netdev - Re: [RFC] Arp announce (for Xen)

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Message-ID: <Pine.LNX.4.64.0703021006470.27021@netcore.fi>
Date:	Fri, 2 Mar 2007 10:09:13 +0200 (EET)
From:	Pekka Savola <pekkas@...core.fi>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
cc:	netdev@...r.kernel.org
Subject: Re: [RFC] Arp announce (for Xen)

On Thu, 1 Mar 2007, Stephen Hemminger wrote:
> What about implementing the unused arp_announce flag on the inetdevice?
> Something like the following.  Totally untested...
>
> Looks like it either was there (and got removed) or was planned but
> never implemented.

If something like this goes in, it wouldn't hurt to do similar with 
IPv6 (RFC2461 section 7.2.6).

There are very popular hardware-based routers which refresh their NDP 
caches only every 24 hours or 20 minutes (depending on the software 
version).  Sending unsolicited NAs would eliminate traffic 
blackholing.

> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index e10794d..cefc339 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1089,6 +1089,16 @@ static int inetdev_event(struct notifier
> 			}
> 		}
> 		ip_mc_up(in_dev);
> +		/* fallthru */
> +
> +	case NETDEV_CHANGEADDR:
> +		/* Send gratuitous ARP in case of address change or new device */
> +		if (IN_DEV_ARP_ANNOUNCE(in_dev))
> +			arp_send(ARPOP_REQUEST, ETH_P_ARP,
> +				 in_dev->ifa_list->ifa_address, dev,
> +				 in_dev->ifa_list->ifa_address, NULL,
> +				 dev->dev_addr, NULL);
> +
> 		break;
> 	case NETDEV_DOWN:
> 		ip_mc_down(in_dev);
>
> -
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-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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