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[ovs-dev,PATCHv2,4/6] datapath: geneve: Refine MTU limit.

Message ID 1455907481-24507-5-git-send-email-joe@ovn.org
State Accepted
Headers show

Commit Message

Joe Stringer Feb. 19, 2016, 6:44 p.m. UTC 
From: David Wragg <david@weave.works>

Upstream commit:
    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>
    Acked-by: Jesse Gross <jesse@kernel.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Upstream: aeee0e66c6b4 ("geneve: Refine MTU limit")
Signed-off-by: Joe Stringer <joe@ovn.org>
---
 datapath/linux/compat/geneve.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)
diff mbox

Patch

diff --git a/datapath/linux/compat/geneve.c b/datapath/linux/compat/geneve.c
index 50ed3936d038..92feeef0900c 100644
--- a/datapath/linux/compat/geneve.c
+++ b/datapath/linux/compat/geneve.c
@@ -742,17 +742,34 @@  static netdev_tx_t geneve_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
-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 const struct net_device_ops geneve_netdev_ops = {
 #ifdef HAVE_DEV_TSTATS
 	.ndo_init		= geneve_init,
@@ -1045,7 +1062,7 @@  struct net_device *rpl_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;