Hi, This is the code snippet from DPDK 19.11 i40evf PMD on setting mtu which would fail if port/device is already started. Does vppctl set interface mtu command stops, sets mtu and then starts the device or is this NIC specific? What is the approach or advice dealing with NIC specific limitations or quirk?
Appreciate your feedback Thank you - Pranab K Das On Wed, Oct 6, 2021 at 5:34 PM PRANAB DAS via lists.fd.io <pkdas.boston= gmail....@lists.fd.io> wrote: > Hi > > We noticed that after an interface (physical > interface VirtualFunctionEthernet0/7/0) is up state > (vppctl set interface state <ifname> up), if we modify the mtu of the > interface (e.g. vppctl set interface <ifname> mtu 1500) the interface > starts doing rx-miss forever. The interface becomes completely blocked and > is not transient. It is possible that the interface is receiving and > transmitting packets while mtu is being altered from default 8000 to 1500. > > This occurs with i40e VF interfaces and VPP 20.05. I am wondering if this > is observed by others as well. It is not clear from the documentation > (either DPDK or VPP) if an interface needs to be in "down" (link down) > state before the mtu can be modified. The VPP document does say it programs > the NIC but does not clearly state if the interface must be in down state. > The DPDK rte_dev_ether_set_mtu() API does not mention any such restriction > either. > > I am wondering if this is specific to i40e VF only or applies for other > NIC as well. > What's the recommended way of updating mtu? If we modify the mtu of > logical/sub interface (e.g. VirtualFunctionEthernet0/7/0.400) will alter > the mtu of the physical interface ( VirtualFunctionEthernet0/7/0) as well. > How could we ensure that mtu setting is consistent on a VF which might have > multiple sub interfaces in use including the raw physical interface > (without any VLAN) > > I would really appreciate it if you could provide some advice in this > regard. We use physical interface (e.g. VirtualFunctionEthernet0/7/0) for > internal communication between two applications since memif is not high > performance and use sub interfaces (VirtualFunctionEthernet0/7/0.400, 500, > 600) for external networks. > > Thank you very much > > - Pranab K Das > > > > > > > >
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