xfrm interfaces currently test for !skb->ignore_df when deciding
whether to update the pmtu on the skb's dst. Because of this, no pmtu
exception is created when we do something like:
ping -s 1438 <dest>
By dropping this check, the pmtu exception will be created and the
next ping attempt will work.
Fixes: f203b76d78 ("xfrm: Add virtual xfrm interfaces")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>