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Date: Tue, 9 Feb 2016 16:47:03 +0000 From: David Wragg <david@...ve.works> To: netdev@...r.kernel.org, dev@...nvswitch.org Cc: Jesse Gross <jesse@...nel.org>, David Miller <davem@...emloft.net>, Hannes Frederic Sowa <hannes@...essinduktion.org>, Thomas Graf <tgraf@...g.ch>, Roopa Prabhu <roopa@...ulusnetworks.com>, David Wragg <david@...ve.works> Subject: [PATCH net v2 2/3] geneve: Relax MTU constraints Allow the MTU of geneve devices to be set to large values, in order to exploit underlying networks with larger frame sizes. GENEVE does not have a fixed encapsulation overhead (an openvswitch rule can add variable length options), so there is no relevant maximum MTU to enforce. A maximum of IP_MAX_MTU is used instead. Encapsulated packets that are too big for the underlying network will get dropped on the floor. Signed-off-by: David Wragg <david@...ve.works> --- drivers/net/geneve.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c index 0b14ac3..05cef11 100644 --- a/drivers/net/geneve.c +++ b/drivers/net/geneve.c @@ -1039,6 +1039,16 @@ 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) +{ + /* GENEVE overhead is not fixed, so we can't enforce a more + precise max MTU. */ + if (new_mtu < 68 || new_mtu > IP_MAX_MTU) + return -EINVAL; + dev->mtu = new_mtu; + return 0; +} + static int geneve_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb) { struct ip_tunnel_info *info = skb_tunnel_info(skb); @@ -1083,7 +1093,7 @@ static const struct net_device_ops geneve_netdev_ops = { .ndo_stop = geneve_stop, .ndo_start_xmit = geneve_xmit, .ndo_get_stats64 = ip_tunnel_get_stats64, - .ndo_change_mtu = eth_change_mtu, + .ndo_change_mtu = geneve_change_mtu, .ndo_validate_addr = eth_validate_addr, .ndo_set_mac_address = eth_mac_addr, .ndo_fill_metadata_dst = geneve_fill_metadata_dst, -- 2.5.0
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