From: Eyal Birger <redacted>
Date: Thu, 26 Feb 2015 21:07:01 +0200

As part of an effort to move skb->dropcount to skb->cb[], 4 bytes
of additional room are needed in skb->cb[] in packet sockets.

Store the skb original length in skb->dev instead of skb->cb[] for
this purpose.

Signed-off-by: Eyal Birger <redacted>

I'm a little confused, why is this even needed?

packet_skb_cb is 24 bytes by my calculations, which is much
smaller than the cb[] size which is 48 bytes.