网络子系统66_策略路由初始化

//	策略路由链表
//		系统中所有策略路由通过fib_rules链接在一起

static struct fib_rule default_rule = {
	.r_clntref =	ATOMIC_INIT(2),//引用计数
	.r_preference =	0x7FFF,//路由规则优先级
	.r_table =	RT_TABLE_DEFAULT,//路由表标示符
	.r_action =	RTN_UNICAST,//路由类型，间接定义了当路由查找匹配时应采取的动作
};

static struct fib_rule main_rule = {
	.r_next =	&default_rule,
	.r_clntref =	ATOMIC_INIT(2),
	.r_preference =	0x7FFE,
	.r_table =	RT_TABLE_MAIN,
	.r_action =	RTN_UNICAST,
};

static struct fib_rule local_rule = {
	.r_next =	&main_rule,
	.r_clntref =	ATOMIC_INIT(2),
	.r_table =	RT_TABLE_LOCAL,
	.r_action =	RTN_UNICAST,
};

static struct fib_rule *fib_rules = &local_rule;

//	策略路由初始化
//		向netdev_chain注册监听块
//	调用路径：ip_rt_init->ip_fib_init->fib_rules_init
2.1 void __init fib_rules_init(void)
{
	register_netdevice_notifier(&fib_rules_notifier);
}

2.1 static struct notifier_block fib_rules_notifier = {
	.notifier_call =fib_rules_event,
};

//	策略路由对设备事件的处理
//		只处理设备注册，注销事件
static int fib_rules_event(struct notifier_block *this, unsigned long event, void *ptr)
{
	struct net_device *dev = ptr;
	//设备注销，删除与设备相关的策略路由
	if (event == NETDEV_UNREGISTER)
		fib_rules_detach(dev);
	else if (event == NETDEV_REGISTER)
		fib_rules_attach(dev);//添加与设备相关的策略
	return NOTIFY_DONE;
}

//	禁止与设备相关的策略路由
//		将策略路由r_ifindex=-1，禁止策略路由
2.2 static void fib_rules_detach(struct net_device *dev)
{
	struct fib_rule *r;
	//遍历系统中所有的策略路由
	for (r=fib_rules; r; r=r->r_next) {
		if (r->r_ifindex == dev->ifindex) {//策略路由使用的设备index
			write_lock_bh(&fib_rules_lock);
			r->r_ifindex = -1;//禁止该策略路由
			write_unlock_bh(&fib_rules_lock);
		}
	}
}

//	激活设备的策略路由
//		fib_rule->r_ifname表示策略应用的设备
2.3 static void fib_rules_attach(struct net_device *dev)
{
	struct fib_rule *r;

	for (r=fib_rules; r; r=r->r_next) {
		if (r->r_ifindex == -1 && strcmp(dev->name, r->r_ifname) == 0) {
			write_lock_bh(&fib_rules_lock);
			r->r_ifindex = dev->ifindex;
			write_unlock_bh(&fib_rules_lock);
		}
	}
}