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Commit aeee0e66 authored by David Wragg's avatar David Wragg Committed by David S. Miller
Browse files

geneve: Refine MTU limit 



Calculate the maximum MTU taking into account the size of headers
involved in GENEVE encapsulation, as for other tunnel types.

Changes in v3:
- Correct comment style
Changes in v2:
- Conform more closely to ip_tunnel_change_mtu
- Exclude GENEVE options from max MTU calculation

Signed-off-by: default avatarDavid Wragg <david@weave.works>
Acked-by: default avatarJesse Gross <jesse@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7716682c

drivers/net/geneve.c

+22 −5
Original line number Diff line number Diff line
@@ -1039,17 +1039,34 @@ static netdev_tx_t geneve_xmit(struct sk_buff *skb, struct net_device *dev) 
	return geneve_xmit_skb(skb, dev, info);

}



static int geneve_change_mtu(struct net_device *dev, int new_mtu)

static int __geneve_change_mtu(struct net_device *dev, int new_mtu, bool strict)

{

	/* GENEVE overhead is not fixed, so we can't enforce a more

	 * precise max MTU.

	/* The max_mtu calculation does not take account of GENEVE

	 * options, to avoid excluding potentially valid

	 * configurations.

	 */

	if (new_mtu < 68 || new_mtu > IP_MAX_MTU)

	int max_mtu = IP_MAX_MTU - GENEVE_BASE_HLEN - sizeof(struct iphdr)

		- dev->hard_header_len;



	if (new_mtu < 68)

		return -EINVAL;



	if (new_mtu > max_mtu) {

		if (strict)

			return -EINVAL;



		new_mtu = max_mtu;

	}



	dev->mtu = new_mtu;

	return 0;

}



static int geneve_change_mtu(struct net_device *dev, int new_mtu)

{

	return __geneve_change_mtu(dev, new_mtu, true);

}



static int geneve_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)

{

	struct ip_tunnel_info *info = skb_tunnel_info(skb);
@@ -1459,7 +1476,7 @@ struct net_device *geneve_dev_create_fb(struct net *net, const char *name, 
	/* openvswitch users expect packet sizes to be unrestricted,

	 * so set the largest MTU we can.

	 */

	err = geneve_change_mtu(dev, IP_MAX_MTU);

	err = __geneve_change_mtu(dev, IP_MAX_MTU, false);

	if (err)

		goto err;