hlist_for_each_entry(fdb, h, &br->hash[hash], hlist) {
//如果表中已经包含了此项
if (!memcmp(fdb->addr.addr, addr, ETH_ALEN)) {
//如果为本机MAC
/* attempt to update an entry for a local interface */
if (fdb->is_local) {
/* it is okay to have multiple ports with same
* address, just don't allow to be spoofed.
*/
if (is_local)
return 0;
if (net_ratelimit())
printk(KERN_WARNING "%s: received packet with "
" own address as source address\n",
source->dev->name);
return -EEXIST;
}