Re: [PATCH net] macvlan: Disable LRO on lowerdev; warn if it's turned back on

On Tue, 2012-02-21 at 12:01 -0800, John Fastabend wrote:

On 2/21/2012 11:13 AM, Ben Hutchings wrote:

quoted

Large Receive Offload (LRO) is only appropriate for packets that are
destined for the host, and should be disabled if received packets may
be forwarded.

Further, macvtap_skb_to_vnet_hdr() will BUG() on a packet received
with LRO (but not GRO).

Signed-off-by: Ben Hutchings <redacted>
---
I'm not really familiar with macvlan so I'm not certain that this should
be applied to all modes.

Ben.

 drivers/net/macvlan.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

But this patch assumes the macvlan is forwarding traffic to a guest
via macvtap. Which is an assumption that may not be true.

It seems more appropriate for the macvtap driver to do these checks
after all its the driver that may BUG() with LRO.

That's what I thought at first, but then I looked through what macvlan
was doing and it certainly appears to re-transmit skbs in all modes.
That's not valid when gso_size != 0 and gso_type == 0.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.