[Openvpn-devel] [PATCH ovpn net v2 1/2] ovpn: add missing rtnl_link_ops->get_size callback

ovpn_fill_info emits IFLA_OVPN_MODE inside IFLA_INFO_DATA, but
ovpn_link_ops does not provide a get_size callback. Consequently,
rtnetlink's size estimate for ovpn link messages does not include the
nested mode attribute.

Available skb tailroom may hide this mismatch. When the remaining space
is insufficient, however, ovpn_fill_info returns -EMSGSIZE and message
construction fails.

Add the callback and account for IFLA_OVPN_MODE.

Fixes: c2d950c4672a ("ovpn: add basic interface creation/destruction/management routines")
Signed-off-by: Ralf Lici <[email protected]>
---
Changes since v1 https://lore.kernel.org/openvpn-devel/[email protected]/
- Clarify in the commit message that the incorrect size estimate causes
  a failure when skb tailroom is insufficient.
- Add the selftest as patch 2/2.

 drivers/net/ovpn/main.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index 9993c1dfe471..9d9a0ff690d6 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -210,6 +210,12 @@ static int ovpn_newlink(struct net_device *dev,
 	return register_netdevice(dev);
 }
 
+static size_t ovpn_get_size(const struct net_device *dev)
+{
+	/* IFLA_OVPN_MODE */
+	return nla_total_size(sizeof(u8));
+}
+
 static int ovpn_fill_info(struct sk_buff *skb, const struct net_device *dev)
 {
 	struct ovpn_priv *ovpn = netdev_priv(dev);
@@ -228,6 +234,7 @@ static struct rtnl_link_ops ovpn_link_ops = {
 	.policy = ovpn_policy,
 	.maxtype = IFLA_OVPN_MAX,
 	.newlink = ovpn_newlink,
+	.get_size = ovpn_get_size,
 	.fill_info = ovpn_fill_info,
 };
 
-- 
2.55.0



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