慢慢欣赏linux 网络协议栈四 sk_buff以及数据收发

以3c359x.c的网卡为例，因为这是《深入理解Linux网络技术内幕》里面的例子

irqreturn_t vortex_interrupt(int irq, void *dev_id)
	vortex_rx(dev);
	=>int vortex_rx(struct net_device *dev)
		struct vortex_private *vp = netdev_priv(dev);
		void __iomem *ioaddr = vp->ioaddr;
		short rx_status;
		while ((rx_status = ioread16(ioaddr + RxStatus)) > 0)
			int pkt_len = rx_status & 0x1fff;
			struct sk_buff *skb = dev_alloc_skb(pkt_len + 5);
			skb_reserve(skb, 2);	/* Align IP on 16 byte boundaries */
			if (vp->bus_master && ! (ioread16(ioaddr + Wn7_MasterStatus) & 0x8000)) 
				dma_addr_t dma = pci_map_single(VORTEX_PCI(vp), skb_put(skb, pkt_len), pkt_len, PCI_DMA_FROMDEVICE);
				iowrite32(dma, ioaddr + Wn7_MasterAddr);
				iowrite16((skb->len + 3) & ~3, ioaddr + Wn7_MasterLen);
				iowrite16(StartDMAUp, ioaddr + EL3_CMD);
				while (ioread16(ioaddr + Wn7_MasterStatus) & 0x8000)
					;
				pci_unmap_single(VORTEX_PCI(vp), dma, pkt_len, PCI_DMA_FROMDEVICE);
			else 
				ioread32_rep(ioaddr + RX_FIFO, skb_put(skb, pkt_len), (pkt_len + 3) >> 2);
				
			iowrite16(RxDiscard, ioaddr + EL3_CMD); /* Pop top Rx packet. */
			skb->protocol = eth_type_trans(skb, dev);
			netif_rx(skb)
			=>int netif_rx(struct sk_buff *skb)
				if (queue->input_pkt_queue.qlen <= netdev_max_backlog)
					if (queue->input_pkt_queue.qlen)
			enqueue:
						__skb_queue_tail(&queue->input_pkt_queue, skb);
						return NET_RX_SUCCESS;
						
					napi_schedule(&queue->backlog);
					=>inline void napi_schedule(struct napi_struct *n)
						if (napi_schedule_prep(n))
							__napi_schedule(n);
							=>void __napi_schedule(struct napi_struct *n)
								list_add_tail(&n->poll_list, &__get_cpu_var(softnet_data).poll_list);
								__raise_softirq_irqoff(NET_RX_SOFTIRQ);//唤醒软中断
					goto enqueue;

收包软中断入口函数

void net_rx_action(struct softirq_action *h)
	struct list_head *list = &__get_cpu_var(softnet_data).poll_list;
	while (!list_empty(list))
		n = list_first_entry(list, struct napi_struct, poll_list);

		have = netpoll_poll_lock(n);

		weight = n->weight;
		
		n = list_first_entry(list, struct napi_struct, poll_list);

		have = netpoll_poll_lock(n);

		weight = n->weight;
		
		work = 0;
		if (test_bit(NAPI_STATE_SCHED, &n->state))
			work = n->poll(n, weight);
			=>int process_backlog(struct napi_struct *napi, int quota)
			
		budget -= work;

Linux 网络协议栈开发代码分析篇之数据收发（一） —— netif_receive_skb()函数
https://blog.youkuaiyun.com/zqixiao_09/article/details/79185800

Linux内核--网络栈实现分析（二）--数据包的传递过程（上）
https://blog.youkuaiyun.com/geekcome/article/details/7492423