net_namespace.h

/*
 * Operations on the network namespace
 */
#ifndef __NET_NET_NAMESPACE_H
#define __NET_NET_NAMESPACE_H

#include <asm/atomic.h>
#include <linux/workqueue.h>
#include <linux/list.h>

#include <net/netns/core.h>
#include <net/netns/mib.h>
#include <net/netns/unix.h>
#include <net/netns/packet.h>
#include <net/netns/ipv4.h>
#include <net/netns/ipv6.h>
#include <net/netns/dccp.h>
#include <net/netns/x_tables.h>
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
#include <net/netns/conntrack.h>
#endif
#include <net/netns/xfrm.h>

/*struct proc_dir_entry;
struct net_device;
struct sock;
struct ctl_table_header;
struct net_generic;
struct sock;
*/

#define NETDEV_HASHBITS    8
#define NETDEV_HASHENTRIES (1 << NETDEV_HASHBITS)

struct neAAt {
	atomic_t		count;		/* To decided when the network
						 *  namespace should be freed.
						 */
#ifdef NETNS_REFCNT_DEBUG
	atomic_t		use_count;	/* To track references we
						 * destroy on demand
						 */
#endif
	struct list_head	list;		/* list of network namespaces */
	struct list_head	cleanup_list;	/* namespaces on death row */
	struct list_head	exit_list;	/* Use only net_mutex */

	struct proc_dir_entry 	*proc_net;
	struct proc_dir_entry 	*proc_net_stat;

#ifdef CONFIG_SYSCTL
	struct ctl_table_set	sysctls;
#endif

	struct net_device       *loopback_dev;          /* The loopback */

	struct list_head 	dev_base_head;
	struct hlist_head 	*dev_name_head; //dev name链表，查找dev的时候可以根据eth0做键值找  struct net_dev
	struct hlist_head	*dev_index_head; //dev索引号，创建dev的时候，都会有一个，不会重复

	/* core fib_rules */
	struct list_head	rules_ops;
	spinlock_t		rules_mod_lock;

	struct sock 		*rtnl;			/* rtnetlink socket */
	struct sock		*genl_sock;

	struct netns_core	core;
	struct netns_mib	mib;
	struct netns_packet	packet;
	struct netns_unix	unx;
	struct netns_ipv4	ipv4;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
	struct netns_ipv6	ipv6;
#endif
#if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE)
	struct netns_dccp	dccp;
#endif
#ifdef CONFIG_NETFILTER
	struct netns_xt		xt;
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	struct netns_ct		ct;
#endif
	struct sock		*nfnl;
	struct sock		*nfnl_stash;
#endif
#ifdef CONFIG_XFRM
	struct netns_xfrm	xfrm;
#endif
#ifdef CONFIG_WEXT_CORE
	struct sk_buff_head	wext_nlevents;
#endif
	struct net_generic	*gen;
};

struct proc_dir_entry;
struct net_device;
struct sock;
struct ctl_table_header;
struct net_generic;
struct sock;

//可以通过sock_net(skb->sk);获取
struct net {
     /* 用于判断何时释放网络命名空间
         在使用特定的net实例前后，需要分别调用
         辅助函数get_net和put_net
     */
	atomic_t		count;		/* To decided when the network
						 *  namespace should be freed.
						 */
#ifdef NETNS_REFCNT_DEBUG
	atomic_t		use_count;	/* To track references we
						 * destroy on demand
						 */
#endif
       /* 网络命名空间的链接 */
	struct list_head	list;		/* list of network namespaces */
	struct work_struct	work;		/* work struct for freeing */

       /*  由于每个命名空间都包含不同的网络设备，
        *  这必然会反映到procfs的内容上。
        *  各命名空间的处理需要三个数据项:
        *  /proc/net由proc_net表示，而/proc/net/stat由proc_net_stats
        *  表示，proc_net_root(现在已不用)指向当前命名空间的procfs实例
        *  的根节点,即/proc
        */
	struct proc_dir_entry 	*proc_net;
	struct proc_dir_entry 	*proc_net_stat;

#ifdef CONFIG_SYSCTL
	struct ctl_table_set	sysctls;
#endif
       /* 环回接口设备*/
	struct net_device       *loopback_dev;          /* The loopback */

       /* 与特定命名空间关联的所有设备都保存在
         * 一个双向链表上，表头为dev_base_head 
         */ //所有的net_device都添加到该链表中
    //struct net_device会添加到struct net的下面的dev_base_head链表中，同时散列到dev_name_head和dev_index_head中,见樊东东上P72
    //通过list_netdevice添加到该链表和下面的hash表中
    //dev_getbyhwaddr   __dev_getfirstbyhwtype    dev_get_by_flags      通过for_each_netdev变量dev_base_head链表
	struct list_head 	dev_base_head; //见list_netdevice            一般基于MAC地址或者设备类型就用该链表查找，基于接口名或者索引使用下面两个查找
       /*
         * 将设备名作为散列键的链表
         *///dev_get_by_name
	struct hlist_head 	*dev_name_head;//dev name链表，查找dev的时候可以根据eth0做键值找  struct net_dev   
       /*
         * 将接口索引用作散列键
         *///dev_get_by_index
	struct hlist_head	*dev_index_head;//dev索引号，创建dev的时候，都会有一个，不会重复

	/* core fib_rules */
	struct list_head	rules_ops;
	spinlock_t		rules_mod_lock;

	struct sock 		*rtnl;			/* rtnetlink socket */
	struct sock		*genl_sock;

	struct netns_core	core;
	struct netns_mib	mib;
	struct netns_packet	packet;
	struct netns_unix	unx;
	struct netns_ipv4	ipv4;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
	struct netns_ipv6	ipv6;
#endif
#if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE)
	struct netns_dccp	dccp;
#endif
#ifdef CONFIG_NETFILTER
	struct netns_xt		xt;
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	struct netns_ct		ct;
#endif
#endif
#ifdef CONFIG_XFRM
	struct netns_xfrm	xfrm;
#endif
#ifdef CONFIG_WIRELESS_EXT
	struct sk_buff_head	wext_nlevents;
#endif
	struct net_generic	*gen;
};


#include <linux/seq_file_net.h>

/* Init's network namespace */
extern struct net init_net;

#ifdef CONFIG_NET
extern struct net *copy_net_ns(unsigned long flags, struct net *net_ns);

#else /* CONFIG_NET */
static inline struct net *copy_net_ns(unsigned long flags, struct net *net_ns)
{
	/* There is nothing to copy so this is a noop */
	return net_ns;
}
#endif /* CONFIG_NET */


extern struct list_head net_namespace_list;//init_net有加到该链表中

extern struct net *get_net_ns_by_pid(pid_t pid);

#ifdef CONFIG_NET_NS
extern void __put_net(struct net *net);

static inline struct net *get_net(struct net *net)
{
	atomic_inc(&net->count);
	return net;
}

static inline struct net *maybe_get_net(struct net *net)
{
	/* Used when we know struct net exists but we
	 * aren't guaranteed a previous reference count
	 * exists.  If the reference count is zero this
	 * function fails and returns NULL.
	 */
	if (!atomic_inc_not_zero(&net->count))
		net = NULL;
	return net;
}

static inline void put_net(struct net *net)
{
	if (atomic_dec_and_test(&net->count))
		__put_net(net);
}

static inline
int net_eq(const struct net *net1, const struct net *net2)
{
	return net1 == net2;
}
#else

static inline struct net *get_net(struct net *net)
{
	return net;
}

static inline void put_net(struct net *net)
{
}

static inline struct net *maybe_get_net(struct net *net)
{
	return net;
}

static inline
int net_eq(const struct net *net1, const struct net *net2)
{
	return 1;
}
#endif


#ifdef NETNS_REFCNT_DEBUG
static inline struct net *hold_net(struct net *net)
{
	if (net)
		atomic_inc(&net->use_count);
	return net;
}

static inline void release_net(struct net *net)
{
	if (net)
		atomic_dec(&net->use_count);
}
#else
static inline struct net *hold_net(struct net *net)
{
	return net;
}

static inline void release_net(struct net *net)
{
}
#endif

#ifdef CONFIG_NET_NS

static inline void write_pnet(struct net **pnet, struct net *net)
{
	*pnet = net;
}

static inline struct net *read_pnet(struct net * const *pnet)
{
	return *pnet;
}

#else

#define write_pnet(pnet, net)	do { (void)(net);} while (0)
#define read_pnet(pnet)		(&init_net)

#endif

#define for_each_net(VAR)				\
	list_for_each_entry(VAR, &net_namespace_list, list)

#define for_each_net_rcu(VAR)				\
	list_for_each_entry_rcu(VAR, &net_namespace_list, list)

#ifdef CONFIG_NET_NS
#define __net_init
#define __net_exit
#define __net_initdata
#else
#define __net_init	__init
#define __net_exit	__exit_refok
#define __net_initdata	__initdata
#endif

struct pernet_operations {
	struct list_head list;
	int (*init)(struct net *net);
	void (*exit)(struct net *net);
	void (*exit_batch)(struct list_head *net_exit_list);
	int *id;
	size_t size;
};

/*
 * Use these carefully.  If you implement a network device and it
 * needs per network namespace operations use device pernet operations,
 * otherwise use pernet subsys operations.
 *
 * Network interfaces need to be removed from a dying netns _before_
 * subsys notifiers can be called, as most of the network code cleanup
 * (which is done from subsys notifiers) runs with the assumption that
 * dev_remove_pack has been called so no new packets will arrive during
 * and after the cleanup functions have been called.  dev_remove_pack
 * is not per namespace so instead the guarantee of no more packets
 * arriving in a network namespace is provided by ensuring that all
 * network devices and all sockets have left the network namespace
 * before the cleanup methods are called.
 *
 * For the longest time the ipv4 icmp code was registered as a pernet
 * device which caused kernel oops, and panics during network
 * namespace cleanup.   So please don't get this wrong.
 */
extern int register_pernet_subsys(struct pernet_operations *);
extern void unregister_pernet_subsys(struct pernet_operations *);
extern int register_pernet_device(struct pernet_operations *);
extern void unregister_pernet_device(struct pernet_operations *);

struct ctl_path;
struct ctl_table;
struct ctl_table_header;

extern struct ctl_table_header *register_net_sysctl_table(struct net *net,
	const struct ctl_path *path, struct ctl_table *table);
extern struct ctl_table_header *register_net_sysctl_rotable(
	const struct ctl_path *path, struct ctl_table *table);
extern void unregister_net_sysctl_table(struct ctl_table_header *header);

#endif /* __NET_NET_NAMESPACE_H */