how to catch the NIC interrupt(up/down) event?

User Space:

open a netlink socket and listen to the RTMGRP_LINK (network interface create/delete/up/down events) multicast groups

Kernel Space:

Look in <linux/netdevice.h>, specifically the stuff about the netdev notifier chain. You can call register_netdevice_notifier() to register a callback that (among many other event types) will receive NETDEV_UP and NETDEV_DOWN events.

<linux/notifier.h>

#define NETDEV_UP 0x0001 /* For now you can't veto a device up/down */
#define NETDEV_DOWN 0x0002
#define NETDEV_REBOOT 0x0003 /* Tell a protocol stack a network interface
  detected a hardware crash and restarted
  - we can use this eg to kick tcp sessions
  once done */
#define NETDEV_CHANGE 0x0004 /* Notify device state change */
#define NETDEV_REGISTER 0x0005
#define NETDEV_UNREGISTER 0x0006
#define NETDEV_CHANGEMTU 0x0007
#define NETDEV_CHANGEADDR 0x0008
#define NETDEV_GOING_DOWN 0x0009
#define NETDEV_CHANGENAME 0x000A
#define NETDEV_FEAT_CHANGE 0x000B
#define NETDEV_BONDING_FAILOVER 0x000C
#define NETDEV_PRE_UP 0x000D
#define NETDEV_PRE_TYPE_CHANGE 0x000E
#define NETDEV_POST_TYPE_CHANGE 0x000F
#define NETDEV_POST_INIT 0x0010
#define NETDEV_UNREGISTER_BATCH 0x0011
#define NETDEV_RELEASE 0x0012
#define NETDEV_NOTIFY_PEERS 0x0013
#define NETDEV_JOIN 0x0014

<net/core/dev.c>

/**
 * register_netdevice_notifier - register a network notifier block
 * @nb: notifier
 *
 * Register a notifier to be called when network device events occur.
 * The notifier passed is linked into the kernel structures and must
 * not be reused until it has been unregistered. A negative errno code
 * is returned on a failure.
 *
 * When registered all registration and up events are replayed
 * to the new notifier to allow device to have a race free
 * view of the network device list.
 */


int register_netdevice_notifier(struct notifier_block *nb)

//arp handle:

static int arp_netdev_event(struct notifier_block *this, unsigned long event,
   void *ptr)
{
struct net_device *dev = ptr;


switch (event) {
case NETDEV_CHANGEADDR:
neigh_changeaddr(&arp_tbl, dev);
rt_cache_flush(dev_net(dev), 0);
break;
default:
break;
}


return NOTIFY_DONE;
}

///dst handle:

static int dst_dev_event(struct notifier_block *this, unsigned long event,
void *ptr)
{
struct net_device *dev = ptr;
struct dst_entry *dst, *last = NULL;


switch (event) {
case NETDEV_UNREGISTER:
case NETDEV_DOWN:
mutex_lock(&dst_gc_mutex);
for (dst = dst_busy_list; dst; dst = dst->next) {
last = dst;
dst_ifdown(dst, dev, event != NETDEV_DOWN);
}


spin_lock_bh(&dst_garbage.lock);
dst = dst_garbage.list;
dst_garbage.list = NULL;
spin_unlock_bh(&dst_garbage.lock);


if (last)
last->next = dst;
else
dst_busy_list = dst;
for (; dst; dst = dst->next)
dst_ifdown(dst, dev, event != NETDEV_DOWN);
mutex_unlock(&dst_gc_mutex);
break;
}
return NOTIFY_DONE;
}

//fib

void __init ip_fib_init(void)

{

...

register_netdevice_notifier(&fib_netdev_notifier);
register_inetaddr_notifier(&fib_inetaddr_notifier);

...

}