xfrm: Linearize the skb after offloading if needed.
With offloading enabled, esp_xmit() gets invoked very late, from within
validate_xmit_xfrm() which is after validate_xmit_skb() validates and
linearizes the skb if the underlying device does not support fragments.
esp_output_tail() may add a fragment to the skb while adding the auth
tag/ IV. Devices without the proper support will then send skb->data
points to with the correct length so the packet will have garbage at the
end. A pcap sniffer will claim that the proper data has been sent since
it parses the skb properly.
It is not affected with INET_ESP_OFFLOAD disabled.
Linearize the skb after offloading if the sending hardware requires it.
It was tested on v4, v6 has been adopted.
Fixes: 7785bba299a8d ("esp: Add a software GRO codepath") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>