目录
网络收包过程
1，数据帧从外部网络到达网卡
2，网卡把帧使用DMA方式搬到内存
3，硬中断通知CPU
4，CPU响应硬中断，通知软中断处理数据
5，ksoftirqd内核进程处理软中断，调用网卡驱动注册的poll函数开始收包
6，帧从Ring buffer上取出
7，协议层处理网络帧将数据data放到socket接收队列中
创建ksoftirqd内核线程
软中断在内核线程ksoftirqd中进行 [kernel/softirq.c]
static struct smp_hotplug_thread softirq_threads = {
.store = &ksoftirqd,
.thread_should_run = ksoftirqd_should_run,
.thread_fn = run_ksoftirqd,
.thread_comm = "ksoftirqd/%u",
};
static __init int spawn_ksoftirqd(void)
{
cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
takeover_tasklets);
BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
return 0;
}
early_initcall(spawn_ksoftirqd);ksoftirqd被创建出来以后，进入循环函数ksoftirqd_should_run与run_ksoftirqd，判断有没有软中断需要被处理。
网络子系统初始化
static int __init net_dev_init(void)
{
for_each_possible_cpu(i) {
struct work_struct *flush = per_cpu_ptr(&flush_works, i);
struct softnet_data *sd = &per_cpu(softnet_data, i);
skb_queue_head_init(&sd->input_pkt_queue);
skb_queue_head_init(&sd->process_queue);
}
...
open_softirq(NET_TX_SOFTIRQ, net_tx_action);
open_softirq(NET_RX_SOFTIRQ, net_rx_action);
}
subsys_initcall(net_dev_init);
open_softirq注册软中断NET_TX_SOFTIRQ发送与NET_RX_SOFTIRQ接收。
void open_softirq(int nr, void (*action)(struct softirq_action *))
{
softirq_vec[nr].action = action;
}softirq_vec中断向量，根据软中断枚举，注册相应的函数。
协议栈注册
网络层ip协议，传输层tcp/udp协议
static struct packet_type ip_packet_type __read_mostly = {
.type = cpu_to_be16(ETH_P_IP),
.func = ip_rcv,
.list_func = ip_list_rcv,
};
static struct net_protocol tcp_protocol = {
.early_demux = tcp_v4_early_demux,
.early_demux_handler = tcp_v4_early_demux,
.handler = tcp_v4_rcv,
.err_handler = tcp_v4_err,
.no_policy = 1,
.netns_ok = 1,
.icmp_strict_tag_validation = 1,
};
static struct net_protocol udp_protocol = {
.early_demux = udp_v4_early_demux,
.early_demux_handler = udp_v4_early_demux,
.handler = udp_rcv,
.err_handler = udp_err,
.no_policy = 1,
.netns_ok = 1,
};
static int __init inet_init(void)
{
//注册tcp_port
rc = proto_register(&tcp_prot, 1);
//注册udp_port
rc = proto_register(&udp_prot, 1);
...
//注册udp协议
if (inet_add_protocol(&udp_protocol, IPPROTO_UDP) < 0)
pr_crit("%s: Cannot add UDP protocol\n", __func__);
//注册tcp协议
if (inet_add_protocol(&tcp_protocol, IPPROTO_TCP) < 0)
pr_crit("%s: Cannot add TCP protocol\n", __func__);
dev_add_pack(&ip_packet_type);
}?先看一下inet_add_protocol
struct net_protocol __rcu *inet_protos[MAX_INET_PROTOS] __read_mostly;
inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
{
...
return !cmpxchg((const struct net_protocol **)&inet_protos[protocol],
NULL, prot) ? 0 : -1;
}inet_add_protocol将tcp,udp相应的函数注册到inet_protos数组中。即inet_protos 记录着 udp，tcp 的处理函数地址
再看一下dev_add_pack
void dev_add_pack(struct packet_type *pt)
{
struct list_head *head = ptype_head(pt);
...
}
static inline struct list_head *ptype_head(const struct packet_type *pt)
{
if (pt->type == htons(ETH_P_ALL))
return pt->dev ? &pt->dev->ptype_all : &ptype_all;
else
return pt->dev ? &pt->dev->ptype_specific :
&ptype_base[ntohs(pt->type) & PTYPE_HASH_MASK];
}
ptype_base
存储着ip_rcv() 函数的处理地址。
网卡驱动初始化
驱动程序会使? module_init 向内核注册?个初始化函数，以igb网卡驱动为例
static struct pci_driver igb_driver = {
.name = igb_driver_name,
.id_table = igb_pci_tbl,
.probe = igb_probe,
.remove = igb_remove,
...
};
static int __init igb_init_module(void)
{
int ret;
ret = pci_register_driver(&igb_driver);
return ret;
}
module_init(igb_init_module);
当网卡设备被识别后，内核会调用其驱动probe方法（igb_probe）
static int igb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
{
//DMA初始化
err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
//ethools注册igb_netdev_ops
netdev->netdev_ops = &igb_netdev_ops;
igb_set_ethtool_ops(netdev);
err = igb_sw_init(adapter);
//注册netdev
err = register_netdev(netdev);
dev_pm_set_driver_flags(&pdev->dev, DPM_FLAG_NEVER_SKIP);
}igb_sw_init-> igb_init_interrupt_scheme->igb_alloc_q_vectors->igb_alloc_q_vector
static int igb_alloc_q_vector(struct igb_adapter *adapter,
int v_count, int v_idx,
int txr_count, int txr_idx,
int rxr_count, int rxr_idx)
{
netif_napi_add(adapter->netdev, &q_vector->napi,
igb_poll, 64);
...
}
NAPI 机制所必须的 poll 函数，对于 igb ?卡驱动来说是 igb_poll。
启动网卡
当启??个?卡时（例通过
ifconfig eth0 up
），net_device_ops 中的
igb_open
?法会被调?
- 启动网卡
- 分配RX TX队列内存
- 调用net_device_ops中注册open等函数
- 注册中断处理函数
- 开硬中断，等待数据包
static int __igb_open(struct net_device *netdev, bool resuming)
{
/* allocate transmit descriptors */
err = igb_setup_all_tx_resources(adapter);
/* allocate receive descriptors */
err = igb_setup_all_rx_resources(adapter);
//处理中断
err = igb_request_irq(adapter);
//使能napi
for (i = 0; i < adapter->num_q_vectors; i++)
napi_enable(&(adapter->q_vector[i]->napi));
...
return 0;
}中断处理igb_request_irq
static int igb_request_irq(struct igb_adapter *adapter)
{
struct net_device *netdev = adapter->netdev;
struct pci_dev *pdev = adapter->pdev;
int err = 0;
if (adapter->flags & IGB_FLAG_HAS_MSIX) {
err = igb_request_msix(adapter);
...
}
...
}
static int igb_request_msix(struct igb_adapter *adapter)
{
for (i = 0; i < adapter->num_q_vectors; i++) {
struct igb_q_vector *q_vector = adapter->q_vector[i];
vector++;
err = request_irq(adapter->msix_entries[vector].vector,
igb_msix_ring, 0, q_vector->name,
q_vector);
}
igb_configure_msix(adapter);
return 0;
...
}
在
igb_request_msix
中对于多队列的?卡，为每?个队列都注册了中断，其对应的中断处理函数为?igb_msix_ring。
参考
