gre: Move MTU setting out of ipgre_tunnel_bind_dev

This patch moves the dev->mtu setting out of ipgre_tunnel_bind_dev.
This is in prepartion of using rtnl_link where we'll need to make
the MTU setting conditional on whether the user has supplied an
MTU.  This also requires the move of the ipgre_tunnel_bind_dev
call out of the dev->init function so that we can access the user
parameters later.

This patch also adds a check to prevent setting the MTU below
the minimum of 68.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 5 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index fd192d67695..80622dd6fb3 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -119,6 +119,7 @@
 
 static int ipgre_tunnel_init(struct net_device *dev);
 static void ipgre_tunnel_setup(struct net_device *dev);
+static int ipgre_tunnel_bind_dev(struct net_device *dev);
 
 /* Fallback tunnel: no source, no destination, no key, no options */
 
@@ -289,6 +290,8 @@ static struct ip_tunnel * ipgre_tunnel_locate(struct net *net,
         nt = netdev_priv(dev);
         nt->parms = *parms;
 
+        dev->mtu = ipgre_tunnel_bind_dev(dev);
+
         if (register_netdevice(dev) < 0)
                 goto failed_free;
 
@@ -773,7 +776,7 @@ tx_error:
         return 0;
 }
 
-static void ipgre_tunnel_bind_dev(struct net_device *dev)
+static int ipgre_tunnel_bind_dev(struct net_device *dev)
 {
         struct net_device *tdev = NULL;
         struct ip_tunnel *tunnel;
@@ -821,9 +824,14 @@ static void ipgre_tunnel_bind_dev(struct net_device *dev)
                         addend += 4;
         }
         dev->needed_headroom = addend + hlen;
-        dev->mtu = mtu - dev->hard_header_len - addend;
+        mtu -= dev->hard_header_len - addend;
+
+        if (mtu < 68)
+                mtu = 68;
+
         tunnel->hlen = addend;
 
+        return mtu;
 }
 
 static int
@@ -917,7 +925,7 @@ ipgre_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
                                 t->parms.iph.frag_off = p.iph.frag_off;
                                 if (t->parms.link != p.link) {
                                         t->parms.link = p.link;
-                                        ipgre_tunnel_bind_dev(dev);
+                                        dev->mtu = ipgre_tunnel_bind_dev(dev);
                                         netdev_state_change(dev);
                                 }
                         }
@@ -1108,8 +1116,6 @@ static int ipgre_tunnel_init(struct net_device *dev)
         memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
         memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);
 
-        ipgre_tunnel_bind_dev(dev);
-
         if (iph->daddr) {
 #ifdef CONFIG_NET_IPGRE_BROADCAST
                 if (ipv4_is_multicast(iph->daddr)) {