[Bridge] Originating device info for Packets trapped on Bridge

[Bridge] Originating device info for Packets trapped on Bridge

[dhan lin]

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Hi All,

I've a few doubts w.r.t layer2-frame processing in linux and PACKET_ORIGDEV
socket option for getting origdev info.

For example, lets assume below given is the set of net devices that my
frame is intended to traverse over.

eth0(1) -> bond0(2) -> bridge(3) -> vlan100(4). >>> (x) ifindex for
each netdevice

I have created a  RAW socket ( not binded to any interface) , attached with
a socket filter to trap only interested packets.
I am getting a copy of frame trapped from each of the netdevice. is this
expected?

frame trapped from eth0 will have from.sll_ifindex=1
frame trapped from bond0 will have from.sll_ifindex=2
frame trapped from bridge will have from.sll_ifindex=3
frame trapped from vlan100 will have from.sll_ifindex=4

If I set the following socket option PACKET_ORIGDEV , I get the following
result

frame trapped from eth0 will have from.sll_ifindex=1
frame trapped from bond0 will have from.sll_ifindex=1
frame trapped from bridge will have from.sll_ifindex=3.  >> why is this not
set to 1 or 2?
frame trapped from vlan100 will have from.sll_ifindex=3

can someone help me understand the role played by PACKET_ORIGDEV socket
option in the above scenario.

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