From aeee0e66c6b46cee311be22cb82735763eceb7c3 Mon Sep 17 00:00:00 2001 From: David Wragg Date: Thu, 18 Feb 2016 17:43:29 +0000 Subject: [PATCH] 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: David Wragg Acked-by: Jesse Gross Signed-off-by: David S. Miller --- drivers/net/geneve.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c index 028e3873c310..70975700f91d 100644 --- a/drivers/net/geneve.c +++ b/drivers/net/geneve.c @@ -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; -- 2.39.5