root/net/netfilter/nfnetlink.c

DEFINITIONS

1. nfnl_lock
2. nfnl_unlock
3. nfnetlink_subsys_register
4. nfnetlink_subsys_unregister
5. nfnetlink_get_subsys
6. nfnetlink_find_client
7. nfnetlink_has_listeners
8. nfnetlink_send
9. nfnetlink_unicast
10. nfnetlink_rcv_msg
11. nfnetlink_rcv
12. nfnetlink_exit
13. nfnetlink_init

/* Netfilter messages via netlink socket. Allows for user space
 * protocol helpers and general trouble making from userspace.
 *
 * (C) 2001 by Jay Schulist <jschlst@samba.org>,
 * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
 * (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
 *
 * Initial netfilter messages via netlink development funded and
 * generally made possible by Network Robots, Inc. (www.networkrobots.com)
 *
 * Further development of this code funded by Astaro AG (http://www.astaro.com)
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/fcntl.h>
#include <linux/skbuff.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <net/sock.h>
#include <net/netlink.h>
#include <linux/init.h>

#include <linux/netlink.h>
#include <linux/netfilter/nfnetlink.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);

static char __initdata nfversion[] = "0.30";

static struct sock *nfnl = NULL;
static const struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
static DEFINE_MUTEX(nfnl_mutex);

static inline void nfnl_lock(void)
{
        mutex_lock(&nfnl_mutex);
}

static inline void nfnl_unlock(void)
{
        mutex_unlock(&nfnl_mutex);
}

int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
{
        nfnl_lock();
        if (subsys_table[n->subsys_id]) {
                nfnl_unlock();
                return -EBUSY;
        }
        subsys_table[n->subsys_id] = n;
        nfnl_unlock();

        return 0;
}
EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);

int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
{
        nfnl_lock();
        subsys_table[n->subsys_id] = NULL;
        nfnl_unlock();

        return 0;
}
EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);

static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
{
        u_int8_t subsys_id = NFNL_SUBSYS_ID(type);

        if (subsys_id >= NFNL_SUBSYS_COUNT)
                return NULL;

        return subsys_table[subsys_id];
}

static inline const struct nfnl_callback *
nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
{
        u_int8_t cb_id = NFNL_MSG_TYPE(type);

        if (cb_id >= ss->cb_count)
                return NULL;

        return &ss->cb[cb_id];
}

int nfnetlink_has_listeners(unsigned int group)
{
        return netlink_has_listeners(nfnl, group);
}
EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);

int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
{
        return nlmsg_notify(nfnl, skb, pid, group, echo, gfp_any());
}
EXPORT_SYMBOL_GPL(nfnetlink_send);

int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
{
        return netlink_unicast(nfnl, skb, pid, flags);
}
EXPORT_SYMBOL_GPL(nfnetlink_unicast);

/* Process one complete nfnetlink message. */
static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
{
        const struct nfnl_callback *nc;
        const struct nfnetlink_subsystem *ss;
        int type, err;

        if (security_netlink_recv(skb, CAP_NET_ADMIN))
                return -EPERM;

        /* All the messages must at least contain nfgenmsg */
        if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
                return 0;

        type = nlh->nlmsg_type;
        ss = nfnetlink_get_subsys(type);
        if (!ss) {
#ifdef CONFIG_KMOD
                nfnl_unlock();
                request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
                nfnl_lock();
                ss = nfnetlink_get_subsys(type);
                if (!ss)
#endif
                        return -EINVAL;
        }

        nc = nfnetlink_find_client(type, ss);
        if (!nc)
                return -EINVAL;

        {
                int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
                u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
                u_int16_t attr_count = ss->cb[cb_id].attr_count;
                struct nlattr *cda[attr_count+1];

                if (likely(nlh->nlmsg_len >= min_len)) {
                        struct nlattr *attr = (void *)nlh + NLMSG_ALIGN(min_len);
                        int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);

                        err = nla_parse(cda, attr_count, attr, attrlen,
                                        ss->cb[cb_id].policy);
                        if (err < 0)
                                return err;
                } else
                        return -EINVAL;

                return nc->call(nfnl, skb, nlh, cda);
        }
}

static void nfnetlink_rcv(struct sk_buff *skb)
{
        nfnl_lock();
        netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
        nfnl_unlock();
}

static void __exit nfnetlink_exit(void)
{
        printk("Removing netfilter NETLINK layer.\n");
        netlink_kernel_release(nfnl);
        return;
}

static int __init nfnetlink_init(void)
{
        printk("Netfilter messages via NETLINK v%s.\n", nfversion);

        nfnl = netlink_kernel_create(&init_net, NETLINK_NETFILTER, NFNLGRP_MAX,
                                     nfnetlink_rcv, NULL, THIS_MODULE);
        if (!nfnl) {
                printk(KERN_ERR "cannot initialize nfnetlink!\n");
                return -1;
        }

        return 0;
}

module_init(nfnetlink_init);
module_exit(nfnetlink_exit);