/*
 * netfilter module for userspace bridged Ethernet frames logging daemons
 *
 *      Authors:
 *      Bart De Schuymer <bdschuym@pandora.be>
 *      Harald Welte <laforge@netfilter.org>
 *
 *  November, 2004
 *
 * Based on ipt_ULOG.c, which is
 * (C) 2000-2002 by Harald Welte <laforge@netfilter.org>
 *
 * This module accepts two parameters:
 *
 * nlbufsiz:
 *   The parameter specifies how big the buffer for each netlink multicast
 * group is. e.g. If you say nlbufsiz=8192, up to eight kb of packets will
 * get accumulated in the kernel until they are sent to userspace. It is
 * NOT possible to allocate more than 128kB, and it is strongly discouraged,
 * because atomically allocating 128kB inside the network rx softirq is not
 * reliable. Please also keep in mind that this buffer size is allocated for
 * each nlgroup you are using, so the total kernel memory usage increases
 * by that factor.
 *
 * flushtimeout:
 *   Specify, after how many hundredths of a second the queue should be
 *   flushed even if it is not full yet.
 *
 */

#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/socket.h>
#include <linux/skbuff.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/netlink.h>
#include <linux/netdevice.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_ulog.h>
#include <net/netfilter/nf_log.h>
#include <net/sock.h>
#include "../br_private.h"

#define PRINTR(format, args...) do { if (net_ratelimit()) \
                                printk(format , ## args); } while (0)

static unsigned int nlbufsiz = NLMSG_GOODSIZE;
module_param(nlbufsiz, uint, 0600);
MODULE_PARM_DESC(nlbufsiz, "netlink buffer size (number of bytes) "
                           "(defaults to 4096)");

static unsigned int flushtimeout = 10;
module_param(flushtimeout, uint, 0600);
MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths ofa second) "
                               "(defaults to 10)");

typedef struct {
        unsigned int qlen;              /* number of nlmsgs' in the skb */
        struct nlmsghdr *lastnlh;       /* netlink header of last msg in skb */
        struct sk_buff *skb;            /* the pre-allocated skb */
        struct timer_list timer;        /* the timer function */
        spinlock_t lock;                /* the per-queue lock */
} ebt_ulog_buff_t;

static ebt_ulog_buff_t ulog_buffers[EBT_ULOG_MAXNLGROUPS];
static struct sock *ebtulognl;

/* send one ulog_buff_t to userspace */
static void ulog_send(unsigned int nlgroup)
{
        ebt_ulog_buff_t *ub = &ulog_buffers[nlgroup];

        if (timer_pending(&ub->timer))
                del_timer(&ub->timer);

        if (!ub->skb)
                return;

        /* last nlmsg needs NLMSG_DONE */
        if (ub->qlen > 1)
                ub->lastnlh->nlmsg_type = NLMSG_DONE;

        NETLINK_CB(ub->skb).dst_group = nlgroup + 1;
        netlink_broadcast(ebtulognl, ub->skb, 0, nlgroup + 1, GFP_ATOMIC);

        ub->qlen = 0;
        ub->skb = NULL;
}

/* timer function to flush queue in flushtimeout time */
static void ulog_timer(unsigned long data)
{
        spin_lock_bh(&ulog_buffers[data].lock);
        if (ulog_buffers[data].skb)
                ulog_send(data);
        spin_unlock_bh(&ulog_buffers[data].lock);
}

static struct sk_buff *ulog_alloc_skb(unsigned int size)
{
        struct sk_buff *skb;
        unsigned int n;

        n = max(size, nlbufsiz);
        skb = alloc_skb(n, GFP_ATOMIC);
        if (!skb) {
                PRINTR(KERN_ERR "ebt_ulog: can't alloc whole buffer "
                       "of size %ub!\n", n);
                if (n > size) {
                        /* try to allocate only as much as we need for
                         * current packet */
                        skb = alloc_skb(size, GFP_ATOMIC);
                        if (!skb)
                                PRINTR(KERN_ERR "ebt_ulog: can't even allocate "
                                       "buffer of size %ub\n", size);
                }
        }

        return skb;
}

static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
   const struct net_device *in, const struct net_device *out,
   const struct ebt_ulog_info *uloginfo, const char *prefix)
{
        ebt_ulog_packet_msg_t *pm;
        size_t size, copy_len;
        struct nlmsghdr *nlh;
        unsigned int group = uloginfo->nlgroup;
        ebt_ulog_buff_t *ub = &ulog_buffers[group];
        spinlock_t *lock = &ub->lock;
        ktime_t kt;

        if ((uloginfo->cprange == 0) ||
            (uloginfo->cprange > skb->len + ETH_HLEN))
                copy_len = skb->len + ETH_HLEN;
        else
                copy_len = uloginfo->cprange;

        size = NLMSG_SPACE(sizeof(*pm) + copy_len);
        if (size > nlbufsiz) {
                PRINTR("ebt_ulog: Size %Zd needed, but nlbufsiz=%d\n",
                       size, nlbufsiz);
                return;
        }

        spin_lock_bh(lock);

        if (!ub->skb) {
                if (!(ub->skb = ulog_alloc_skb(size)))
                        goto alloc_failure;
        } else if (size > skb_tailroom(ub->skb)) {
                ulog_send(group);

                if (!(ub->skb = ulog_alloc_skb(size)))
                        goto alloc_failure;
        }

        nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, 0,
                        size - NLMSG_ALIGN(sizeof(*nlh)));
        ub->qlen++;

        pm = NLMSG_DATA(nlh);

        /* Fill in the ulog data */
        pm->version = EBT_ULOG_VERSION;
        kt = ktime_get_real();
        pm->stamp = ktime_to_timeval(kt);
        if (ub->qlen == 1)
                ub->skb->tstamp = kt;
        pm->data_len = copy_len;
        pm->mark = skb->mark;
        pm->hook = hooknr;
        if (uloginfo->prefix != NULL)
                strcpy(pm->prefix, uloginfo->prefix);
        else
                *(pm->prefix) = '\0';

        if (in) {
                strcpy(pm->physindev, in->name);
                /* If in isn't a bridge, then physindev==indev */
                if (in->br_port)
                        strcpy(pm->indev, in->br_port->br->dev->name);
                else
                        strcpy(pm->indev, in->name);
        } else
                pm->indev[0] = pm->physindev[0] = '\0';

        if (out) {
                /* If out exists, then out is a bridge port */
                strcpy(pm->physoutdev, out->name);
                strcpy(pm->outdev, out->br_port->br->dev->name);
        } else
                pm->outdev[0] = pm->physoutdev[0] = '\0';

        if (skb_copy_bits(skb, -ETH_HLEN, pm->data, copy_len) < 0)
                BUG();

        if (ub->qlen > 1)
                ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;

        ub->lastnlh = nlh;

        if (ub->qlen >= uloginfo->qthreshold)
                ulog_send(group);
        else if (!timer_pending(&ub->timer)) {
                ub->timer.expires = jiffies + flushtimeout * HZ / 100;
                add_timer(&ub->timer);
        }

unlock:
        spin_unlock_bh(lock);

        return;

nlmsg_failure:
        printk(KERN_CRIT "ebt_ulog: error during NLMSG_PUT. This should "
               "not happen, please report to author.\n");
        goto unlock;
alloc_failure:
        goto unlock;
}

/* this function is registered with the netfilter core */
static void ebt_log_packet(unsigned int pf, unsigned int hooknum,
   const struct sk_buff *skb, const struct net_device *in,
   const struct net_device *out, const struct nf_loginfo *li,
   const char *prefix)
{
        struct ebt_ulog_info loginfo;

        if (!li || li->type != NF_LOG_TYPE_ULOG) {
                loginfo.nlgroup = EBT_ULOG_DEFAULT_NLGROUP;
                loginfo.cprange = 0;
                loginfo.qthreshold = EBT_ULOG_DEFAULT_QTHRESHOLD;
                loginfo.prefix[0] = '\0';
        } else {
                loginfo.nlgroup = li->u.ulog.group;
                loginfo.cprange = li->u.ulog.copy_len;
                loginfo.qthreshold = li->u.ulog.qthreshold;
                strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
        }

        ebt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
}

static void ebt_ulog(const struct sk_buff *skb, unsigned int hooknr,
   const struct net_device *in, const struct net_device *out,
   const void *data, unsigned int datalen)
{
        const struct ebt_ulog_info *uloginfo = data;

        ebt_ulog_packet(hooknr, skb, in, out, uloginfo, NULL);
}


static int ebt_ulog_check(const char *tablename, unsigned int hookmask,
   const struct ebt_entry *e, void *data, unsigned int datalen)
{
        struct ebt_ulog_info *uloginfo = data;

        if (datalen != EBT_ALIGN(sizeof(struct ebt_ulog_info)) ||
            uloginfo->nlgroup > 31)
                return -EINVAL;

        uloginfo->prefix[EBT_ULOG_PREFIX_LEN - 1] = '\0';

        if (uloginfo->qthreshold > EBT_ULOG_MAX_QLEN)
                uloginfo->qthreshold = EBT_ULOG_MAX_QLEN;

        return 0;
}

static struct ebt_watcher ulog __read_mostly = {
        .name           = EBT_ULOG_WATCHER,
        .watcher        = ebt_ulog,
        .check          = ebt_ulog_check,
        .me             = THIS_MODULE,
};

static const struct nf_logger ebt_ulog_logger = {
        .name           = EBT_ULOG_WATCHER,
        .logfn          = &ebt_log_packet,
        .me             = THIS_MODULE,
};

static int __init ebt_ulog_init(void)
{
        int i, ret = 0;

        if (nlbufsiz >= 128*1024) {
                printk(KERN_NOTICE "ebt_ulog: Netlink buffer has to be <= 128kB,"
                       " please try a smaller nlbufsiz parameter.\n");
                return -EINVAL;
        }

        /* initialize ulog_buffers */
        for (i = 0; i < EBT_ULOG_MAXNLGROUPS; i++) {
                setup_timer(&ulog_buffers[i].timer, ulog_timer, i);
                spin_lock_init(&ulog_buffers[i].lock);
        }

        ebtulognl = netlink_kernel_create(&init_net, NETLINK_NFLOG,
                                          EBT_ULOG_MAXNLGROUPS, NULL, NULL,
                                          THIS_MODULE);
        if (!ebtulognl)
                ret = -ENOMEM;
        else if ((ret = ebt_register_watcher(&ulog)))
                netlink_kernel_release(ebtulognl);

        if (ret == 0)
                nf_log_register(PF_BRIDGE, &ebt_ulog_logger);

        return ret;
}

static void __exit ebt_ulog_fini(void)
{
        ebt_ulog_buff_t *ub;
        int i;

        nf_log_unregister(&ebt_ulog_logger);
        ebt_unregister_watcher(&ulog);
        for (i = 0; i < EBT_ULOG_MAXNLGROUPS; i++) {
                ub = &ulog_buffers[i];
                if (timer_pending(&ub->timer))
                        del_timer(&ub->timer);
                spin_lock_bh(&ub->lock);
                if (ub->skb) {
                        kfree_skb(ub->skb);
                        ub->skb = NULL;
                }
                spin_unlock_bh(&ub->lock);
        }
        netlink_kernel_release(ebtulognl);
}

module_init(ebt_ulog_init);
module_exit(ebt_ulog_fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
MODULE_DESCRIPTION("Ebtables: Packet logging to netlink using ULOG");