Martin Willi [off-list ref] writes:

Hi,

Thanks for your comments.

quoted

quoted

 	eth = (struct ethhdr *)xdp->data;
+	orig_host = ether_addr_equal_64bits(eth->h_dest, skb->dev->dev_addr);

ether_addr_equal_64bits() seems to assume that the addresses passed to 
it are padded to be 8 bytes long, which is not the case for eth->h_dest.
AFAICT the only reason the _64bits variant works for multicast is that
it happens to be only checking the top-most bit, but unless I'm missing
something you'll have to use the boring old ether_addr_equal() here, no?

This is what eth_type_trans() uses below, so I assumed it is safe to
use. Isn't that working on the same data?

Also, the destination address in Ethernet is followed by the source
address, so two extra bytes in the source are used as padding. These
are then shifted out by ether_addr_equal_64bits(), no?

Ohh, you're right, it's shifting off the two extra bytes afterwards.
Clever! I obviously missed that, but yeah, that means it just needs the
two extra bytes to not be out-of-bounds reads, so this usage should be
fine :)

quoted

quoted

+		skb->pkt_type = PACKET_HOST;
 		skb->protocol = eth_type_trans(skb, skb->dev);
 	}

Okay, so this was a bit confusing to me at fist glance:
eth_type_trans() will reset the type, but not back to PACKET_HOST. So
this works, just a bit confusing :)

Indeed. I considered changing eth_type_trans() to always reset
pkt_type, but I didn't want to take the risk for any side effects.

Hmm, yeah, it does seem there are quite a few call sites to audit if you
were to change the behaviour. I guess we'll have to live with the slight
confusion, then :)

-Toke


Given the above:

Acked-by: Toke Høiland-Jørgensen <redacted>