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Commit be680f4b authored by Hangbin Liu's avatar Hangbin Liu Committed by Greg Kroah-Hartman
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net: ip_tunnel: fix mtu calculation for ETHER tunnel devices 



commit 9992a078b1771da354ac1f9737e1e639b687caa2 upstream.

Commit 28e104d00281 ("net: ip_tunnel: fix mtu calculation") removed
dev->hard_header_len subtraction when calculate MTU for tunnel devices
as there is an overhead for device that has header_ops.

But there are ETHER tunnel devices, like gre_tap or erspan, which don't
have header_ops but set dev->hard_header_len during setup. This makes
pkts greater than (MTU - ETH_HLEN) could not be xmited. Fix it by
subtracting the ETHER tunnel devices' dev->hard_header_len for MTU
calculation.

Fixes: 28e104d00281 ("net: ip_tunnel: fix mtu calculation")
Reported-by: default avatarJianlin Shi <jishi@redhat.com>
Signed-off-by: default avatarHangbin Liu <liuhangbin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent dd1f607c

net/ipv4/ip_tunnel.c

+18 −4
Original line number Diff line number Diff line
@@ -330,7 +330,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev) 
	}



	dev->needed_headroom = t_hlen + hlen;

	mtu -= t_hlen;

	mtu -= t_hlen + (dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0);



	if (mtu < IPV4_MIN_MTU)

		mtu = IPV4_MIN_MTU;
@@ -361,6 +361,9 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net, 
	t_hlen = nt->hlen + sizeof(struct iphdr);

	dev->min_mtu = ETH_MIN_MTU;

	dev->max_mtu = IP_MAX_MTU - t_hlen;

	if (dev->type == ARPHRD_ETHER)

		dev->max_mtu -= dev->hard_header_len;



	ip_tunnel_add(itn, nt);

	return nt;
@@ -502,13 +505,18 @@ static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb, 
			    const struct iphdr *inner_iph)

{

	struct ip_tunnel *tunnel = netdev_priv(dev);

	int pkt_size = skb->len - tunnel->hlen;

	int pkt_size;

	int mtu;



	if (df)

	pkt_size = skb->len - tunnel->hlen;

	pkt_size -= dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0;



	if (df) {

		mtu = dst_mtu(&rt->dst) - (sizeof(struct iphdr) + tunnel->hlen);

	else

		mtu -= dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0;

	} else {

		mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;

	}



	skb_dst_update_pmtu_no_confirm(skb, mtu);
@@ -936,6 +944,9 @@ int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict) 
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);

	int max_mtu = IP_MAX_MTU - t_hlen;



	if (dev->type == ARPHRD_ETHER)

		max_mtu -= dev->hard_header_len;



	if (new_mtu < ETH_MIN_MTU)

		return -EINVAL;
@@ -1113,6 +1124,9 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[], 
	if (tb[IFLA_MTU]) {

		unsigned int max = IP_MAX_MTU - (nt->hlen + sizeof(struct iphdr));



		if (dev->type == ARPHRD_ETHER)

			max -= dev->hard_header_len;



		mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU, max);

	}