ipv: Re-enable IP when MTU > 68

Re-enable IP when the MTU gets back to a valid size.

This patch just checks if the in_dev is NULL on a NETDEV_CHANGEMTU event
and if MTU is valid (bigger than 68), then re-enable in_dev.

Also a function that checks valid MTU size was created.

Signed-off-by: Breno Leitao <leitao@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 91d3d96805d03aef392e0f514b1bd1750a9757d4..b12dae2b0b2dbcc527eee09a5d7309ffd4852ebc 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1029,6 +1029,11 @@ skip:
        }
 }
 
+static inline bool inetdev_valid_mtu(unsigned mtu)
+{
+       return mtu >= 68;
+}
+
 /* Called only under RTNL semaphore */
 
 static int inetdev_event(struct notifier_block *this, unsigned long event,
@@ -1048,6 +1053,10 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
                                IN_DEV_CONF_SET(in_dev, NOXFRM, 1);
                                IN_DEV_CONF_SET(in_dev, NOPOLICY, 1);
                        }
+               } else if (event == NETDEV_CHANGEMTU) {
+                       /* Re-enabling IP */
+                       if (inetdev_valid_mtu(dev->mtu))
+                               in_dev = inetdev_init(dev);
                }
                goto out;
        }
@@ -1058,7 +1067,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
                dev->ip_ptr = NULL;
                break;
        case NETDEV_UP:
-               if (dev->mtu < 68)
+               if (!inetdev_valid_mtu(dev->mtu))
                        break;
                if (dev->flags & IFF_LOOPBACK) {
                        struct in_ifaddr *ifa;
@@ -1080,9 +1089,9 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
                ip_mc_down(in_dev);
                break;
        case NETDEV_CHANGEMTU:
-               if (dev->mtu >= 68)
+               if (inetdev_valid_mtu(dev->mtu))
                        break;
-               /* MTU falled under 68, disable IP */
+               /* disable IP when MTU is not enough */
        case NETDEV_UNREGISTER:
                inetdev_destroy(in_dev);
                break;