Linux Networking Internals 5 - Network Device Notification Chains

Network Device Notification Chains

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notifier_block 结构体

struct notifier_block
{
    int (*notifier_call)(struct notifier_block *self, unsigned long, void *);
    struct notifier_block *next;
    int priority;
};

注册函数： notifier_chain_register

网络相关的 chain： inetaddr_chain , inet6addr_chain , and netdev_chain.

Notifying Events on a Chain:

函数 notifier_call_chain

int notifier_call_chain(struct notifier_block **n, unsigned long val, void *v)
{
    int ret = NOTIFY_DONE;
    struct notifier_block *nb = *n;
    while (nb)
    {
        ret = nb->notifier_call(nb, val, v);
        if (ret & NOTIFY_STOP_MASK)
        {
            return ret;
        }
        nb = nb->next;
    }
    return ret;
}

该函数返回值类型位于 include/linux/notifier.h 文件中。

Notification Chains for the Networking Subsystems:

inetaddr_chain netdev_chain

inetaddr_chain: sends notifications about insertion/removal/change of an IPv4 address on a local interface.
netdev_chain: sends notifications about the registration status of network devices.

int register_netdevice_notifier(struct notifier_block *nb)
{
        return notifier_chain_register(&netdev_chain, nb);
}

Common names for wrappers include [un]register_xxxnotifier, xxx[un]registernotifier, and xxx[un]register.

2017-07-20