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Commit 9c7b01fc authored by Vadim Fedorenko's avatar Vadim Fedorenko Committed by Greg Kroah-Hartman
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net: ip_tunnel: fix mtu calculation 



commit 28e104d00281ade30250b24e098bf50887671ea4 upstream.

dev->hard_header_len for tunnel interface is set only when header_ops
are set too and already contains full overhead of any tunnel encapsulation.
That's why there is not need to use this overhead twice in mtu calc.

Fixes: fdafed459998 ("ip_gre: set dev->hard_header_len and dev->needed_headroom properly")
Reported-by: default avatarSlava Bacherikov <mail@slava.cc>
Signed-off-by: default avatarVadim Fedorenko <vfedorenko@novek.ru>
Link: https://lore.kernel.org/r/1611959267-20536-1-git-send-email-vfedorenko@novek.ru


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ada82f99

net/ipv4/ip_tunnel.c

+7 −9
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 -= (dev->hard_header_len + t_hlen);

	mtu -= t_hlen;



	if (mtu < IPV4_MIN_MTU)

		mtu = IPV4_MIN_MTU;
@@ -360,7 +360,7 @@ 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 = IP_MAX_MTU - dev->hard_header_len - t_hlen;

	dev->max_mtu = IP_MAX_MTU - t_hlen;

	ip_tunnel_add(itn, nt);

	return nt;
@@ -502,12 +502,11 @@ 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 - dev->hard_header_len;

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

	int mtu;



	if (df)

		mtu = dst_mtu(&rt->dst) - dev->hard_header_len

					- sizeof(struct iphdr) - tunnel->hlen;

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

	else

		mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
@@ -935,7 +934,7 @@ 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 = IP_MAX_MTU - dev->hard_header_len - t_hlen;

	int max_mtu = IP_MAX_MTU - t_hlen;



	if (new_mtu < ETH_MIN_MTU)

		return -EINVAL;
@@ -1112,10 +1111,9 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[], 


	mtu = ip_tunnel_bind_dev(dev);

	if (tb[IFLA_MTU]) {

		unsigned int max = IP_MAX_MTU - dev->hard_header_len - nt->hlen;

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



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

			    (unsigned int)(max - sizeof(struct iphdr)));

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

	}



	err = dev_set_mtu(dev, mtu);