在Linux系統中，網絡設備都被抽象為struct net_device結構體。它是網絡設備硬件與上層協議之間聯系的接口，了解它對編寫網絡驅動程序非常有益，所以本文將著手簡要介紹linux-2.6.38.8/include/linux/netdevice.h文件中struct net_device結構體的所有成員（沒有按照它們定義的順序）。

1、網絡設備相關信息

（1）、設備名?

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char????name[IFNAMSIZ];??

char????*ifalias;??//用于SNMP協議??

在Linux系統中，每個網絡設備都有一個唯一的設備名（如eth0，字母部分代表網絡設備的類型，數字部分代表此類網絡設備的數量）。

（2）、電源管理服務質量（?power managementQuality Of Service）?

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struct?pm_qos_request_list?pm_qos_req;??

用于Wi-Fi和千兆以太網，可以幫助控制網絡的延遲和帶寬的需求，以達到在可用的前提下省電的目的。

（3）、硬件信息?

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//網絡設備內存映射時在主機中的內存區域??

unsigned?long???mem_end;??

unsigned?long???mem_start;??

//網絡設備I/O基地址??

unsigned?long???base_addr;??

//中斷號??

unsigned?int????irq;??

//傳輸介質，如雙絞線、同軸電纜等，在多端口設備中指定使用哪個端口??

unsigned?char???if_port;??

/*?if_port可能的取值如下：?

enum?{?

IF_PORT_UNKNOWN?=?0,?

IF_PORT_10BASE2,?

IF_PORT_10BASET,?

IF_PORT_AUI,?

IF_PORT_100BASET,?

IF_PORT_100BASETX,?

IF_PORT_100BASEFX?

};?

**/???

//?DMA通道??

unsigned?char???dma;??

//最大傳輸單元，以太網數據幀最大為1500字節??

unsigned?int????mtu;??

//網絡設備硬件類型，如10Mbps以太網ARPHRD_ETHER??

unsigned?short??type;??

//硬件數據幀頭的長度，以太網為14字節??

unsigned?short??hard_header_len;??

//廣播地址??

unsigned?char???broadcast[MAX_ADDR_LEN];??

//硬件(如MAC)地址長度以及設備的硬件地址??

unsigned?char???addr_len;??

unsigned?char???*dev_addr;??

unsigned?char???perm_addr[MAX_ADDR_LEN];??

unsigned?char???addr_assign_type;??

（4）、標識符?

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int?ifindex;?//標識網絡設備的唯一索引號??

int?iflink;??//用于虛擬網絡設備??

unsigned?short??dev_id;?//用于共享網絡設備??

（5）、分配套接字緩沖區時預留空間的長度?

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unsigned?short??needed_headroom;??

unsigned?short??needed_tailroom;??

（6）、在sysfs文件系統中輸出網絡設備信息?

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struct?device???dev;??

const?struct?attribute_group?*sysfs_groups[4];??

（7）、網絡設備相關鏈表?

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//以設備名為關鍵字的網絡設備哈希鏈表??

struct?hlist_node???name_hlist;??

//網絡設備鏈表??

struct?list_head????dev_list;??

//支持NAPI傳輸的網絡設備鏈表??

struct?list_head????napi_list;??

//被注銷的網絡設備鏈表??

struct?list_head????unreg_list;??

//網絡設備硬件地址組成的鏈表??

struct?netdev_hw_addr_list??dev_addrs;???

/*?n-tuple?filter?list?attached?to?this?device?*/??

struct?ethtool_rx_ntuple_list?ethtool_ntuple_list;??

//單播地址鏈表??

struct?netdev_hw_addr_list??uc;??

//組播地址鏈表??

struct?netdev_hw_addr_list??mc;??

//防止單播地址鏈表和組播地址鏈表被并發訪問的自旋鎖??

spinlock_t??????addr_list_lock;??

//監聽所有組播地址??

unsigned?int????????allmulti;??

//延遲注冊/注銷的網絡設備鏈表??

struct?list_head????todo_list;??

//以索引號為關鍵字的網絡設備哈希鏈表??

struct?hlist_node???index_hlist;??

//鏈路查看機制鏈表??

struct?list_head????link_watch_list;??

（8）、混雜模式?

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//混雜模式時的單播地址個數??

int?????uc_promisc;??

//混雜模式的計數器??

unsigned?int????promiscuity;??

（9）、網絡層協議特定數據?

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struct?vlan_group?__rcu?*vlgrp;?????/*?VLAN?group?*/??

void????????????*dsa_ptr;???/*?dsa?specific?data?*/??

void????????????*atalk_ptr;?/*?AppleTalk?link???*/??

struct?in_device?__rcu??*ip_ptr;????/*?IPv4?specific?data???*/??

struct?dn_dev?__rcu?????*dn_ptr;????????/*?DECnet?specific?data?*/??

struct?inet6_dev?__rcu??*ip6_ptr;???????/*?IPv6?specific?data?*/??

void????????????*ec_ptr;????/*?Econet?specific?data?*/??

void????????????*ax25_ptr;??/*?AX.25?specific?data?*/??

struct?wireless_dev?*ieee80211_ptr;?/*?IEEE?802.11?specific?data,?

assign?before?registering?*/??

（10）、設備硬件功能特性?

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unsigned?long???????features;??

//?features的可能取值如下：??

#define?NETIF_F_SG??????1???/*?Scatter/gather?IO.?*/??

#define?NETIF_F_IP_CSUM?????2???/*?Can?checksum?TCP/UDP?over?IPv4.?*/??

#define?NETIF_F_NO_CSUM?????4???/*?Does?not?require?checksum.?F.e.?loopack.?*/??

#define?NETIF_F_HW_CSUM?????8???/*?Can?checksum?all?the?packets.?*/??

#define?NETIF_F_IPV6_CSUM???16??/*?Can?checksum?TCP/UDP?over?IPV6?*/??

#define?NETIF_F_HIGHDMA?????32??/*?Can?DMA?to?high?memory.?*/??

#define?NETIF_F_FRAGLIST????64??/*?Scatter/gather?IO.?*/??

#define?NETIF_F_HW_VLAN_TX??128?/*?Transmit?VLAN?hw?acceleration?*/??

#define?NETIF_F_HW_VLAN_RX??256?/*?Receive?VLAN?hw?acceleration?*/??

#define?NETIF_F_HW_VLAN_FILTER??512?/*?Receive?filtering?on?VLAN?*/??

#define?NETIF_F_VLAN_CHALLENGED?1024????/*?Device?cannot?handle?VLAN?packets?*/??

#define?NETIF_F_GSO?????2048????/*?Enable?software?GSO.?*/??

#define?NETIF_F_LLTX????????4096????/*?LockLess?TX?-?deprecated.?Please?*/??

/*?do?not?use?LLTX?in?new?drivers?*/??

#define?NETIF_F_NETNS_LOCAL?8192????/*?Does?not?change?network?namespaces?*/??

#define?NETIF_F_GRO?????16384???/*?Generic?receive?offload?*/??

#define?NETIF_F_LRO?????32768???/*?large?receive?offload?*/??

#define?NETIF_F_FCOE_CRC????(1?<

#define?NETIF_F_SCTP_CSUM???(1?<

#define?NETIF_F_FCOE_MTU????(1?<

#define?NETIF_F_NTUPLE??????(1?<

#define?NETIF_F_RXHASH??????(1?<

#define?NETIF_F_GSO_SHIFT???16??

#define?NETIF_F_GSO_MASK????0x00ff0000??

#define?NETIF_F_TSO?????(SKB_GSO_TCPV4?<

#define?NETIF_F_UFO?????(SKB_GSO_UDP?<

#define?NETIF_F_GSO_ROBUST??(SKB_GSO_DODGY?<

#define?NETIF_F_TSO_ECN?????(SKB_GSO_TCP_ECN?<

#define?NETIF_F_TSO6????????(SKB_GSO_TCPV6?<

#define?NETIF_F_FSO?????(SKB_GSO_FCOE?<

#define?NETIF_F_GSO_SOFTWARE????(NETIF_F_TSO?|?NETIF_F_TSO_ECN?|?\??

NETIF_F_TSO6?|?NETIF_F_UFO)??

#define?NETIF_F_GEN_CSUM????(NETIF_F_NO_CSUM?|?NETIF_F_HW_CSUM)??

#define?NETIF_F_V4_CSUM?????(NETIF_F_GEN_CSUM?|?NETIF_F_IP_CSUM)??

#define?NETIF_F_V6_CSUM?????(NETIF_F_GEN_CSUM?|?NETIF_F_IPV6_CSUM)??

#define?NETIF_F_ALL_CSUM????(NETIF_F_V4_CSUM?|?NETIF_F_V6_CSUM)??

#define?NETIF_F_ONE_FOR_ALL?(NETIF_F_GSO_SOFTWARE?|?NETIF_F_GSO_ROBUST?|?\??

NETIF_F_SG?|?NETIF_F_HIGHDMA?|?????\??

NETIF_F_FRAGLIST)??

（11）、分配net_device結構體及其私有數據時為對齊所需的填充位數目

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unsigned?short??padded;???

（12）、其他信息?

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//NETPOLL相關信息??

struct?netpoll_info?*npinfo;??

//網絡命名空間??

struct?net??????*nd_net;??

//中間層的私有數據??

union?{??

void????????????????*ml_priv;??

struct?pcpu_lstats?__percpu?*lstats;?/*?loopback?stats?*/??

struct?pcpu_tstats?__percpu?*tstats;?/*?tunnel?stats?*/??

struct?pcpu_dstats?__percpu?*dstats;?/*?dummy?stats?*/??

};??

//GARP協議相關??

struct?garp_port?__rcu??*garp_port;??

//虛擬局域網相關??

unsigned?long?vlan_features;??

//GSO最大值??

unsigned?int????????gso_max_size;??

//max?exchange?id?for?FCoE?LRO?by?ddp??

unsigned?int????????fcoe_ddp_xid;??

//PHY實例??

struct?phy_device?*phydev;??

2、網絡設備的運行狀態

（1）、網絡設備物理上的工作狀態?

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unsigned?long???????state;??

/*?state的可能取值如下：?

enum?netdev_state_t?{?

__LINK_STATE_START,?

__LINK_STATE_PRESENT,?

__LINK_STATE_NOCARRIER,?

__LINK_STATE_LINKWATCH_PENDING,?

__LINK_STATE_DORMANT,?

};?

**/??

（2）、網絡設備通信模式或狀態?

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//它們的可能取值定義在linux-2.6.38.8/include/linux/if.h文件中。??

unsigned?int????????flags;??

unsigned?short??????gflags;??

unsigned?int????????????priv_flags;?//類似flags,但對用戶空間不可見??

（3）、統計信息?

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struct?net_device_stats?stats;??

//在接收過程中丟棄的數據包數目（在網絡驅動中不使用此項）??

atomic_long_t???????rx_dropped;???

（4）、RFC2863協議相關?

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//RFC?2863操作狀態??

unsigned?char???????operstate;??

/*?operstate的可能取值如下：?

enum?{?

IF_OPER_UNKNOWN,?

IF_OPER_NOTPRESENT,?

IF_OPER_DOWN,?

IF_OPER_LOWERLAYERDOWN,?

IF_OPER_TESTING,?

IF_OPER_DORMANT,?

IF_OPER_UP,?

};?

**/???

//映射到RFC2863兼容狀態的策略??

unsigned?char???????link_mode;??

/*?link_mode的可能取值如下：?

enum?{?

IF_LINK_MODE_DEFAULT,?

IF_LINK_MODE_DORMANT,?

};?

**/??

（5）、傳輸超時?

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//最后接收數據包的時間??

unsigned?long???????last_rx;??

//最近傳送數據包的時間??

unsigned?long???????trans_start;??

//發生傳輸超時時，設置的標志??

int?????????watchdog_timeo;??

//網絡層設置的傳送數據包超時的時鐘????

struct?timer_list???watchdog_timer;??

（6）、設備注冊/注銷狀態機?

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enum?{?NETREG_UNINITIALIZED=0,??

NETREG_REGISTERED,???/*?completed?register_netdevice?*/??

NETREG_UNREGISTERING,????/*?called?unregister_netdevice?*/??

NETREG_UNREGISTERED,?/*?completed?unregister?todo?*/??

NETREG_RELEASED,?????/*?called?free_netdev?*/??

NETREG_DUMMY,????????/*?dummy?device?for?NAPI?poll?*/??

}?reg_state:16;??

（7）、引用計數?

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int?__percpu????????*pcpu_refcnt;??

（8）、分組狀態?

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struct?net_device???*master;??

（9）、RTNL初始化狀態?

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enum?{??

RTNL_LINK_INITIALIZED,??

RTNL_LINK_INITIALIZING,??

}?rtnl_link_state:16;??

3、網絡設備的操作函數?

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//使用無線網絡設備擴展功能的一組操作函數??

const?struct?iw_handler_def?*???wireless_handlers;??

//無線網絡設備處理函數所使用的數據??

struct?iw_public_data?*?wireless_data;??

//網絡設備驅動程序需要實現的一組操作函數??

const?struct?net_device_ops?*netdev_ops;??

//支持ethtool功能的一組操作函數??

const?struct?ethtool_ops?*ethtool_ops;??

//數據鏈路層協議頭相關的一組操作函數??

const?struct?header_ops?*header_ops;??

//析構函數，注銷網絡設備時被調用??

void?(*destructor)(struct?net_device?*dev);??

//rtnetlink操作函數??

const?struct?rtnl_link_ops?*rtnl_link_ops;??

//DCB操作函數??

const?struct?dcbnl_rtnl_ops?*dcbnl_ops;??

4、數據包的收發隊列

（1）、接收隊列?

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//RPS(Receive?Packet?Steering)特性??

struct?kset?????*queues_kset;??

struct?netdev_rx_queue??*_rx;??

unsigned?int????????num_rx_queues;??

unsigned?int????????real_num_rx_queues;??

rx_handler_func_t?__rcu?*rx_handler;??

void?__rcu??????*rx_handler_data;??

struct?netdev_queue?__rcu?*ingress_queue;??

（2）、發送隊列?

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struct?netdev_queue?*_tx?____cacheline_aligned_in_smp;??

unsigned?int????????num_tx_queues;??

unsigned?int????????real_num_tx_queues;??

struct?Qdisc????????*qdisc;??

unsigned?long???????tx_queue_len;??

spinlock_t??????tx_global_lock;??

//XPS(Transmit?Packet?Steering)特性??

struct?xps_dev_maps?__rcu?*xps_maps; ?

?