Hi Qi, > > > > On 3/22/2019 1:01 PM, Ian Stokes wrote: > > > This commit sets the min and max supported MTU values for igb devices > > > via the eth_igb_info_get() function. Min MTU supported is set to > > > ETHER_MIN_MTU and max mtu is calculated as the max packet length > > > supported minus the transport overhead. To aid in these calculations a > > > new MACRO 'E1000_ETH_OVERHEAD' has been introduced to consolidate > > > overhead calculation and avoid duplication. > > > > > > Signed-off-by: Ian Stokes <ian.sto...@intel.com> > > > --- > > > drivers/net/e1000/e1000_ethdev.h | 6 ++++++ > > > drivers/net/e1000/igb_ethdev.c | 7 +++++-- > > > 2 files changed, 11 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/net/e1000/e1000_ethdev.h > > > b/drivers/net/e1000/e1000_ethdev.h > > > index 94edff08e..3e74cd8fe 100644 > > > --- a/drivers/net/e1000/e1000_ethdev.h > > > +++ b/drivers/net/e1000/e1000_ethdev.h > > > @@ -89,6 +89,12 @@ > > > ETH_RSS_IPV6_UDP_EX) > > > > > > /* > > > + * The overhead from MTU to max frame size. > > > + * Considering VLAN so a tag needs to be counted. > > > + */ > > > +#define E1000_ETH_OVERHEAD (ETHER_HDR_LEN + ETHER_CRC_LEN + > > > +VLAN_TAG_SIZE) > > > > As an overhead, following drivers set: > > i40e: HDR + CRC + 2 * VLAN > > ixgbe: HDR + CRC > > e1000: HDR + CRC + VLAN > > > > I wonder if this difference is HW limitation, or driver limitation or just > > implementation inconsistency. > > I think this is implementation inconsistency > > The NIC only accept Max Frame Size. > > The problem here is seems all of three setup are not perfect. > > HDR + CRC + 2 * VLAN - it may allow non vlan or single vlan packet that > exceed mtu.
Hmm, wonder how? > HDR + CRC - it may reject vlan or double vlan packet that follow mtu. > HDR + CRC + VLAN , it may reject double vlan packet that follow mtu > > I agree it's better to keep consistent on all drivers, but before this, we > may need to decide which one we should take :) > > Regards > Qi > > > > > Better to confirm it that it is not implementation inconsistency. > > > > Wenzhuo, Konstantin, Beilei, Qi, > > > > Can you please comment? > > > > Thanks, > > ferruh
