Linux内核中游量控制(9)

Linux内核中流量控制(9)
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5.9 ingress

ingress流控方法是针对输入数据进行流控处理的，在net/sched/sch_ingress.c中定义, 使用时要求在内核配置中定义CONFIG_NET_CLS_ACT或CONFIG_NETFILTER，不过从代码实现看起来好象没什么意义。
5.9.1 ingress操作结构定义
// ingress私有数据结构

struct ingress_qdisc_data {

// 内部流控

 struct Qdisc  *q;

// 过滤规则

 struct tcf_proto *filter_list;

};
// ingress流控操作结构

static struct Qdisc_ops ingress_qdisc_ops = {

 .next  = NULL,

 .cl_ops  = &ingress_class_ops,

 .id  = "ingress",

 .priv_size = sizeof(struct ingress_qdisc_data),

 .enqueue = ingress_enqueue,

 .dequeue = ingress_dequeue,

 .requeue = ingress_requeue,

 .drop  = ingress_drop,

 .init  = ingress_init,

 .reset  = ingress_reset,

 .destroy = ingress_destroy,

// 无change函数

 .change  = NULL,

 .dump  = ingress_dump,

 .owner  = THIS_MODULE,

};
// ingress类别操作结构

static struct Qdisc_class_ops ingress_class_ops = {

 .graft  = ingress_graft,

 .leaf  = ingress_leaf,

 .get  = ingress_get,

 .put  = ingress_put,

 .change  = ingress_change,

 .delete  = NULL,

 .walk  = ingress_walk,

 .tcf_chain = ingress_find_tcf,

 .bind_tcf = ingress_bind_filter,

 .unbind_tcf = ingress_put,

 .dump  = NULL,

};
5.9.1 ingress的netfilter节点
// 没定义NET_CLS_ACT, 而定义了NETFILTER的情况下才有效, 在netfilter节点中进行

// 数据包是否接收的判断

// 但如果定义了NET_CLS_ACT后, 该段代码无效

#ifndef CONFIG_NET_CLS_ACT

#ifdef CONFIG_NETFILTER

/* after ipt_filter */

static struct nf_hook_ops ing_ops = {

// 钩子函数

 .hook           = ing_hook,

 .owner  = THIS_MODULE,

 .pf             = PF_INET,

// 挂接在PREROUTING点

 .hooknum        = NF_IP_PRE_ROUTING,

// 优先权NF_IP_PRI_FILTER + 1, 不过在PREROUTING点缺省好象没定义NF_IP_PRI_FILTER

// 级别的节点

 .priority       = NF_IP_PRI_FILTER + 1,

};

static struct nf_hook_ops ing6_ops = {

 .hook           = ing_hook,

 .owner  = THIS_MODULE,

 .pf             = PF_INET6,

 .hooknum        = NF_IP6_PRE_ROUTING,

 .priority       = NF_IP6_PRI_FILTER + 1,

};
static unsigned int

ing_hook(unsigned int hook, struct sk_buff **pskb,

                             const struct net_device *indev,

                             const struct net_device *outdev,

                      int (*okfn)(struct sk_buff *))

{
 struct Qdisc *q;

 struct sk_buff *skb = *pskb;

        struct net_device *dev = skb->dev;

// 缺省动作, 接受

 int fwres=NF_ACCEPT;

 DPRINTK("ing_hook: skb %s dev=%s len=%u\n",

  skb->sk ? "(owned)" : "(unowned)",

  skb->dev ? (*pskb)->dev->name : "(no dev)",

  skb->len);

/*

revisit later: Use a private since lock dev->queue_lock is also

used on the egress (might slow things for an iota)

*/

// 如果设备里定义了接收流控

 if (dev->qdisc_ingress) {

  spin_lock(&dev->queue_lock);

  if ((q = dev->qdisc_ingress) != NULL)

// 调用接收流控的入队函数, 返回值是对数据包的判断结果

   fwres = q->enqueue(skb, q);

  spin_unlock(&dev->queue_lock);

        }

// 如果没定义, 就直接返回缺省动作: 通过

 return fwres;

}

#endif

#endif
5.9.3 初始化
static int ingress_init(struct Qdisc *sch,struct rtattr *opt)

{

 struct ingress_qdisc_data *p = PRIV(sch);

/* Make sure either netfilter or preferably CLS_ACT is

* compiled in */

// 输入接收流控必须在内核选项中定义分类动作NET_CLS_ACT或NETFILTER

#ifndef CONFIG_NET_CLS_ACT

#ifndef CONFIG_NETFILTER

// 两者都没定义的话就初始化失败

 printk("You MUST compile classifier actions into the kernel\n");

 return -EINVAL;

#else

// 使用NET_CLS_ACT优于使用NETFILTER

 printk("Ingress scheduler: Classifier actions prefered over netfilter\n");

#endif

#endif
#ifndef CONFIG_NET_CLS_ACT

#ifdef CONFIG_NETFILTER

// 没定义NET_CLS_ACT, 而定义了NETFILTER的情况

// 登记输入流控的netfilter钩子节点函数

 if (!nf_registered) {

// 登记IPV4钩子节点

  if (nf_register_hook(&ing_ops) < 0) {

   printk("ingress qdisc registration error \n");

   return -EINVAL;

  }

// 非0表示已经登记了

  nf_registered++;
// 登记IPV4钩子节点

  if (nf_register_hook(&ing6_ops) < 0) {

   printk("IPv6 ingress qdisc registration error, " \

       "disabling IPv6 support.\n");

  } else