《linux设备驱动开发详解》笔记——14 linux网络设备驱动

 

14.1 网络设备驱动结构

 

• 网络协议接口层：硬件无关，标准收发函数dev_queue_xmit()和netif_rx();  注意，netif_rx是将接收到的数据给上层，有时也在驱动收到数据以后调用。
• 网络设备接口层，net_device，统一接口名称，使上层独立于具体硬件。
• 设备驱动功能层，实现net_device的各成员
• 物理层

 在整个以太网架构里，有两个数据结构非常重要，即sk_buff和net_device，后面两节有说明。

 还有一些与内核交互的函数，需要掌握，如netif_start_queue()，netif_stop_queue()，netif_wakeup_queue()，netif_rx()，netif_carrier_on/off_ok()

14.1.1 sk_buff

　　以太网各层之间用sk_buff结构体传递数据，该结构体是很多函数的形参。

#include 

/** 
 *    struct sk_buff - socket buffer
 *    @next: Next buffer in list
 *    @prev: Previous buffer in list
 *    @tstamp: Time we arrived
 *    @sk: Socket we are owned by
 *    @dev: Device we arrived on/are leaving by
 *    @cb: Control buffer. Free for use by every layer. Put private vars here
 *    @_skb_refdst: destination entry (with norefcount bit)
 *    @sp: the security path, used for xfrm
 *    @len: Length of actual data
 *    @data_len: Data length
 *    @mac_len: Length of link layer header
 *    @hdr_len: writable header length of cloned skb
 *    @csum: Checksum (must include start/offset pair)
 *    @csum_start: Offset from skb->head where checksumming should start
 *    @csum_offset: Offset from csum_start where checksum should be stored
 *    @priority: Packet queueing priority
 *    @local_df: allow local fragmentation
 *    @cloned: Head may be cloned (check refcnt to be sure)
 *    @ip_summed: Driver fed us an IP checksum
 *    @nohdr: Payload reference only, must not modify header
 *    @nfctinfo: Relationship of this skb to the connection
 *    @pkt_type: Packet class
 *    @fclone: skbuff clone status
 *    @ipvs_property: skbuff is owned by ipvs
 *    @peeked: this packet has been seen already, so stats have been
 *        done for it, don't do them again
 *    @nf_trace: netfilter packet trace flag
 *    @protocol: Packet protocol from driver
 *    @destructor: Destruct function
 *    @nfct: Associated connection, if any
 *    @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
 *    @skb_iif: ifindex of device we arrived on
 *    @tc_index: Traffic control index
 *    @tc_verd: traffic control verdict
 *    @rxhash: the packet hash computed on receive
 *    @queue_mapping: Queue mapping for multiqueue devices
 *    @ndisc_nodetype: router type (from link layer)
 *    @ooo_okay: allow the mapping of a socket to a queue to be changed
 *    @l4_rxhash: indicate rxhash is a canonical 4-tuple hash over transport
 *        ports.
 *    @wifi_acked_valid: wifi_acked was set
 *    @wifi_acked: whether frame was acked on wifi or not
 *    @no_fcs:  Request NIC to treat last 4 bytes as Ethernet FCS
 *    @dma_cookie: a cookie to one of several possible DMA operations
 *        done by skb DMA functions
  *    @napi_id: id of the NAPI struct this skb came from
 *    @secmark: security marking
 *    @mark: Generic packet mark
 *    @dropcount: total number of sk_receive_queue overflows
 *    @vlan_proto: vlan encapsulation protocol
 *    @vlan_tci: vlan tag control information
 *    @inner_protocol: Protocol (encapsulation)
 *    @inner_transport_header: Inner transport layer header (encapsulation)
 *    @inner_network_header: Network layer header (encapsulation)
 *    @inner_mac_header: Link layer header (encapsulation)
 *    @transport_header: Transport layer header
 *    @network_header: Network layer header
 *    @mac_header: Link layer header
 *    @tail: Tail pointer
 *    @end: End pointer
 *    @head: Head of buffer
 *    @data: Data head pointer
 *    @truesize: Buffer size
 *    @users: User count - see {datagram,tcp}.c
 */

struct sk_buff {
    /* These two members must be first. */
    struct sk_buff        *next;
    struct sk_buff        *prev;

    ktime_t            tstamp;

    struct sock        *sk;
    struct net_device    *dev;

    /*
     * This is the control buffer. It is free to use for every
     * layer. Please put your private variables there. If you
     * want to keep them across layers you have to do a skb_clone()
     * first. This is owned by whoever has the skb queued ATM.
     */
    char            cb[48] __aligned(8);

    unsigned long        _skb_refdst;
#ifdef CONFIG_XFRM
    struct    sec_path    *sp;
#endif
    unsigned int        len,　　　　// data段的长度
                data_len;
    __u16            mac_len,
                hdr_len;
    union {
        __wsum        csum;
        struct {
            __u16    csum_start;
            __u16    csum_offset;
        };
    };
    __u32            priority;
    kmemcheck_bitfield_begin(flags1);
    __u8            local_df:1,
                cloned:1,
                ip_summed:2,
                nohdr:1,
                nfctinfo:3;
    __u8            pkt_type:3,
                fclone:2,
                ipvs_property:1,
                peeked:1,
                nf_trace:1;
    kmemcheck_bitfield_end(flags1);
    __be16            protocol;

    void            (*destructor)(struct sk_buff *skb);
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
    struct nf_conntrack    *nfct;
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
    struct nf_bridge_info    *nf_bridge;
#endif

    int            skb_iif;

    __u32            rxhash;

    __be16            vlan_proto;
    __u16            vlan_tci;

#ifdef CONFIG_NET_SCHED
    __u16            tc_index;    /* traffic control index */
#ifdef CONFIG_NET_CLS_ACT
    __u16            tc_verd;    /* traffic control verdict */
#endif
#endif

    __u16            queue_mapping;
    kmemcheck_bitfield_begin(flags2);
#ifdef CONFIG_IPV6_NDISC_NODETYPE
    __u8            ndisc_nodetype:2;
#endif
    __u8            pfmemalloc:1;
    __u8            ooo_okay:1;
    __u8            l4_rxhash:1;
    __u8            wifi_acked_valid:1;
    __u8            wifi_acked:1;
    __u8            no_fcs:1;
    __u8            head_frag:1;
    /* Encapsulation protocol and NIC drivers should use
     * this flag to indicate to each other if the skb contains
     * encapsulated packet or not and maybe use the inner packet
     * headers if needed
     */
    __u8            encapsulation:1;
    /* 6/8 bit hole (depending on ndisc_nodetype presence) */
    kmemcheck_bitfield_end(flags2);

#if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL
    union {
        unsigned int    napi_id;
        dma_cookie_t    dma_cookie;
    };
#endif
#ifdef CONFIG_NETWORK_SECMARK
    __u32            secmark;
#endif
    union {
        __u32        mark;
        __u32        dropcount;
        __u32        reserved_tailroom;
    };

    __be16            inner_protocol;
    __u16            inner_transport_header;
    __u16            inner_network_header;
    __u16            inner_mac_header;
    __u16            transport_header;
    __u16            network_header;
    __u16            mac_header;
    /* These elements must be at the end, see alloc_skb() for details.  */
    sk_buff_data_t        tail;
    sk_buff_data_t        end;
    unsigned char        *head,
                *data;
    unsigned int        truesize;
    atomic_t        users;
};

• 接收时，各层去掉自己的协议，把数据给上层；
• 发送时，各层添加自己的协议，最终给物理网口。
• 上图指针可以动态调整，下面是若干函数

/**   tail后移，即在data中增加数据
 *    skb_put - add data to a buffer
 *    @skb: buffer to use
 *    @len: amount of data to add
 *
 *    This function extends the used data area of the buffer. If this would
 *    exceed the total buffer size the kernel will panic. A pointer to the
 *    first byte of the extra data is returned.
 */
unsigned char *skb_put(struct sk_buff *skb, unsigned int len)
{
    unsigned char *tmp = skb_tail_pointer(skb);
    SKB_LINEAR_ASSERT(skb);
    skb->tail += len;
    skb->len  += len;
    if (unlikely(skb->tail > skb->end))
        skb_over_panic(skb, len, __builtin_return_address(0));
    return tmp;
}


/**
 *    skb_push - add data to the start of a buffer，data前移
 *    @skb: buffer to use
 *    @len: amount of data to add
 *
 *    This function extends the used data area of the buffer at the buffer
 *    start. If this would exceed the total buffer headroom the kernel will
 *    panic. A pointer to the first byte of the extra data is returned.
 */
unsigned char *skb_push(struct sk_buff *skb, unsigned int len)
{
    skb->data -= len;
    skb->len  += len;
    if (unlikely(skb->datahead))
        skb_under_panic(skb, len, __builtin_return_address(0));
    return skb->data;
}


/**
 *    skb_pull - remove data from the start of a buffer，data后移
 *    @skb: buffer to use
 *    @len: amount of data to remove
 *
 *    This function removes data from the start of a buffer, returning
 *    the memory to the headroom. A pointer to the next data in the buffer
 *    is returned. Once the data has been pulled future pushes will overwrite
 *    the old data.
 */
unsigned char *skb_pull(struct sk_buff *skb, unsigned int len)
{
    return skb_pull_inline(skb, len);
}

static inline unsigned char *skb_pull_inline(struct sk_buff *skb, unsigned int len)
{
    return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
}

static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
{
    skb->len -= len;
    BUG_ON(skb->len < skb->data_len);
    return skb->data += len;
}
/**
 *    skb_reserve - adjust headroom
 *    @skb: buffer to alter
 *    @len: bytes to move
 *
 *    Increase the headroom of an empty &sk_buff by reducing the tail
 *    room. This is only allowed for an empty buffer.
 */
static inline void skb_reserve(struct sk_buff *skb, int len)
{
    skb->data += len;
    skb->tail += len;
}

// 例子：
skb=alloc_skb(len+headspace, GFP_KERNEL);　　// 分配
skb_reserve(skb, headspace);　　　　　　　　　 // tail=data=起始位置+headspace
skb_put(skb,len);　　　　　　　　　　　　　　　　// tail += len
memcpy_fromfs(skb->data,data,len);
pass_to_m_protocol(skb); 

• sk_buff的动态分配和释放

static inline struct sk_buff *alloc_skb(unsigned int size,
                    gfp_t priority);/* legacy helper around netdev_alloc_skb() */
static inline struct sk_buff *dev_alloc_skb(unsigned int length);void kfree_skb(struct sk_buff *skb);
void dev_kfree_skb)(struct sk_buff * skb);

/*
 * It is not allowed to call kfree_skb() or consume_skb() from hardware
 * interrupt context or with hardware interrupts being disabled.
 * (in_irq() || irqs_disabled())
 *
 * We provide four helpers that can be used in following contexts :
 *
 * dev_kfree_skb_irq(skb) when caller drops a packet from irq context,
 *  replacing kfree_skb(skb)
 *
 * dev_consume_skb_irq(skb) when caller consumes a packet from irq context.
 *  Typically used in place of consume_skb(skb) in TX completion path
 *
 * dev_kfree_skb_any(skb) when caller doesn't know its current irq context,
 *  replacing kfree_skb(skb)
 *
 * dev_consume_skb_any(skb) when caller doesn't know its current irq context,
 *  and consumed a packet. Used in place of consume_skb(skb)
 */
static inline void dev_kfree_skb_irq(struct sk_buff *skb);
static inline void dev_kfree_skb_any(struct sk_buff *skb);

 

14.1.2 net_device 

net_device有点类似字符设备中的file_opretions,里面定义了很多标准成员函数，驱动需要实现里面的函数。

/*
 *    The DEVICE structure.
 *    Actually, this whole structure is a big mistake.  It mixes I/O
 *    data with strictly "high-level" data, and it has to know about
 *    almost every data structure used in the INET module.
 *
 *    FIXME: cleanup struct net_device such that network protocol info
 *    moves out.
 */

struct net_device {

    /*
     * This is the first field of the "visible" part of this structure
     * (i.e. as seen by users in the "Space.c" file).  It is the name
     * of the interface.
     */
    char            name[IFNAMSIZ];　　　　　　/* device name hash chain, please keep it close to name[] */
    struct hlist_node    name_hlist;

    /* snmp alias */
    char             *ifalias;

    /*
     *    I/O specific fields
     *    FIXME: Merge these and struct ifmap into one
     */
    unsigned long        mem_end;    /* shared mem end    */
    unsigned long        mem_start;    /* shared mem start    */
    unsigned long        base_addr;    /* device I/O address    */
    int            irq;        /* device IRQ number    */

    /*
     *    Some hardware also needs these fields, but they are not
     *    part of the usual set specified in Space.c.
     */

    unsigned long        state;

    struct list_head    dev_list;
    struct list_head    napi_list;
    struct list_head    unreg_list;
    struct list_head    close_list;

    /* directly linked devices, like slaves for bonding */
    struct {
        struct list_head upper;
        struct list_head lower;
    } adj_list;

    /* all linked devices, *including* neighbours */
    struct {
        struct list_head upper;
        struct list_head lower;
    } all_adj_list;


    /* currently active device features */
    netdev_features_t    features;
    /* user-changeable features */
    netdev_features_t    hw_features;
    /* user-requested features */
    netdev_features_t    wanted_features;
    /* mask of features inheritable by VLAN devices */
    netdev_features_t    vlan_features;
    /* mask of features inherited by encapsulating devices
     * This field indicates what encapsulation offloads
     * the hardware is capable of doing, and drivers will
     * need to set them appropriately.
     */
    netdev_features_t    hw_enc_features;
    /* mask of fetures inheritable by MPLS */
    netdev_features_t    mpls_features;

    /* Interface index. Unique device identifier    */
    int            ifindex;
    int            iflink;

    struct net_device_stats    stats;　　// 各种统计信息
    atomic_long_t        rx_dropped; /* dropped packets by core network
                         * Do not use this in drivers.
                         */

#ifdef CONFIG_WIRELESS_EXT
    /* List of functions to handle Wireless Extensions (instead of ioctl).
     * See  for details. Jean II */
    const struct iw_handler_def *    wireless_handlers;
    /* Instance data managed by the core of Wireless Extensions. */
    struct iw_public_data *    wireless_data;
#endif
    /* Management operations */
    const struct net_device_ops *netdev_ops;　　// 具体函数，需驱动填充
    const struct ethtool_ops *ethtool_ops;
    const struct forwarding_accel_ops *fwd_ops;

    /* Hardware header description */
    const struct header_ops *header_ops;

    unsigned int        flags;    /* interface flags (a la BSD)    ,接口标记，以IFF_开头，说明设备接口的能力和特性*/
    unsigned int        priv_flags; /* Like 'flags' but invisible to userspace.
                         * See if.h for definitions. */
    unsigned short        gflags;
    unsigned short        padded;    /* How much padding added by alloc_netdev() */

    unsigned char        operstate; /* RFC2863 operstate */
    unsigned char        link_mode; /* mapping policy to operstate */

    unsigned char        if_port;    /* Selectable AUI, TP,..*/
    unsigned char        dma;        /* DMA channel        */

    unsigned int        mtu;    /* interface MTU value，最单传输单元        */
    unsigned short        type;    /* interface hardware type，硬件类型    */
    unsigned short        hard_header_len;    /* hardware hdr length，Dmac+Smac+type=14    */

    /* extra head- and tailroom the hardware may need, but not in all cases
     * can this be guaranteed, especially tailroom. Some cases also use
     * LL_MAX_HEADER instead to allocate the skb.
     */
    unsigned short        needed_headroom;
    unsigned short        needed_tailroom;

    /* Interface address info. */
    unsigned char        perm_addr[MAX_ADDR_LEN]; /* permanent hw address */
    unsigned char        addr_assign_type; /* hw address assignment type */
    unsigned char        addr_len;    /* hardware address length    */
    unsigned short        neigh_priv_len;
    unsigned short          dev_id;        /* Used to differentiate devices
                         * that share the same link
                         * layer address
                         */
    spinlock_t        addr_list_lock;
    struct netdev_hw_addr_list    uc;    /* Unicast mac addresses */
    struct netdev_hw_addr_list    mc;    /* Multicast mac addresses */
    struct netdev_hw_addr_list    dev_addrs; /* list of device
                            * hw addresses
                            */
#ifdef CONFIG_SYSFS
    struct kset        *queues_kset;
#endif

    bool            uc_promisc;
    unsigned int        promiscuity;
    unsigned int        allmulti;


    /* Protocol specific pointers */

#if IS_ENABLED(CONFIG_VLAN_8021Q)
    struct vlan_info __rcu    *vlan_info;    /* VLAN info */
#endif
#if IS_ENABLED(CONFIG_NET_DSA)
    struct dsa_switch_tree    *dsa_ptr;    /* dsa specific data */
#endif
#if IS_ENABLED(CONFIG_TIPC)
    struct tipc_bearer __rcu *tipc_ptr;    /* TIPC specific data */
#endif
    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            *ax25_ptr;    /* AX.25 specific data */
    struct wireless_dev    *ieee80211_ptr;    /* IEEE 802.11 specific data,
                           assign before registering */

/*
 * Cache lines mostly used on receive path (including eth_type_trans())
 */
    unsigned long        last_rx;    /* Time of last Rx
                         * This should not be set in
                         * drivers, unless really needed,
                         * because network stack (bonding)
                         * use it if/when necessary, to
                         * avoid dirtying this cache line.
                         */

    /* Interface address info used in eth_type_trans() */
    unsigned char        *dev_addr;    /* hw address, (before bcast
                           because most packets are
                           unicast) */


#ifdef CONFIG_SYSFS
    struct netdev_rx_queue    *_rx;

    /* Number of RX queues allocated at register_netdev() time */
    unsigned int        num_rx_queues;

    /* Number of RX queues currently active in device */
    unsigned int        real_num_rx_queues;

#endif

    rx_handler_func_t __rcu    *rx_handler;
    void __rcu        *rx_handler_data;

    struct netdev_queue __rcu *ingress_queue;
    unsigned char        broadcast[MAX_ADDR_LEN];    /* hw bcast add    */


/*
 * Cache lines mostly used on transmit path
 */
    struct netdev_queue    *_tx ____cacheline_aligned_in_smp;

    /* Number of TX queues allocated at alloc_netdev_mq() time  */
    unsigned int        num_tx_queues;

    /* Number of TX queues currently active in device  */
    unsigned int        real_num_tx_queues;

    /* root qdisc from userspace point of view */
    struct Qdisc        *qdisc;

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

#ifdef CONFIG_XPS
    struct xps_dev_maps __rcu *xps_maps;
#endif
#ifdef CONFIG_RFS_ACCEL
    /* CPU reverse-mapping for RX completion interrupts, indexed
     * by RX queue number.  Assigned by driver.  This must only be
     * set if the ndo_rx_flow_steer operation is defined. */
    struct cpu_rmap        *rx_cpu_rmap;
#endif

    /* These may be needed for future network-power-down code. */

    /*
     * trans_start here is expensive for high speed devices on SMP,
     * please use netdev_queue->trans_start instead.
     */
    unsigned long        trans_start;    /* Time (in jiffies) of last Tx    */

    int            watchdog_timeo; /* used by dev_watchdog() */
    struct timer_list    watchdog_timer;

    /* Number of references to this device */
    int __percpu        *pcpu_refcnt;

    /* delayed register/unregister */
    struct list_head    todo_list;
    /* device index hash chain */
    struct hlist_node    index_hlist;

    struct list_head    link_watch_list;

    /* register/unregister state machine */
    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:8;

    bool dismantle; /* device is going do be freed */

    enum {
        RTNL_LINK_INITIALIZED,
        RTNL_LINK_INITIALIZING,
    } rtnl_link_state:16;

    /* Called from unregister, can be used to call free_netdev */
    void (*destructor)(struct net_device *dev);

#ifdef CONFIG_NETPOLL
    struct netpoll_info __rcu    *npinfo;
#endif

#ifdef CONFIG_NET_NS
    /* Network namespace this network device is inside */
    struct net        *nd_net;
#endif

    /* mid-layer private */
    union {
        void                *ml_priv;
        struct pcpu_lstats __percpu    *lstats; /* loopback stats */
        struct pcpu_sw_netstats __percpu    *tstats;
        struct pcpu_dstats __percpu    *dstats; /* dummy stats */
        struct pcpu_vstats __percpu    *vstats; /* veth stats */
    };
    /* GARP */
    struct garp_port __rcu    *garp_port;
    /* MRP */
    struct mrp_port __rcu    *mrp_port;

    /* class/net/name entry */
    struct device        dev;
    /* space for optional device, statistics, and wireless sysfs groups */
    const struct attribute_group *sysfs_groups[4];
    /* space for optional per-rx queue attributes */
    const struct attribute_group *sysfs_rx_queue_group;

    /* rtnetlink link ops */
    const struct rtnl_link_ops *rtnl_link_ops;

    /* for setting kernel sock attribute on TCP connection setup */
#define GSO_MAX_SIZE        65536
    unsigned int        gso_max_size;
#define GSO_MAX_SEGS        65535
    u16            gso_max_segs;

#ifdef CONFIG_DCB
    /* Data Center Bridging netlink ops */
    const struct dcbnl_rtnl_ops *dcbnl_ops;
#endif
    u8 num_tc;
    struct netdev_tc_txq tc_to_txq[TC_MAX_QUEUE];
    u8 prio_tc_map[TC_BITMASK + 1];

#if IS_ENABLED(CONFIG_FCOE)
    /* max exchange id for FCoE LRO by ddp */
    unsigned int        fcoe_ddp_xid;
#endif
#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
    struct netprio_map __rcu *priomap;
#endif
    /* phy device may attach itself for hardware timestamping */
    struct phy_device *phydev;

    struct lock_class_key *qdisc_tx_busylock;

    /* group the device belongs to */
    int group;

    struct pm_qos_request    pm_qos_req;
};

* Standard interface flags (netdevice->flags). */
#define IFF_UP 0x1 /* interface is up */
#define IFF_BROADCAST 0x2 /* broadcast address valid */
#define IFF_DEBUG 0x4 /* turn on debugging */
#define IFF_LOOPBACK 0x8 /* is a loopback net */
#define IFF_POINTOPOINT 0x10 /* interface is has p-p link */
#define IFF_NOTRAILERS 0x20 /* avoid use of trailers */
#define IFF_RUNNING 0x40 /* interface RFC2863 OPER_UP */
#define IFF_NOARP 0x80 /* no ARP protocol */
#define IFF_PROMISC 0x100 /* receive all packets */
#define IFF_ALLMULTI 0x200 /* receive all multicast packets*/

#define IFF_MASTER 0x400 /* master of a load balancer */
#define IFF_SLAVE 0x800 /* slave of a load balancer */

#define IFF_MULTICAST 0x1000 /* Supports multicast */

#define IFF_PORTSEL 0x2000 /* can set media type */

#define IFF_AUTOMEDIA 0x4000 /* auto media select active */
#define IFF_DYNAMIC 0x8000 /* dialup device with changing addresses*/

#define IFF_LOWER_UP 0x10000 /* driver signals L1 up */
#define IFF_DORMANT 0x20000 /* driver signals dormant */

#define IFF_ECHO 0x40000 /* echo sent packets */

#define IFF_VOLATILE (IFF_LOOPBACK|IFF_POINTOPOINT|IFF_BROADCAST|IFF_ECHO|\
IFF_MASTER|IFF_SLAVE|IFF_RUNNING|IFF_LOWER_UP|IFF_DORMANT)

/* Private (from user) interface flags (netdevice->priv_flags). */
#define IFF_802_1Q_VLAN 0x1 /* 802.1Q VLAN device. */
#define IFF_EBRIDGE 0x2 /* Ethernet bridging device. */
#define IFF_SLAVE_INACTIVE 0x4 /* bonding slave not the curr. active */
#define IFF_MASTER_8023AD 0x8 /* bonding master, 802.3ad. */
#define IFF_MASTER_ALB 0x10 /* bonding master, balance-alb. */
#define IFF_BONDING 0x20 /* bonding master or slave */
#define IFF_SLAVE_NEEDARP 0x40 /* need ARPs for validation */
#define IFF_ISATAP 0x80 /* ISATAP interface (RFC4214) */
#define IFF_MASTER_ARPMON 0x100 /* bonding master, ARP mon in use */
#define IFF_WAN_HDLC 0x200 /* WAN HDLC device */
#define IFF_XMIT_DST_RELEASE 0x400 /* dev_hard_start_xmit() is allowed to
* release skb->dst
*/
#define IFF_DONT_BRIDGE 0x800 /* disallow bridging this ether dev */
#define IFF_DISABLE_NETPOLL 0x1000 /* disable netpoll at run-time */
#define IFF_MACVLAN_PORT 0x2000 /* device used as macvlan port */
#define IFF_BRIDGE_PORT 0x4000 /* device used as bridge port */
#define IFF_OVS_DATAPATH 0x8000 /* device used as Open vSwitch
* datapath port */
#define IFF_TX_SKB_SHARING 0x10000 /* The interface supports sharing
* skbs on transmit */
#define IFF_UNICAST_FLT 0x20000 /* Supports unicast filtering */
#define IFF_TEAM_PORT 0x40000 /* device used as team port */
#define IFF_SUPP_NOFCS 0x80000 /* device supports sending custom FCS */
#define IFF_LIVE_ADDR_CHANGE 0x100000 /* device supports hardware address
* change when it's running */
#define IFF_MACVLAN 0x200000 /* Macvlan device */

 net_device中的一个重要结构体是net_device_ops,驱动需要填充里面的成员。

/*
 * This structure defines the management hooks for network devices.
 * The following hooks can be defined; unless noted otherwise, they are
 * optional and can be filled with a null pointer.
 *
 * int (*ndo_init)(struct net_device *dev);
 *     This function is called once when network device is registered.
 *     The network device can use this to any late stage initializaton
 *     or semantic validattion. It can fail with an error code which will
 *     be propogated back to register_netdev
 *
 * void (*ndo_uninit)(struct net_device *dev);
 *     This function is called when device is unregistered or when registration
 *     fails. It is not called if init fails.
 *
 * int (*ndo_open)(struct net_device *dev);一般在次获取设备需要的IO地址、IRQ、DMA通道等
 *     This function is called when network device transistions to the up
 *     state.
 *
 * int (*ndo_stop)(struct net_device *dev);
 *     This function is called when network device transistions to the down
 *     state.
 *
 * netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb,
 *                               struct net_device *dev);
 *    Called when a packet needs to be transmitted.
 *    Must return NETDEV_TX_OK , NETDEV_TX_BUSY.
 *        (can also return NETDEV_TX_LOCKED iff NETIF_F_LLTX)
 *    Required can not be NULL.　　不能为空，必须实现，启动发送
 *
 * u16 (*ndo_select_queue)(struct net_device *dev, struct sk_buff *skb,
 *                         void *accel_priv, select_queue_fallback_t fallback);
 *    Called to decide which queue to when device supports multiple
 *    transmit queues.
 *
 * void (*ndo_change_rx_flags)(struct net_device *dev, int flags);
 *    This function is called to allow device receiver to make
 *    changes to configuration when multicast or promiscious is enabled.
 *
 * void (*ndo_set_rx_mode)(struct net_device *dev);
 *    This function is called device changes address list filtering.
 *    If driver handles unicast address filtering, it should set
 *    IFF_UNICAST_FLT to its priv_flags.
 *
 * int (*ndo_set_mac_address)(struct net_device *dev, void *addr);
 *    This function  is called when the Media Access Control address
 *    needs to be changed. If this interface is not defined, the
 *    mac address can not be changed.
 *
 * int (*ndo_validate_addr)(struct net_device *dev);
 *    Test if Media Access Control address is valid for the device.
 *
 * int (*ndo_do_ioctl)(struct net_device *dev, struct ifreq *ifr, int cmd);
 *    Called when a user request an ioctl which can't be handled by
 *    the generic interface code. If not defined ioctl's return
 *    not supported error code.
 *
 * int (*ndo_set_config)(struct net_device *dev, struct ifmap *map);
 *    Used to set network devices bus interface parameters. This interface
 *    is retained for legacy reason, new devices should use the bus
 *    interface (PCI) for low level management.　　配置接口，也可以改变设备IO地址和中断号
 *
 * int (*ndo_change_mtu)(struct net_device *dev, int new_mtu);
 *    Called when a user wants to change the Maximum Transfer Unit
 *    of a device. If not defined, any request to change MTU will
 *    will return an error.
 *
 * void (*ndo_tx_timeout)(struct net_device *dev);
 *    Callback uses when the transmitter has not made any progress
 *    for dev->watchdog ticks. 发送超时以后调用
 *
 * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev,
 *                      struct rtnl_link_stats64 *storage);
 * struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);　　　　返回的结构体包含若干统计信息
 *    Called when a user wants to get the network device usage
 *    statistics. Drivers must do one of the following:
 *    1. Define @ndo_get_stats64 to fill in a zero-initialised
 *       rtnl_link_stats64 structure passed by the caller.
 *    2. Define @ndo_get_stats to update a net_device_stats structure
 *       (which should normally be dev->stats) and return a pointer to
 *       it. The structure may be changed asynchronously only if each
 *       field is written atomically.
 *    3. Update dev->stats asynchronously and atomically, and define
 *       neither operation.
 *
 * int (*ndo_vlan_rx_add_vid)(struct net_device *dev, __be16 proto, u16t vid);
 *    If device support VLAN filtering this function is called when a
 *    VLAN id is registered.
 *
 * int (*ndo_vlan_rx_kill_vid)(struct net_device *dev, unsigned short vid);
 *    If device support VLAN filtering this function is called when a
 *    VLAN id is unregistered.
 *
 * void (*ndo_poll_controller)(struct net_device *dev);
 *
 *    SR-IOV management functions.
 * int (*ndo_set_vf_mac)(struct net_device *dev, int vf, u8* mac);
 * int (*ndo_set_vf_vlan)(struct net_device *dev, int vf, u16 vlan, u8 qos);
 * int (*ndo_set_vf_tx_rate)(struct net_device *dev, int vf, int rate);
 * int (*ndo_set_vf_spoofchk)(struct net_device *dev, int vf, bool setting);
 * int (*ndo_get_vf_config)(struct net_device *dev,
 *                int vf, struct ifla_vf_info *ivf);
 * int (*ndo_set_vf_link_state)(struct net_device *dev, int vf, int link_state);
 * int (*ndo_set_vf_port)(struct net_device *dev, int vf,
 *              struct nlattr *port[]);
 * int (*ndo_get_vf_port)(struct net_device *dev, int vf, struct sk_buff *skb);
 * int (*ndo_setup_tc)(struct net_device *dev, u8 tc)
 *     Called to setup 'tc' number of traffic classes in the net device. This
 *     is always called from the stack with the rtnl lock held and netif tx
 *     queues stopped. This allows the netdevice to perform queue management
 *     safely.
 *
 *    Fiber Channel over Ethernet (FCoE) offload functions.
 * int (*ndo_fcoe_enable)(struct net_device *dev);
 *    Called when the FCoE protocol stack wants to start using LLD for FCoE
 *    so the underlying device can perform whatever needed configuration or
 *    initialization to support acceleration of FCoE traffic.
 *
 * int (*ndo_fcoe_disable)(struct net_device *dev);
 *    Called when the FCoE protocol stack wants to stop using LLD for FCoE
 *    so the underlying device can perform whatever needed clean-ups to
 *    stop supporting acceleration of FCoE traffic.
 *
 * int (*ndo_fcoe_ddp_setup)(struct net_device *dev, u16 xid,
 *                 struct scatterlist *sgl, unsigned int sgc);
 *    Called when the FCoE Initiator wants to initialize an I/O that
 *    is a possible candidate for Direct Data Placement (DDP). The LLD can
 *    perform necessary setup and returns 1 to indicate the device is set up
 *    successfully to perform DDP on this I/O, otherwise this returns 0.
 *
 * int (*ndo_fcoe_ddp_done)(struct net_device *dev,  u16 xid);
 *    Called when the FCoE Initiator/Target is done with the DDPed I/O as
 *    indicated by the FC exchange id 'xid', so the underlying device can
 *    clean up and reuse resources for later DDP requests.
 *
 * int (*ndo_fcoe_ddp_target)(struct net_device *dev, u16 xid,
 *                  struct scatterlist *sgl, unsigned int sgc);
 *    Called when the FCoE Target wants to initialize an I/O that
 *    is a possible candidate for Direct Data Placement (DDP). The LLD can
 *    perform necessary setup and returns 1 to indicate the device is set up
 *    successfully to perform DDP on this I/O, otherwise this returns 0.
 *
 * int (*ndo_fcoe_get_hbainfo)(struct net_device *dev,
 *                   struct netdev_fcoe_hbainfo *hbainfo);
 *    Called when the FCoE Protocol stack wants information on the underlying
 *    device. This information is utilized by the FCoE protocol stack to
 *    register attributes with Fiber Channel management service as per the
 *    FC-GS Fabric Device Management Information(FDMI) specification.
 *
 * int (*ndo_fcoe_get_wwn)(struct net_device *dev, u64 *wwn, int type);
 *    Called when the underlying device wants to override default World Wide
 *    Name (WWN) generation mechanism in FCoE protocol stack to pass its own
 *    World Wide Port Name (WWPN) or World Wide Node Name (WWNN) to the FCoE
 *    protocol stack to use.
 *
 *    RFS acceleration.
 * int (*ndo_rx_flow_steer)(struct net_device *dev, const struct sk_buff *skb,
 *                u16 rxq_index, u32 flow_id);
 *    Set hardware filter for RFS.  rxq_index is the target queue index;
 *    flow_id is a flow ID to be passed to rps_may_expire_flow() later.
 *    Return the filter ID on success, or a negative error code.
 *
 *    Slave management functions (for bridge, bonding, etc).
 * int (*ndo_add_slave)(struct net_device *dev, struct net_device *slave_dev);
 *    Called to make another netdev an underling.
 *
 * int (*ndo_del_slave)(struct net_device *dev, struct net_device *slave_dev);
 *    Called to release previously enslaved netdev.
 *
 *      Feature/offload setting functions.
 * netdev_features_t (*ndo_fix_features)(struct net_device *dev,
 *        netdev_features_t features);
 *    Adjusts the requested feature flags according to device-specific
 *    constraints, and returns the resulting flags. Must not modify
 *    the device state.
 *
 * int (*ndo_set_features)(struct net_device *dev, netdev_features_t features);
 *    Called to update device configuration to new features. Passed
 *    feature set might be less than what was returned by ndo_fix_features()).
 *    Must return >0 or -errno if it changed dev->features itself.
 *
 * int (*ndo_fdb_add)(struct ndmsg *ndm, struct nlattr *tb[],
 *              struct net_device *dev,
 *              const unsigned char *addr, u16 flags)
 *    Adds an FDB entry to dev for addr.
 * int (*ndo_fdb_del)(struct ndmsg *ndm, struct nlattr *tb[],
 *              struct net_device *dev,
 *              const unsigned char *addr)
 *    Deletes the FDB entry from dev coresponding to addr.
 * int (*ndo_fdb_dump)(struct sk_buff *skb, struct netlink_callback *cb,
 *               struct net_device *dev, int idx)
 *    Used to add FDB entries to dump requests. Implementers should add
 *    entries to skb and update idx with the number of entries.
 *
 * int (*ndo_bridge_setlink)(struct net_device *dev, struct nlmsghdr *nlh)
 * int (*ndo_bridge_getlink)(struct sk_buff *skb, u32 pid, u32 seq,
 *                 struct net_device *dev, u32 filter_mask)
 *
 * int (*ndo_change_carrier)(struct net_device *dev, bool new_carrier);
 *    Called to change device carrier. Soft-devices (like dummy, team, etc)
 *    which do not represent real hardware may define this to allow their
 *    userspace components to manage their virtual carrier state. Devices
 *    that determine carrier state from physical hardware properties (eg
 *    network cables) or protocol-dependent mechanisms (eg
 *    USB_CDC_NOTIFY_NETWORK_CONNECTION) should NOT implement this function.
 *
 * int (*ndo_get_phys_port_id)(struct net_device *dev,
 *                   struct netdev_phys_port_id *ppid);
 *    Called to get ID of physical port of this device. If driver does
 *    not implement this, it is assumed that the hw is not able to have
 *    multiple net devices on single physical port.
 *
 * void (*ndo_add_vxlan_port)(struct  net_device *dev,
 *                  sa_family_t sa_family, __be16 port);
 *    Called by vxlan to notiy a driver about the UDP port and socket
 *    address family that vxlan is listnening to. It is called only when
 *    a new port starts listening. The operation is protected by the
 *    vxlan_net->sock_lock.
 *
 * void (*ndo_del_vxlan_port)(struct  net_device *dev,
 *                  sa_family_t sa_family, __be16 port);
 *    Called by vxlan to notify the driver about a UDP port and socket
 *    address family that vxlan is not listening to anymore. The operation
 *    is protected by the vxlan_net->sock_lock.
 *
 * void* (*ndo_dfwd_add_station)(struct net_device *pdev,
 *                 struct net_device *dev)
 *    Called by upper layer devices to accelerate switching or other
 *    station functionality into hardware. 'pdev is the lowerdev
 *    to use for the offload and 'dev' is the net device that will
 *    back the offload. Returns a pointer to the private structure
 *    the upper layer will maintain.
 * void (*ndo_dfwd_del_station)(struct net_device *pdev, void *priv)
 *    Called by upper layer device to delete the station created
 *    by 'ndo_dfwd_add_station'. 'pdev' is the net device backing
 *    the station and priv is the structure returned by the add
 *    operation.
 * netdev_tx_t (*ndo_dfwd_start_xmit)(struct sk_buff *skb,
 *                      struct net_device *dev,
 *                      void *priv);
 *    Callback to use for xmit over the accelerated station. This
 *    is used in place of ndo_start_xmit on accelerated net
 *    devices.
 */
struct net_device_ops {
    int            (*ndo_init)(struct net_device *dev);
    void            (*ndo_uninit)(struct net_device *dev);
    int            (*ndo_open)(struct net_device *dev);
    int            (*ndo_stop)(struct net_device *dev);
    netdev_tx_t        (*ndo_start_xmit) (struct sk_buff *skb,
                           struct net_device *dev);
    u16            (*ndo_select_queue)(struct net_device *dev,
                            struct sk_buff *skb,
                            void *accel_priv,
                            select_queue_fallback_t fallback);
    void            (*ndo_change_rx_flags)(struct net_device *dev,
                               int flags);
    void            (*ndo_set_rx_mode)(struct net_device *dev);
    int            (*ndo_set_mac_address)(struct net_device *dev,
                               void *addr);
    int            (*ndo_validate_addr)(struct net_device *dev);
    int            (*ndo_do_ioctl)(struct net_device *dev,
                            struct ifreq *ifr, int cmd);
    int            (*ndo_set_config)(struct net_device *dev,
                              struct ifmap *map);
    int            (*ndo_change_mtu)(struct net_device *dev,
                          int new_mtu);
    int            (*ndo_neigh_setup)(struct net_device *dev,
                           struct neigh_parms *);
    void            (*ndo_tx_timeout) (struct net_device *dev);

    struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev,
                             struct rtnl_link_stats64 *storage);
    struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);

    int            (*ndo_vlan_rx_add_vid)(struct net_device *dev,
                               __be16 proto, u16 vid);
    int            (*ndo_vlan_rx_kill_vid)(struct net_device *dev,
                                __be16 proto, u16 vid);
#ifdef CONFIG_NET_POLL_CONTROLLER
    void                    (*ndo_poll_controller)(struct net_device *dev);
    int            (*ndo_netpoll_setup)(struct net_device *dev,
                             struct netpoll_info *info,
                             gfp_t gfp);
    void            (*ndo_netpoll_cleanup)(struct net_device *dev);
#endif
#ifdef CONFIG_NET_RX_BUSY_POLL
    int            (*ndo_busy_poll)(struct napi_struct *dev);
#endif
    int            (*ndo_set_vf_mac)(struct net_device *dev,
                          int queue, u8 *mac);
    int            (*ndo_set_vf_vlan)(struct net_device *dev,
                           int queue, u16 vlan, u8 qos);
    int            (*ndo_set_vf_tx_rate)(struct net_device *dev,
                              int vf, int rate);
    int            (*ndo_set_vf_spoofchk)(struct net_device *dev,
                               int vf, bool setting);
    int            (*ndo_get_vf_config)(struct net_device *dev,
                             int vf,
                             struct ifla_vf_info *ivf);
    int            (*ndo_set_vf_link_state)(struct net_device *dev,
                             int vf, int link_state);
    int            (*ndo_set_vf_port)(struct net_device *dev,
                           int vf,
                           struct nlattr *port[]);
    int            (*ndo_get_vf_port)(struct net_device *dev,
                           int vf, struct sk_buff *skb);
    int            (*ndo_setup_tc)(struct net_device *dev, u8 tc);
#if IS_ENABLED(CONFIG_FCOE)
    int            (*ndo_fcoe_enable)(struct net_device *dev);
    int            (*ndo_fcoe_disable)(struct net_device *dev);
    int            (*ndo_fcoe_ddp_setup)(struct net_device *dev,
                              u16 xid,
                              struct scatterlist *sgl,
                              unsigned int sgc);
    int            (*ndo_fcoe_ddp_done)(struct net_device *dev,
                             u16 xid);
    int            (*ndo_fcoe_ddp_target)(struct net_device *dev,
                               u16 xid,
                               struct scatterlist *sgl,
                               unsigned int sgc);
    int            (*ndo_fcoe_get_hbainfo)(struct net_device *dev,
                            struct netdev_fcoe_hbainfo *hbainfo);
#endif

#if IS_ENABLED(CONFIG_LIBFCOE)
#define NETDEV_FCOE_WWNN 0
#define NETDEV_FCOE_WWPN 1
    int            (*ndo_fcoe_get_wwn)(struct net_device *dev,
                            u64 *wwn, int type);
#endif

#ifdef CONFIG_RFS_ACCEL
    int            (*ndo_rx_flow_steer)(struct net_device *dev,
                             const struct sk_buff *skb,
                             u16 rxq_index,
                             u32 flow_id);
#endif
    int            (*ndo_add_slave)(struct net_device *dev,
                         struct net_device *slave_dev);
    int            (*ndo_del_slave)(struct net_device *dev,
                         struct net_device *slave_dev);
    netdev_features_t    (*ndo_fix_features)(struct net_device *dev,
                            netdev_features_t features);
    int            (*ndo_set_features)(struct net_device *dev,
                            netdev_features_t features);
    int            (*ndo_neigh_construct)(struct neighbour *n);
    void            (*ndo_neigh_destroy)(struct neighbour *n);

    int            (*ndo_fdb_add)(struct ndmsg *ndm,
                           struct nlattr *tb[],
                           struct net_device *dev,
                           const unsigned char *addr,
                           u16 flags);
    int            (*ndo_fdb_del)(struct ndmsg *ndm,
                           struct nlattr *tb[],
                           struct net_device *dev,
                           const unsigned char *addr);
    int            (*ndo_fdb_dump)(struct sk_buff *skb,
                        struct netlink_callback *cb,
                        struct net_device *dev,
                        int idx);

    int            (*ndo_bridge_setlink)(struct net_device *dev,
                              struct nlmsghdr *nlh);
    int            (*ndo_bridge_getlink)(struct sk_buff *skb,
                              u32 pid, u32 seq,
                              struct net_device *dev,
                              u32 filter_mask);
    int            (*ndo_bridge_dellink)(struct net_device *dev,
                              struct nlmsghdr *nlh);
    int            (*ndo_change_carrier)(struct net_device *dev,
                              bool new_carrier);
    int            (*ndo_get_phys_port_id)(struct net_device *dev,
                            struct netdev_phys_port_id *ppid);
    void            (*ndo_add_vxlan_port)(struct  net_device *dev,
                              sa_family_t sa_family,
                              __be16 port);
    void            (*ndo_del_vxlan_port)(struct  net_device *dev,
                              sa_family_t sa_family,
                              __be16 port);

    void*            (*ndo_dfwd_add_station)(struct net_device *pdev,
                            struct net_device *dev);
    void            (*ndo_dfwd_del_station)(struct net_device *pdev,
                            void *priv);

    netdev_tx_t        (*ndo_dfwd_start_xmit) (struct sk_buff *skb,
                            struct net_device *dev,
                            void *priv);
};

 

 

14.2 注册与注销

14.2.1 注册与注销

register时，net_device的net_device_ops的ndo_init()会执行。

/**
 *    register_netdev    - register a network device
 *    @dev: device to register
 *
 *    Take a completed network device structure and add it to the kernel
 *    interfaces. A %NETDEV_REGISTER message is sent to the netdev notifier
 *    chain. 0 is returned on success. A negative errno code is returned
 *    on a failure to set up the device, or if the name is a duplicate.
 *
 *    This is a wrapper around register_netdevice that takes the rtnl semaphore
 *    and expands the device name if you passed a format string to
 *    alloc_netdev.
 */
int register_netdev(struct net_device *dev);

/**
 *    unregister_netdev - remove device from the kernel
 *    @dev: device
 *
 *    This function shuts down a device interface and removes it
 *    from the kernel tables.
 *
 *    This is just a wrapper for unregister_netdevice that takes
 *    the rtnl semaphore.  In general you want to use this and not
 *    unregister_netdevice.
 */
void unregister_netdev(struct net_device *dev);

 

14.2.2 申请和释放

可以自己定义net_device结构体，也可以动态申请和释放空间。

// sizeof_priv是自定义数据结构的大小
// setup是动态申请后，自动执行的初始化函数，下面两个ether申请函数，都有默认的setup函数
#define alloc_netdev(sizeof_priv, name, setup) \
    alloc_netdev_mqs(sizeof_priv, name, setup, 1, 1)
#define alloc_etherdev(sizeof_priv) alloc_etherdev_mq(sizeof_priv, 1)
#define alloc_etherdev_mq(sizeof_priv, count) alloc_etherdev_mqs(sizeof_priv, count, count)


/**
 * alloc_etherdev_mqs - Allocates and sets up an Ethernet device
 * @sizeof_priv: Size of additional driver-private structure to be allocated
 *    for this Ethernet device
 * @txqs: The number of TX queues this device has.
 * @rxqs: The number of RX queues this device has.
 *
 * Fill in the fields of the device structure with Ethernet-generic
 * values. Basically does everything except registering the device.
 *
 * Constructs a new net device, complete with a private data area of
 * size (sizeof_priv).  A 32-byte (not bit) alignment is enforced for
 * this private data area.
 */

struct net_device *alloc_etherdev_mqs(int sizeof_priv, unsigned int txqs,
                      unsigned int rxqs)
{
    return alloc_netdev_mqs(sizeof_priv, "eth%d", ether_setup, txqs, rxqs);
}


/**
 *    alloc_netdev_mqs - allocate network device
 *    @sizeof_priv:    size of private data to allocate space for
 *    @name:        device name format string
 *    @setup:        callback to initialize device
 *    @txqs:        the number of TX subqueues to allocate
 *    @rxqs:        the number of RX subqueues to allocate
 *
 *    Allocates a struct net_device with private data area for driver use
 *    and performs basic initialization.  Also allocates subqueue structs
 *    for each queue on the device.
 */
struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
        void (*setup)(struct net_device *),
        unsigned int txqs, unsigned int rxqs)
{
    struct net_device *dev;
    size_t alloc_size;
    struct net_device *p;

    BUG_ON(strlen(name) >= sizeof(dev->name));

    if (txqs < 1) {
        pr_err("alloc_netdev: Unable to allocate device with zero queues\n");
        return NULL;
    }

#ifdef CONFIG_SYSFS
    if (rxqs < 1) {
        pr_err("alloc_netdev: Unable to allocate device with zero RX queues\n");
        return NULL;
    }
#endif

    alloc_size = sizeof(struct net_device);
    if (sizeof_priv) {
        /* ensure 32-byte alignment of private area */
        alloc_size = ALIGN(alloc_size, NETDEV_ALIGN);
        alloc_size += sizeof_priv;
    }
    /* ensure 32-byte alignment of whole construct */
    alloc_size += NETDEV_ALIGN - 1;

    p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
    if (!p)
        p = vzalloc(alloc_size);
    if (!p)
        return NULL;

    dev = PTR_ALIGN(p, NETDEV_ALIGN);
    dev->padded = (char *)dev - (char *)p;

    dev->pcpu_refcnt = alloc_percpu(int);
    if (!dev->pcpu_refcnt)
        goto free_dev;

    if (dev_addr_init(dev))
        goto free_pcpu;

    dev_mc_init(dev);
    dev_uc_init(dev);

    dev_net_set(dev, &init_net);

    dev->gso_max_size = GSO_MAX_SIZE;
    dev->gso_max_segs = GSO_MAX_SEGS;

    INIT_LIST_HEAD(&dev->napi_list);
    INIT_LIST_HEAD(&dev->unreg_list);
    INIT_LIST_HEAD(&dev->close_list);
    INIT_LIST_HEAD(&dev->link_watch_list);
    INIT_LIST_HEAD(&dev->adj_list.upper);
    INIT_LIST_HEAD(&dev->adj_list.lower);
    INIT_LIST_HEAD(&dev->all_adj_list.upper);
    INIT_LIST_HEAD(&dev->all_adj_list.lower);
    dev->priv_flags = IFF_XMIT_DST_RELEASE;
    setup(dev);

    dev->num_tx_queues = txqs;
    dev->real_num_tx_queues = txqs;
    if (netif_alloc_netdev_queues(dev))
        goto free_all;

#ifdef CONFIG_SYSFS
    dev->num_rx_queues = rxqs;
    dev->real_num_rx_queues = rxqs;
    if (netif_alloc_rx_queues(dev))
        goto free_all;
#endif

    strcpy(dev->name, name);
    dev->group = INIT_NETDEV_GROUP;
    if (!dev->ethtool_ops)
        dev->ethtool_ops = &default_ethtool_ops;
    return dev;

free_all:
    free_netdev(dev);
    return NULL;

free_pcpu:
    free_percpu(dev->pcpu_refcnt);
    netif_free_tx_queues(dev);
#ifdef CONFIG_SYSFS
    kfree(dev->_rx);
#endif

free_dev:
    netdev_freemem(dev);
    return NULL;
}

//  释放net_device
void free_netdev(struct net_device *dev);

 模板：

static int xxx_register(void)
{
    ...
    
    /* 分配 net_device 结构体并对其成员赋值 */
    xxx_dev = alloc_netdev(sizeof(struct xxx_priv), "sn%d", xxx_init);
    if (xxx_dev == NULL)
        ... /* 分配 net_device 失败 */

    /* 注册 net_device 结构体 */
    if ((result = register_netdev(xxx_dev)))
    ...
}

static void xxx_unregister(void)
{
    ...
    /* 注销 net_device 结构体 */
    unregister_netdev(xxx_dev);
    /* 释放 net_device 结构体 */
    free_netdev(xxx_dev);
}

 

14.3 初始化ndo_init()

向内核register时，ndo_init()函数会被执行。

int register_netdev(struct net_device *dev)
{
    int err;

    rtnl_lock();
    err = register_netdevice(dev);
    rtnl_unlock();
    return err;
}

int register_netdevice(struct net_device *dev)
{    
    ...
    /* Init, if this function is available */
    if (dev->netdev_ops->ndo_init) {
        ret = dev->netdev_ops->ndo_init(dev);
        if (ret) {
            if (ret > 0)
                ret = -EIO;
            goto out;
        }
    }
    ...
}

 

ndo_init()要干的事：

• 准备硬件
• 初始化net_device结构体的相关内容
• 获取私有指针，并初始化

ndo_init()模板：

xxx_netdev_ops.ndo_init = xxx_init;

void xxx_init(struct net_device *dev)
{
    /* 设备的私有信息结构体 */
    struct xxx_priv *priv;
    
    /* 检查设备是否存在和设备所使用的硬件资源 */
    xxx_hw_init();

    /* 初始化以太网设备的公用成员 */
    ether_setup(dev);

    /* 设置设备的成员函数指针 */
    ndev->netdev_ops = &xxx_netdev_ops;
    ndev->ethtool_ops = &xxx_ethtool_ops;
    dev->watchdog_timeo = timeout;

    /* 取得私有信息， 并初始化它 */
    priv = netdev_priv(dev);
    ... /* 初始化设备私有数据区 */
}

 

14.4 打开和释放ndo_open()/ndo_stop()

ndo_open()的工作：

• 使能硬件资源，申请IO区域、中断和DMA通道等；
• 调用netif_start_queue()函数，激活设备发送队列

ndo_stop()的工作：

• 调用netif_stop_queue()函数，停止设备发送队列
• 释放IO区域、中断和DMA资源　　

原来这两个函数只针对 tx queue
/** 
 *    netif_start_queue - allow transmit
 *    @dev: network device
 *
 *    Allow upper layers to call the device hard_start_xmit routine.
 */
static inline void netif_start_queue(struct net_device *dev)
{
    netif_tx_start_queue(netdev_get_tx_queue(dev, 0));
}
/**
 *    netif_stop_queue - stop transmitted packets
 *    @dev: network device
 *
 *    Stop upper layers calling the device hard_start_xmit routine.
 *    Used for flow control when transmit resources are unavailable.
 */
static inline void netif_stop_queue(struct net_device *dev)
{
    netif_tx_stop_queue(netdev_get_tx_queue(dev, 0));
}

/**
* netif_wake_queue - restart transmit
* @dev: network device
*
* Allow upper layers to call the device hard_start_xmit routine.
* Used for flow control when transmit resources are available.
*/
static inline void netif_wake_queue(struct net_device *dev)
{
　　netif_tx_wake_queue(netdev_get_tx_queue(dev, 0));
}

 

模板：

xxx_netdev_ops.ndo_open = xxx_open;

xxx_netdev_ops.ndo_stop = xxx_stop;

static int xxx_open(struct net_device *dev)
{
    /* 申请端口、 IRQ 等， 类似于 fops->open */
    ret = request_irq(dev->irq, &xxx_interrupt, 0, dev->name, dev);
    ...
    netif_start_queue(dev);
    ...
}

static int xxx_stop(struct net_device *dev)
{
    /* 释放端口、 IRQ 等， 类似于 fops->close */
    free_irq(dev->irq, dev);
    ...
    netif_stop_queue(dev); /* can't transmit any more */
    ...
}

 

14.5 发送 ndo_start_xmit()/ndo_tx_timeout()

ndo_start_xmit()主要流程：

• 解析sk_buff，缓存有效数据
• 校验数据长度，若小于ETH_ZLEN（60，不包含FCS），则尾部填充0
• 控制硬件发送数据

int xxx_tx(struct sk_buff *skb, struct net_device *dev)
{
    int len;
    char *data, shortpkt[ETH_ZLEN];
    if (xxx_send_available(...)) { /* 发送队列未满， 可以发送 */
        /* 获得有效数据指针和长度 */
        data = skb->data;
        len = skb->len;
        if (len < ETH_ZLEN) {
        　　/* 如果帧长小于以太网帧最小长度， 补 0 */
        　　memset(shortpkt, 0, ETH_ZLEN);
       　　 memcpy(shortpkt, skb->data, skb->len);
        　　len = ETH_ZLEN;
       　　 data = shortpkt;
　　　　  }

    　　 dev->trans_start = jiffies; /* 记录发送时间戳 */

   　　 if (avail) {/* 设置硬件寄存器， 让硬件把数据包发送出去 */
        　　xxx_hw_tx(data, len, dev);
    　　} else {
        　　netif_stop_queue(dev);　　// 不一定非要这么搞，返回busy也可以，如果调用了，需要在TX结束中断或者超时中断里唤醒
        　　...
    　　}
　　}
}

void xxx_tx_timeout(struct net_device *dev)
{
　　...
　　netif_wake_queue(dev); /* 重新启动设备发送队列 */ 
}

 

14.6 接收

没有固定形式，在需要的地方调用netif_rx()即可。

 

static void xxx_interrupt(int irq, void *dev_id)
{
    ...
    switch (status &ISQ_EVENT_MASK) {
    case ISQ_RECEIVER_EVENT:
        /* 获取数据包 */
        xxx_rx(dev);
        break;
    /* 其他类型的中断 */
    }
}

static void xxx_rx(struct xxx_device *dev)
{
    ...
    length = get_rev_len (...);
    /* 分配新的套接字缓冲区 */
    skb = dev_alloc_skb(length + 2);

    skb_reserve(skb, 2); /* 对齐 */
    skb->dev = dev;

    /* 读取硬件上接收到的数据 */
    insw(ioaddr + RX_FRAME_PORT, skb_put(skb, length), length >> 1);
    if (length &1)
    skb->data[length - 1] = inw(ioaddr + RX_FRAME_PORT);
    
    /* 获取上层协议类型 */
    skb->protocol = eth_type_trans(skb, dev);

    /* 把数据包交给上层 */
    netif_rx(skb);

    /* 记录接收时间戳 */
    dev->last_rx = jiffies;
    ...
}

 

 

 

14.7 连接状态

一般在定时中断里，检查并更新连接状态。

static inline bool netif_carrier_ok(const struct net_device *dev);　　// 连接是否ok
void netif_carrier_on(struct net_device *dev);　　　　　　　　　　　　　 // 改变连接状态，on
void netif_carrier_off(struct net_device *dev);　　　　　　　　　　　　　// 改变连接状态，off

 

 

14.8 参数设置和统计数据

参数设置可以通过ioctl()，传入的描述符为socket，linux对命令做了统一规定，如下：

/*路径： include/uapi/linux/sockios.h */
/*
 * INET        An implementation of the TCP/IP protocol suite for the LINUX
 *        operating system.  INET is implemented using the  BSD Socket
 *        interface as the means of communication with the user level.
 *
 *        Definitions of the socket-level I/O control calls.
 *
 * Version:    @(#)sockios.h    1.0.2    03/09/93
 *
 * Authors:    Ross Biro
 *        Fred N. van Kempen, 
 *
 *        This program is free software; you can redistribute it and/or
 *        modify it under the terms of the GNU General Public License
 *        as published by the Free Software Foundation; either version
 *        2 of the License, or (at your option) any later version.
 */
#ifndef _LINUX_SOCKIOS_H
#define _LINUX_SOCKIOS_H

#include 

/* Linux-specific socket ioctls */
#define SIOCINQ        FIONREAD
#define SIOCOUTQ    TIOCOUTQ        /* output queue size (not sent + not acked) */

/* Routing table calls. */
#define SIOCADDRT    0x890B        /* add routing table entry    */
#define SIOCDELRT    0x890C        /* delete routing table entry    */
#define SIOCRTMSG    0x890D        /* call to routing system    */

/* Socket configuration controls. */
#define SIOCGIFNAME    0x8910        /* get iface name        */
#define SIOCSIFLINK    0x8911        /* set iface channel        */
#define SIOCGIFCONF    0x8912        /* get iface list        */
#define SIOCGIFFLAGS    0x8913        /* get flags            */
#define SIOCSIFFLAGS    0x8914        /* set flags            */
#define SIOCGIFADDR    0x8915        /* get PA address        */
#define SIOCSIFADDR    0x8916        /* set PA address        */
#define SIOCGIFDSTADDR    0x8917        /* get remote PA address    */
#define SIOCSIFDSTADDR    0x8918        /* set remote PA address    */
#define SIOCGIFBRDADDR    0x8919        /* get broadcast PA address    */
#define SIOCSIFBRDADDR    0x891a        /* set broadcast PA address    */
#define SIOCGIFNETMASK    0x891b        /* get network PA mask        */
#define SIOCSIFNETMASK    0x891c        /* set network PA mask        */
#define SIOCGIFMETRIC    0x891d        /* get metric            */
#define SIOCSIFMETRIC    0x891e        /* set metric            */
#define SIOCGIFMEM    0x891f        /* get memory address (BSD)    */
#define SIOCSIFMEM    0x8920        /* set memory address (BSD)    */
#define SIOCGIFMTU    0x8921        /* get MTU size            */
#define SIOCSIFMTU    0x8922        /* set MTU size            */
#define SIOCSIFNAME    0x8923        /* set interface name */
#define    SIOCSIFHWADDR    0x8924        /* set hardware address     */
#define SIOCGIFENCAP    0x8925        /* get/set encapsulations       */
#define SIOCSIFENCAP    0x8926        
#define SIOCGIFHWADDR    0x8927        /* Get hardware address        */
#define SIOCGIFSLAVE    0x8929        /* Driver slaving support    */
#define SIOCSIFSLAVE    0x8930
#define SIOCADDMULTI    0x8931        /* Multicast address lists    */
#define SIOCDELMULTI    0x8932
#define SIOCGIFINDEX    0x8933        /* name -> if_index mapping    */
#define SIOGIFINDEX    SIOCGIFINDEX    /* misprint compatibility :-)    */
#define SIOCSIFPFLAGS    0x8934        /* set/get extended flags set    */
#define SIOCGIFPFLAGS    0x8935
#define SIOCDIFADDR    0x8936        /* delete PA address        */
#define    SIOCSIFHWBROADCAST    0x8937    /* set hardware broadcast addr    */
#define SIOCGIFCOUNT    0x8938        /* get number of devices */

#define SIOCGIFBR    0x8940        /* Bridging support        */
#define SIOCSIFBR    0x8941        /* Set bridging options     */

#define SIOCGIFTXQLEN    0x8942        /* Get the tx queue length    */
#define SIOCSIFTXQLEN    0x8943        /* Set the tx queue length     */

/* SIOCGIFDIVERT was:    0x8944        Frame diversion support */
/* SIOCSIFDIVERT was:    0x8945        Set frame diversion options */

#define SIOCETHTOOL    0x8946        /* Ethtool interface        */

#define SIOCGMIIPHY    0x8947        /* Get address of MII PHY in use. */
#define SIOCGMIIREG    0x8948        /* Read MII PHY register.    */
#define SIOCSMIIREG    0x8949        /* Write MII PHY register.    */

#define SIOCWANDEV    0x894A        /* get/set netdev parameters    */

#define SIOCOUTQNSD    0x894B        /* output queue size (not sent only) */

/* ARP cache control calls. */
            /*  0x8950 - 0x8952  * obsolete calls, don't re-use */
#define SIOCDARP    0x8953        /* delete ARP table entry    */
#define SIOCGARP    0x8954        /* get ARP table entry        */
#define SIOCSARP    0x8955        /* set ARP table entry        */

/* RARP cache control calls. */
#define SIOCDRARP    0x8960        /* delete RARP table entry    */
#define SIOCGRARP    0x8961        /* get RARP table entry        */
#define SIOCSRARP    0x8962        /* set RARP table entry        */

/* Driver configuration calls */

#define SIOCGIFMAP    0x8970        /* Get device parameters    */
#define SIOCSIFMAP    0x8971        /* Set device parameters    */

/* DLCI configuration calls */

#define SIOCADDDLCI    0x8980        /* Create new DLCI device    */
#define SIOCDELDLCI    0x8981        /* Delete DLCI device        */

#define SIOCGIFVLAN    0x8982        /* 802.1Q VLAN support        */
#define SIOCSIFVLAN    0x8983        /* Set 802.1Q VLAN options     */

/* bonding calls */

#define SIOCBONDENSLAVE    0x8990        /* enslave a device to the bond */
#define SIOCBONDRELEASE 0x8991        /* release a slave from the bond*/
#define SIOCBONDSETHWADDR      0x8992    /* set the hw addr of the bond  */
#define SIOCBONDSLAVEINFOQUERY 0x8993   /* rtn info about slave state   */
#define SIOCBONDINFOQUERY      0x8994    /* rtn info about bond state    */
#define SIOCBONDCHANGEACTIVE   0x8995   /* update to a new active slave */
            
/* bridge calls */
#define SIOCBRADDBR     0x89a0        /* create new bridge device     */
#define SIOCBRDELBR     0x89a1        /* remove bridge device         */
#define SIOCBRADDIF    0x89a2        /* add interface to bridge      */
#define SIOCBRDELIF    0x89a3        /* remove interface from bridge */

/* hardware time stamping: parameters in linux/net_tstamp.h */
#define SIOCSHWTSTAMP    0x89b0        /* set and get config        */
#define SIOCGHWTSTAMP    0x89b1        /* get config            */

/* Device private ioctl calls */

/*
 *    These 16 ioctls are available to devices via the do_ioctl() device
 *    vector. Each device should include this file and redefine these names
 *    as their own. Because these are device dependent it is a good idea
 *    _NOT_ to issue them to random objects and hope.
 *
 *    THESE IOCTLS ARE _DEPRECATED_ AND WILL DISAPPEAR IN 2.5.X -DaveM
 */
 
#define SIOCDEVPRIVATE    0x89F0    /* to 89FF */

/*
 *    These 16 ioctl calls are protocol private
 */
 
#define SIOCPROTOPRIVATE 0x89E0 /* to 89EF */
#endif    /* _LINUX_SOCKIOS_H */

 

ndo_get_stats()模板，在程序合适的地方对各种计数进行设置即可。

struct net_device_stats *xxx_stats(struct net_device *dev)
{
    …
    return &dev->stats;
}

struct net_device_stats
{
    unsigned long rx_packets; /* 收到的数据包数 */
    unsigned long tx_packets; /* 发送的数据包数 */
    unsigned long rx_bytes; /* 收到的字节数 */
    unsigned long tx_bytes; /* 发送的字节数 */
    unsigned long rx_errors; /* 收到的错误数据包数 */
    unsigned long tx_errors; /* 发生发送错误的数据包数 */
     ...
};

 

 

14.9 DM9000实例

14.10 总结

 

转载于:https://www.cnblogs.com/liuwanpeng/p/7484395.html