Restrict max packet size on rx

[Stephen Hemminger]

On Fri, 18 Oct 2024 22:05:24 +0530
Rajasekhar Pulluru <pullururajasekhar at gmail.com> wrote:

> Team,
> Does setting mtu using rte_eth_dev_set_mtu limit the maximum size of the
> packet received on the dpdk port to the configured mtu size?
> 
> On an intel machine with ixgbe port, with mtu set to 1500, no rx-offloads
> enabled, ixgbe dpdk port is able to receive packets greater than 1500 size
> and even jumbo frames of size 9000, even though the peer is sending them
> fragmented with mtu of 1500.
> 
> How do I restrict the port not to receive any frame greater than mtu size?
> 
> Appreciate any help,
> Thanks.
> Rajasekhar


In networking, MTU and MRU are overlapping concepts.
The MTU value is used as a hint to the driver as to what size buffer to allocate
but it can use larger if it wants. If you have restrictions, then the application
needs to enforce them.