gre: Fix MTU calculation for bound GRE tunnels

[ Upstream commit 8cdb045632e5ee22854538619ac6f150eb0a4894 ]

The GRE header length should be subtracted when the tunnel MTU is
calculated.  This just corrects for the associativity change
introduced by commit 42aa916265d740d66ac1f17290366e9494c884c2
("gre: Move MTU setting out of ipgre_tunnel_bind_dev").

Signed-off-by: Tom Goff <thomas.goff@boeing.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e62510d5ea5a60df6b806342e870ace458108962..3491c93fb449bdfa69afd3c1f2238fba1582499b 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -952,7 +952,7 @@ static int ipgre_tunnel_bind_dev(struct net_device *dev)
                        addend += 4;
        }
        dev->needed_headroom = addend + hlen;
-       mtu -= dev->hard_header_len - addend;
+       mtu -= dev->hard_header_len + addend;
 
        if (mtu < 68)
                mtu = 68;