Date: Thu, 5 Jul 2018 08:47:10 -0700 From: "np@freebsd.org" <np@freebsd.org> To: "Eggert, Lars" <lars@netapp.com> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Giuseppe Lettieri <g.lettieri@iet.unipi.it> Subject: Re: netmap & chelsio Message-ID: <20180705154710.GA3353@ox> In-Reply-To: <94019926-B14F-47AB-8AD9-C01B4A0E199F@netapp.com> References: <94019926-B14F-47AB-8AD9-C01B4A0E199F@netapp.com>
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On Thu, Jul 05, 2018 at 03:09:33PM +0000, Eggert, Lars wrote: > Hi, > > when receiving packets via netmap (current GitHub version) on a Chelsio T6 > vcc0 device on -CURRENT, it appears that the Ethernet header starts at an > offset of two bytes into the netmap slot. So far, I have only used netmap with > various Intel NICs, where the Ethernet header starts at offset zero. > > Is this a bug? Is this to be expected? Set hw.cxgbe.fl_pktshift=0 in loader.conf to stop the chip from doing this. See cxgbe(4) for details on the knob. It's a historic optimization that doesn't seem to matter on modern CPUs, so the driver default should probably be 0 instead of 2. Regards, Navdeep
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