Subject: [PATCH net-next 2/2] veth: allow configuring GSO maximums

From: Stephen Hemminger <[email-masked]>
Date: Fri, 1 Dec 2017 12:11:58 -0800

Veth's can be used in environments (like Azure) where the underlying
network device is impacted by large GSO packets. This patch allows
gso maximum values to be passed in when creating the device via
netlink.

In theory, other pseudo devices could also use netlink attributes
to set GSO maximums but for now veth is what has been observed
to be an issue.

Signed-off-by: Stephen Hemminger <[email-masked]>
---
 drivers/net/veth.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index f5438d0978ca..510c058ba227 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -410,6 +410,26 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 	if (ifmp && (dev->ifindex != 0))
 		peer->ifindex = ifmp->ifi_index;
 
+	if (tbp[IFLA_GSO_MAX_SIZE]) {
+		u32 max_size = nla_get_u32(tbp[IFLA_GSO_MAX_SIZE]);
+
+		if (max_size > GSO_MAX_SIZE)
+			return -EINVAL;
+
+		peer->gso_max_size = max_size;
+		dev->gso_max_size = max_size;
+	}
+
+	if (tbp[IFLA_GSO_MAX_SEGS]) {
+		u32 max_segs = nla_get_u32(tbp[IFLA_GSO_MAX_SEGS]);
+
+		if (max_segs > GSO_MAX_SEGS)
+			return -EINVAL;
+
+		peer->gso_max_segs = max_segs;
+		dev->gso_max_segs = max_segs;
+	}
+
 	err = register_netdevice(peer);
 	put_net(net);
 	net = NULL;
-- 
2.11.0