linux 内核协议栈收报流程（一）ixgbe网卡驱动
首先模块加载insmod ixgbe.ko
module_init(ixgbe_init_module);
module_init(ixgbe_init_module);
{
int ret;
pr_info("%s - version %s\n", ixgbe_driver_string, ixgbe_driver_version);
pr_info("%s\n", ixgbe_copyright);
ixgbe_dbg_init();
ret = pci_register_driver(&ixgbe_driver);
if (ret) {
ixgbe_dbg_exit();
return ret;
}
#ifdef CONFIG_IXGBE_DCA
dca_register_notify(&dca_notifier);
#endif
return 0;
}
于是看pci设备的核心结构体
static struct pci_driver ixgbe_driver = {
.name = ixgbe_driver_name,
.id_table = ixgbe_pci_tbl,
.probe = ixgbe_probe,
.remove = ixgbe_remove,
#ifdef CONFIG_PM
.suspend = ixgbe_suspend,
.resume = ixgbe_resume,
#endif
.shutdown = ixgbe_shutdown,
.sriov_configure = ixgbe_pci_sriov_configure,
.err_handler = &ixgbe_err_handler
};
当设备加载成功后，会执行ixgbe_probe函数
static int ixgbe_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
{
/*分配struct net_device *netdev 结构体*/
netdev = alloc_etherdev_mq(sizeof(struct ixgbe_adapter), indices);
if (!netdev) {
err = -ENOMEM;
goto err_alloc_etherdev;
}
SET_NETDEV_DEV(netdev, &pdev->dev);
/*分配struct ixgbe_adapter *adapter结构体*/
adapter = netdev_priv(netdev);
/*分配dev结构体的ops函数指针集合*/
netdev->netdev_ops = &ixgbe_netdev_ops;
err = ixgbe_sw_init(adapter);
err = ixgbe_init_interrupt_scheme(adapter);
/*设备注册完毕*/
err = register_netdev(netdev);
}
重点看ixgbe_init_interrupt_scheme(adapter)函数，该函数里面会初始化adapter结构体以及napi相关的东西
int ixgbe_init_interrupt_scheme(struct ixgbe_adapter *adapter)
{
err = ixgbe_alloc_q_vectors(adapter);
}
static int ixgbe_alloc_q_vectors(struct ixgbe_adapter *adapter)
{
if (q_vectors >= (rxr_remaining + txr_remaining)) {
for (; rxr_remaining; v_idx++) {
err = ixgbe_alloc_q_vector(adapter, q_vectors, v_idx,
0, 0, 1, rxr_idx);
if (err)
goto err_out;
/* update counts and index */
rxr_remaining--;
rxr_idx++;
}
}
}
static int ixgbe_alloc_q_vector(struct ixgbe_adapter *adapter,
int v_count, int v_idx,
int txr_count, int txr_idx,
int rxr_count, int rxr_idx)
{
/* setup affinity mask and node */
if (cpu != -1)
cpumask_set_cpu(cpu, &q_vector->affinity_mask);
q_vector->numa_node = node;
#ifdef CONFIG_IXGBE_DCA
/* initialize CPU for DCA */
q_vector->cpu = -1;
#endif
/* initialize NAPI */
netif_napi_add(adapter->netdev, &q_vector->napi,
ixgbe_poll, 64);
napi_hash_add(&q_vector->napi);
}
到此为止，网卡设置初始化完毕
其中涉及到如下几个结构体
ixgbe_adapter
/* board specific private data structure */
struct ixgbe_adapter {
//发送的rings
struct ixgbe_ring *tx_ring[MAX_TX_QUEUES] ____cacheline_aligned_in_smp;
//接收的rings
struct ixgbe_ring *rx_ring[MAX_RX_QUEUES];
//这个vector里面包含了napi结构
//应该是跟下面的entries一一对应起来做为是一个中断向量的东西吧
struct ixgbe_q_vector *q_vector[MAX_Q_VECTORS];
//这个里面估计是MSIX的多个中断对应的响应接口
struct msix_entry *msix_entries;
}
struct ixgbe_q_vector {
struct ixgbe_adapter *adapter;
ifdef CONFIG_IXGBE_DCA
int cpu; /* CPU for DCA */
#endif
u16 v_idx; /* index of q_vector within array, also used for
* finding the bit in EICR and friends that
* represents the vector for this ring */
u16 itr; /* Interrupt throttle rate written to EITR */
struct ixgbe_ring_container rx, tx;
struct napi_struct napi;/*napi结构体*/
cpumask_t affinity_mask;
int numa_node;
struct rcu_head rcu; /* to avoid race with update stats on free */
char name[IFNAMSIZ + 9];
/* for dynamic allocation of rings associated with this q_vector */
struct ixgbe_ring ring[0] ____cacheline_internodealigned_in_smp;
};
struct napi_struct {
/* The poll_list must only be managed by the entity which
* changes the state of the NAPI_STATE_SCHED bit. This means
* whoever atomically sets that bit can add this napi_struct
* to the per-cpu poll_list, and whoever clears that bit
* can remove from the list right before clearing the bit.
*/
struct list_head poll_list;
unsigned long state;
int weight;
unsigned int gro_count;
int (*poll)(struct napi_struct *, int);//poll的接口实现
#ifdef CONFIG_NETPOLL
spinlock_t poll_lock;
int poll_owner;
#endif
struct net_device *dev;
struct sk_buff *gro_list;
struct sk_buff *skb;
struct list_head dev_list;
};
然后当我们ifconfig dev up 时，会执行dev_ops->open函数
static int ixgbe_open(struct net_device *netdev)
{
/* allocate transmit descriptors */
err = ixgbe_setup_all_tx_resources(adapter);
if (err)
goto err_setup_tx;
/* allocate receive descriptors */
err = ixgbe_setup_all_rx_resources(adapter);
/*注册中断*/
err = ixgbe_request_irq(adapter);
}
static int ixgbe_request_irq(struct ixgbe_adapter *adapter)
{
struct net_device *netdev = adapter->netdev;
int err;
if (adapter->flags & IXGBE_FLAG_MSIX_ENABLED)
err = ixgbe_request_msix_irqs(adapter);
else if (adapter->flags & IXGBE_FLAG_MSI_ENABLED)
err = request_irq(adapter->pdev->irq, ixgbe_intr, 0,
netdev->name, adapter);
else
err = request_irq(adapter->pdev->irq, ixgbe_intr, IRQF_SHARED,
netdev->name, adapter);
if (err)
e_err(probe, "request_irq failed, Error %d\n", err);
return err;
}
static int ixgbe_request_msix_irqs(struct ixgbe_adapter *adapter)
{
for (vector = 0; vector < adapter->num_q_vectors; vector++) {
struct ixgbe_q_vector *q_vector = adapter->q_vector[vector];
struct msix_entry *entry = &adapter->msix_entries[vector];
err = request_irq(entry->vector, &ixgbe_msix_clean_rings, 0,
q_vector->name, q_vector);
}
从上面的代码流程可以看出，最终注册的中断处理函数为ixgbe_msix_clean_rings
static irqreturn_t ixgbe_msix_clean_rings(int irq, void *data)
{
struct ixgbe_q_vector *q_vector = data;
/* EIAM disabled interrupts (on this vector) for us */
if (q_vector->rx.ring || q_vector->tx.ring)
napi_schedule(&q_vector->napi);
return IRQ_HANDLED;
}
从上述代码中可以看，该中断处理函数仅仅作为napi的调度者
当数据包到来时，首先唤醒硬中断执行ixgbe_msix_clean_rings函数，最终napi_schedule会调用__raise_softirq_irqoff去触发一个软中断NET_RX_SOFTIRQ，然后又对应的软中断接口去实现往上的协议栈逻辑
然后看看napi 调度函数都做了些什么工作
static inline void napi_schedule(struct napi_struct *n)
{
if (napi_schedule_prep(n))
__napi_schedule(n);
}
void __napi_schedule(struct napi_struct *n)
{
unsigned long flags;
local_irq_save(flags);
____napi_schedule(this_cpu_ptr(&softnet_data), n);
local_irq_restore(flags);
}
最终可以看出napi调度函数把napi结构体挂到了per cpu的私有数据结构softnet_data上
struct softnet_data {
struct Qdisc *output_queue;
struct Qdisc **output_queue_tailp;
struct list_head poll_list;
struct sk_buff *completion_queue;
struct sk_buff_head process_queue;
/* stats */
unsigned int processed;
unsigned int time_squeeze;
unsigned int cpu_collision;
unsigned int received_rps;
#ifdef CONFIG_RPS
struct softnet_data *rps_ipi_list;
/* Elements below can be accessed between CPUs for RPS */
struct call_single_data csd ____cacheline_aligned_in_smp;
struct softnet_data *rps_ipi_next;
unsigned int cpu;
unsigned int input_queue_head;
unsigned int input_queue_tail;
#endif
unsigned int dropped;
struct sk_buff_head input_pkt_queue;
struct napi_struct backlog;/*napi结构体里面的双向链表中*/
};
NET_RX_SOFTIRQ是收到数据包的软中断信号对应的接口是net_rx_action
NET_TX_SOFTIRQ是发送完数据包后的软中断信号对应的接口是net_tx_action
static void net_rx_action(struct softirq_action *h)
{
/* 获取每个cpu的数据*/
struct softnet_data *sd = this_cpu_ptr(&softnet_data);
while (!list_empty(&sd->poll_list)) {
struct napi_struct *n;
n = list_first_entry(&sd->poll_list, struct napi_struct, poll_list);
if (test_bit(NAPI_STATE_SCHED, &n->state)) {
work = n->poll(n, weight);
trace_napi_poll(n);
}
}
于是就执行到初始化napi结构体中的poll函数，在这里为ixgbe_poll
int ixgbe_poll(struct napi_struct *napi, int budget)
{
struct ixgbe_q_vector *q_vector =
container_of(napi, struct ixgbe_q_vector, napi);
struct ixgbe_adapter *adapter = q_vector->adapter;
struct ixgbe_ring *ring;
int per_ring_budget;
bool clean_complete = true;
#ifdef CONFIG_IXGBE_DCA
if (adapter->flags & IXGBE_FLAG_DCA_ENABLED)
ixgbe_update_dca(q_vector);
#endif
ixgbe_for_each_ring(ring, q_vector->tx)
clean_complete &= !!ixgbe_clean_tx_irq(q_vector, ring);
if (!ixgbe_qv_lock_napi(q_vector))
return budget;
/* attempt to distribute budget to each queue fairly, but don't allow
* the budget to go below 1 because we'll exit polling */
if (q_vector->rx.count > 1)
per_ring_budget = max(budget/q_vector->rx.count, 1);
else
per_ring_budget = budget;
ixgbe_for_each_ring(ring, q_vector->rx)
clean_complete &= (ixgbe_clean_rx_irq(q_vector, ring,
per_ring_budget) < per_ring_budget);
ixgbe_qv_unlock_napi(q_vector);
/* If all work not completed, return budget and keep polling */
if (!clean_complete)
return budget;
/* all work done, exit the polling mode */
napi_complete(napi);
if (adapter->rx_itr_setting & 1)
ixgbe_set_itr(q_vector);
if (!test_bit(__IXGBE_DOWN, &adapter->state))
ixgbe_irq_enable_queues(adapter, ((u64)1 << q_vector->v_idx));
return 0;
}
static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
struct ixgbe_ring *rx_ring,
const int budget)
{
ixgbe_rx_skb(q_vector, skb);
}
static void ixgbe_rx_skb(struct ixgbe_q_vector *q_vector,
struct sk_buff *skb)
{
if (ixgbe_qv_busy_polling(q_vector))
netif_receive_skb(skb);
else
napi_gro_receive(&q_vector->napi, skb);
}
int netif_receive_skb(struct sk_buff *skb)
{
int ret;
net_timestamp_check(netdev_tstamp_prequeue, skb);
if (skb_defer_rx_timestamp(skb))
return NET_RX_SUCCESS;
rcu_read_lock();
#ifdef CONFIG_RPS
if (static_key_false(&rps_needed)) {
struct rps_dev_flow voidflow, *rflow = &voidflow;
int cpu = get_rps_cpu(skb->dev, skb, &rflow);
if (cpu >= 0) {
ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
rcu_read_unlock();
return ret;
}
}
#endif
/*最终协议栈开始收报*/
ret = __netif_receive_skb(skb);
rcu_read_unlock();
return ret;
}
