[PATCH net] net: ipv6: Fix a bug in ndisc_send_ns when netdev only has a global address

[Su Yanjun <suyj.fnst@cn.fujitsu.com>]

When we send mpls packets and the interface only has a
manual global ipv6 address, then the two hosts cant communicate.
I find that in ndisc_send_ns it only tries to get a ll address.
In my case, the executive path is as below.
ip6_output
 ->ip6_finish_output
  ->lwtunnel_xmit
   ->mpls_xmit
    ->neigh_resolve_output
     ->neigh_probe
      ->ndisc_solicit
       ->ndisc_send_ns

In RFC4861, 7.2.2 says
"If the source address of the packet prompting the solicitation is the
same as one of the addresses assigned to the outgoing interface, that
address SHOULD be placed in the IP Source Address of the outgoing
solicitation.  Otherwise, any one of the addresses assigned to the
interface should be used."

In this patch we try get a global address if we get ll address failed.

Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
---
 include/net/addrconf.h |  4 ++++
 net/ipv6/addrconf.c    | 34 ++++++++++++++++++++++++++++++++++
 net/ipv6/ndisc.c       |  8 ++++++--
 3 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index becdad5..006db8e 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -107,6 +107,10 @@ int __ipv6_get_lladdr(struct inet6_dev *idev, struct in6_addr *addr,
 		      u32 banned_flags);
 int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr,
 		    u32 banned_flags);
+int __ipv6_get_addr(struct inet6_dev *idev, struct in6_addr *addr,
+		      u32 banned_flags);
+int ipv6_get_addr(struct net_device *dev, struct in6_addr *addr,
+		    u32 banned_flags);
 bool inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
 			  bool match_wildcard);
 bool inet_rcv_saddr_any(const struct sock *sk);
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 521e320..4c0a43f 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1870,6 +1870,40 @@ int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr,
 	return err;
 }
 
+int __ipv6_get_addr(struct inet6_dev *idev, struct in6_addr *addr,
+		    u32 banned_flags)
+{
+	struct inet6_ifaddr *ifp;
+	int err = -EADDRNOTAVAIL;
+
+	list_for_each_entry_reverse(ifp, &idev->addr_list, if_list) {
+		if (ifp->scope == 0 &&
+		    !(ifp->flags & banned_flags)) {
+			*addr = ifp->addr;
+			err = 0;
+			break;
+		}
+	}
+	return err;
+}
+
+int ipv6_get_addr(struct net_device *dev, struct in6_addr *addr,
+		  u32 banned_flags)
+{
+	struct inet6_dev *idev;
+	int err = -EADDRNOTAVAIL;
+
+	rcu_read_lock();
+	idev = __in6_dev_get(dev);
+	if (idev) {
+		read_lock_bh(&idev->lock);
+		err = __ipv6_get_addr(idev, addr, banned_flags);
+		read_unlock_bh(&idev->lock);
+	}
+	rcu_read_unlock();
+	return err;
+}
+
 static int ipv6_count_addresses(const struct inet6_dev *idev)
 {
 	const struct inet6_ifaddr *ifp;
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 083cc1c..18ac2fb 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -606,8 +606,12 @@ void ndisc_send_ns(struct net_device *dev, const struct in6_addr *solicit,
 
 	if (!saddr) {
 		if (ipv6_get_lladdr(dev, &addr_buf,
-				   (IFA_F_TENTATIVE|IFA_F_OPTIMISTIC)))
-			return;
+				   (IFA_F_TENTATIVE | IFA_F_OPTIMISTIC))) {
+			/* try global address */
+			if (ipv6_get_addr(dev, &addr_buf,
+					  (IFA_F_TENTATIVE | IFA_F_OPTIMISTIC)))
+				return;
+		}
 		saddr = &addr_buf;
 	}
 
-- 
2.7.4