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 <david@weave.works>
---
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 028e387..7097570 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;
--
2.5.0
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