nfnetlink_log.c

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/*
 * This is a module which is used for logging packets to userspace via
 * nfetlink.
 *
 * (C) 2005 by Harald Welte <[email protected]>
 *
 * Based on the old ipv4-only ipt_ULOG.c:
 * (C) 2000-2004 by Harald Welte <[email protected]>
 *
 * 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 <linux/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;
    struct user_namespace *peer_user_ns;    /* User namespace of the peer process */
    int peer_portid;            /* PORTID 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 portid, struct user_namespace *user_ns)
{
    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_user_ns = user_ns;
    inst->peer_portid = portid;
    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) {
        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) {
        struct nlmsghdr *nlh = nlmsg_put(inst->skb, 0, 0,
                         NLMSG_DONE,
                         sizeof(struct nfgenmsg),
                         0);
        if (!nlh)
            goto out;
    }
    status = nfnetlink_unicast(inst->skb, &init_net, inst->peer_portid,
                   MSG_DONTWAIT);

    inst->qlen = 0;
    inst->skb = NULL;
out:
    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 char *prefix, unsigned int plen)
{
    struct nfulnl_msg_packet_hdr pmsg;
    struct nlmsghdr *nlh;
    struct nfgenmsg *nfmsg;
    sk_buff_data_t old_tail = inst->skb->tail;
    struct sock *sk;

    nlh = nlmsg_put(inst->skb, 0, 0,
            NFNL_SUBSYS_ULOG << 8 | NFULNL_MSG_PACKET,
            sizeof(struct nfgenmsg), 0);
    if (!nlh)
        return -1;
    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;

    if (nla_put(inst->skb, NFULA_PACKET_HDR, sizeof(pmsg), &pmsg))
        goto nla_put_failure;

    if (prefix &&
        nla_put(inst->skb, NFULA_PREFIX, plen, prefix))
        goto nla_put_failure;

    if (indev) {
#ifndef CONFIG_BRIDGE_NETFILTER
        if (nla_put_be32(inst->skb, NFULA_IFINDEX_INDEV,
                 htonl(indev->ifindex)))
            goto nla_put_failure;
#else
        if (pf == PF_BRIDGE) {
            /* Case 1: outdev is physical input device, we need to
             * look for bridge group (when called from
             * netfilter_bridge) */
            if (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)))
                goto nla_put_failure;
        } else {
            /* Case 2: indev is bridge group, we need to look for
             * physical device (when called from ipv4) */
            if (nla_put_be32(inst->skb, NFULA_IFINDEX_INDEV,
                     htonl(indev->ifindex)))
                goto nla_put_failure;
            if (skb->nf_bridge && skb->nf_bridge->physindev &&
                nla_put_be32(inst->skb, NFULA_IFINDEX_PHYSINDEV,
                     htonl(skb->nf_bridge->physindev->ifindex)))
                goto nla_put_failure;
        }
#endif
    }

    if (outdev) {
#ifndef CONFIG_BRIDGE_NETFILTER
        if (nla_put_be32(inst->skb, NFULA_IFINDEX_OUTDEV,
                 htonl(outdev->ifindex)))
            goto nla_put_failure;
#else
        if (pf == PF_BRIDGE) {
            /* Case 1: outdev is physical output device, we need to
             * look for bridge group (when called from
             * netfilter_bridge) */
            if (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)))
                goto nla_put_failure;
        } else {
            /* Case 2: indev is a bridge group, we need to look
             * for physical device (when called from ipv4) */
            if (nla_put_be32(inst->skb, NFULA_IFINDEX_OUTDEV,
                     htonl(outdev->ifindex)))
                goto nla_put_failure;
            if (skb->nf_bridge && skb->nf_bridge->physoutdev &&
                nla_put_be32(inst->skb, NFULA_IFINDEX_PHYSOUTDEV,
                     htonl(skb->nf_bridge->physoutdev->ifindex)))
                goto nla_put_failure;
        }
#endif
    }

    if (skb->mark &&
        nla_put_be32(inst->skb, NFULA_MARK, htonl(skb->mark)))
        goto nla_put_failure;

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

    if (indev && skb_mac_header_was_set(skb)) {
        if (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)))
            goto nla_put_failure;
    }

    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);

        if (nla_put(inst->skb, NFULA_TIMESTAMP, sizeof(ts), &ts))
            goto nla_put_failure;
    }

    /* UID */
    sk = skb->sk;
    if (sk && sk->sk_state != TCP_TIME_WAIT) {
        read_lock_bh(&sk->sk_callback_lock);
        if (sk->sk_socket && sk->sk_socket->file) {
            struct file *file = sk->sk_socket->file;
            const struct cred *cred = file->f_cred;
            struct user_namespace *user_ns = inst->peer_user_ns;
            __be32 uid = htonl(from_kuid_munged(user_ns, cred->fsuid));
            __be32 gid = htonl(from_kgid_munged(user_ns, cred->fsgid));
            read_unlock_bh(&sk->sk_callback_lock);
            if (nla_put_be32(inst->skb, NFULA_UID, uid) ||
                nla_put_be32(inst->skb, NFULA_GID, gid))
                goto nla_put_failure;
        } else
            read_unlock_bh(&sk->sk_callback_lock);
    }

    /* local sequence number */
    if ((inst->flags & NFULNL_CFG_F_SEQ) &&
        nla_put_be32(inst->skb, NFULA_SEQ, htonl(inst->seq++)))
        goto nla_put_failure;

    /* 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))))
        goto nla_put_failure;

    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");
            return -1;
        }

        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;

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, 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 portid */
        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->portid == inst->peer_portid))
                    __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_portid != NETLINK_CB(skb).portid) {
        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).portid,
                           sk_user_ns(NETLINK_CB(skb).ssk));
            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(hlist_first_rcu(&instance_table[st->bucket]));
    }
    return NULL;
}

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

        h = rcu_dereference_bh(hlist_first_rcu(&instance_table[st->bucket]));
    }
    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_portid, 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)) {
        status = -ENOMEM;
        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 <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_ULOG);

module_init(nfnetlink_log_init);
module_exit(nfnetlink_log_fini);