net/bridge/netfilter/ebt_ulog.c

   1 /*
   2  * netfilter module for userspace bridged Ethernet frames logging daemons
   3  *
   4  *      Authors:
   5  *      Bart De Schuymer <bdschuym@pandora.be>
   6  *      Harald Welte <laforge@netfilter.org>
   7  *
   8  *  November, 2004
   9  *
  10  * Based on ipt_ULOG.c, which is
  11  * (C) 2000-2002 by Harald Welte <laforge@netfilter.org>
  12  *
  13  * This module accepts two parameters:
  14  *
  15  * nlbufsiz:
  16  *   The parameter specifies how big the buffer for each netlink multicast
  17  * group is. e.g. If you say nlbufsiz=8192, up to eight kb of packets will
  18  * get accumulated in the kernel until they are sent to userspace. It is
  19  * NOT possible to allocate more than 128kB, and it is strongly discouraged,
  20  * because atomically allocating 128kB inside the network rx softirq is not
  21  * reliable. Please also keep in mind that this buffer size is allocated for
  22  * each nlgroup you are using, so the total kernel memory usage increases
  23  * by that factor.
  24  *
  25  * flushtimeout:
  26  *   Specify, after how many hundredths of a second the queue should be
  27  *   flushed even if it is not full yet.
  28  *
  29  */
  30 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  31 #include <linux/module.h>
  32 #include <linux/slab.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/socket.h>
  35 #include <linux/skbuff.h>
  36 #include <linux/kernel.h>
  37 #include <linux/timer.h>
  38 #include <linux/netlink.h>
  39 #include <linux/netdevice.h>
  40 #include <linux/netfilter/x_tables.h>
  41 #include <linux/netfilter_bridge/ebtables.h>
  42 #include <linux/netfilter_bridge/ebt_ulog.h>
  43 #include <net/netfilter/nf_log.h>
  44 #include <net/sock.h>
  45 #include "../br_private.h"
  46
  47 static unsigned int nlbufsiz = NLMSG_GOODSIZE;
  48 module_param(nlbufsiz, uint, 0600);
  49 MODULE_PARM_DESC(nlbufsiz, "netlink buffer size (number of bytes) "
  50                            "(defaults to 4096)");
  51
  52 static unsigned int flushtimeout = 10;
  53 module_param(flushtimeout, uint, 0600);
  54 MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths ofa second) "
  55                                "(defaults to 10)");
  56
  57 typedef struct {
  58         unsigned int qlen;              /* number of nlmsgs' in the skb */
  59         struct nlmsghdr *lastnlh;       /* netlink header of last msg in skb */
  60         struct sk_buff *skb;            /* the pre-allocated skb */
  61         struct timer_list timer;        /* the timer function */
  62         spinlock_t lock;                /* the per-queue lock */
  63 } ebt_ulog_buff_t;
  64
  65 static ebt_ulog_buff_t ulog_buffers[EBT_ULOG_MAXNLGROUPS];
  66 static struct sock *ebtulognl;
  67
  68 /* send one ulog_buff_t to userspace */
  69 static void ulog_send(unsigned int nlgroup)
  70 {
  71         ebt_ulog_buff_t *ub = &ulog_buffers[nlgroup];
  72
  73         if (timer_pending(&ub->timer))
  74                 del_timer(&ub->timer);
  75
  76         if (!ub->skb)
  77                 return;
  78
  79         /* last nlmsg needs NLMSG_DONE */
  80         if (ub->qlen > 1)
  81                 ub->lastnlh->nlmsg_type = NLMSG_DONE;
  82
  83         NETLINK_CB(ub->skb).dst_group = nlgroup + 1;
  84         netlink_broadcast(ebtulognl, ub->skb, 0, nlgroup + 1, GFP_ATOMIC);
  85
  86         ub->qlen = 0;
  87         ub->skb = NULL;
  88 }
  89
  90 /* timer function to flush queue in flushtimeout time */
  91 static void ulog_timer(unsigned long data)
  92 {
  93         spin_lock_bh(&ulog_buffers[data].lock);
  94         if (ulog_buffers[data].skb)
  95                 ulog_send(data);
  96         spin_unlock_bh(&ulog_buffers[data].lock);
  97 }
  98
  99 static struct sk_buff *ulog_alloc_skb(unsigned int size)
 100 {
 101         struct sk_buff *skb;
 102         unsigned int n;
 103
 104         n = max(size, nlbufsiz);
 105         skb = alloc_skb(n, GFP_ATOMIC);
 106         if (!skb) {
 107                 pr_debug("cannot alloc whole buffer of size %ub!\n", n);
 108                 if (n > size) {
 109                         /* try to allocate only as much as we need for
 110                          * current packet */
 111                         skb = alloc_skb(size, GFP_ATOMIC);
 112                         if (!skb)
 113                                 pr_debug("cannot even allocate "
 114                                          "buffer of size %ub\n", size);
 115                 }
 116         }
 117
 118         return skb;
 119 }
 120
 121 static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
 122    const struct net_device *in, const struct net_device *out,
 123    const struct ebt_ulog_info *uloginfo, const char *prefix)
 124 {
 125         ebt_ulog_packet_msg_t *pm;
 126         size_t size, copy_len;
 127         struct nlmsghdr *nlh;
 128         unsigned int group = uloginfo->nlgroup;
 129         ebt_ulog_buff_t *ub = &ulog_buffers[group];
 130         spinlock_t *lock = &ub->lock;
 131         ktime_t kt;
 132
 133         if ((uloginfo->cprange == 0) ||
 134             (uloginfo->cprange > skb->len + ETH_HLEN))
 135                 copy_len = skb->len + ETH_HLEN;
 136         else
 137                 copy_len = uloginfo->cprange;
 138
 139         size = NLMSG_SPACE(sizeof(*pm) + copy_len);
 140         if (size > nlbufsiz) {
 141                 pr_debug("Size %Zd needed, but nlbufsiz=%d\n", size, nlbufsiz);
 142                 return;
 143         }
 144
 145         spin_lock_bh(lock);
 146
 147         if (!ub->skb) {
 148                 if (!(ub->skb = ulog_alloc_skb(size)))
 149                         goto alloc_failure;
 150         } else if (size > skb_tailroom(ub->skb)) {
 151                 ulog_send(group);
 152
 153                 if (!(ub->skb = ulog_alloc_skb(size)))
 154                         goto alloc_failure;
 155         }
 156
 157         nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, 0,
 158                         size - NLMSG_ALIGN(sizeof(*nlh)));
 159         ub->qlen++;
 160
 161         pm = NLMSG_DATA(nlh);
 162
 163         /* Fill in the ulog data */
 164         pm->version = EBT_ULOG_VERSION;
 165         kt = ktime_get_real();
 166         pm->stamp = ktime_to_timeval(kt);
 167         if (ub->qlen == 1)
 168                 ub->skb->tstamp = kt;
 169         pm->data_len = copy_len;
 170         pm->mark = skb->mark;
 171         pm->hook = hooknr;
 172         if (uloginfo->prefix != NULL)
 173                 strcpy(pm->prefix, uloginfo->prefix);
 174         else
 175                 *(pm->prefix) = '\0';
 176
 177         if (in) {
 178                 strcpy(pm->physindev, in->name);
 179                 /* If in isn't a bridge, then physindev==indev */
 180                 if (br_port_exists(in))
 181                         /* rcu_read_lock()ed by nf_hook_slow */
 182                         strcpy(pm->indev, br_port_get_rcu(in)->br->dev->name);
 183                 else
 184                         strcpy(pm->indev, in->name);
 185         } else
 186                 pm->indev[0] = pm->physindev[0] = '\0';
 187
 188         if (out) {
 189                 /* If out exists, then out is a bridge port */
 190                 strcpy(pm->physoutdev, out->name);
 191                 /* rcu_read_lock()ed by nf_hook_slow */
 192                 strcpy(pm->outdev, br_port_get_rcu(out)->br->dev->name);
 193         } else
 194                 pm->outdev[0] = pm->physoutdev[0] = '\0';
 195
 196         if (skb_copy_bits(skb, -ETH_HLEN, pm->data, copy_len) < 0)
 197                 BUG();
 198
 199         if (ub->qlen > 1)
 200                 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
 201
 202         ub->lastnlh = nlh;
 203
 204         if (ub->qlen >= uloginfo->qthreshold)
 205                 ulog_send(group);
 206         else if (!timer_pending(&ub->timer)) {
 207                 ub->timer.expires = jiffies + flushtimeout * HZ / 100;
 208                 add_timer(&ub->timer);
 209         }
 210
 211 unlock:
 212         spin_unlock_bh(lock);
 213
 214         return;
 215
 216 nlmsg_failure:
 217         pr_debug("error during NLMSG_PUT. This should "
 218                  "not happen, please report to author.\n");
 219         goto unlock;
 220 alloc_failure:
 221         goto unlock;
 222 }
 223
 224 /* this function is registered with the netfilter core */
 225 static void ebt_log_packet(u_int8_t pf, unsigned int hooknum,
 226    const struct sk_buff *skb, const struct net_device *in,
 227    const struct net_device *out, const struct nf_loginfo *li,
 228    const char *prefix)
 229 {
 230         struct ebt_ulog_info loginfo;
 231
 232         if (!li || li->type != NF_LOG_TYPE_ULOG) {
 233                 loginfo.nlgroup = EBT_ULOG_DEFAULT_NLGROUP;
 234                 loginfo.cprange = 0;
 235                 loginfo.qthreshold = EBT_ULOG_DEFAULT_QTHRESHOLD;
 236                 loginfo.prefix[0] = '\0';
 237         } else {
 238                 loginfo.nlgroup = li->u.ulog.group;
 239                 loginfo.cprange = li->u.ulog.copy_len;
 240                 loginfo.qthreshold = li->u.ulog.qthreshold;
 241                 strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
 242         }
 243
 244         ebt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
 245 }
 246
 247 static unsigned int
 248 ebt_ulog_tg(struct sk_buff *skb, const struct xt_action_param *par)
 249 {
 250         ebt_ulog_packet(par->hooknum, skb, par->in, par->out,
 251                         par->targinfo, NULL);
 252         return EBT_CONTINUE;
 253 }
 254
 255 static int ebt_ulog_tg_check(const struct xt_tgchk_param *par)
 256 {
 257         struct ebt_ulog_info *uloginfo = par->targinfo;
 258
 259         if (uloginfo->nlgroup > 31)
 260                 return -EINVAL;
 261
 262         uloginfo->prefix[EBT_ULOG_PREFIX_LEN - 1] = '\0';
 263
 264         if (uloginfo->qthreshold > EBT_ULOG_MAX_QLEN)
 265                 uloginfo->qthreshold = EBT_ULOG_MAX_QLEN;
 266
 267         return 0;
 268 }
 269
 270 static struct xt_target ebt_ulog_tg_reg __read_mostly = {
 271         .name           = "ulog",
 272         .revision       = 0,
 273         .family         = NFPROTO_BRIDGE,
 274         .target         = ebt_ulog_tg,
 275         .checkentry     = ebt_ulog_tg_check,
 276         .targetsize     = sizeof(struct ebt_ulog_info),
 277         .me             = THIS_MODULE,
 278 };
 279
 280 static struct nf_logger ebt_ulog_logger __read_mostly = {
 281         .name           = "ebt_ulog",
 282         .logfn          = &ebt_log_packet,
 283         .me             = THIS_MODULE,
 284 };
 285
 286 static int __init ebt_ulog_init(void)
 287 {
 288         int ret;
 289         int i;
 290
 291         if (nlbufsiz >= 128*1024) {
 292                 pr_warning("Netlink buffer has to be <= 128kB,"
 293                            " please try a smaller nlbufsiz parameter.\n");
 294                 return -EINVAL;
 295         }
 296
 297         /* initialize ulog_buffers */
 298         for (i = 0; i < EBT_ULOG_MAXNLGROUPS; i++) {
 299                 setup_timer(&ulog_buffers[i].timer, ulog_timer, i);
 300                 spin_lock_init(&ulog_buffers[i].lock);
 301         }
 302
 303         ebtulognl = netlink_kernel_create(&init_net, NETLINK_NFLOG,
 304                                           EBT_ULOG_MAXNLGROUPS, NULL, NULL,
 305                                           THIS_MODULE);
 306         if (!ebtulognl)
 307                 ret = -ENOMEM;
 308         else if ((ret = xt_register_target(&ebt_ulog_tg_reg)) != 0)
 309                 netlink_kernel_release(ebtulognl);
 310
 311         if (ret == 0)
 312                 nf_log_register(NFPROTO_BRIDGE, &ebt_ulog_logger);
 313
 314         return ret;
 315 }
 316
 317 static void __exit ebt_ulog_fini(void)
 318 {
 319         ebt_ulog_buff_t *ub;
 320         int i;
 321
 322         nf_log_unregister(&ebt_ulog_logger);
 323         xt_unregister_target(&ebt_ulog_tg_reg);
 324         for (i = 0; i < EBT_ULOG_MAXNLGROUPS; i++) {
 325                 ub = &ulog_buffers[i];
 326                 if (timer_pending(&ub->timer))
 327                         del_timer(&ub->timer);
 328                 spin_lock_bh(&ub->lock);
 329                 if (ub->skb) {
 330                         kfree_skb(ub->skb);
 331                         ub->skb = NULL;
 332                 }
 333                 spin_unlock_bh(&ub->lock);
 334         }
 335         netlink_kernel_release(ebtulognl);
 336 }
 337
 338 module_init(ebt_ulog_init);
 339 module_exit(ebt_ulog_fini);
 340 MODULE_LICENSE("GPL");
 341 MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
 342 MODULE_DESCRIPTION("Ebtables: Packet logging to netlink using ULOG");