netdev - Re: [PATCH bpf-next V2 0/7] xdp: Allow BPF to set RX hints for XDP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250805165414.032db0b1@kernel.org>
Date: Tue, 5 Aug 2025 16:54:14 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: Jesper Dangaard Brouer <hawk@...nel.org>, Stanislav Fomichev
 <stfomichev@...il.com>, bpf@...r.kernel.org, netdev@...r.kernel.org, Alexei
 Starovoitov <ast@...nel.org>, Daniel Borkmann <borkmann@...earbox.net>,
 Eric Dumazet <eric.dumazet@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, sdf@...ichev.me,
 kernel-team@...udflare.com, arthur@...hurfabre.com, jakub@...udflare.com,
 Jesse Brandeburg <jbrandeburg@...udflare.com>
Subject: Re: [PATCH bpf-next V2 0/7] xdp: Allow BPF to set RX hints for
 XDP_REDIRECTed packets

On Tue, 5 Aug 2025 15:18:52 +0200 Lorenzo Bianconi wrote:
> > 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.  
> 
> ack, I am fine to delay the translation of the HW metadata from a HW
> specific format (the one contained in the DMA descriptor) to the network one
> when they are consumed to create the SKB (the veth driver in this case) but I
> guess we need to copy the info contained in the DMA descriptor into a buffer
> that is still valid when veth driver consumes them since the DMA descriptor
> can be no longer available at that time. Do you agree or am I missing
> something?

That's right, we need to carry the metadata we need with the packet
(in an XDP program-specific md prepend, presumably).