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Date: Fri, 1 Aug 2025 13:40:45 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Lorenzo Bianconi <lorenzo@kernel.org>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>, Stanislav Fomichev
 <stfomichev@gmail.com>, bpf@vger.kernel.org, netdev@vger.kernel.org, Alexei
 Starovoitov <ast@kernel.org>, Daniel Borkmann <borkmann@iogearbox.net>,
 Eric Dumazet <eric.dumazet@gmail.com>, "David S. Miller"
 <davem@davemloft.net>, Paolo Abeni <pabeni@redhat.com>, sdf@fomichev.me,
 kernel-team@cloudflare.com, arthur@arthurfabre.com, jakub@cloudflare.com,
 Jesse Brandeburg <jbrandeburg@cloudflare.com>
Subject: Re: [PATCH bpf-next V2 0/7] xdp: Allow BPF to set RX hints for
 XDP_REDIRECTed packets
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On Thu, 31 Jul 2025 23:18:12 +0200 Lorenzo Bianconi wrote:
> IIUC the 'set' proposal (please correct me if I am wrong), the eBPF program
> running on the NIC that is receiving the packet from the wire is supposed
> to set (or update) the hw metadata info (e.g. RX HASH or RX checksum) in
> the RX DMA descriptor associated to the packet to be successively consumed.
> Am I right?

I was thinking of doing the SET on the veth side. Basically the
metadata has to be understood by the stack only at the xdp->skb
transition point. So we can delay the SET until that moment, carrying
the information in program-specific format.