> -----Original Message----- > From: David Miller [mailto:davem@xxxxxxxxxxxxx] > Sent: Wednesday, November 12, 2014 2:47 PM > To: Haiyang Zhang > Cc: netdev@xxxxxxxxxxxxxxx; KY Srinivasan; olaf@xxxxxxxxx; > jasowang@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; driverdev- > devel@xxxxxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH net-next] hyperv: Add processing of MTU reduced by > the host > > From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > Date: Tue, 11 Nov 2014 15:27:52 -0800 > > > - if (mtu < 68 || mtu > limit) > > + if (mtu < ETH_DATA_LEN || mtu > limit) > > return -EINVAL; > > This is not correct. > > The test is against the minimally supported MTU, which should > be 68 not ETH_DATA_LEN which is 1500. The Hyper-V host doesn't support MTU below 1500. If we try setting MTU to a value < 1500, the host will use 1500 automatically and return 1500 in the RNDIS_OID_GEN_MAXIMUM_FRAME_SIZE query and guest will also use it. That's why I set the lower limit to ETH_DATA_LEN. Are you suggesting that we keep the 68 as the lower limit, and let the host auto-reset it to 1500 when we trying to set an MTU < 1500? Thanks, - Haiyang _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
