net-device

  成都的天气好像越来越好了，前几天还穿着穿着外套直打哆嗦，到今天已经“拨开阴云见太阳”，暖洋洋的，心情也暖洋洋的。暖和的正好想睡觉。打个呵欠，把网络设备管理这部份总结下吧。    

     Linux素以优秀的网络管理能力而著称，linux为何具有这么高的效率？我们从网络设备的管理说起。

     Linux为何要对网络设备单独管理呢？这是因为。协议栈很多地方都会涉及到网络设备。小至IP地址的设置。大至IP路由的更新。都离不开高效的网络设备管理。将网络设备单独管理可以提高效率！

     每个网络设备，在linux中都会对应一个数据结构,net_device。 就从这个结构说起

Linux 2。6。21中，对net_device定义如下：

struct net_device

{

     //设备的名称，例如常见的“eth0”等

     char          name[IFNAMSIZ];

     //共享内存的起始，结束地址

     unsigned long      mem_end; /* shared mem end  */

     unsigned long      mem_start;    /* shared mem start    */

     //网络设备的I/O基地址

     unsigned long      base_addr;    /* device I/O address  */

     //被赋予的中断号

     unsigned int       irq;     /* device IRQ number   */

     //在多端口设备上使用哪一个端口

     unsigned char      if_port; /* Selectable AUI, TP,..*/

     //为设备分配的DMA通道

     unsigned char      dma;     /* DMA channel         */

     //设备的状态

     unsigned long      state;

     // 下一个net_device

     struct net_device  *next;

     //初始化函数。

     int           (*init)(struct net_device *dev);

     struct net_device  *next_sched;

 

     /* Interface index. Unique device identifier   */

     //设备在内核中对应的序号

     int           ifindex;

     int           iflink;

 

     //获得接口状态的函数指针

     struct net_device_stats* (*get_stats)(struct net_device *dev);

     struct iw_statistics*  (*get_wireless_stats)(struct net_device *dev);

 

     struct iw_handler_def * wireless_handlers;

     struct ethtool_ops *ethtool_ops;

     //传输状态。检查传输是否被锁住

     unsigned long      trans_start;  /* Time (in jiffies) of last Tx  */

     //最使使用的时间

     unsigned long      last_rx; /* Time of last Rx */

     //接口标志

     unsigned short         flags;   /* interface flags (a la BSD)    */

     unsigned short         gflags;

        unsigned short          priv_flags; /* Like 'flags' but invisible to userspace. */

        unsigned short          unused_alignment_fixer; /* Because we need priv_flags,

                                                         * and we want to be 32-bit aligned.

                                                         */

 

     unsigned      mtu; /* interface MTU value      */

     unsigned short         type;    /* interface hardware type  */

     unsigned short         hard_header_len;   /* hardware hdr length */

     void          *priv;   /* pointer to private data  */

 

     struct net_device  *master; /* Pointer to master device of a group,

                         * which this device is member of.

                         */

 

     /* Interface address info. */

     unsigned char      broadcast[MAX_ADDR_LEN];    /* hw bcast add    */

     unsigned char      dev_addr[MAX_ADDR_LEN]; /* hw address */

     unsigned char      addr_len; /* hardware address length  */

 

     struct dev_mc_list *mc_list; /* Multicast mac addresses  */

     int           mc_count; /* Number of installed mcasts    */

     int           promiscuity;

     int           allmulti;

 

     int           watchdog_timeo;

     struct timer_list  watchdog_timer;

 

     /* Protocol specific pointers */

    

     void               *atalk_ptr;   /* AppleTalk link */

     void          *ip_ptr; /* IPv4 specific data  */ 

     void                    *dn_ptr;        /* DECnet specific data */

     void                    *ip6_ptr;       /* IPv6 specific data */

     void          *ec_ptr; /* Econet specific data */

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

 

     struct list_head   poll_list;    /* Link to poll list   */

     int           quota;

     int           weight;

 

     struct Qdisc       *qdisc;

     struct Qdisc       *qdisc_sleeping;

     struct Qdisc       *qdisc_ingress;

     struct list_head   qdisc_list;

     unsigned long      tx_queue_len; /* Max frames per queue allowed */

 

     /* ingress path synchronizer */

     spinlock_t         ingress_lock;

     /* hard_start_xmit synchronizer */

     spinlock_t         xmit_lock;

     /* cpu id of processor entered to hard_start_xmit or -1,

        if nobody entered there.

      */

     int           xmit_lock_owner;

     /* device queue lock */

     spinlock_t         queue_lock;

     /* Number of references to this device */

     atomic_t      refcnt;

     /* delayed register/unregister */

     struct list_head   todo_list;

     /* device name hash chain */

     struct hlist_node  name_hlist;

     /* device index hash chain */

     struct hlist_node  index_hlist;

 

     /* register/unregister state machine */

     enum { NETREG_UNINITIALIZED=0,

            NETREG_REGISTERING,  /* called register_netdevice */

            NETREG_REGISTERED,   /* completed register todo */

            NETREG_UNREGISTERING,     /* called unregister_netdevice */

            NETREG_UNREGISTERED, /* completed unregister todo */

            NETREG_RELEASED,     /* called free_netdev */

     } reg_state;

 

     /* Net device features */

     int           features;

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

#define NETIF_F_IP_CSUM     2    /* Can checksum only 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_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_TSO         2048 /* Can offload TCP/IP segmentation */

#define NETIF_F_LLTX        4096 /* LockLess TX */

 

     /* Called after device is detached from network. */

     void          (*uninit)(struct net_device *dev);

     /* Called after last user reference disappears. */

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

 

     /* Pointers to interface service routines.     */

     //打开函数指针

     int           (*open)(struct net_device *dev);

     //设备停用时调用此函数

     int           (*stop)(struct net_device *dev);

     //初始化数据包的传输

     int           (*hard_start_xmit) (struct sk_buff *skb,

                                struct net_device *dev);

#define HAVE_NETDEV_POLL

     //轮询函数

     int           (*poll) (struct net_device *dev, int *quota);

     //建立硬件头信息

     int           (*hard_header) (struct sk_buff *skb,

                            struct net_device *dev,

                            unsigned short type,

                            void *daddr,

                            void *saddr,

                            unsigned len);

     //ARP解析之后，重构头部

     int           (*rebuild_header)(struct sk_buff *skb);

#define HAVE_MULTICAST     

     //多播支持函数    

     void          (*set_multicast_list)(struct net_device *dev);

#define HAVE_SET_MAC_ADDR         

     int           (*set_mac_address)(struct net_device *dev,

                               void *addr);

#define HAVE_PRIVATE_IOCTL

     int           (*do_ioctl)(struct net_device *dev,

                           struct ifreq *ifr, int cmd);

#define HAVE_SET_CONFIG

     int           (*set_config)(struct net_device *dev,

                             struct ifmap *map);

#define HAVE_HEADER_CACHE

     int           (*hard_header_cache)(struct neighbour *neigh,

                                 struct hh_cache *hh);

     void          (*header_cache_update)(struct hh_cache *hh,

                                   struct net_device *dev,

                                   unsigned char *  haddr);

#define HAVE_CHANGE_MTU

     int           (*change_mtu)(struct net_device *dev, int new_mtu);

 

#define HAVE_TX_TIMEOUT

     void          (*tx_timeout) (struct net_device *dev);

 

     void          (*vlan_rx_register)(struct net_device *dev,

                                struct vlan_group *grp);

     void          (*vlan_rx_add_vid)(struct net_device *dev,

                               unsigned short vid);

     void          (*vlan_rx_kill_vid)(struct net_device *dev,

                                unsigned short vid);

 

     int           (*hard_header_parse)(struct sk_buff *skb,

                                 unsigned char *haddr);

     int           (*neigh_setup)(struct net_device *dev, struct neigh_parms *);

     int           (*accept_fastpath)(struct net_device *, struct dst_entry*);

#ifdef CONFIG_NETPOLL

     int           netpoll_rx;

#endif

#ifdef CONFIG_NET_POLL_CONTROLLER

     void                    (*poll_controller)(struct net_device *dev);

#endif

 

     /* bridge stuff */

     //对应的网桥端口（以后分析）

     struct net_bridge_port *br_port;

 

#ifdef CONFIG_NET_DIVERT

     /* this will get initialized at each interface type init routine */

     struct divert_blk  *divert;

#endif /* CONFIG_NET_DIVERT */

 

     /* class/net/name entry */

     struct class_device    class_dev;

     /* how much padding had been added by alloc_netdev() */

     int padded;

}

晕，太多的成员。太庞大了。不要紧，等到要使用到相应成员的时候再来解释好了。

转自：http://ericxiao.cublog.cn/