setting if_hw_tsomax{segcount, segsize} in net drivers

Christopher Forgeron csforgeron at
Tue Jun 9 14:10:15 UTC 2015

Thanks for keeping up on this Rick. TSO needs to be fixed on FreeBSD, but
it does not seem to be a hot-button topic.

 I still suffer from TSO issues, and thus turn it off in a standard build -
but I noticed that machines that were VMWare 5.1-6.0, running the vmx
driver, they did not have problems if TSO was on.

 I dug into the source far enough to see that vmx doesn't look to allocate
more than a 4k mbuf unlike ixgeb/others, but I didn't test/dig further.

On Mon, Jun 8, 2015 at 7:45 PM, Rick Macklem <rmacklem at> wrote:

> Hi,
> I just looked at stable/10 and found the following 4 drivers have
> set the if_hw_tsomax, if_hw_tsomaxsegcount and if_hw_tsomaxsegsize
> fields:
> ./xen/netfront/netfront.c
> ./cxgbe/t4_main.c
> ./oce/oce_if.c
> ./vmware/vmxnet3/if_vmx.c
> If you are the author/maintainer for a network device driver that does
> TSO and is not on the above list...please, please fill in the above
> fields before the call to ether_ifattach(), so that TSO will hopefully
> work correctly with NFS/iSCSI. (I said "hopefully" because there might
> be other bugs related to TSO in your driver that I wouldn't know about.)
> Maybe someone could mention this at BSDCan too?
> Thanks in advance for doing this, rick
> ps: I would be really nice to get this done for 10.2 imho.
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