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arp_notify: unconditionally send gratuitous ARP for NETDEV_NOTIFY_PEERS.

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NETDEV_NOTIFY_PEER is an explicit request by the driver to send a link
notification while NETDEV_UP/NETDEV_CHANGEADDR generate link
notifications as a sort of side effect.

In the later cases the sysctl option is present because link
notification events can have undesired effects e.g. if the link is
flapping. I don't think this applies in the case of an explicit
request from a driver.

This patch makes NETDEV_NOTIFY_PEER unconditional, if preferred we
could add a new sysctl for this case which defaults to on.

This change causes Xen post-migration ARP notifications (which cause
switches to relearn their MAC tables etc) to be sent by default.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ian Campbell 2011-02-11 07:44:16 +00:00 committed by David S. Miller
parent 0550769bb7
commit d11327ad66
1 changed files with 20 additions and 10 deletions
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30
net/ipv4/devinet.c
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@ -1030,6 +1030,21 @@ static inline bool inetdev_valid_mtu(unsigned mtu)
return mtu >= 68;
}
static void inetdev_send_gratuitous_arp(struct net_device *dev,
struct in_device *in_dev)
{
struct in_ifaddr *ifa = in_dev->ifa_list;
if (!ifa)
return;
arp_send(ARPOP_REQUEST, ETH_P_ARP,
ifa->ifa_address, dev,
ifa->ifa_address, NULL,
dev->dev_addr, NULL);
}
/* Called only under RTNL semaphore */
static int inetdev_event(struct notifier_block *this, unsigned long event,
@ -1082,18 +1097,13 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
}
ip_mc_up(in_dev);
/* fall through */
case NETDEV_NOTIFY_PEERS:
case NETDEV_CHANGEADDR:
if (!IN_DEV_ARP_NOTIFY(in_dev))
break;
/* fall through */
case NETDEV_NOTIFY_PEERS:
/* Send gratuitous ARP to notify of link change */
if (IN_DEV_ARP_NOTIFY(in_dev)) {
struct in_ifaddr *ifa = in_dev->ifa_list;
if (ifa)
arp_send(ARPOP_REQUEST, ETH_P_ARP,
ifa->ifa_address, dev,
ifa->ifa_address, NULL,
dev->dev_addr, NULL);
}
inetdev_send_gratuitous_arp(dev, in_dev);
break;
case NETDEV_DOWN:
ip_mc_down(in_dev);