netdev - Re: Packet not rerouting via different bridge interface after modifying destination IP in TC ingress hook

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Date:   Thu, 06 Aug 2020 08:33:34 +0000
From:   Swarm NameRedacted <thesw4rm@...me>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     netdev@...r.kernel.org
Subject: Re: Packet not rerouting via different bridge interface after modifying destination IP in TC ingress hook

Ok that makes sense. I'll try it. However, doesn't hairpin imply that
the packet will be routed back into the same machine via some public
address and separate router? I'm just trying to redirect it to
10.10.4.1, not loop it back to 10.10.3.1. Or is this an
unorthodox/modified usage of hairpinning?

On Thu, Aug 06, 2020 at 10:49:09AM +0300, Ido Schimmel wrote:
> 
> On Thu, Aug 06, 2020 at 07:00:15AM +0000, Swarm NameRedacted wrote:
> > Not sure this applies. There's no NAT since everything is on the same
> > subnet.
> 
> IIUC, packet is received on eth0, you then change the DMAC to SMAC on
> ingress (among other things) and then packet continues to the bridge.
> The bridge checks the DMAC and sees that the packet is supposed to be
> forwarded out of eth0. Since it's also the ingress interface the packet
> is dropped. To overcome this you need to enable hairpin.