[PATCH v3 1/2] ip_tunnel: fix ip tunnel lookup in collect_md mode

In collect_md mode, if the tun dev is down, it still can call
ip_tunnel_rcv to receive on packets, and the rx statistics increase
improperly.

Fixes: 2e15ea390e6f ("ip_gre: Add support to collect tunnel metadata.")
Cc: Pravin B Shelar <redacted>
Signed-off-by: Haishuang Yan <redacted>

---
Change since v3:
  * Increment rx_dropped if tunnel device is not up, suggested by
  Pravin B Shelar
  * Fix wrong recipient addresss
---
 net/ipv4/ip_tunnel.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index e1856bf..5b2e542 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c

@@ -176,8 +176,11 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
 		return cand;
 
 	t = rcu_dereference(itn->collect_md_tun);
-	if (t)
-		return t;
+	if (t) {
+		if (t->dev->flags & IFF_UP)
+			return t;
+		t->dev->stats.rx_dropped++;
+	}
 
 	if (itn->fb_tunnel_dev && itn->fb_tunnel_dev->flags & IFF_UP)
 		return netdev_priv(itn->fb_tunnel_dev);

-- 
1.8.3.1