[PATCH AUTOSEL for 4.9 054/281] ipv6: avoid dad-failures for addresses with NODAD

[Sasha Levin]

From: Mahesh Bandewar <maheshb@xxxxxxxxxx>

[ Upstream commit 66eb9f86e50547ec2a8ff7a75997066a74ef584b ]

Every address gets added with TENTATIVE flag even for the addresses with
IFA_F_NODAD flag and dad-work is scheduled for them. During this DAD process
we realize it's an address with NODAD and complete the process without
sending any probe. However the TENTATIVE flags stays on the
address for sometime enough to cause misinterpretation when we receive a NS.
While processing NS, if the address has TENTATIVE flag, we mark it DADFAILED
and endup with an address that was originally configured as NODAD with
DADFAILED.

We can't avoid scheduling dad_work for addresses with NODAD but we can
avoid adding TENTATIVE flag to avoid this racy situation.

Signed-off-by: Mahesh Bandewar <maheshb@xxxxxxxxxx>
Acked-by: David Ahern <dsahern@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 net/ipv6/addrconf.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 1594d9fc9c92..3a27cf762da1 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -988,7 +988,10 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 	INIT_HLIST_NODE(&ifa->addr_lst);
 	ifa->scope = scope;
 	ifa->prefix_len = pfxlen;
-	ifa->flags = flags | IFA_F_TENTATIVE;
+	ifa->flags = flags;
+	/* No need to add the TENTATIVE flag for addresses with NODAD */
+	if (!(flags & IFA_F_NODAD))
+		ifa->flags |= IFA_F_TENTATIVE;
 	ifa->valid_lft = valid_lft;
 	ifa->prefered_lft = prefered_lft;
 	ifa->cstamp = ifa->tstamp = jiffies;
-- 
2.14.1