netdev - Re: [PATCH] net: Fix tentative IPv6 address due to DAD looping back

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Message-ID: <20130411115544.GA19782@order.stressinduktion.org>
Date:	Thu, 11 Apr 2013 13:55:44 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	"Meng, Jilin" <Jilin.Meng@....com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"Sun, Yinglin" <yinglin.sun@....com>,
	"Prithviraj, Lakshmanan" <lakshmanan.prithviraj@....com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: Fix tentative IPv6 address due to DAD looping back

On Thu, Apr 11, 2013 at 03:06:23AM +0000, Meng, Jilin wrote:
> we should ignore the looped-back IPv6 DAD packet to avoid configuration failure.
> This occurs when a bonding interface with roundrobin mode is being configured an IPv6 address while the switch side isn't configured bonding/channel yet.

I am very uncomfortable with this change in ndisc layer. I would
prefer DAD kicking in and disabling ipv6 on that interface in such a
situation. The likelihood that an interface with the same mac address
has the same ll ipv6 address is very high and DAD must guard that.

> Signed-off-by: Jilin Meng <jilin.meng@....com>
> Signed-off-by: Yinglin Sun <yinglin.sun@....com>
> Signed-off-by: Lakshmanan Prithviraj <lakshmanan.prithviraj@....com>
> ---
> --- linux/net/ipv6/ndisc.c.orig	2013-03-12 17:16:18.000000000 +0800
> +++ linux/net/ipv6/ndisc.c	2013-04-11 09:00:45.000000000 +0800
> @@ -71,6 +71,7 @@
>  
>  #include <linux/netfilter.h>
>  #include <linux/netfilter_ipv6.h>
> +#include <linux/etherdevice.h>
>  
>  /* Set to 3 to get tracing... */
>  #define ND_DEBUG 1
> @@ -757,6 +758,19 @@ static void ndisc_recv_ns(struct sk_buff
>  
>  		if (ifp->flags & (IFA_F_TENTATIVE|IFA_F_OPTIMISTIC)) {
>  			if (dad) {
> +				if (dev->type == ARPHRD_ETHER) {
> +					const unsigned char *sadr;
> +					sadr = skb_mac_header(skb);
> +					if (ether_addr_equal_64bits(sadr + 6, dev->dev_addr))

Minor improvment:

struct ethhdr *eth = eth_hdr(skb);
if (ether_addr_equal_64bits(eth->h_source, dev->dev_addr))

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