Merge branch 'tunnel-mtus'

Nicolas Dichtel says:

====================
ip[6] tunnels: fix mtu calculations

The first patch restores the possibility to bind an ip4 tunnel to an
interface whith a large mtu.
The second patch was spotted after the first fix. I also target it to net
because it fixes the max mtu value that can be used for ipv6 tunnels.

v2: remove the 0xfff8 in ip_tunnel_newlink()
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 15 insertions, 9 deletions

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 6b0e362cc99b..38d906baf1df 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -328,7 +328,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
 
 	if (tdev) {
 		hlen = tdev->hard_header_len + tdev->needed_headroom;
-		mtu = tdev->mtu;
+		mtu = min(tdev->mtu, IP_MAX_MTU);
 	}
 
 	dev->needed_headroom = t_hlen + hlen;
@@ -362,7 +362,7 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
 	nt = netdev_priv(dev);
 	t_hlen = nt->hlen + sizeof(struct iphdr);
 	dev->min_mtu = ETH_MIN_MTU;
-	dev->max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;
+	dev->max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
 	ip_tunnel_add(itn, nt);
 	return nt;
 
@@ -930,7 +930,7 @@ int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 	int t_hlen = tunnel->hlen + sizeof(struct iphdr);
-	int max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;
+	int max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
 
 	if (new_mtu < ETH_MIN_MTU)
 		return -EINVAL;
@@ -1107,7 +1107,7 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
 
 	mtu = ip_tunnel_bind_dev(dev);
 	if (tb[IFLA_MTU]) {
-		unsigned int max = 0xfff8 - dev->hard_header_len - nt->hlen;
+		unsigned int max = IP_MAX_MTU - dev->hard_header_len - nt->hlen;
 
 		mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU,
 			    (unsigned int)(max - sizeof(struct iphdr)));
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index da66aaac51ce..00e138a44cbb 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1692,8 +1692,13 @@ int ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
 		if (new_mtu < ETH_MIN_MTU)
 			return -EINVAL;
 	}
-	if (new_mtu > 0xFFF8 - dev->hard_header_len)
-		return -EINVAL;
+	if (tnl->parms.proto == IPPROTO_IPV6 || tnl->parms.proto == 0) {
+		if (new_mtu > IP6_MAX_MTU - dev->hard_header_len)
+			return -EINVAL;
+	} else {
+		if (new_mtu > IP_MAX_MTU - dev->hard_header_len)
+			return -EINVAL;
+	}
 	dev->mtu = new_mtu;
 	return 0;
 }
@@ -1841,7 +1846,7 @@ ip6_tnl_dev_init_gen(struct net_device *dev)
 	if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
 		dev->mtu -= 8;
 	dev->min_mtu = ETH_MIN_MTU;
-	dev->max_mtu = 0xFFF8 - dev->hard_header_len;
+	dev->max_mtu = IP6_MAX_MTU - dev->hard_header_len;
 
 	return 0;
 
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 2afce37a7177..e9400ffa7875 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1371,7 +1371,7 @@ static void ipip6_tunnel_setup(struct net_device *dev)
 	dev->hard_header_len	= LL_MAX_HEADER + t_hlen;
 	dev->mtu		= ETH_DATA_LEN - t_hlen;
 	dev->min_mtu		= IPV6_MIN_MTU;
-	dev->max_mtu		= 0xFFF8 - t_hlen;
+	dev->max_mtu		= IP6_MAX_MTU - t_hlen;
 	dev->flags		= IFF_NOARP;
 	netif_keep_dst(dev);
 	dev->addr_len		= 4;
@@ -1583,7 +1583,8 @@ static int ipip6_newlink(struct net *src_net, struct net_device *dev,
 	if (tb[IFLA_MTU]) {
 		u32 mtu = nla_get_u32(tb[IFLA_MTU]);
 
-		if (mtu >= IPV6_MIN_MTU && mtu <= 0xFFF8 - dev->hard_header_len)
+		if (mtu >= IPV6_MIN_MTU &&
+		    mtu <= IP6_MAX_MTU - dev->hard_header_len)
 			dev->mtu = mtu;
 	}