|
1 pppoe kernel 分析 【2.6.16】static int __init pppoe_init(void){int err = proto_register(&pppoe_sk_proto, 0);//注册socket协议，协议名称PPPOEif (err)goto out;err = register_pppox_proto(PX_PROTO_OE, &pppoe_proto);/*注册pppoe协议类型，这个是在pppox内部注册这个注册后将为socket提高一个重要的调用 pppoe_create(struct socket *sock)在这个函数中sk->sk_backlog_rcv = pppoe_rcv_core;//这个函数提供了接收报文处理函数,当sk_state置PPPOX_BOUND标志位的话，这个报文将首先在内核处理ppp_input(),如果没有改标志位的话交到sock接收队列sock_queue_rcv_skb(sk, skb)。将在用户空间进行处理sk->sk_state = PPPOX_NONE;sk->sk_type = SOCK_STREAM;sk->sk_family = PF_PPPOX;sk->sk_protocol = PX_PROTO_OE;*/if (err)goto out_unregister_pppoe_proto;err = pppoe_proc_init();if (err)goto out_unregister_pppox_proto;dev_add_pack(&pppoes_ptype);dev_add_pack(&pppoed_ptype);register_netdevice_notifier(&pppoe_notifier);out:return err;out_unregister_pppox_proto:unregister_pppox_proto(PX_PROTO_OE);out_unregister_pppoe_proto:proto_unregister(&pppoe_sk_proto);goto out;}2 ppp Genericppp_input() ,这个函数将判断ppp报文是链路控制报文还是数据报文来决定处理方式如果为 Link Control Protocol 那么就会将包围挂到pch->file.rq ，pppd来负责接收控制报文的队列如果为其他类型的，将通过ppp_do_recv 来对报文（如果是压缩报文：解压），去ppp头。 最后调用netif_rx(skb);来实现ppp网口收报文的处理。3 netif_rx 的作用？{struct softnet_data *queue;unsigned long flags;/* if netpoll wants it, pretend we never saw it */if (netpoll_rx(skb))return NET_RX_DROP;//首先如果存在netpoll启用netpoll机制来接收处理报文if (!skb->tstamp.off_sec)net_timestamp(skb);// 如果没有注册netpoll处理函数，则放到cpu的接收队列/** The code is rearranged so that the path is the most* short when CPU is congested, but is still operating.*/local_irq_save(flags);queue = &__get_cpu_var(softnet_data);__get_cpu_var(netdev_rx_stat).total++;if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {if (queue->input_pkt_queue.qlen) {enqueue:dev_hold(skb->dev);__skb_queue_tail(&queue->input_pkt_queue, skb);local_irq_restore(flags);return NET_RX_SUCCESS;}//数据报文放到cpu接收队列，由cpu默认net_dev提供的poll函数即：process_backlog处理报文//下面引发软中断netif_rx_schedule(&queue->backlog_dev);goto enqueue;}__get_cpu_var(netdev_rx_stat).dropped++;local_irq_restore(flags);kfree_skb(skb);return NET_RX_DROP;}4 疑问pppoe为什么还要占用pty/tty设备文件呢？5 netif_receive_skb() 函数分析负责把数据报文按packet_type丢到上层协议处理, 所有数据往上送到协议栈的必经之路ptype_all 优先处理，这个是RAW socket走过的路径之地，socket没打开一个会加到这个链表中来。处理过程数据包被复制一份处理。可以看到桥模式处理在真正的数据报文处理之前int netif_receive_skb(struct sk_buff *skb){struct packet_type *ptype, *pt_prev;struct net_device *orig_dev;int ret = NET_RX_DROP;unsigned short type;/* if we've gotten here through NAPI, check netpoll */if (skb->dev->poll && netpoll_rx(skb))return NET_RX_DROP;if (!skb->tstamp.off_sec)net_timestamp(skb);if (!skb->input_dev)skb->input_dev = skb->dev;orig_dev = skb_bond(skb);__get_cpu_var(netdev_rx_stat).total++;skb->h.raw = skb->nh.raw = skb->data;skb->mac_len = skb->nh.raw - skb->mac.raw;pt_prev = NULL;rcu_read_lock();#ifdef CONFIG_NET_CLS_ACTif (skb->tc_verd & TC_NCLS) {skb->tc_verd = CLR_TC_NCLS(skb->tc_verd);goto ncls;}#endif// RAW socket 优先处理， pppoe discovery 要走这里list_for_each_entry_rcu(ptype, &ptype_all, list) {if (!ptype->dev || ptype->dev == skb->dev) {if (pt_prev)ret = deliver_skb(skb, pt_prev, orig_dev);pt_prev = ptype;}}#ifdef CONFIG_NET_CLS_ACTif (pt_prev) {ret = deliver_skb(skb, pt_prev, orig_dev);pt_prev = NULL; /* noone else should process this after*/} else {skb->tc_verd = SET_TC_OK2MUNGE(skb->tc_verd);}ret = ing_filter(skb);if (ret == TC_ACT_SHOT || (ret == TC_ACT_STOLEN)) {kfree_skb(skb);goto out;}skb->tc_verd = 0;ncls:#endifhandle_diverter(skb);//先处理桥模式情况if (handle_bridge(&skb, &pt_prev, &ret, orig_dev))goto out;type = skb->protocol;//再如果桥模式没有转发掉，进入路由模式处理list_for_each_entry_rcu(ptype, &ptype_base[ntohs(type)&15], list) {if (ptype->type == type &&(!ptype->dev || ptype->dev == skb->dev)) {if (pt_prev)ret = deliver_skb(skb, pt_prev, orig_dev);pt_prev = ptype;}}if (pt_prev) {ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);} else {kfree_skb(skb);/* Jamal, now you will not able to escape explaining* me how you were going to use this. :-)*/ret = NET_RX_DROP;}out:rcu_read_unlock();return ret;}6 net_dev_init 这个函数告诉我们很多东西static int __init net_dev_init(void){int i, rc = -ENOMEM;BUG_ON(!dev_boot_phase);net_random_init();if (dev_proc_init())goto out;if (netdev_sysfs_init())goto out;INIT_LIST_HEAD(&ptype_all);for (i = 0; i < 16; i++)INIT_LIST_HEAD(&ptype_base[i]);for (i = 0; i < ARRAY_SIZE(dev_name_head); i++)INIT_HLIST_HEAD(&dev_name_head[i]);for (i = 0; i < ARRAY_SIZE(dev_index_head); i++)INIT_HLIST_HEAD(&dev_index_head[i]);/** Initialise the packet receive queues.*/for_each_cpu(i) {struct softnet_data *queue;queue = &per_cpu(softnet_data, i);skb_queue_head_init(&queue->input_pkt_queue);queue->completion_queue = NULL;INIT_LIST_HEAD(&queue->poll_list);set_bit(__LINK_STATE_START, &queue->backlog_dev.state);queue->backlog_dev.weight = weight_p;//cpu默认处理接收队列的函数在此queue->backlog_dev.poll = process_backlog;atomic_set(&queue->backlog_dev.refcnt, 1);}dev_boot_phase = 0;// 收发报文软中断在此open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL);hotcpu_notifier(dev_cpu_callback, 0);dst_init();dev_mcast_init();rc = 0;out:return rc;}接着看看下面的几个调用static int process_backlog(struct net_device *backlog_dev, int *budget){int work = 0;int quota = min(backlog_dev->quota, *budget);//取到cpu接收队列struct softnet_data *queue = &__get_cpu_var(softnet_data);unsigned long start_time = jiffies;backlog_dev->weight = weight_p;for (;;) {struct sk_buff *skb;struct net_device *dev;local_irq_disable();skb = __skb_dequeue(&queue->input_pkt_queue);if (!skb)goto job_done;local_irq_enable();dev = skb->dev;//上送到协议栈进行数据报文，从此结束底层的绕来绕去netif_receive_skb(skb);dev_put(dev);work++;if (work >= quota || jiffies - start_time > 1)break;}backlog_dev->quota -= work;*budget -= work;return -1;job_done:backlog_dev->quota -= work;*budget -= work;list_del(&backlog_dev->poll_list);smp_mb__before_clear_bit();netif_poll_enable(backlog_dev);local_irq_enable();return 0;}//static void net_rx_action(struct softirq_action *h){struct softnet_data *queue = &__get_cpu_var(softnet_data);unsigned long start_time = jiffies;int budget = netdev_budget;void *have;local_irq_disable();while (!list_empty(&queue->poll_list)) {struct net_device *dev;if (budget <= 0 || jiffies - start_time > 1)goto softnet_break;local_irq_enable();dev = list_entry(queue->poll_list.next,struct net_device, poll_list);have = netpoll_poll_lock(dev);//调用设备的poll函数来掉netif_receive_skb()提交到上层协议if (dev->quota <= 0 || dev->poll(dev, &budget)) {netpoll_poll_unlock(have);local_irq_disable();//如果某个设备级别太低，放在对尾处理list_del(&dev->poll_list);list_add_tail(&dev->poll_list, &queue->poll_list);if (dev->quota < 0)dev->quota += dev->weight;elsedev->quota = dev->weight;} else {netpoll_poll_unlock(have);dev_put(dev);local_irq_disable();}}out:local_irq_enable();return;softnet_break:// 时间太久，超过1个时钟滴答退出__get_cpu_var(netdev_rx_stat).time_squeeze++;__raise_softirq_irqoff(NET_RX_SOFTIRQ);goto out;}
(以上内容不代表本站观点。) --------------------------------- |
本網站是"非商業"(non-commercial)。
