/*
 * netfilter module for userspace packet logging daemons
 *
 * (C) 2000-2004 by Harald Welte <laforge@netfilter.org>
 * (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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.
 *
 * Actually you should use nlbufsiz a bit smaller than PAGE_SIZE, since
 * nlbufsiz is used with alloc_skb, which adds another
 * sizeof(struct skb_shared_info).  Use NLMSG_GOODSIZE instead.
 *
 * 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/mm.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ipt_ULOG.h>
#include <net/netfilter/nf_log.h>
#include <net/sock.h>
#include <linux/bitops.h>
#include <asm/unaligned.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
MODULE_DESCRIPTION("Xtables: packet logging to netlink using ULOG");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NFLOG);

#define ULOG_NL_EVENT           111             /* Harald's favorite number */
#define ULOG_MAXNLGROUPS        32              /* numer of nlgroups */

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

static unsigned int nlbufsiz = NLMSG_GOODSIZE;
module_param(nlbufsiz, uint, 0400);
MODULE_PARM_DESC(nlbufsiz, "netlink buffer size");

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

static int nflog = 1;
module_param(nflog, bool, 0400);
MODULE_PARM_DESC(nflog, "register as internal netfilter logging module");

/* global data structures */

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 */
} ulog_buff_t;

static ulog_buff_t ulog_buffers[ULOG_MAXNLGROUPS];      /* array of buffers */

static struct sock *nflognl;            /* our socket */
static DEFINE_SPINLOCK(ulog_lock);      /* spinlock */

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

        if (timer_pending(&ub->timer)) {
                pr_debug("ipt_ULOG: ulog_send: timer was pending, deleting\n");
                del_timer(&ub->timer);
        }

        if (!ub->skb) {
                pr_debug("ipt_ULOG: ulog_send: nothing to send\n");
                return;
        }

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

        NETLINK_CB(ub->skb).dst_group = nlgroupnum + 1;
        pr_debug("ipt_ULOG: throwing %d packets to netlink group %u\n",
                 ub->qlen, nlgroupnum + 1);
        netlink_broadcast(nflognl, ub->skb, 0, nlgroupnum + 1, GFP_ATOMIC);

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


/* timer function to flush queue in flushtimeout time */
static void ulog_timer(unsigned long data)
{
        pr_debug("ipt_ULOG: timer function called, calling ulog_send\n");

        /* lock to protect against somebody modifying our structure
         * from ipt_ulog_target at the same time */
        spin_lock_bh(&ulog_lock);
        ulog_send(data);
        spin_unlock_bh(&ulog_lock);
}

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

        /* alloc skb which should be big enough for a whole
         * multipart message. WARNING: has to be <= 131000
         * due to slab allocator restrictions */

        n = max(size, nlbufsiz);
        skb = alloc_skb(n, GFP_ATOMIC);
        if (!skb) {
                PRINTR("ipt_ULOG: can't alloc whole buffer %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("ipt_ULOG: can't even allocate %ub\n",
                                       size);
                }
        }

        return skb;
}

static void ipt_ulog_packet(unsigned int hooknum,
                            const struct sk_buff *skb,
                            const struct net_device *in,
                            const struct net_device *out,
                            const struct ipt_ulog_info *loginfo,
                            const char *prefix)
{
        ulog_buff_t *ub;
        ulog_packet_msg_t *pm;
        size_t size, copy_len;
        struct nlmsghdr *nlh;
        struct timeval tv;

        /* ffs == find first bit set, necessary because userspace
         * is already shifting groupnumber, but we need unshifted.
         * ffs() returns [1..32], we need [0..31] */
        unsigned int groupnum = ffs(loginfo->nl_group) - 1;

        /* calculate the size of the skb needed */
        if (loginfo->copy_range == 0 || loginfo->copy_range > skb->len)
                copy_len = skb->len;
        else
                copy_len = loginfo->copy_range;

        size = NLMSG_SPACE(sizeof(*pm) + copy_len);

        ub = &ulog_buffers[groupnum];

        spin_lock_bh(&ulog_lock);

        if (!ub->skb) {
                if (!(ub->skb = ulog_alloc_skb(size)))
                        goto alloc_failure;
        } else if (ub->qlen >= loginfo->qthreshold ||
                   size > skb_tailroom(ub->skb)) {
                /* either the queue len is too high or we don't have
                 * enough room in nlskb left. send it to userspace. */

                ulog_send(groupnum);

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

        pr_debug("ipt_ULOG: qlen %d, qthreshold %Zu\n", ub->qlen,
                 loginfo->qthreshold);

        /* NLMSG_PUT contains a hidden goto nlmsg_failure !!! */
        nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
                        sizeof(*pm)+copy_len);
        ub->qlen++;

        pm = NLMSG_DATA(nlh);

        /* We might not have a timestamp, get one */
        if (skb->tstamp.tv64 == 0)
                __net_timestamp((struct sk_buff *)skb);

        /* copy hook, prefix, timestamp, payload, etc. */
        pm->data_len = copy_len;
        tv = ktime_to_timeval(skb->tstamp);
        put_unaligned(tv.tv_sec, &pm->timestamp_sec);
        put_unaligned(tv.tv_usec, &pm->timestamp_usec);
        put_unaligned(skb->mark, &pm->mark);
        pm->hook = hooknum;
        if (prefix != NULL)
                strncpy(pm->prefix, prefix, sizeof(pm->prefix));
        else if (loginfo->prefix[0] != '\0')
                strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
        else
                *(pm->prefix) = '\0';

        if (in && in->hard_header_len > 0
            && skb->mac_header != skb->network_header
            && in->hard_header_len <= ULOG_MAC_LEN) {
                memcpy(pm->mac, skb_mac_header(skb), in->hard_header_len);
                pm->mac_len = in->hard_header_len;
        } else
                pm->mac_len = 0;

        if (in)
                strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
        else
                pm->indev_name[0] = '\0';

        if (out)
                strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
        else
                pm->outdev_name[0] = '\0';

        /* copy_len <= skb->len, so can't fail. */
        if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
                BUG();

        /* check if we are building multi-part messages */
        if (ub->qlen > 1)
                ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;

        ub->lastnlh = nlh;

        /* if timer isn't already running, start it */
        if (!timer_pending(&ub->timer)) {
                ub->timer.expires = jiffies + flushtimeout * HZ / 100;
                add_timer(&ub->timer);
        }

        /* if threshold is reached, send message to userspace */
        if (ub->qlen >= loginfo->qthreshold) {
                if (loginfo->qthreshold > 1)
                        nlh->nlmsg_type = NLMSG_DONE;
                ulog_send(groupnum);
        }

        spin_unlock_bh(&ulog_lock);

        return;

nlmsg_failure:
        PRINTR("ipt_ULOG: error during NLMSG_PUT\n");

alloc_failure:
        PRINTR("ipt_ULOG: Error building netlink message\n");

        spin_unlock_bh(&ulog_lock);
}

static unsigned int
ulog_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        ipt_ulog_packet(par->hooknum, skb, par->in, par->out,
                        par->targinfo, NULL);
        return XT_CONTINUE;
}

static void ipt_logfn(u_int8_t 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 ipt_ulog_info loginfo;

        if (!li || li->type != NF_LOG_TYPE_ULOG) {
                loginfo.nl_group = ULOG_DEFAULT_NLGROUP;
                loginfo.copy_range = 0;
                loginfo.qthreshold = ULOG_DEFAULT_QTHRESHOLD;
                loginfo.prefix[0] = '\0';
        } else {
                loginfo.nl_group = li->u.ulog.group;
                loginfo.copy_range = li->u.ulog.copy_len;
                loginfo.qthreshold = li->u.ulog.qthreshold;
                strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
        }

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

static bool ulog_tg_check(const struct xt_tgchk_param *par)
{
        const struct ipt_ulog_info *loginfo = par->targinfo;

        if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
                pr_debug("ipt_ULOG: prefix term %i\n",
                         loginfo->prefix[sizeof(loginfo->prefix) - 1]);
                return false;
        }
        if (loginfo->qthreshold > ULOG_MAX_QLEN) {
                pr_debug("ipt_ULOG: queue threshold %Zu > MAX_QLEN\n",
                         loginfo->qthreshold);
                return false;
        }
        return true;
}

#ifdef CONFIG_COMPAT
struct compat_ipt_ulog_info {
        compat_uint_t   nl_group;
        compat_size_t   copy_range;
        compat_size_t   qthreshold;
        char            prefix[ULOG_PREFIX_LEN];
};

static void ulog_tg_compat_from_user(void *dst, void *src)
{
        const struct compat_ipt_ulog_info *cl = src;
        struct ipt_ulog_info l = {
                .nl_group       = cl->nl_group,
                .copy_range     = cl->copy_range,
                .qthreshold     = cl->qthreshold,
        };

        memcpy(l.prefix, cl->prefix, sizeof(l.prefix));
        memcpy(dst, &l, sizeof(l));
}

static int ulog_tg_compat_to_user(void __user *dst, void *src)
{
        const struct ipt_ulog_info *l = src;
        struct compat_ipt_ulog_info cl = {
                .nl_group       = l->nl_group,
                .copy_range     = l->copy_range,
                .qthreshold     = l->qthreshold,
        };

        memcpy(cl.prefix, l->prefix, sizeof(cl.prefix));
        return copy_to_user(dst, &cl, sizeof(cl)) ? -EFAULT : 0;
}
#endif /* CONFIG_COMPAT */

static struct xt_target ulog_tg_reg __read_mostly = {
        .name           = "ULOG",
        .family         = NFPROTO_IPV4,
        .target         = ulog_tg,
        .targetsize     = sizeof(struct ipt_ulog_info),
        .checkentry     = ulog_tg_check,
#ifdef CONFIG_COMPAT
        .compatsize     = sizeof(struct compat_ipt_ulog_info),
        .compat_from_user = ulog_tg_compat_from_user,
        .compat_to_user = ulog_tg_compat_to_user,
#endif
        .me             = THIS_MODULE,
};

static struct nf_logger ipt_ulog_logger __read_mostly = {
        .name           = "ipt_ULOG",
        .logfn          = ipt_logfn,
        .me             = THIS_MODULE,
};

static int __init ulog_tg_init(void)
{
        int ret, i;

        pr_debug("ipt_ULOG: init module\n");

        if (nlbufsiz > 128*1024) {
                printk("Netlink buffer has to be <= 128kB\n");
                return -EINVAL;
        }

        /* initialize ulog_buffers */
        for (i = 0; i < ULOG_MAXNLGROUPS; i++)
                setup_timer(&ulog_buffers[i].timer, ulog_timer, i);

        nflognl = netlink_kernel_create(&init_net,
                                        NETLINK_NFLOG, ULOG_MAXNLGROUPS, NULL,
                                        NULL, THIS_MODULE);
        if (!nflognl)
                return -ENOMEM;

        ret = xt_register_target(&ulog_tg_reg);
        if (ret < 0) {
                netlink_kernel_release(nflognl);
                return ret;
        }
        if (nflog)
                nf_log_register(NFPROTO_IPV4, &ipt_ulog_logger);

        return 0;
}

static void __exit ulog_tg_exit(void)
{
        ulog_buff_t *ub;
        int i;

        pr_debug("ipt_ULOG: cleanup_module\n");

        if (nflog)
                nf_log_unregister(&ipt_ulog_logger);
        xt_unregister_target(&ulog_tg_reg);
        netlink_kernel_release(nflognl);

        /* remove pending timers and free allocated skb's */
        for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
                ub = &ulog_buffers[i];
                if (timer_pending(&ub->timer)) {
                        pr_debug("timer was pending, deleting\n");
                        del_timer(&ub->timer);
                }

                if (ub->skb) {
                        kfree_skb(ub->skb);
                        ub->skb = NULL;
                }
        }
}

module_init(ulog_tg_init);
module_exit(ulog_tg_exit);