netdev - [PATCH net v2] ibmveth: Fix max MTU limit

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Message-Id: <1592517353-16844-1-git-send-email-tlfalcon@linux.ibm.com>
Date:   Thu, 18 Jun 2020 16:55:53 -0500
From:   Thomas Falcon <tlfalcon@...ux.ibm.com>
To:     kuba@...nel.org
Cc:     netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Thomas Falcon <tlfalcon@...ux.ibm.com>
Subject: [PATCH net v2] ibmveth: Fix max MTU limit

The max MTU limit defined for ibmveth is not accounting for
virtual ethernet buffer overhead, which is twenty-two additional
bytes set aside for the ethernet header and eight additional bytes
of an opaque handle reserved for use by the hypervisor. Update the
max MTU to reflect this overhead.

Signed-off-by: Thomas Falcon <tlfalcon@...ux.ibm.com>
Fixes: d894be57ca92 ("ethernet: use net core MTU range checking in more drivers")
Fixes: 110447f8269a ("ethernet: fix min/max MTU typos")
---
v2: Include Fixes tags suggested by Jakub Kicisnki
---
 drivers/net/ethernet/ibm/ibmveth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 96d36ae5049e..c5c732601e35 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -1715,7 +1715,7 @@ static int ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
 	}
 
 	netdev->min_mtu = IBMVETH_MIN_MTU;
-	netdev->max_mtu = ETH_MAX_MTU;
+	netdev->max_mtu = ETH_MAX_MTU - IBMVETH_BUFF_OH;
 
 	memcpy(netdev->dev_addr, mac_addr_p, ETH_ALEN);
 
-- 
2.26.2