ipv6: ignore looped-back NA while dad is running

[ipv6] Ignore looped-back NAs while in Duplicate Address Detection

If we send an unsolicited NA shortly after bringing up an IPv6 address, the duplicate address detection algorithm fails and the ip stays in tentative mode forever. This is due a missing check if the NA is looped-back to us.

---
apply against linux-2.6 HEAD

 net/ipv6/ndisc.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

---

index 92f952d..f057ff3 100644
@@ -945,9 +945,10 @@ static void ndisc_recv_na(struct sk_buff *skb)
 	}
 	ifp = ipv6_get_ifaddr(dev_net(dev), &msg->target, dev, 1);
 	if (ifp) {
-		if (ifp->flags & IFA_F_TENTATIVE) {
-			addrconf_dad_failure(ifp);
-			return;
+		if (skb->pkt_type != PACKET_LOOPBACK
+		    && (ifp->flags & IFA_F_TENTATIVE)) {
+				addrconf_dad_failure(ifp);
+				return;
 		}
 		/* What should we make now? The advertisement
 		   is invalid, but ndisc specs say nothing

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From: Daniel Walter <[email protected]>
Date: Wed, 13 Apr 2011 17:02:43 +0200

I'm not applying patches that have legal disclaimers like this.

It has no place in a posting made on a public mailing list where open and unrestricted discussions are essential.