than PAGE_SIZE, since
  39  * nlbufsiz is used with alloc_skb, which adds another
  40  * sizeof(struct skb_shared_info).  Use NLMSG_GOODSIZE instead.
  41  *
  42  * flushtimeout:
  43  *   Specify, after how many hundredths of a second the queue should be
  44  *   flushed even if it is not full yet.
  45  *
  46  * ipt_ULOG.c,v 1.22 2002/10/30 09:07:31 laforge Exp
  47  */
  48
  49 #include <linux/module.h>
  50 #include <linux/spinlock.h>
  51 #include <linux/socket.h>
  52 #include <linux/skbuff.h>
  53 #include <linux/kernel.h>
  54 #include <linux/timer.h>
  55 #include <linux/netlink.h>
  56 #include <linux/netdevice.h>
  57 #include <linux/mm.h>
  58 #include <linux/moduleparam.h>
  59 #include <linux/netfilter.h>
  60 #include <linux/netfilter/x_tables.h>
  61 #include <linux/netfilter_ipv4/ipt_ULOG.h>
  62 #include <net/sock.h>
  63 #include <linux/bitops.h>
  64 #include <asm/unaligned.h>
  65
  66 MODULE_LICENSE("GPL");
  67 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  68 MODULE_DESCRIPTION("iptables userspace logging module");
  69 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NFLOG);
  70
  71 #define ULOG_NL_EVENT           111             /* Harald's favorite number */
  72 #define ULOG_MAXNLGROUPS        32              /* numer of nlgroups */
  73
  74 #if 0
  75 #define DEBUGP(format, args...) printk("%s:%s:" format, \
  76                                        __FILE__, __FUNCTION__ , ## args)
  77 #else
  78 #define DEBUGP(format, args...)
  79 #endif
  80
  81 #define PRINTR(format, args...) do { if (net_ratelimit()) printk(format , ## args); } while (0)
  82
  83 static unsigned int nlbufsiz = NLMSG_GOODSIZE;
  84 module_param(nlbufsiz, uint, 0400);
  85 MODULE_PARM_DESC(nlbufsiz, "netlink buffer size");
  86
  87 static unsigned int flushtimeout = 10;
  88 module_param(flushtimeout, uint, 0600);
  89 MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths of a second)");
  90
  91 static int nflog = 1;
  92 module_param(nflog, bool, 0400);
  93 MODULE_PARM_DESC(nflog, "register as internal netfilter logging module");
  94
  95 /* global data structures */
  96
  97 typedef struct {
  98         unsigned int qlen;              /* number of nlmsgs' in the skb */
  99         struct nlmsghdr *lastnlh;       /* netlink header of last msg in skb */
 100         struct sk_buff *skb;            /* the pre-allocated skb */
 101         struct timer_list timer;        /* the timer function */
 102 } ulog_buff_t;
 103
 104 static ulog_buff_t ulog_buffers[ULOG_MAXNLGROUPS];      /* array of buffers */
 105
 106 static struct sock *nflognl;            /* our socket */
 107 static DEFINE_SPINLOCK(ulog_lock);      /* spinlock */
 108
 109 /* send one ulog_buff_t to userspace */
 110 static void ulog_send(unsigned int nlgroupnum)
 111 {
 112         ulog_buff_t *ub = &ulog_buffers[nlgroupnum];
 113
 114         if (timer_pending(&ub->timer)) {
 115                 DEBUGP("ipt_ULOG: ulog_send: timer was pending, deleting\n");
 116                 del_timer(&ub->timer);
 117         }
 118
 119         if (!ub->skb) {
 120                 DEBUGP("ipt_ULOG: ulog_send: nothing to send\n");
 121                 return;
 122         }
 123
 124         /* last nlmsg needs NLMSG_DONE */
 125         if (ub->qlen > 1)
 126                 ub->lastnlh->nlmsg_type = NLMSG_DONE;
 127
 128         NETLINK_CB(ub->skb).dst_group = nlgroupnum + 1;
 129         DEBUGP("ipt_ULOG: throwing %d packets to netlink group %u\n",
 130                 ub->qlen, nlgroupnum + 1);
 131         netlink_broadcast(nflognl, ub->skb, 0, nlgroupnum + 1, GFP_ATOMIC);
 132
 133         ub->qlen = 0;
 134         ub->skb = NULL;
 135         ub->lastnlh = NULL;
 136 }
 137
 138
 139 /* timer function to flush queue in flushtimeout time */
 140 static void ulog_timer(unsigned long data)
 141 {
 142         DEBUGP("ipt_ULOG: timer function called, calling ulog_send\n");
 143
 144         /* lock to protect against somebody modifying our structure
 145          * from ipt_ulog_target at the same time */
 146         spin_lock_bh(&ulog_lock);
 147         ulog_send(data);
 148         spin_unlock_bh(&ulog_lock);
 149 }
 150
 151 static struct sk_buff *ulog_alloc_skb(unsigned int size)
 152 {
 153         struct sk_buff *skb;
 154         unsigned int n;
 155
 156         /* alloc skb which should be big enough for a whole
 157          * multipart message. WARNING: has to be <= 131000
 158          * due to slab allocator restrictions */
 159
 160         n = max(size, nlbufsiz);
 161         skb = alloc_skb(n, GFP_ATOMIC);
 162         if (!skb) {
 163                 PRINTR("ipt_ULOG: can't alloc whole buffer %ub!\n", n);
 164
 165                 if (n > size) {
 166                         /* try to allocate only as much as we need for
 167                          * current packet */
 168
 169                         skb = alloc_skb(size, GFP_ATOMIC);
 170                         if (!skb)
 171                                 PRINTR("ipt_ULOG: can't even allocate %ub\n",
 172                                        size);
 173                 }
 174         }
 175
 176         return skb;
 177 }
 178
 179 static void ipt_ulog_packet(unsigned int hooknum,
 180                             const struct sk_buff *skb,
 181                             const struct net_device *in,
 182                             const struct net_device *out,
 183                             const struct ipt_ulog_info *loginfo,
 184                             const char *prefix)
 185 {
 186         ulog_buff_t *ub;
 187         ulog_packet_msg_t *pm;
 188         size_t size, copy_len;
 189         struct nlmsghdr *nlh;
 190
 191         /* ffs == find first bit set, necessary because userspace
 192          * is already shifting groupnumber, but we need unshifted.
 193          * ffs() returns [1..32], we need [0..31] */
 194         unsigned int groupnum = ffs(loginfo->nl_group) - 1;
 195
 196         /* calculate the size of the skb needed */
 197         if ((loginfo->copy_range == 0) ||
 198             (loginfo->copy_range > skb->len)) {
 199                 copy_len = skb->len;
 200         } else {
 201                 copy_len = loginfo->copy_range;
 202         }
 203
 204         size = NLMSG_SPACE(sizeof(*pm) + copy_len);
 205
 206         ub = &ulog_buffers[groupnum];
 207
 208         spin_lock_bh(&ulog_lock);
 209
 210         if (!ub->skb) {
 211                 if (!(ub->skb = ulog_alloc_skb(size)))
 212                         goto alloc_failure;
 213         } else if (ub->qlen >= loginfo->qthreshold ||
 214                    size > skb_tailroom(ub->skb)) {
 215                 /* either the queue len is too high or we don't have
 216                  * enough room in nlskb left. send it to userspace. */
 217
 218                 ulog_send(groupnum);
 219
 220                 if (!(ub->skb = ulog_alloc_skb(size)))
 221                         goto alloc_failure;
 222         }
 223
 224         DEBUGP("ipt_ULOG: qlen %d, qthreshold %d\n", ub->qlen,
 225                 loginfo->qthreshold);
 226
 227         /* NLMSG_PUT contains a hidden goto nlmsg_failure !!! */
 228         nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
 229                         sizeof(*pm)+copy_len);
 230         ub->qlen++;
 231
 232         pm = NLMSG_DATA(nlh);
 233
 234         /* We might not have a timestamp, get one */
 235         if (skb->tstamp.off_sec == 0)
 236                 __net_timestamp((struct sk_buff *)skb);
 237
 238         /* copy hook, prefix, timestamp, payload, etc. */
 239         pm->data_len = copy_len;
 240         put_unaligned(skb->tstamp.off_sec, &pm->timestamp_sec);
 241         put_unaligned(skb->tstamp.off_usec, &pm->timestamp_usec);
 242         put_unaligned(skb->mark, &pm->mark);
 243         pm->hook = hooknum;
 244         if (prefix != NULL)
 245                 strncpy(pm->prefix, prefix, sizeof(pm->prefix));
 246         else if (loginfo->prefix[0] != '\0')
 247                 strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
 248         else
 249                 *(pm->prefix) = '\0';
 250
 251         if (in && in->hard_header_len > 0
 252             && skb->mac.raw != (void *) skb->nh.iph
 253             && in->hard_header_len <= ULOG_MAC_LEN) {
 254                 memcpy(pm->mac, skb->mac.raw, in->hard_header_len);
 255                 pm->mac_len = in->hard_header_len;
 256         } else
 257                 pm->mac_len = 0;
 258
 259         if (in)
 260                 strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
 261         else
 262                 pm->indev_name[0] = '\0';
 263
 264         if (out)
 265                 strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
 266         else
 267                 pm->outdev_name[0] = '\0';
 268
 269         /* copy_len <= skb->len, so can't fail. */
 270         if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
 271                 BUG();
 272
 273         /* check if we are building multi-part messages */
 274         if (ub->qlen > 1) {
 275                 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
 276         }
 277
 278         ub->lastnlh = nlh;
 279
 280         /* if timer isn't already running, start it */
 281         if (!timer_pending(&ub->timer)) {
 282                 ub->timer.expires = jiffies + flushtimeout * HZ / 100;
 283                 add_timer(&ub->timer);
 284         }
 285
 286         /* if threshold is reached, send message to userspace */
 287         if (ub->qlen >= loginfo->qthreshold) {
 288                 if (loginfo->qthreshold > 1)
 289                         nlh->nlmsg_type = NLMSG_DONE;
 290                 ulog_send(groupnum);
 291         }
 292
 293         spin_unlock_bh(&ulog_lock);
 294
 295         return;
 296
 297 nlmsg_failure:
 298         PRINTR("ipt_ULOG: error during NLMSG_PUT\n");
 299
 300 alloc_failure:
 301         PRINTR("ipt_ULOG: Error building netlink message\n");
 302
 303         spin_unlock_bh(&ulog_lock);
 304 }
 305
 306 static unsigned int ipt_ulog_target(struct sk_buff **pskb,
 307                                     const struct net_device *in,
 308                                     const struct net_device *out,
 309                                     unsigned int hooknum,
 310                                     const struct xt_target *target,
 311                                     const void *targinfo)
 312 {
 313         struct ipt_ulog_info *loginfo = (struct ipt_ulog_info *) targinfo;
 314
 315         ipt_ulog_packet(hooknum, *pskb, in, out, loginfo, NULL);
 316
 317         return XT_CONTINUE;
 318 }
 319
 320 static void ipt_logfn(unsigned int pf,
 321                       unsigned int hooknum,
 322                       const struct sk_buff *skb,
 323                       const struct net_device *in,
 324                       const struct net_device *out,
 325                       const struct nf_loginfo *li,
 326                       const char *prefix)
 327 {
 328         struct ipt_ulog_info loginfo;
 329
 330         if (!li || li->type != NF_LOG_TYPE_ULOG) {
 331                 loginfo.nl_group = ULOG_DEFAULT_NLGROUP;
 332                 loginfo.copy_range = 0;
 333                 loginfo.qthreshold = ULOG_DEFAULT_QTHRESHOLD;
 334                 loginfo.prefix[0] = '\0';
 335         } else {
 336                 loginfo.nl_group = li->u.ulog.group;
 337                 loginfo.copy_range = li->u.ulog.copy_len;
 338                 loginfo.qthreshold = li->u.ulog.qthreshold;
 339                 strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
 340         }
 341
 342         ipt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
 343 }
 344
 345 static int ipt_ulog_checkentry(const char *tablename,
 346                                const void *e,
 347                                const struct xt_target *target,
 348                                void *targinfo,
 349                                unsigned int hookmask)
 350 {
 351         struct ipt_ulog_info *loginfo = (struct ipt_ulog_info *) targinfo;
 352
 353         if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
 354                 DEBUGP("ipt_ULOG: prefix term %i\n",
 355                        loginfo->prefix[sizeof(loginfo->prefix) - 1]);
 356                 return 0;
 357         }
 358         if (loginfo->qthreshold > ULOG_MAX_QLEN) {
 359                 DEBUGP("ipt_ULOG: queue threshold %i > MAX_QLEN\n",
 360                         loginfo->qthreshold);
 361                 return 0;
 362         }
 363         return 1;
 364 }
 365
 366 static struct xt_target ipt_ulog_reg = {
 367         .name           = "ULOG",
 368         .family         = AF_INET,
 369         .target         = ipt_ulog_target,
 370         .targetsize     = sizeof(struct ipt_ulog_info),
 371         .checkentry     = ipt_ulog_checkentry,
 372         .me             = THIS_MODULE,
 373 };
 374
 375 static struct nf_logger ipt_ulog_logger = {
 376         .name           = "ipt_ULOG",
 377         .logfn          = ipt_logfn,
 378         .me             = THIS_MODULE,
 379 };
 380
 381 static int __init ipt_ulog_init(void)
 382 {
 383         int ret, i;
 384
 385         DEBUGP("ipt_ULOG: init module\n");
 386
 387         if (nlbufsiz > 128*1024) {
 388                 printk("Netlink buffer has to be <= 128kB\n");
 389                 return -EINVAL;
 390         }
 391
 392         /* initialize ulog_buffers */
 393         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 394                 init_timer(&ulog_buffers[i].timer);
 395                 ulog_buffers[i].timer.function = ulog_timer;
 396                 ulog_buffers[i].timer.data = i;
 397         }
 398
 399         nflognl = netlink_kernel_create(NETLINK_NFLOG, ULOG_MAXNLGROUPS, NULL,
 400                                         THIS_MODULE);
 401         if (!nflognl)
 402                 return -ENOMEM;
 403
 404         ret = xt_register_target(&ipt_ulog_reg);
 405         if (ret < 0) {
 406                 sock_release(nflognl->sk_socket);
 407                 return ret;
 408         }
 409         if (nflog)
 410                 nf_log_register(PF_INET, &ipt_ulog_logger);
 411
 412         return 0;
 413 }
 414
 415 static void __exit ipt_ulog_fini(void)
 416 {
 417         ulog_buff_t *ub;
 418         int i;
 419
 420         DEBUGP("ipt_ULOG: cleanup_module\n");
 421
 422         if (nflog)
 423                 nf_log_unregister(&ipt_ulog_logger);
 424         xt_unregister_target(&ipt_ulog_reg);
 425         sock_release(nflognl->sk_socket);
 426
 427         /* remove pending timers and free allocated skb's */
 428         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 429                 ub = &ulog_buffers[i];
 430                 if (timer_pending(&ub->timer)) {
 431                         DEBUGP("timer was pending, deleting\n");
 432                         del_timer(&ub->timer);
 433                 }
 434
 435                 if (ub->skb) {
 436                         kfree_skb(ub->skb);
 437                         ub->skb = NULL;
 438                 }
 439         }
 440 }
 441
 442 module_init(ipt_ulog_init);
 443 module_exit(ipt_ulog_fini);