Hello,
This is a resend of the patch according to Yoshifuji comment. I will
send a patch for IPv6 later.
We know that changes in MAC addresses are not frequent but
we are working on a special, highly advanced networking Linux based project
in our LABs, where we do change MAC addresses of an interface quite frequently.
(We do not go totally wild; the MAC addresses we are changing into are
from a set of given MAC addresses).
Normally, when we change a MAC address of some interface, the
relevant neighbours in the LAN which have entries with the previous MAC
address are not sent any update notification; instead, it is there
regular timers mechanisms which update the MAC address to the new
one in their ARP tables.
I had written a small patch to neigh_changeaddr() in net/ipv4/arp.c
against the 2.6 git net tree, which sends a gratuitous ARP to update
the list of
all the involved neighbours with the change of MAC address.
The patch is for arp_netdev_event() only.
This patch was tested and it does work in my LAB; if such a patch is
not needed,
I wonder why ?
It seems to me that it could not cause any troubles.
BTW, I had noticed that in irlan driver, there is such a mechanism
of sending a gratuitous ARP to update all the
neighbours when a MAC address is changed.
Signed-off-by: David Shwartz <[EMAIL PROTECTED]>
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 08174a2..7b1162b 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1185,6 +1185,8 @@ out:
static int arp_netdev_event(struct notifier_block *this, unsigned long event,
void *ptr)
{
+ struct in_device *in_dev;
+ struct in_ifaddr *ifa;
struct net_device *dev = ptr;
if (dev->nd_net != &init_net)
@@ -1194,6 +1196,22 @@ static int arp_netdev_event(struct notifier_block *this,
unsigned long event, vo
case NETDEV_CHANGEADDR:
neigh_changeaddr(&arp_tbl, dev);
rt_cache_flush(0);
+
+ /* Send gratuitous ARP to the neighbours to update their arp
tables */
+
+ rcu_read_lock();
+ in_dev = __in_dev_get_rcu(dev);
+ if (in_dev == NULL)
+ goto out;
+ for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next)
+ arp_send(ARPOP_REQUEST, ETH_P_ARP,
+ ifa->ifa_address,
+ dev,
+ ifa->ifa_address,
+ NULL, dev->dev_addr, NULL);
+out:
+ rcu_read_unlock();
+
break;
default:
break;
