Re: Sending 802.1Q packets using AF_PACKET socket on filtered bridge forwards with wrong MAC addresses

From: Brandon Carpenter
Date: Tue Nov 28 2017 - 18:38:07 EST


I tracked down the function responsible for changing the MAC header.
It is skb_vlan_untag() called from __allowed_ingress() in
net/bridge/br_vlan.c. Before skb_vlan_untag() is called, the MAC
headers are perfect and afterward they are altered as previously
described. I'll continue digging into that function, but if any of you
have insight into what skb_vlan_untag() does and why it might alter
the MAC header the way it does in this special case, I would
appreciate the help.

Thanks,

Brandon

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