netdev - Re: [PATCH] ipv6: Log the explicit address that triggered DAD failure

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Date:	Thu, 13 Aug 2009 10:16:04 +0200
From:	Jens Rosenboom <jens@...one.net>
To:	Brian Haley <brian.haley@...com>
Cc:	Linux Network Developers <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] ipv6: Log the explicit address that triggered DAD
 failure

On Wed, 2009-08-12 at 21:33 -0400, Brian Haley wrote:
[...]
> The other thing I've come across that is similar to this is the
> issue that when DAD fails, /sbin/ip doesn't show that it did,
> the address just stays in a tentative state forever:
> 
>     inet6 dead:beef::1/64 scope global tentative 
>        valid_lft forever preferred_lft forever
> 
> Does anyone have an issue of adding a "dadfailed" flag to make
> this more obvious:
> 
>     inet6 dead:beef::1/64 scope global tentative dadfailed
>        valid_lft forever preferred_lft forever

It looks like you would have to spend the last available bit in
ifa_flags for that, not sure if that is worth it, how about setting it
to tentative|deprecated instead?

Some action should maybe also happen in the case that the address wasn't
tentative anymore in ndisc_recv_na(). At least it should also log the
address itself:

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 9eb68e9..1ba42bd 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -955,8 +955,8 @@ static void ndisc_recv_na(struct sk_buff *skb)
 		 */
 		if (skb->pkt_type != PACKET_LOOPBACK)
 			ND_PRINTK1(KERN_WARNING
-			   "ICMPv6 NA: someone advertises our address on %s!\n",
-			   ifp->idev->dev->name);
+			   "ICMPv6 NA: someone advertises our address %pI6 on %s!\n",
+			   &ifp->addr, ifp->idev->dev->name);
 		in6_ifa_put(ifp);
 		return;
 	}


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