[ipxe-devel] REG: Query on 9K MTU Testing flow

Michael Brown mcb30 at ipxe.org
Mon Mar 13 13:02:07 UTC 2023

On 13/03/2023 03:16, MohamedShah R via ipxe-devel wrote:
>  1. If our device configures netdev->mtu as 1500  and
>     netdev->max_pkt_len is 9128(above 9k).
>  2. If the DHCP server sends MTU size as 9K.   
> As per the code walk-through, I understand that this api 
> "staticintapply_netdev_settings” get invoke and call the below part of 
> code to handle the above scenario: In this case, as part of netdev_close 
> , it gets called the intf_close and it didn’t call the intf_init/openas 
> part of netdev_open api.

I think you've got lost somewhere in the code, sorry.  There is no path 
from netdev_close() to intf_close().  The generic object interfaces 
handled by intf_init(), intf_close(), etc, exist at a higher layer in 
the stack.

An MTU change for an open network interface via apply_netdev_setting() 
will result in the network devices .close() and .open() methods both 
being called.  Since receive buffers are allocated during .open(), this 
will result in all receive buffers having the correct size for the new MTU.


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