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 | __GFP_NOWARN);
 106         if (!skb) {
 107                 if (n > size) {
 108                         /* try to allocate only as much as we need for
 109                          * current packet */
 110                         skb = alloc_skb(size, GFP_ATOMIC);
 111                         if (!skb)
 112                                 pr_debug("cannot even allocate buffer of size %ub\n",
 113                                          size);
 114                 }
 115         }
 116
 117         return skb;
 118 }
 119
 120 static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
 121    const struct net_device *in, const struct net_device *out,
 122    const struct ebt_ulog_info *uloginfo, const char *prefix)
 123 {
 124         ebt_ulog_packet_msg_t *pm;
 125         size_t size, copy_len;
 126         struct nlmsghdr *nlh;
 127         unsigned int group = uloginfo->nlgroup;
 128         ebt_ulog_buff_t *ub = &ulog_buffers[group];
 129         spinlock_t *lock = &ub->lock;
 130         ktime_t kt;
 131
 132         if ((uloginfo->cprange == 0) ||
 133             (uloginfo->cprange > skb->len + ETH_HLEN))
 134                 copy_len = skb->len + ETH_HLEN;
 135         else
 136                 copy_len = uloginfo->cprange;
 137
 138         size = NLMSG_SPACE(sizeof(*pm) + copy_len);
 139         if (size > nlbufsiz) {
 140                 pr_debug("Size %Zd needed, but nlbufsiz=%d\n", size, nlbufsiz);
 141                 return;
 142         }
 143
 144         spin_lock_bh(lock);
 145
 146         if (!ub->skb) {
 147                 if (!(ub->skb = ulog_alloc_skb(size)))
 148                         goto unlock;
 149         } else if (size > skb_tailroom(ub->skb)) {
 150                 ulog_send(group);
 151
 152                 if (!(ub->skb = ulog_alloc_skb(size)))
 153                         goto unlock;
 154         }
 155
 156         nlh = nlmsg_put(ub->skb, 0, ub->qlen, 0,
 157                         size - NLMSG_ALIGN(sizeof(*nlh)), 0);
 158         if (!nlh) {
 159                 kfree_skb(ub->skb);
 160                 ub->skb = NULL;
 161                 goto unlock;
 162         }
 163         ub->qlen++;
 164
 165         pm = nlmsg_data(nlh);
 166
 167         /* Fill in the ulog data */
 168         pm->version = EBT_ULOG_VERSION;
 169         kt = ktime_get_real();
 170         pm->stamp = ktime_to_timeval(kt);
 171         if (ub->qlen == 1)
 172                 ub->skb->tstamp = kt;
 173         pm->data_len = copy_len;
 174         pm->mark = skb->mark;
 175         pm->hook = hooknr;
 176         if (uloginfo->prefix != NULL)
 177                 strcpy(pm->prefix, uloginfo->prefix);
 178         else
 179                 *(pm->prefix) = '\0';
 180
 181         if (in) {
 182                 strcpy(pm->physindev, in->name);
 183                 /* If in isn't a bridge, then physindev==indev */
 184                 if (br_port_exists(in))
 185                         /* rcu_read_lock()ed by nf_hook_slow */
 186                         strcpy(pm->indev, br_port_get_rcu(in)->br->dev->name);
 187                 else
 188                         strcpy(pm->indev, in->name);
 189         } else
 190                 pm->indev[0] = pm->physindev[0] = '\0';
 191
 192         if (out) {
 193                 /* If out exists, then out is a bridge port */
 194                 strcpy(pm->physoutdev, out->name);
 195                 /* rcu_read_lock()ed by nf_hook_slow */
 196                 strcpy(pm->outdev, br_port_get_rcu(out)->br->dev->name);
 197         } else
 198                 pm->outdev[0] = pm->physoutdev[0] = '\0';
 199
 200         if (skb_copy_bits(skb, -ETH_HLEN, pm->data, copy_len) < 0)
 201                 BUG();
 202
 203         if (ub->qlen > 1)
 204                 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
 205
 206         ub->lastnlh = nlh;
 207
 208         if (ub->qlen >= uloginfo->qthreshold)
 209                 ulog_send(group);
 210         else if (!timer_pending(&ub->timer)) {
 211                 ub->timer.expires = jiffies + flushtimeout * HZ / 100;
 212                 add_timer(&ub->timer);
 213         }
 214
 215 unlock:
 216         spin_unlock_bh(lock);
 217 }
 218
 219 /* this function is registered with the netfilter core */
 220 static void ebt_log_packet(u_int8_t pf, unsigned int hooknum,
 221    const struct sk_buff *skb, const struct net_device *in,
 222    const struct net_device *out, const struct nf_loginfo *li,
 223    const char *prefix)
 224 {
 225         struct ebt_ulog_info loginfo;
 226
 227         if (!li || li->type != NF_LOG_TYPE_ULOG) {
 228                 loginfo.nlgroup = EBT_ULOG_DEFAULT_NLGROUP;
 229                 loginfo.cprange = 0;
 230                 loginfo.qthreshold = EBT_ULOG_DEFAULT_QTHRESHOLD;
 231                 loginfo.prefix[0] = '\0';
 232         } else {
 233                 loginfo.nlgroup = li->u.ulog.group;
 234                 loginfo.cprange = li->u.ulog.copy_len;
 235                 loginfo.qthreshold = li->u.ulog.qthreshold;
 236                 strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
 237         }
 238
 239         ebt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
 240 }
 241
 242 static unsigned int
 243 ebt_ulog_tg(struct sk_buff *skb, const struct xt_action_param *par)
 244 {
 245         ebt_ulog_packet(par->hooknum, skb, par->in, par->out,
 246                         par->targinfo, NULL);
 247         return EBT_CONTINUE;
 248 }
 249
 250 static int ebt_ulog_tg_check(const struct xt_tgchk_param *par)
 251 {
 252         struct ebt_ulog_info *uloginfo = par->targinfo;
 253
 254         if (uloginfo->nlgroup > 31)
 255                 return -EINVAL;
 256
 257         uloginfo->prefix[EBT_ULOG_PREFIX_LEN - 1] = '\0';
 258
 259         if (uloginfo->qthreshold > EBT_ULOG_MAX_QLEN)
 260                 uloginfo->qthreshold = EBT_ULOG_MAX_QLEN;
 261
 262         return 0;
 263 }
 264
 265 static struct xt_target ebt_ulog_tg_reg __read_mostly = {
 266         .name           = "ulog",
 267         .revision       = 0,
 268         .family         = NFPROTO_BRIDGE,
 269         .target         = ebt_ulog_tg,
 270         .checkentry     = ebt_ulog_tg_check,
 271         .targetsize     = sizeof(struct ebt_ulog_info),
 272         .me             = THIS_MODULE,
 273 };
 274
 275 static struct nf_logger ebt_ulog_logger __read_mostly = {
 276         .name           = "ebt_ulog",
 277         .logfn          = &ebt_log_packet,
 278         .me             = THIS_MODULE,
 279 };
 280
 281 static int __init ebt_ulog_init(void)
 282 {
 283         int ret;
 284         int i;
 285         struct netlink_kernel_cfg cfg = {
 286                 .groups = EBT_ULOG_MAXNLGROUPS,
 287         };
 288
 289         if (nlbufsiz >= 128*1024) {
 290                 pr_warning("Netlink buffer has to be <= 128kB,"
 291                            " please try a smaller nlbufsiz parameter.\n");
 292                 return -EINVAL;
 293         }
 294
 295         /* initialize ulog_buffers */
 296         for (i = 0; i < EBT_ULOG_MAXNLGROUPS; i++) {
 297                 setup_timer(&ulog_buffers[i].timer, ulog_timer, i);
 298                 spin_lock_init(&ulog_buffers[i].lock);
 299         }
 300
 301         ebtulognl = netlink_kernel_create(&init_net, NETLINK_NFLOG, &cfg);
 302         if (!ebtulognl)
 303                 ret = -ENOMEM;
 304         else if ((ret = xt_register_target(&ebt_ulog_tg_reg)) != 0)
 305                 netlink_kernel_release(ebtulognl);
 306
 307         if (ret == 0)
 308                 nf_log_register(NFPROTO_BRIDGE, &ebt_ulog_logger);
 309
 310         return ret;
 311 }
 312
 313 static void __exit ebt_ulog_fini(void)
 314 {
 315         ebt_ulog_buff_t *ub;
 316         int i;
 317
 318         nf_log_unregister(&ebt_ulog_logger);
 319         xt_unregister_target(&ebt_ulog_tg_reg);
 320         for (i = 0; i < EBT_ULOG_MAXNLGROUPS; i++) {
 321                 ub = &ulog_buffers[i];
 322                 if (timer_pending(&ub->timer))
 323                         del_timer(&ub->timer);
 324                 spin_lock_bh(&ub->lock);
 325                 if (ub->skb) {
 326                         kfree_skb(ub->skb);
 327                         ub->skb = NULL;
 328                 }
 329                 spin_unlock_bh(&ub->lock);
 330         }
 331         netlink_kernel_release(ebtulognl);
 332 }
 333
 334 module_init(ebt_ulog_init);
 335 module_exit(ebt_ulog_fini);
 336 MODULE_LICENSE("GPL");
 337 MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
 338 MODULE_DESCRIPTION("Ebtables: Packet logging to netlink using ULOG");