netdev - [PATCH net-next 6/6] i40e: Log error for oversized MTU on device

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Date:   Mon,  1 Feb 2021 18:24:20 -0800
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     Eryk Rybak <eryk.roch.rybak@...el.com>, netdev@...r.kernel.org,
        sassmann@...hat.com, anthony.l.nguyen@...el.com,
        bjorn.topel@...el.com, maciej.fijalkowski@...el.com,
        magnus.karlsson@...el.com,
        Aleksandr Loktionov <aleksandr.loktionov@...el.com>,
        Kiran Bhandare <kiranx.bhandare@...el.com>
Subject: [PATCH net-next 6/6] i40e: Log error for oversized MTU on device

From: Eryk Rybak <eryk.roch.rybak@...el.com>

When attempting to link XDP prog with MTU larger than supported,
user is not informed why XDP linking fails. Adding proper
error message: "MTU too large to enable XDP".
Due to the lack of support for non-static variables in netlinks
extended ACK feature, additional information has been added to dmesg
to better inform about invalid MTU setting.

Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Signed-off-by: Eryk Rybak <eryk.roch.rybak@...el.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/i40e/i40e_main.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index f35bd9164106..b52a324a9f28 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -12448,9 +12448,10 @@ static netdev_features_t i40e_features_check(struct sk_buff *skb,
  * i40e_xdp_setup - add/remove an XDP program
  * @vsi: VSI to changed
  * @prog: XDP program
+ * @extack: netlink extended ack
  **/
-static int i40e_xdp_setup(struct i40e_vsi *vsi,
-			  struct bpf_prog *prog)
+static int i40e_xdp_setup(struct i40e_vsi *vsi, struct bpf_prog *prog,
+			  struct netlink_ext_ack *extack)
 {
 	int frame_size = vsi->netdev->mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN;
 	struct i40e_pf *pf = vsi->back;
@@ -12459,8 +12460,13 @@ static int i40e_xdp_setup(struct i40e_vsi *vsi,
 	int i;
 
 	/* Don't allow frames that span over multiple buffers */
-	if (frame_size > vsi->rx_buf_len)
+	if (frame_size > vsi->rx_buf_len) {
+		NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP");
+		dev_info(&pf->pdev->dev,
+			 "MTU of %u bytes is too large to enable XDP (maximum: %u bytes)\n",
+			 vsi->netdev->mtu, vsi->rx_buf_len);
 		return -EINVAL;
+	}
 
 	if (!i40e_enabled_xdp_vsi(vsi) && !prog)
 		return 0;
@@ -12772,7 +12778,7 @@ static int i40e_xdp(struct net_device *dev,
 
 	switch (xdp->command) {
 	case XDP_SETUP_PROG:
-		return i40e_xdp_setup(vsi, xdp->prog);
+		return i40e_xdp_setup(vsi, xdp->prog, xdp->extack);
 	case XDP_SETUP_XSK_POOL:
 		return i40e_xsk_pool_setup(vsi, xdp->xsk.pool,
 					   xdp->xsk.queue_id);
-- 
2.26.2