/*
 * This is a module which is used for logging packets to userspace via
 * nfetlink.
 *
 * (C) 2005 by Harald Welte <laforge@netfilter.org>
 *
 * Based on the old ipv4-only ipt_ULOG.c:
 * (C) 2000-2004 by Harald Welte <laforge@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.
 */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/netlink.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_log.h>
#include <linux/spinlock.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/netfilter/nf_log.h>
#include <net/netfilter/nfnetlink_log.h>

#include <asm/atomic.h>

#ifdef CONFIG_BRIDGE_NETFILTER
#include "../bridge/br_private.h"
#endif

#define NFULNL_NLBUFSIZ_DEFAULT NLMSG_GOODSIZE
#define NFULNL_TIMEOUT_DEFAULT  100     /* every second */
#define NFULNL_QTHRESH_DEFAULT  100     /* 100 packets */
#define NFULNL_COPY_RANGE_MAX   0xFFFF  /* max packet size is limited by 16-bit struct nfattr nfa_len field */

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

struct nfulnl_instance {
        struct hlist_node hlist;        /* global list of instances */
        spinlock_t lock;
        atomic_t use;                   /* use count */

        unsigned int qlen;              /* number of nlmsgs in skb */
        struct sk_buff *skb;            /* pre-allocatd skb */
        struct timer_list timer;
        int peer_pid;                   /* PID of the peer process */

        /* configurable parameters */
        unsigned int flushtimeout;      /* timeout until queue flush */
        unsigned int nlbufsiz;          /* netlink buffer allocation size */
        unsigned int qthreshold;        /* threshold of the queue */
        u_int32_t copy_range;
        u_int32_t seq;                  /* instance-local sequential counter */
        u_int16_t group_num;            /* number of this queue */
        u_int16_t flags;
        u_int8_t copy_mode;
        struct rcu_head rcu;
};

static DEFINE_SPINLOCK(instances_lock);
static atomic_t global_seq;

#define INSTANCE_BUCKETS        16
static struct hlist_head instance_table[INSTANCE_BUCKETS];
static unsigned int hash_init;

static inline u_int8_t instance_hashfn(u_int16_t group_num)
{
        return ((group_num & 0xff) % INSTANCE_BUCKETS);
}

static struct nfulnl_instance *
__instance_lookup(u_int16_t group_num)
{
        struct hlist_head *head;
        struct hlist_node *pos;
        struct nfulnl_instance *inst;

        head = &instance_table[instance_hashfn(group_num)];
        hlist_for_each_entry_rcu(inst, pos, head, hlist) {
                if (inst->group_num == group_num)
                        return inst;
        }
        return NULL;
}

static inline void
instance_get(struct nfulnl_instance *inst)
{
        atomic_inc(&inst->use);
}

static struct nfulnl_instance *
instance_lookup_get(u_int16_t group_num)
{
        struct nfulnl_instance *inst;

        rcu_read_lock_bh();
        inst = __instance_lookup(group_num);
        if (inst && !atomic_inc_not_zero(&inst->use))
                inst = NULL;
        rcu_read_unlock_bh();

        return inst;
}

static void nfulnl_instance_free_rcu(struct rcu_head *head)
{
        kfree(container_of(head, struct nfulnl_instance, rcu));
        module_put(THIS_MODULE);
}

static void
instance_put(struct nfulnl_instance *inst)
{
        if (inst && atomic_dec_and_test(&inst->use))
                call_rcu_bh(&inst->rcu, nfulnl_instance_free_rcu);
}

static void nfulnl_timer(unsigned long data);

static struct nfulnl_instance *
instance_create(u_int16_t group_num, int pid)
{
        struct nfulnl_instance *inst;
        int err;

        spin_lock_bh(&instances_lock);
        if (__instance_lookup(group_num)) {
                err = -EEXIST;
                goto out_unlock;
        }

        inst = kzalloc(sizeof(*inst), GFP_ATOMIC);
        if (!inst) {
                err = -ENOMEM;
                goto out_unlock;
        }

        if (!try_module_get(THIS_MODULE)) {
                kfree(inst);
                err = -EAGAIN;
                goto out_unlock;
        }

        INIT_HLIST_NODE(&inst->hlist);
        spin_lock_init(&inst->lock);
        /* needs to be two, since we _put() after creation */
        atomic_set(&inst->use, 2);

        setup_timer(&inst->timer, nfulnl_timer, (unsigned long)inst);

        inst->peer_pid = pid;
        inst->group_num = group_num;

        inst->qthreshold        = NFULNL_QTHRESH_DEFAULT;
        inst->flushtimeout      = NFULNL_TIMEOUT_DEFAULT;
        inst->nlbufsiz          = NFULNL_NLBUFSIZ_DEFAULT;
        inst->copy_mode         = NFULNL_COPY_PACKET;
        inst->copy_range        = NFULNL_COPY_RANGE_MAX;

        hlist_add_head_rcu(&inst->hlist,
                       &instance_table[instance_hashfn(group_num)]);

        spin_unlock_bh(&instances_lock);

        return inst;

out_unlock:
        spin_unlock_bh(&instances_lock);
        return ERR_PTR(err);
}

static void __nfulnl_flush(struct nfulnl_instance *inst);

/* called with BH disabled */
static void
__instance_destroy(struct nfulnl_instance *inst)
{
        /* first pull it out of the global list */
        hlist_del_rcu(&inst->hlist);

        /* then flush all pending packets from skb */

        spin_lock(&inst->lock);

        /* lockless readers wont be able to use us */
        inst->copy_mode = NFULNL_COPY_DISABLED;

        if (inst->skb)
                __nfulnl_flush(inst);
        spin_unlock(&inst->lock);

        /* and finally put the refcount */
        instance_put(inst);
}

static inline void
instance_destroy(struct nfulnl_instance *inst)
{
        spin_lock_bh(&instances_lock);
        __instance_destroy(inst);
        spin_unlock_bh(&instances_lock);
}

static int
nfulnl_set_mode(struct nfulnl_instance *inst, u_int8_t mode,
                  unsigned int range)
{
        int status = 0;

        spin_lock_bh(&inst->lock);

        switch (mode) {
        case NFULNL_COPY_NONE:
        case NFULNL_COPY_META:
                inst->copy_mode = mode;
                inst->copy_range = 0;
                break;

        case NFULNL_COPY_PACKET:
                inst->copy_mode = mode;
                inst->copy_range = min_t(unsigned int,
                                         range, NFULNL_COPY_RANGE_MAX);
                break;

        default:
                status = -EINVAL;
                break;
        }

        spin_unlock_bh(&inst->lock);

        return status;
}

static int
nfulnl_set_nlbufsiz(struct nfulnl_instance *inst, u_int32_t nlbufsiz)
{
        int status;

        spin_lock_bh(&inst->lock);
        if (nlbufsiz < NFULNL_NLBUFSIZ_DEFAULT)
                status = -ERANGE;
        else if (nlbufsiz > 131072)
                status = -ERANGE;
        else {
                inst->nlbufsiz = nlbufsiz;
                status = 0;
        }
        spin_unlock_bh(&inst->lock);

        return status;
}

static int
nfulnl_set_timeout(struct nfulnl_instance *inst, u_int32_t timeout)
{
        spin_lock_bh(&inst->lock);
        inst->flushtimeout = timeout;
        spin_unlock_bh(&inst->lock);

        return 0;
}

static int
nfulnl_set_qthresh(struct nfulnl_instance *inst, u_int32_t qthresh)
{
        spin_lock_bh(&inst->lock);
        inst->qthreshold = qthresh;
        spin_unlock_bh(&inst->lock);

        return 0;
}

static int
nfulnl_set_flags(struct nfulnl_instance *inst, u_int16_t flags)
{
        spin_lock_bh(&inst->lock);
        inst->flags = flags;
        spin_unlock_bh(&inst->lock);

        return 0;
}

static struct sk_buff *
nfulnl_alloc_skb(unsigned int inst_size, unsigned int pkt_size)
{
        struct sk_buff *skb;
        unsigned int n;

        /* alloc skb which should be big enough for a whole multipart
         * message.  WARNING: has to be <= 128k due to slab restrictions */

        n = max(inst_size, pkt_size);
        skb = alloc_skb(n, GFP_ATOMIC);
        if (!skb) {
                pr_notice("nfnetlink_log: can't alloc whole buffer (%u bytes)\n",
                        inst_size);

                if (n > pkt_size) {
                        /* try to allocate only as much as we need for current
                         * packet */

                        skb = alloc_skb(pkt_size, GFP_ATOMIC);
                        if (!skb)
                                pr_err("nfnetlink_log: can't even alloc %u "
                                       "bytes\n", pkt_size);
                }
        }

        return skb;
}

static int
__nfulnl_send(struct nfulnl_instance *inst)
{
        int status = -1;

        if (inst->qlen > 1)
                NLMSG_PUT(inst->skb, 0, 0,
                          NLMSG_DONE,
                          sizeof(struct nfgenmsg));

        status = nfnetlink_unicast(inst->skb, &init_net, inst->peer_pid,
                                   MSG_DONTWAIT);

        inst->qlen = 0;
        inst->skb = NULL;

nlmsg_failure:
        return status;
}

static void
__nfulnl_flush(struct nfulnl_instance *inst)
{
        /* timer holds a reference */
        if (del_timer(&inst->timer))
                instance_put(inst);
        if (inst->skb)
                __nfulnl_send(inst);
}

static void
nfulnl_timer(unsigned long data)
{
        struct nfulnl_instance *inst = (struct nfulnl_instance *)data;

        spin_lock_bh(&inst->lock);
        if (inst->skb)
                __nfulnl_send(inst);
        spin_unlock_bh(&inst->lock);
        instance_put(inst);
}

/* This is an inline function, we don't really care about a long
 * list of arguments */
static inline int
__build_packet_message(struct nfulnl_instance *inst,
                        const struct sk_buff *skb,
                        unsigned int data_len,
                        u_int8_t pf,
                        unsigned int hooknum,
                        const struct net_device *indev,
                        const struct net_device *outdev,
                        const struct nf_loginfo *li,
                        const char *prefix, unsigned int plen)
{
        struct nfulnl_msg_packet_hdr pmsg;
        struct nlmsghdr *nlh;
        struct nfgenmsg *nfmsg;
        __be32 tmp_uint;
        sk_buff_data_t old_tail = inst->skb->tail;

        nlh = NLMSG_PUT(inst->skb, 0, 0,
                        NFNL_SUBSYS_ULOG << 8 | NFULNL_MSG_PACKET,
                        sizeof(struct nfgenmsg));
        nfmsg = NLMSG_DATA(nlh);
        nfmsg->nfgen_family = pf;
        nfmsg->version = NFNETLINK_V0;
        nfmsg->res_id = htons(inst->group_num);

        pmsg.hw_protocol        = skb->protocol;
        pmsg.hook               = hooknum;

        NLA_PUT(inst->skb, NFULA_PACKET_HDR, sizeof(pmsg), &pmsg);

        if (prefix)
                NLA_PUT(inst->skb, NFULA_PREFIX, plen, prefix);

        if (indev) {
#ifndef CONFIG_BRIDGE_NETFILTER
                NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_INDEV,
                             htonl(indev->ifindex));
#else
                if (pf == PF_BRIDGE) {
                        /* Case 1: outdev is physical input device, we need to
                         * look for bridge group (when called from
                         * netfilter_bridge) */
                        NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_PHYSINDEV,
                                     htonl(indev->ifindex));
                        /* this is the bridge group "brX" */
                        /* rcu_read_lock()ed by nf_hook_slow or nf_log_packet */
                        NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_INDEV,
                                     htonl(br_port_get_rcu(indev)->br->dev->ifindex));
                } else {
                        /* Case 2: indev is bridge group, we need to look for
                         * physical device (when called from ipv4) */
                        NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_INDEV,
                                     htonl(indev->ifindex));
                        if (skb->nf_bridge && skb->nf_bridge->physindev)
                                NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_PHYSINDEV,
                                             htonl(skb->nf_bridge->physindev->ifindex));
                }
#endif
        }

        if (outdev) {
                tmp_uint = htonl(outdev->ifindex);
#ifndef CONFIG_BRIDGE_NETFILTER
                NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_OUTDEV,
                             htonl(outdev->ifindex));
#else
                if (pf == PF_BRIDGE) {
                        /* Case 1: outdev is physical output device, we need to
                         * look for bridge group (when called from
                         * netfilter_bridge) */
                        NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_PHYSOUTDEV,
                                     htonl(outdev->ifindex));
                        /* this is the bridge group "brX" */
                        /* rcu_read_lock()ed by nf_hook_slow or nf_log_packet */
                        NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_OUTDEV,
                                     htonl(br_port_get_rcu(outdev)->br->dev->ifindex));
                } else {
                        /* Case 2: indev is a bridge group, we need to look
                         * for physical device (when called from ipv4) */
                        NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_OUTDEV,
                                     htonl(outdev->ifindex));
                        if (skb->nf_bridge && skb->nf_bridge->physoutdev)
                                NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_PHYSOUTDEV,
                                             htonl(skb->nf_bridge->physoutdev->ifindex));
                }
#endif
        }

        if (skb->mark)
                NLA_PUT_BE32(inst->skb, NFULA_MARK, htonl(skb->mark));

        if (indev && skb->dev) {
                struct nfulnl_msg_packet_hw phw;
                int len = dev_parse_header(skb, phw.hw_addr);
                if (len > 0) {
                        phw.hw_addrlen = htons(len);
                        NLA_PUT(inst->skb, NFULA_HWADDR, sizeof(phw), &phw);
                }
        }

        if (indev && skb_mac_header_was_set(skb)) {
                NLA_PUT_BE16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type));
                NLA_PUT_BE16(inst->skb, NFULA_HWLEN,
                             htons(skb->dev->hard_header_len));
                NLA_PUT(inst->skb, NFULA_HWHEADER, skb->dev->hard_header_len,
                        skb_mac_header(skb));
        }

        if (skb->tstamp.tv64) {
                struct nfulnl_msg_packet_timestamp ts;
                struct timeval tv = ktime_to_timeval(skb->tstamp);
                ts.sec = cpu_to_be64(tv.tv_sec);
                ts.usec = cpu_to_be64(tv.tv_usec);

                NLA_PUT(inst->skb, NFULA_TIMESTAMP, sizeof(ts), &ts);
        }

        /* UID */
        if (skb->sk) {
                read_lock_bh(&skb->sk->sk_callback_lock);
                if (skb->sk->sk_socket && skb->sk->sk_socket->file) {
                        struct file *file = skb->sk->sk_socket->file;
                        __be32 uid = htonl(file->f_cred->fsuid);
                        __be32 gid = htonl(file->f_cred->fsgid);
                        /* need to unlock here since NLA_PUT may goto */
                        read_unlock_bh(&skb->sk->sk_callback_lock);
                        NLA_PUT_BE32(inst->skb, NFULA_UID, uid);
                        NLA_PUT_BE32(inst->skb, NFULA_GID, gid);
                } else
                        read_unlock_bh(&skb->sk->sk_callback_lock);
        }

        /* local sequence number */
        if (inst->flags & NFULNL_CFG_F_SEQ)
                NLA_PUT_BE32(inst->skb, NFULA_SEQ, htonl(inst->seq++));

        /* global sequence number */
        if (inst->flags & NFULNL_CFG_F_SEQ_GLOBAL)
                NLA_PUT_BE32(inst->skb, NFULA_SEQ_GLOBAL,
                             htonl(atomic_inc_return(&global_seq)));

        if (data_len) {
                struct nlattr *nla;
                int size = nla_attr_size(data_len);

                if (skb_tailroom(inst->skb) < nla_total_size(data_len)) {
                        printk(KERN_WARNING "nfnetlink_log: no tailroom!\n");
                        goto nlmsg_failure;
                }

                nla = (struct nlattr *)skb_put(inst->skb, nla_total_size(data_len));
                nla->nla_type = NFULA_PAYLOAD;
                nla->nla_len = size;

                if (skb_copy_bits(skb, 0, nla_data(nla), data_len))
                        BUG();
        }

        nlh->nlmsg_len = inst->skb->tail - old_tail;
        return 0;

nlmsg_failure:
nla_put_failure:
        PRINTR(KERN_ERR "nfnetlink_log: error creating log nlmsg\n");
        return -1;
}

#define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err)); return; } while (0)

static struct nf_loginfo default_loginfo = {
        .type =         NF_LOG_TYPE_ULOG,
        .u = {
                .ulog = {
                        .copy_len       = 0xffff,
                        .group          = 0,
                        .qthreshold     = 1,
                },
        },
};

/* log handler for internal netfilter logging api */
void
nfulnl_log_packet(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_user,
                  const char *prefix)
{
        unsigned int size, data_len;
        struct nfulnl_instance *inst;
        const struct nf_loginfo *li;
        unsigned int qthreshold;
        unsigned int plen;

        if (li_user && li_user->type == NF_LOG_TYPE_ULOG)
                li = li_user;
        else
                li = &default_loginfo;

        inst = instance_lookup_get(li->u.ulog.group);
        if (!inst)
                return;

        plen = 0;
        if (prefix)
                plen = strlen(prefix) + 1;

        /* FIXME: do we want to make the size calculation conditional based on
         * what is actually present?  way more branches and checks, but more
         * memory efficient... */
        size =    NLMSG_SPACE(sizeof(struct nfgenmsg))
                + nla_total_size(sizeof(struct nfulnl_msg_packet_hdr))
                + nla_total_size(sizeof(u_int32_t))     /* ifindex */
                + nla_total_size(sizeof(u_int32_t))     /* ifindex */
#ifdef CONFIG_BRIDGE_NETFILTER
                + nla_total_size(sizeof(u_int32_t))     /* ifindex */
                + nla_total_size(sizeof(u_int32_t))     /* ifindex */
#endif
                + nla_total_size(sizeof(u_int32_t))     /* mark */
                + nla_total_size(sizeof(u_int32_t))     /* uid */
                + nla_total_size(sizeof(u_int32_t))     /* gid */
                + nla_total_size(plen)                  /* prefix */
                + nla_total_size(sizeof(struct nfulnl_msg_packet_hw))
                + nla_total_size(sizeof(struct nfulnl_msg_packet_timestamp));

        if (in && skb_mac_header_was_set(skb)) {
                size +=   nla_total_size(skb->dev->hard_header_len)
                        + nla_total_size(sizeof(u_int16_t))     /* hwtype */
                        + nla_total_size(sizeof(u_int16_t));    /* hwlen */
        }

        spin_lock_bh(&inst->lock);

        if (inst->flags & NFULNL_CFG_F_SEQ)
                size += nla_total_size(sizeof(u_int32_t));
        if (inst->flags & NFULNL_CFG_F_SEQ_GLOBAL)
                size += nla_total_size(sizeof(u_int32_t));

        qthreshold = inst->qthreshold;
        /* per-rule qthreshold overrides per-instance */
        if (li->u.ulog.qthreshold)
                if (qthreshold > li->u.ulog.qthreshold)
                        qthreshold = li->u.ulog.qthreshold;


        switch (inst->copy_mode) {
        case NFULNL_COPY_META:
        case NFULNL_COPY_NONE:
                data_len = 0;
                break;

        case NFULNL_COPY_PACKET:
                if (inst->copy_range == 0
                    || inst->copy_range > skb->len)
                        data_len = skb->len;
                else
                        data_len = inst->copy_range;

                size += nla_total_size(data_len);
                break;

        case NFULNL_COPY_DISABLED:
        default:
                goto unlock_and_release;
        }

        if (inst->skb &&
            size > skb_tailroom(inst->skb) - sizeof(struct nfgenmsg)) {
                /* either the queue len is too high or we don't have
                 * enough room in the skb left. flush to userspace. */
                __nfulnl_flush(inst);
        }

        if (!inst->skb) {
                inst->skb = nfulnl_alloc_skb(inst->nlbufsiz, size);
                if (!inst->skb)
                        goto alloc_failure;
        }

        inst->qlen++;

        __build_packet_message(inst, skb, data_len, pf,
                                hooknum, in, out, li, prefix, plen);

        if (inst->qlen >= qthreshold)
                __nfulnl_flush(inst);
        /* timer_pending always called within inst->lock, so there
         * is no chance of a race here */
        else if (!timer_pending(&inst->timer)) {
                instance_get(inst);
                inst->timer.expires = jiffies + (inst->flushtimeout*HZ/100);
                add_timer(&inst->timer);
        }

unlock_and_release:
        spin_unlock_bh(&inst->lock);
        instance_put(inst);
        return;

alloc_failure:
        /* FIXME: statistics */
        goto unlock_and_release;
}
EXPORT_SYMBOL_GPL(nfulnl_log_packet);

static int
nfulnl_rcv_nl_event(struct notifier_block *this,
                   unsigned long event, void *ptr)
{
        struct netlink_notify *n = ptr;

        if (event == NETLINK_URELEASE && n->protocol == NETLINK_NETFILTER) {
                int i;

                /* destroy all instances for this pid */
                spin_lock_bh(&instances_lock);
                for  (i = 0; i < INSTANCE_BUCKETS; i++) {
                        struct hlist_node *tmp, *t2;
                        struct nfulnl_instance *inst;
                        struct hlist_head *head = &instance_table[i];

                        hlist_for_each_entry_safe(inst, tmp, t2, head, hlist) {
                                if ((net_eq(n->net, &init_net)) &&
                                    (n->pid == inst->peer_pid))
                                        __instance_destroy(inst);
                        }
                }
                spin_unlock_bh(&instances_lock);
        }
        return NOTIFY_DONE;
}

static struct notifier_block nfulnl_rtnl_notifier = {
        .notifier_call  = nfulnl_rcv_nl_event,
};

static int
nfulnl_recv_unsupp(struct sock *ctnl, struct sk_buff *skb,
                   const struct nlmsghdr *nlh,
                   const struct nlattr * const nfqa[])
{
        return -ENOTSUPP;
}

static struct nf_logger nfulnl_logger __read_mostly = {
        .name   = "nfnetlink_log",
        .logfn  = &nfulnl_log_packet,
        .me     = THIS_MODULE,
};

static const struct nla_policy nfula_cfg_policy[NFULA_CFG_MAX+1] = {
        [NFULA_CFG_CMD]         = { .len = sizeof(struct nfulnl_msg_config_cmd) },
        [NFULA_CFG_MODE]        = { .len = sizeof(struct nfulnl_msg_config_mode) },
        [NFULA_CFG_TIMEOUT]     = { .type = NLA_U32 },
        [NFULA_CFG_QTHRESH]     = { .type = NLA_U32 },
        [NFULA_CFG_NLBUFSIZ]    = { .type = NLA_U32 },
        [NFULA_CFG_FLAGS]       = { .type = NLA_U16 },
};

static int
nfulnl_recv_config(struct sock *ctnl, struct sk_buff *skb,
                   const struct nlmsghdr *nlh,
                   const struct nlattr * const nfula[])
{
        struct nfgenmsg *nfmsg = NLMSG_DATA(nlh);
        u_int16_t group_num = ntohs(nfmsg->res_id);
        struct nfulnl_instance *inst;
        struct nfulnl_msg_config_cmd *cmd = NULL;
        int ret = 0;

        if (nfula[NFULA_CFG_CMD]) {
                u_int8_t pf = nfmsg->nfgen_family;
                cmd = nla_data(nfula[NFULA_CFG_CMD]);

                /* Commands without queue context */
                switch (cmd->command) {
                case NFULNL_CFG_CMD_PF_BIND:
                        return nf_log_bind_pf(pf, &nfulnl_logger);
                case NFULNL_CFG_CMD_PF_UNBIND:
                        nf_log_unbind_pf(pf);
                        return 0;
                }
        }

        inst = instance_lookup_get(group_num);
        if (inst && inst->peer_pid != NETLINK_CB(skb).pid) {
                ret = -EPERM;
                goto out_put;
        }

        if (cmd != NULL) {
                switch (cmd->command) {
                case NFULNL_CFG_CMD_BIND:
                        if (inst) {
                                ret = -EBUSY;
                                goto out_put;
                        }

                        inst = instance_create(group_num,
                                               NETLINK_CB(skb).pid);
                        if (IS_ERR(inst)) {
                                ret = PTR_ERR(inst);
                                goto out;
                        }
                        break;
                case NFULNL_CFG_CMD_UNBIND:
                        if (!inst) {
                                ret = -ENODEV;
                                goto out;
                        }

                        instance_destroy(inst);
                        goto out_put;
                default:
                        ret = -ENOTSUPP;
                        break;
                }
        }

        if (nfula[NFULA_CFG_MODE]) {
                struct nfulnl_msg_config_mode *params;
                params = nla_data(nfula[NFULA_CFG_MODE]);

                if (!inst) {
                        ret = -ENODEV;
                        goto out;
                }
                nfulnl_set_mode(inst, params->copy_mode,
                                ntohl(params->copy_range));
        }

        if (nfula[NFULA_CFG_TIMEOUT]) {
                __be32 timeout = nla_get_be32(nfula[NFULA_CFG_TIMEOUT]);

                if (!inst) {
                        ret = -ENODEV;
                        goto out;
                }
                nfulnl_set_timeout(inst, ntohl(timeout));
        }

        if (nfula[NFULA_CFG_NLBUFSIZ]) {
                __be32 nlbufsiz = nla_get_be32(nfula[NFULA_CFG_NLBUFSIZ]);

                if (!inst) {
                        ret = -ENODEV;
                        goto out;
                }
                nfulnl_set_nlbufsiz(inst, ntohl(nlbufsiz));
        }

        if (nfula[NFULA_CFG_QTHRESH]) {
                __be32 qthresh = nla_get_be32(nfula[NFULA_CFG_QTHRESH]);

                if (!inst) {
                        ret = -ENODEV;
                        goto out;
                }
                nfulnl_set_qthresh(inst, ntohl(qthresh));
        }

        if (nfula[NFULA_CFG_FLAGS]) {
                __be16 flags = nla_get_be16(nfula[NFULA_CFG_FLAGS]);

                if (!inst) {
                        ret = -ENODEV;
                        goto out;
                }
                nfulnl_set_flags(inst, ntohs(flags));
        }

out_put:
        instance_put(inst);
out:
        return ret;
}

static const struct nfnl_callback nfulnl_cb[NFULNL_MSG_MAX] = {
        [NFULNL_MSG_PACKET]     = { .call = nfulnl_recv_unsupp,
                                    .attr_count = NFULA_MAX, },
        [NFULNL_MSG_CONFIG]     = { .call = nfulnl_recv_config,
                                    .attr_count = NFULA_CFG_MAX,
                                    .policy = nfula_cfg_policy },
};

static const struct nfnetlink_subsystem nfulnl_subsys = {
        .name           = "log",
        .subsys_id      = NFNL_SUBSYS_ULOG,
        .cb_count       = NFULNL_MSG_MAX,
        .cb             = nfulnl_cb,
};

#ifdef CONFIG_PROC_FS
struct iter_state {
        unsigned int bucket;
};

static struct hlist_node *get_first(struct iter_state *st)
{
        if (!st)
                return NULL;

        for (st->bucket = 0; st->bucket < INSTANCE_BUCKETS; st->bucket++) {
                if (!hlist_empty(&instance_table[st->bucket]))
                        return rcu_dereference_bh(instance_table[st->bucket].first);
        }
        return NULL;
}

static struct hlist_node *get_next(struct iter_state *st, struct hlist_node *h)
{
        h = rcu_dereference_bh(h->next);
        while (!h) {
                if (++st->bucket >= INSTANCE_BUCKETS)
                        return NULL;

                h = rcu_dereference_bh(instance_table[st->bucket].first);
        }
        return h;
}

static struct hlist_node *get_idx(struct iter_state *st, loff_t pos)
{
        struct hlist_node *head;
        head = get_first(st);

        if (head)
                while (pos && (head = get_next(st, head)))
                        pos--;
        return pos ? NULL : head;
}

static void *seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(rcu_bh)
{
        rcu_read_lock_bh();
        return get_idx(seq->private, *pos);
}

static void *seq_next(struct seq_file *s, void *v, loff_t *pos)
{
        (*pos)++;
        return get_next(s->private, v);
}

static void seq_stop(struct seq_file *s, void *v)
        __releases(rcu_bh)
{
        rcu_read_unlock_bh();
}

static int seq_show(struct seq_file *s, void *v)
{
        const struct nfulnl_instance *inst = v;

        return seq_printf(s, "%5d %6d %5d %1d %5d %6d %2d\n",
                          inst->group_num,
                          inst->peer_pid, inst->qlen,
                          inst->copy_mode, inst->copy_range,
                          inst->flushtimeout, atomic_read(&inst->use));
}

static const struct seq_operations nful_seq_ops = {
        .start  = seq_start,
        .next   = seq_next,
        .stop   = seq_stop,
        .show   = seq_show,
};

static int nful_open(struct inode *inode, struct file *file)
{
        return seq_open_private(file, &nful_seq_ops,
                        sizeof(struct iter_state));
}

static const struct file_operations nful_file_ops = {
        .owner   = THIS_MODULE,
        .open    = nful_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release_private,
};

#endif /* PROC_FS */

static int __init nfnetlink_log_init(void)
{
        int i, status = -ENOMEM;

        for (i = 0; i < INSTANCE_BUCKETS; i++)
                INIT_HLIST_HEAD(&instance_table[i]);

        /* it's not really all that important to have a random value, so
         * we can do this from the init function, even if there hasn't
         * been that much entropy yet */
        get_random_bytes(&hash_init, sizeof(hash_init));

        netlink_register_notifier(&nfulnl_rtnl_notifier);
        status = nfnetlink_subsys_register(&nfulnl_subsys);
        if (status < 0) {
                printk(KERN_ERR "log: failed to create netlink socket\n");
                goto cleanup_netlink_notifier;
        }

        status = nf_log_register(NFPROTO_UNSPEC, &nfulnl_logger);
        if (status < 0) {
                printk(KERN_ERR "log: failed to register logger\n");
                goto cleanup_subsys;
        }

#ifdef CONFIG_PROC_FS
        if (!proc_create("nfnetlink_log", 0440,
                         proc_net_netfilter, &nful_file_ops))
                goto cleanup_logger;
#endif
        return status;

#ifdef CONFIG_PROC_FS
cleanup_logger:
        nf_log_unregister(&nfulnl_logger);
#endif
cleanup_subsys:
        nfnetlink_subsys_unregister(&nfulnl_subsys);
cleanup_netlink_notifier:
        netlink_unregister_notifier(&nfulnl_rtnl_notifier);
        return status;
}

static void __exit nfnetlink_log_fini(void)
{
        nf_log_unregister(&nfulnl_logger);
#ifdef CONFIG_PROC_FS
        remove_proc_entry("nfnetlink_log", proc_net_netfilter);
#endif
        nfnetlink_subsys_unregister(&nfulnl_subsys);
        netlink_unregister_notifier(&nfulnl_rtnl_notifier);
}

MODULE_DESCRIPTION("netfilter userspace logging");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_ULOG);

module_init(nfnetlink_log_init);
module_exit(nfnetlink_log_fini);