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 <linux/skbuff.h> /** * 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->data<skb->head)) 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 <net/iw_handler.h> 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 "); return NULL; } #ifdef CONFIG_SYSFS if (rxqs < 1) { pr_err("alloc_netdev: Unable to allocate device with zero RX queues "); 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, <waltje@uWalt.NL.Mugnet.ORG> * * 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 <asm/sockios.h> /* 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 */ ... };