net_dev_init中通過(guò)open_softirq(NET_RX_SOFTIRQ, net_rx_action);注冊了軟中斷處理函數，napi調度中激發(fā)了軟中斷調用net_rx_action： static void net_rx_action(struct softirq_action *h) { struct list_head *list = &__get_cpu_var(softnet_data).poll_list; unsigned long start_time = jiffies; int budget = netdev_budget; void *have;
local_irq_disable();
while (!list_empty(list)) { struct napi_struct *n; int work, weight;
/* If softirq window is exhuasted then punt. * * Note that this is a slight policy change from the * previous NAPI code, which would allow up to 2 * jiffies to pass before breaking out. The test * used to be "jiffies - start_time > 1". */ if (unlikely(budget <= 0 || jiffies != start_time)) goto softnet_break;
local_irq_enable();
/* Even though interrupts have been re-enabled, this * access is safe because interrupts can only add new * entries to the tail of this list, and only ->poll() * calls can remove this head entry from the list. */ n = list_entry(list->next, struct napi_struct, poll_list);
have = netpoll_poll_lock(n); //weight 每次輪詢(xún)最大數量 weight = n->weight;
/* This NAPI_STATE_SCHED test is for avoiding a race * with netpoll's poll_napi(). Only the entity which * obtains the lock and sees NAPI_STATE_SCHED set will * actually make the ->poll() call. Therefore we avoid * accidently calling ->poll() when NAPI is not scheduled. */ work = 0; if (test_bit(NAPI_STATE_SCHED, &n->state)) //napi的狀態(tài)是否為NAPI_STATE_SCHED work = n->poll(n, weight); //執行輪詢(xún)，輪詢(xún)函數初始化是在net_dev_init中： //queue->backlog.poll = process_backlog;（默認） WARN_ON_ONCE(work > weight);
budget -= work;
local_irq_disable();
/* Drivers must not modify the NAPI state if they * consume the entire weight. In such cases this code * still "owns" the NAPI instance and therefore can * move the instance around on the list at-will. */ if (unlikely(work == weight)) { if (unlikely(napi_disable_pending(n))) __napi_complete(n); else list_move_tail(&n->poll_list, list); }
netpoll_poll_unlock(have); } out: local_irq_enable(); 。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。 }
static int process_backlog(struct napi_struct *napi, int quota) { int work = 0; struct softnet_data *queue = &__get_cpu_var(softnet_data); unsigned long start_time = jiffies;
napi->weight = weight_p; do { struct sk_buff *skb;
local_irq_disable(); skb = __skb_dequeue(&queue->input_pkt_queue); if (!skb) { __napi_complete(napi); //從poll隊列中刪除napi local_irq_enable(); break; } local_irq_enable();
netif_receive_skb(skb); } while (++work < quota && jiffies == start_time);
return work; } 在netif_receive_skb中，會(huì )輪詢(xún)ptype_all list找到與packet_bind中協(xié)議類(lèi)型相符的packet_type，然后通過(guò)deliver_skb調用packet type所注冊的接收處理函數。 static inline int deliver_skb(struct sk_buff *skb, struct packet_type *pt_prev, struct net_device *orig_dev) { atomic_inc(&skb->users); return pt_prev->func(skb, skb->dev, pt_prev, orig_dev); //packet_create時(shí)初始化func指向packet_rcv }
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