> -----Original Message----- > From: Yigit, Ferruh > Sent: Monday, March 25, 2019 10:25 PM > To: Stokes, Ian <ian.sto...@intel.com>; dev@dpdk.org > Cc: step...@networkplumber.org; Lu, Wenzhuo <wenzhuo...@intel.com>; > Ananyev, Konstantin <konstantin.anan...@intel.com>; Xing, Beilei > <beilei.x...@intel.com>; Zhang, Qi Z <qi.z.zh...@intel.com> > Subject: Re: [dpdk-dev] [PATCH v2 6/7] net/e1000: set min and max MTU for igb > devices > > 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. 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
