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[79.178.32.166]) by smtp.gmail.com with ESMTPSA id t10sm54905044wrp.39.2020.12.28.09.22.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Dec 2020 09:22:31 -0800 (PST) Date: Mon, 28 Dec 2020 12:22:28 -0500 From: "Michael S. Tsirkin" To: Willem de Bruijn Cc: virtualization@lists.linux-foundation.org, Network Development , Jason Wang Subject: Re: [PATCH rfc 1/3] virtio-net: support transmit hash report Message-ID: <20201228122155-mutt-send-email-mst@kernel.org> References: <20201228162233.2032571-1-willemdebruijn.kernel@gmail.com> <20201228162233.2032571-2-willemdebruijn.kernel@gmail.com> <20201228112657-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Dec 28, 2020 at 11:47:45AM -0500, Willem de Bruijn wrote: > On Mon, Dec 28, 2020 at 11:28 AM Michael S. Tsirkin wrote: > > > > On Mon, Dec 28, 2020 at 11:22:31AM -0500, Willem de Bruijn wrote: > > > From: Willem de Bruijn > > > > > > Virtio-net supports sharing the flow hash from host to guest on rx. > > > Do the same on transmit, to allow the host to infer connection state > > > for more robust routing and telemetry. > > > > > > Linux derives ipv6 flowlabel and ECMP multipath from sk->sk_txhash, > > > and updates these fields on error with sk_rethink_txhash. This feature > > > allows the host to make similar decisions. > > > > > > Besides the raw hash, optionally also convey connection state for > > > this hash. Specifically, the hash rotates on transmit timeout. To > > > avoid having to keep a stateful table in the host to detect flow > > > changes, explicitly notify when a hash changed due to timeout. > > > > I don't actually see code using VIRTIO_NET_HASH_STATE_TIMEOUT_BIT > > in this series. Want to split out that part to a separate patch? > > Will do. > > I wanted to make it clear that these bits must be reserved (i.e., > zero) until a later patch specifies them. Already the case for the padding field I think ... > The timeout notification feature requires additional plumbing between > the TCP protocol stack and device driver, probably an skb bit. I'd > like to leave that as follow-up for now. > > Thanks for the fast feedback!