gro: take care of DODGY packets

gro: take care of DODGY packets

[ Upstream commit 7871f54e3deed68a27111dda162c4fe9b9c65f8f ]

Jaroslav reported a recent throughput regression with virtio_net
caused by blamed commit.

It is unclear if DODGY GSO packets coming from user space
can be accepted by GRO engine in the future with minimal
changes, and if there is any expected gain from it.

In the meantime, make sure to detect and flush DODGY packets.

Fixes: 5eddb24901ee ("gro: add support of (hw)gro packets to gro stack")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-and-bisected-by: Jaroslav Pulchart <jaroslav.pulchart@gooddata.com>
Cc: Coco Li <lixiaoyan@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>