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  * flushtimeout:
  39  *   Specify, after how many hundredths of a second the queue should be
  40  *   flushed even if it is not full yet.
  41  *
  42  * ipt_ULOG.c,v 1.22 2002/10/30 09:07:31 laforge Exp
  43  */
  44
  45 #include <linux/module.h>
  46 #include <linux/config.h>
  47 #include <linux/spinlock.h>
  48 #include <linux/socket.h>
  49 #include <linux/skbuff.h>
  50 #include <linux/kernel.h>
  51 #include <linux/timer.h>
  52 #include <linux/netlink.h>
  53 #include <linux/netdevice.h>
  54 #include <linux/mm.h>
  55 #include <linux/moduleparam.h>
  56 #include <linux/netfilter.h>
  57 #include <linux/netfilter_ipv4/ip_tables.h>
  58 #include <linux/netfilter_ipv4/ipt_ULOG.h>
  59 #include <net/sock.h>
  60 #include <linux/bitops.h>
  61
  62 MODULE_LICENSE("GPL");
  63 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  64 MODULE_DESCRIPTION("iptables userspace logging module");
  65
  66 #define ULOG_NL_EVENT           111             /* Harald's favorite number */
  67 #define ULOG_MAXNLGROUPS        32              /* numer of nlgroups */
  68
  69 #if 0
  70 #define DEBUGP(format, args...) printk("%s:%s:" format, \
  71                                        __FILE__, __FUNCTION__ , ## args)
  72 #else
  73 #define DEBUGP(format, args...)
  74 #endif
  75
  76 #define PRINTR(format, args...) do { if (net_ratelimit()) printk(format , ## args); } while (0)
  77
  78 static unsigned int nlbufsiz = 4096;
  79 module_param(nlbufsiz, uint, 0600); /* FIXME: Check size < 128k --RR */
  80 MODULE_PARM_DESC(nlbufsiz, "netlink buffer size");
  81
  82 static unsigned int flushtimeout = 10;
  83 module_param(flushtimeout, int, 0600);
  84 MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths of a second)");
  85
  86 static unsigned int nflog = 1;
  87 module_param(nflog, int, 0400);
  88 MODULE_PARM_DESC(nflog, "register as internal netfilter logging module");
  89
  90 /* global data structures */
  91
  92 typedef struct {
  93         unsigned int qlen;              /* number of nlmsgs' in the skb */
  94         struct nlmsghdr *lastnlh;       /* netlink header of last msg in skb */
  95         struct sk_buff *skb;            /* the pre-allocated skb */
  96         struct timer_list timer;        /* the timer function */
  97 } ulog_buff_t;
  98
  99 static ulog_buff_t ulog_buffers[ULOG_MAXNLGROUPS];      /* array of buffers */
 100
 101 static struct sock *nflognl;            /* our socket */
 102 static DEFINE_SPINLOCK(ulog_lock);      /* spinlock */
 103
 104 /* send one ulog_buff_t to userspace */
 105 static void ulog_send(unsigned int nlgroupnum)
 106 {
 107         ulog_buff_t *ub = &ulog_buffers[nlgroupnum];
 108
 109         if (timer_pending(&ub->timer)) {
 110                 DEBUGP("ipt_ULOG: ulog_send: timer was pending, deleting\n");
 111                 del_timer(&ub->timer);
 112         }
 113
 114         /* last nlmsg needs NLMSG_DONE */
 115         if (ub->qlen > 1)
 116                 ub->lastnlh->nlmsg_type = NLMSG_DONE;
 117
 118         NETLINK_CB(ub->skb).dst_groups = (1 << nlgroupnum);
 119         DEBUGP("ipt_ULOG: throwing %d packets to netlink mask %u\n",
 120                 ub->qlen, nlgroupnum);
 121         netlink_broadcast(nflognl, ub->skb, 0, (1 << nlgroupnum), GFP_ATOMIC);
 122
 123         ub->qlen = 0;
 124         ub->skb = NULL;
 125         ub->lastnlh = NULL;
 126
 127 }
 128
 129
 130 /* timer function to flush queue in flushtimeout time */
 131 static void ulog_timer(unsigned long data)
 132 {
 133         DEBUGP("ipt_ULOG: timer function called, calling ulog_send\n");
 134
 135         /* lock to protect against somebody modifying our structure
 136          * from ipt_ulog_target at the same time */
 137         spin_lock_bh(&ulog_lock);
 138         ulog_send(data);
 139         spin_unlock_bh(&ulog_lock);
 140 }
 141
 142 static struct sk_buff *ulog_alloc_skb(unsigned int size)
 143 {
 144         struct sk_buff *skb;
 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         skb = alloc_skb(nlbufsiz, GFP_ATOMIC);
 151         if (!skb) {
 152                 PRINTR("ipt_ULOG: can't alloc whole buffer %ub!\n",
 153                         nlbufsiz);
 154
 155                 /* try to allocate only as much as we need for
 156                  * current packet */
 157
 158                 skb = alloc_skb(size, GFP_ATOMIC);
 159                 if (!skb)
 160                         PRINTR("ipt_ULOG: can't even allocate %ub\n", size);
 161         }
 162
 163         return skb;
 164 }
 165
 166 static void ipt_ulog_packet(unsigned int hooknum,
 167                             const struct sk_buff *skb,
 168                             const struct net_device *in,
 169                             const struct net_device *out,
 170                             const struct ipt_ulog_info *loginfo,
 171                             const char *prefix)
 172 {
 173         ulog_buff_t *ub;
 174         ulog_packet_msg_t *pm;
 175         size_t size, copy_len;
 176         struct nlmsghdr *nlh;
 177
 178         /* ffs == find first bit set, necessary because userspace
 179          * is already shifting groupnumber, but we need unshifted.
 180          * ffs() returns [1..32], we need [0..31] */
 181         unsigned int groupnum = ffs(loginfo->nl_group) - 1;
 182
 183         /* calculate the size of the skb needed */
 184         if ((loginfo->copy_range == 0) ||
 185             (loginfo->copy_range > skb->len)) {
 186                 copy_len = skb->len;
 187         } else {
 188                 copy_len = loginfo->copy_range;
 189         }
 190
 191         size = NLMSG_SPACE(sizeof(*pm) + copy_len);
 192
 193         ub = &ulog_buffers[groupnum];
 194
 195         spin_lock_bh(&ulog_lock);
 196
 197         if (!ub->skb) {
 198                 if (!(ub->skb = ulog_alloc_skb(size)))
 199                         goto alloc_failure;
 200         } else if (ub->qlen >= loginfo->qthreshold ||
 201                    size > skb_tailroom(ub->skb)) {
 202                 /* either the queue len is too high or we don't have
 203                  * enough room in nlskb left. send it to userspace. */
 204
 205                 ulog_send(groupnum);
 206
 207                 if (!(ub->skb = ulog_alloc_skb(size)))
 208                         goto alloc_failure;
 209         }
 210
 211         DEBUGP("ipt_ULOG: qlen %d, qthreshold %d\n", ub->qlen,
 212                 loginfo->qthreshold);
 213
 214         /* NLMSG_PUT contains a hidden goto nlmsg_failure !!! */
 215         nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
 216                         sizeof(*pm)+copy_len);
 217         ub->qlen++;
 218
 219         pm = NLMSG_DATA(nlh);
 220
 221         /* We might not have a timestamp, get one */
 222         if (skb->stamp.tv_sec == 0)
 223                 do_gettimeofday((struct timeval *)&skb->stamp);
 224
 225         /* copy hook, prefix, timestamp, payload, etc. */
 226         pm->data_len = copy_len;
 227         pm->timestamp_sec = skb->stamp.tv_sec;
 228         pm->timestamp_usec = skb->stamp.tv_usec;
 229         pm->mark = skb->nfmark;
 230         pm->hook = hooknum;
 231         if (prefix != NULL)
 232                 strncpy(pm->prefix, prefix, sizeof(pm->prefix));
 233         else if (loginfo->prefix[0] != '\0')
 234                 strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
 235         else
 236                 *(pm->prefix) = '\0';
 237
 238         if (in && in->hard_header_len > 0
 239             && skb->mac.raw != (void *) skb->nh.iph
 240             && in->hard_header_len <= ULOG_MAC_LEN) {
 241                 memcpy(pm->mac, skb->mac.raw, in->hard_header_len);
 242                 pm->mac_len = in->hard_header_len;
 243         } else
 244                 pm->mac_len = 0;
 245
 246         if (in)
 247                 strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
 248         else
 249                 pm->indev_name[0] = '\0';
 250
 251         if (out)
 252                 strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
 253         else
 254                 pm->outdev_name[0] = '\0';
 255
 256         /* copy_len <= skb->len, so can't fail. */
 257         if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
 258                 BUG();
 259
 260         /* check if we are building multi-part messages */
 261         if (ub->qlen > 1) {
 262                 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
 263         }
 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(groupnum);
 278         }
 279
 280         spin_unlock_bh(&ulog_lock);
 281
 282         return;
 283
 284 nlmsg_failure:
 285         PRINTR("ipt_ULOG: error during NLMSG_PUT\n");
 286
 287 alloc_failure:
 288         PRINTR("ipt_ULOG: Error building netlink message\n");
 289
 290         spin_unlock_bh(&ulog_lock);
 291 }
 292
 293 static unsigned int ipt_ulog_target(struct sk_buff **pskb,
 294                                     const struct net_device *in,
 295                                     const struct net_device *out,
 296                                     unsigned int hooknum,
 297                                     const void *targinfo, void *userinfo)
 298 {
 299         struct ipt_ulog_info *loginfo = (struct ipt_ulog_info *) targinfo;
 300
 301         ipt_ulog_packet(hooknum, *pskb, in, out, loginfo, NULL);
 302
 303         return IPT_CONTINUE;
 304 }
 305
 306 static void ipt_logfn(unsigned int hooknum,
 307                       const struct sk_buff *skb,
 308                       const struct net_device *in,
 309                       const struct net_device *out,
 310                       const char *prefix)
 311 {
 312         struct ipt_ulog_info loginfo = {
 313                 .nl_group = ULOG_DEFAULT_NLGROUP,
 314                 .copy_range = 0,
 315                 .qthreshold = ULOG_DEFAULT_QTHRESHOLD,
 316                 .prefix = ""
 317         };
 318
 319         ipt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
 320 }
 321
 322 static int ipt_ulog_checkentry(const char *tablename,
 323                                const struct ipt_entry *e,
 324                                void *targinfo,
 325                                unsigned int targinfosize,
 326                                unsigned int hookmask)
 327 {
 328         struct ipt_ulog_info *loginfo = (struct ipt_ulog_info *) targinfo;
 329
 330         if (targinfosize != IPT_ALIGN(sizeof(struct ipt_ulog_info))) {
 331                 DEBUGP("ipt_ULOG: targinfosize %u != 0\n", targinfosize);
 332                 return 0;
 333         }
 334
 335         if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
 336                 DEBUGP("ipt_ULOG: prefix term %i\n",
 337                        loginfo->prefix[sizeof(loginfo->prefix) - 1]);
 338                 return 0;
 339         }
 340
 341         if (loginfo->qthreshold > ULOG_MAX_QLEN) {
 342                 DEBUGP("ipt_ULOG: queue threshold %i > MAX_QLEN\n",
 343                         loginfo->qthreshold);
 344                 return 0;
 345         }
 346
 347         return 1;
 348 }
 349
 350 static struct ipt_target ipt_ulog_reg = {
 351         .name           = "ULOG",
 352         .target         = ipt_ulog_target,
 353         .checkentry     = ipt_ulog_checkentry,
 354         .me             = THIS_MODULE,
 355 };
 356
 357 static int __init init(void)
 358 {
 359         int i;
 360
 361         DEBUGP("ipt_ULOG: init module\n");
 362
 363         if (nlbufsiz >= 128*1024) {
 364                 printk("Netlink buffer has to be <= 128kB\n");
 365                 return -EINVAL;
 366         }
 367
 368         /* initialize ulog_buffers */
 369         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 370                 init_timer(&ulog_buffers[i].timer);
 371                 ulog_buffers[i].timer.function = ulog_timer;
 372                 ulog_buffers[i].timer.data = i;
 373         }
 374
 375         nflognl = netlink_kernel_create(NETLINK_NFLOG, NULL);
 376         if (!nflognl)
 377                 return -ENOMEM;
 378
 379         if (ipt_register_target(&ipt_ulog_reg) != 0) {
 380                 sock_release(nflognl->sk_socket);
 381                 return -EINVAL;
 382         }
 383         if (nflog)
 384                 nf_log_register(PF_INET, &ipt_logfn);
 385
 386         return 0;
 387 }
 388
 389 static void __exit fini(void)
 390 {
 391         ulog_buff_t *ub;
 392         int i;
 393
 394         DEBUGP("ipt_ULOG: cleanup_module\n");
 395
 396         if (nflog)
 397                 nf_log_unregister(PF_INET, &ipt_logfn);
 398         ipt_unregister_target(&ipt_ulog_reg);
 399         sock_release(nflognl->sk_socket);
 400
 401         /* remove pending timers and free allocated skb's */
 402         for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
 403                 ub = &ulog_buffers[i];
 404                 if (timer_pending(&ub->timer)) {
 405                         DEBUGP("timer was pending, deleting\n");
 406                         del_timer(&ub->timer);
 407                 }
 408
 409                 if (ub->skb) {
 410                         kfree_skb(ub->skb);
 411                         ub->skb = NULL;
 412                 }
 413         }
 414
 415 }
 416
 417 module_init(init);
 418 module_exit(fini);