callback notify when add a IPv4 add

0.1. summary

IP4 route register a call back notify in IPv4 address.
When a address is added, fib_inetaddr_event will be called.

and then 4 route entry maybe added in fib_add_ifaddr

1273 int register_inetaddr_notifier(struct notifier_block *nb)
1274 { 
1275         return blocking_notifier_chain_register(&inetaddr_chain, nb);
1276 } 
1277 EXPORT_SYMBOL(register_inetaddr_notifier)

1075 static struct notifier_block fib_inetaddr_notifier = { 
1076         .notifier_call = fib_inetaddr_event,     
1077 };

1008 static int fib_inetaddr_event(struct notifier_block *this, unsigned long event, void *ptr)
1009 {       
1010         struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
1011         struct net_device *dev = ifa->ifa_dev->dev;
1012         struct net *net = dev_net(dev);
1013         
1014         switch (event) {
1015         case NETDEV_UP:
1016                 fib_add_ifaddr(ifa);
1017 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1018                 fib_sync_up(dev);
1019 #endif  
1020                 atomic_inc(&net->ipv4.dev_addr_genid);
1021                 rt_cache_flush(dev_net(dev));
1022                 break;
1023         case NETDEV_DOWN:
1024                 fib_del_ifaddr(ifa, NULL);
1025                 atomic_inc(&net->ipv4.dev_addr_genid);
1026                 if (ifa->ifa_dev->ifa_list == NULL) {
1027                         /* Last address was deleted from this interface.
1028                          * Disable IP.
1029                          */
1030                         fib_disable_ip(dev, 1);
1031                 } else {
1032                         rt_cache_flush(dev_net(dev));
1033                 }
1034                 break;
1035         }
1036         return NOTIFY_DONE;
1037 }

734 void fib_add_ifaddr(struct in_ifaddr *ifa)
735 {               
736         struct in_device *in_dev = ifa->ifa_dev;
737         struct net_device *dev = in_dev->dev;
738         struct in_ifaddr *prim = ifa;
739         __be32 mask = ifa->ifa_mask;
740         __be32 addr = ifa->ifa_local;
741         __be32 prefix = ifa->ifa_address & mask;
742                 
743         if (ifa->ifa_flags & IFA_F_SECONDARY) {
744                 prim = inet_ifa_byprefix(in_dev, prefix, mask);
745                 if (prim == NULL) {
746                         pr_warn("%s: bug: prim == NULL\n", __func__);
747                         return;
748                 } 
749         }               
750                 
751         fib_magic(RTM_NEWROUTE, RTN_LOCAL, addr, 32, prim);
752         
753         if (!(dev->flags & IFF_UP))
754                 return;
755 
756         /* Add broadcast address, if it is explicitly assigned. */
757         if (ifa->ifa_broadcast && ifa->ifa_broadcast != htonl(0xFFFFFFFF))
758                 fib_magic(RTM_NEWROUTE, RTN_BROADCAST, ifa->ifa_broadcast, 32, prim);
759         
760         if (!ipv4_is_zeronet(prefix) && !(ifa->ifa_flags & IFA_F_SECONDARY) &&
761             (prefix != addr || ifa->ifa_prefixlen < 32)) {
762                 fib_magic(RTM_NEWROUTE,
763                           dev->flags & IFF_LOOPBACK ? RTN_LOCAL : RTN_UNICAST,
764                           prefix, ifa->ifa_prefixlen, prim);
765 
766                 /* Add network specific broadcasts, when it takes a sense */
767                 if (ifa->ifa_prefixlen < 31) {
768                         fib_magic(RTM_NEWROUTE, RTN_BROADCAST, prefix, 32, prim);
769                         fib_magic(RTM_NEWROUTE, RTN_BROADCAST, prefix | ~mask,
770                                   32, prim);
771                 }
772         }
773 }