gre: let mac_header point to outer header only when necessary
Commit
e271c7b4420d ("gre: do not keep the GRE header around in collect
medata mode") did reset the mac_header for the collect_md case. Let's
extend this behaviour to classical gre devices as well.
ipgre_header_parse() seems to be the only case that requires mac_header
to point to the outer header. We can detect this case accurately by
checking ->header_ops. For all other cases, we can reset mac_header.
This allows to push an Ethernet header to ipgre packets and redirect
them to an Ethernet device:
$ tc filter add dev gre0 ingress matchall \
action vlan push_eth dst_mac 00:00:5e:00:53:01 \
src_mac 00:00:5e:00:53:00 \
action mirred egress redirect dev eth0
Before this patch, this worked only for collect_md gre devices.
Now this works for regular gre devices as well. Only the special case
of gre devices that use ipgre_header_ops isn't supported.
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>