[PATCH 3.12 103/113] ipv6: simplify detection of first operational link-local address on interface

[Jiri Slaby]

From: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 11ffff752c6a5adc86f7dd397b2f75af8f917c51 upstream.

In commit 1ec047eb4751e3 ("ipv6: introduce per-interface counter for
dad-completed ipv6 addresses") I build the detection of the first
operational link-local address much to complex. Additionally this code
now has a race condition.

Replace it with a much simpler variant, which just scans the address
list when duplicate address detection completes, to check if this is
the first valid link local address and send RS and MLD reports then.

Fixes: 1ec047eb4751e3 ("ipv6: introduce per-interface counter for dad-completed ipv6 addresses")
Reported-by: Jiri Pirko <jiri@xxxxxxxxxxx>
Cc: Flavio Leitner <fbl@xxxxxxxxxx>
Signed-off-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Acked-by: Flavio Leitner <fbl@xxxxxxxxxx>
Acked-by: Jiri Pirko <jiri@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 include/net/if_inet6.h |  1 -
 net/ipv6/addrconf.c    | 38 +++++++++++++++++---------------------
 2 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 02ef7727bb55..587e9dd3e3b4 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -166,7 +166,6 @@ struct inet6_dev {
 	struct net_device	*dev;
 
 	struct list_head	addr_list;
-	int			valid_ll_addr_cnt;
 
 	struct ifmcaddr6	*mc_list;
 	struct ifmcaddr6	*mc_tomb;
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 74fe3375aa7a..1452e113e8e4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3237,6 +3237,22 @@ out:
 	in6_ifa_put(ifp);
 }
 
+/* ifp->idev must be at least read locked */
+static bool ipv6_lonely_lladdr(struct inet6_ifaddr *ifp)
+{
+	struct inet6_ifaddr *ifpiter;
+	struct inet6_dev *idev = ifp->idev;
+
+	list_for_each_entry(ifpiter, &idev->addr_list, if_list) {
+		if (ifp != ifpiter && ifpiter->scope == IFA_LINK &&
+		    (ifpiter->flags & (IFA_F_PERMANENT|IFA_F_TENTATIVE|
+				       IFA_F_OPTIMISTIC|IFA_F_DADFAILED)) ==
+		    IFA_F_PERMANENT)
+			return false;
+	}
+	return true;
+}
+
 static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
 {
 	struct net_device *dev = ifp->idev->dev;
@@ -3256,14 +3272,11 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
 	 */
 
 	read_lock_bh(&ifp->idev->lock);
-	spin_lock(&ifp->lock);
-	send_mld = ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL &&
-		   ifp->idev->valid_ll_addr_cnt == 1;
+	send_mld = ifp->scope == IFA_LINK && ipv6_lonely_lladdr(ifp);
 	send_rs = send_mld &&
 		  ipv6_accept_ra(ifp->idev) &&
 		  ifp->idev->cnf.rtr_solicits > 0 &&
 		  (dev->flags&IFF_LOOPBACK) == 0;
-	spin_unlock(&ifp->lock);
 	read_unlock_bh(&ifp->idev->lock);
 
 	/* While dad is in progress mld report's source address is in6_addrany.
@@ -4558,19 +4571,6 @@ errout:
 		rtnl_set_sk_err(net, RTNLGRP_IPV6_PREFIX, err);
 }
 
-static void update_valid_ll_addr_cnt(struct inet6_ifaddr *ifp, int count)
-{
-	write_lock_bh(&ifp->idev->lock);
-	spin_lock(&ifp->lock);
-	if (((ifp->flags & (IFA_F_PERMANENT|IFA_F_TENTATIVE|IFA_F_OPTIMISTIC|
-			    IFA_F_DADFAILED)) == IFA_F_PERMANENT) &&
-	    (ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL))
-		ifp->idev->valid_ll_addr_cnt += count;
-	WARN_ON(ifp->idev->valid_ll_addr_cnt < 0);
-	spin_unlock(&ifp->lock);
-	write_unlock_bh(&ifp->idev->lock);
-}
-
 static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 {
 	struct net *net = dev_net(ifp->idev->dev);
@@ -4579,8 +4579,6 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 
 	switch (event) {
 	case RTM_NEWADDR:
-		update_valid_ll_addr_cnt(ifp, 1);
-
 		/*
 		 * If the address was optimistic
 		 * we inserted the route at the start of
@@ -4596,8 +4594,6 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 					      ifp->idev->dev, 0, 0);
 		break;
 	case RTM_DELADDR:
-		update_valid_ll_addr_cnt(ifp, -1);
-
 		if (ifp->idev->cnf.forwarding)
 			addrconf_leave_anycast(ifp);
 		addrconf_leave_solict(ifp->idev, &ifp->addr);
-- 
2.12.0