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![Eric Paris](/assets/img/avatar_default.png)
Once upon a time netlink was not sync and we had to get the effective capabilities from the skb that was being received. Today we instead get the capabilities from the current task. This has rendered the entire purpose of the hook moot as it is now functionally equivalent to the capable() call. Signed-off-by: Eric Paris <eparis@redhat.com>
245 lines
6 KiB
C
245 lines
6 KiB
C
/* Netfilter messages via netlink socket. Allows for user space
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* protocol helpers and general trouble making from userspace.
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*
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* (C) 2001 by Jay Schulist <jschlst@samba.org>,
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* (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
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* (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
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*
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* Initial netfilter messages via netlink development funded and
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* generally made possible by Network Robots, Inc. (www.networkrobots.com)
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*
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* Further development of this code funded by Astaro AG (http://www.astaro.com)
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*
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* This software may be used and distributed according to the terms
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* of the GNU General Public License, incorporated herein by reference.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/socket.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/sockios.h>
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#include <linux/net.h>
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#include <linux/skbuff.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <net/sock.h>
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#include <net/netlink.h>
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#include <linux/init.h>
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#include <linux/netlink.h>
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#include <linux/netfilter/nfnetlink.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
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static char __initdata nfversion[] = "0.30";
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static const struct nfnetlink_subsystem __rcu *subsys_table[NFNL_SUBSYS_COUNT];
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static DEFINE_MUTEX(nfnl_mutex);
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void nfnl_lock(void)
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{
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mutex_lock(&nfnl_mutex);
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}
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EXPORT_SYMBOL_GPL(nfnl_lock);
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void nfnl_unlock(void)
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{
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mutex_unlock(&nfnl_mutex);
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}
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EXPORT_SYMBOL_GPL(nfnl_unlock);
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int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
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{
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nfnl_lock();
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if (subsys_table[n->subsys_id]) {
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nfnl_unlock();
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return -EBUSY;
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}
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rcu_assign_pointer(subsys_table[n->subsys_id], n);
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nfnl_unlock();
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return 0;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
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int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
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{
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nfnl_lock();
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subsys_table[n->subsys_id] = NULL;
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nfnl_unlock();
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synchronize_rcu();
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return 0;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
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static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
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{
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u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
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if (subsys_id >= NFNL_SUBSYS_COUNT)
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return NULL;
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return rcu_dereference(subsys_table[subsys_id]);
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}
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static inline const struct nfnl_callback *
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nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
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{
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u_int8_t cb_id = NFNL_MSG_TYPE(type);
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if (cb_id >= ss->cb_count)
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return NULL;
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return &ss->cb[cb_id];
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}
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int nfnetlink_has_listeners(struct net *net, unsigned int group)
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{
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return netlink_has_listeners(net->nfnl, group);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
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int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
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unsigned group, int echo, gfp_t flags)
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{
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return nlmsg_notify(net->nfnl, skb, pid, group, echo, flags);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_send);
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int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
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{
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return netlink_set_err(net->nfnl, pid, group, error);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_set_err);
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int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags)
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{
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return netlink_unicast(net->nfnl, skb, pid, flags);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_unicast);
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/* Process one complete nfnetlink message. */
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static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
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{
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struct net *net = sock_net(skb->sk);
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const struct nfnl_callback *nc;
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const struct nfnetlink_subsystem *ss;
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int type, err;
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if (!capable(CAP_NET_ADMIN))
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return -EPERM;
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/* All the messages must at least contain nfgenmsg */
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if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(struct nfgenmsg)))
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return 0;
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type = nlh->nlmsg_type;
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replay:
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rcu_read_lock();
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ss = nfnetlink_get_subsys(type);
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if (!ss) {
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#ifdef CONFIG_MODULES
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rcu_read_unlock();
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request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
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rcu_read_lock();
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ss = nfnetlink_get_subsys(type);
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if (!ss)
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#endif
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{
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rcu_read_unlock();
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return -EINVAL;
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}
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}
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nc = nfnetlink_find_client(type, ss);
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if (!nc) {
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rcu_read_unlock();
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return -EINVAL;
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}
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{
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int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
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u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
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struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
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struct nlattr *attr = (void *)nlh + min_len;
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int attrlen = nlh->nlmsg_len - min_len;
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err = nla_parse(cda, ss->cb[cb_id].attr_count,
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attr, attrlen, ss->cb[cb_id].policy);
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if (err < 0)
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return err;
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if (nc->call_rcu) {
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err = nc->call_rcu(net->nfnl, skb, nlh,
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(const struct nlattr **)cda);
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rcu_read_unlock();
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} else {
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rcu_read_unlock();
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nfnl_lock();
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if (rcu_dereference_protected(
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subsys_table[NFNL_SUBSYS_ID(type)],
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lockdep_is_held(&nfnl_mutex)) != ss ||
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nfnetlink_find_client(type, ss) != nc)
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err = -EAGAIN;
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else
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err = nc->call(net->nfnl, skb, nlh,
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(const struct nlattr **)cda);
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nfnl_unlock();
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}
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if (err == -EAGAIN)
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goto replay;
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return err;
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}
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}
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static void nfnetlink_rcv(struct sk_buff *skb)
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{
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netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
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}
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static int __net_init nfnetlink_net_init(struct net *net)
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{
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struct sock *nfnl;
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nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, NFNLGRP_MAX,
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nfnetlink_rcv, NULL, THIS_MODULE);
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if (!nfnl)
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return -ENOMEM;
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net->nfnl_stash = nfnl;
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rcu_assign_pointer(net->nfnl, nfnl);
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return 0;
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}
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static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
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{
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struct net *net;
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list_for_each_entry(net, net_exit_list, exit_list)
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rcu_assign_pointer(net->nfnl, NULL);
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synchronize_net();
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list_for_each_entry(net, net_exit_list, exit_list)
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netlink_kernel_release(net->nfnl_stash);
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}
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static struct pernet_operations nfnetlink_net_ops = {
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.init = nfnetlink_net_init,
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.exit_batch = nfnetlink_net_exit_batch,
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};
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static int __init nfnetlink_init(void)
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{
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pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
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return register_pernet_subsys(&nfnetlink_net_ops);
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}
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static void __exit nfnetlink_exit(void)
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{
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pr_info("Removing netfilter NETLINK layer.\n");
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unregister_pernet_subsys(&nfnetlink_net_ops);
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}
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module_init(nfnetlink_init);
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module_exit(nfnetlink_exit);
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