net: skbuff: Limit skb_vlan_pop/push() to expect skb->data at mac header
skb_vlan_pop/push were too generic, trying to support the cases where skb->data is at mac header, and cases where skb->data is arbitrarily elsewhere. Supporting an arbitrary skb->data was complex and bogus: - It failed to unwind skb->data to its original location post actual pop/push. (Also, semantic is not well defined for unwinding: If data was into the eth header, need to use same offset from start; But if data was at network header or beyond, need to adjust the original offset according to the push/pull) - It mangled the rcsum post actual push/pop, without taking into account that the eth bytes might already have been pulled out of the csum. Most callers (ovs, bpf) already had their skb->data at mac_header upon invoking skb_vlan_pop/push. Last caller that failed to do so (act_vlan) has been recently fixed. Therefore, to simplify things, no longer support arbitrary skb->data inputs for skb_vlan_pop/push(). skb->data is expected to be exactly at mac_header; WARN otherwise. Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Pravin Shelar <pshelar@ovn.org> Cc: Jiri Pirko <jiri@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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