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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Andrew Lunn , Vivien Didelot , Florian Fainelli , linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v3 1/4] net: dsa: add support for DSA rx offloading via metadata dst Message-ID: <20221111233714.pmbc5qvq3g3hemhr@skbuf> References: <20221110212212.96825-1-nbd@nbd.name> <20221110212212.96825-2-nbd@nbd.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221110212212.96825-2-nbd@nbd.name> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Nov 10, 2022 at 10:22:08PM +0100, Felix Fietkau wrote: > If a metadata dst is present with the type METADATA_HW_PORT_MUX on a dsa cpu > port netdev, assume that it carries the port number and that there is no DSA > tag present in the skb data. > > Signed-off-by: Felix Fietkau > --- Doesn't look bad to me, but... > net/core/flow_dissector.c | 4 +++- > net/dsa/dsa.c | 19 ++++++++++++++++++- > 2 files changed, 21 insertions(+), 2 deletions(-) > > diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c > index 25cd35f5922e..1f476abc25e1 100644 > --- a/net/core/flow_dissector.c > +++ b/net/core/flow_dissector.c > @@ -972,11 +972,13 @@ bool __skb_flow_dissect(const struct net *net, > if (unlikely(skb->dev && netdev_uses_dsa(skb->dev) && > proto == htons(ETH_P_XDSA))) { > const struct dsa_device_ops *ops; > + struct metadata_dst *md_dst = skb_metadata_dst(skb); > int offset = 0; > > ops = skb->dev->dsa_ptr->tag_ops; > /* Only DSA header taggers break flow dissection */ > - if (ops->needed_headroom) { > + if (ops->needed_headroom && > + (!md_dst || md_dst->type != METADATA_HW_PORT_MUX)) { > if (ops->flow_dissect) > ops->flow_dissect(skb, &proto, &offset); > else > diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c > index 64b14f655b23..0b67622cf905 100644 > --- a/net/dsa/dsa.c > +++ b/net/dsa/dsa.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > > #include "dsa_priv.h" > > @@ -216,6 +217,7 @@ static bool dsa_skb_defer_rx_timestamp(struct dsa_slave_priv *p, > static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev, > struct packet_type *pt, struct net_device *unused) > { > + struct metadata_dst *md_dst = skb_metadata_dst(skb); > struct dsa_port *cpu_dp = dev->dsa_ptr; > struct sk_buff *nskb = NULL; > struct dsa_slave_priv *p; > @@ -229,7 +231,22 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev, > if (!skb) > return 0; > > - nskb = cpu_dp->rcv(skb, dev); > + if (md_dst && md_dst->type == METADATA_HW_PORT_MUX) { > + unsigned int port = md_dst->u.port_info.port_id; > + > + skb_dst_set(skb, NULL); If you insist on not using the refcounting feature and free your metadata_dst in the master's remove() function, that's going to invalidate absolutely any point I'm trying to make. Normally I'd leave you alone, however I really don't like that this is also forcing DSA to not use the refcount, and therefore, that it's forcing any other driver to do the same as mtk_eth_soc. Not sure how that's gonna scale in the hypothetical future when there will be a DSA master which can offload RX DSA tags, *and* the switch can change tagging protocols dynamically (which will force the master to allocate/free its metadata dst's at runtime too). I guess that will be for me to figure out, which I don't like. Jakub, what do you think? Refcounting or no refcounting? > + if (!skb_has_extensions(skb)) > + skb->slow_gro = 0; > + > + skb->dev = dsa_master_find_slave(dev, 0, port); > + if (likely(skb->dev)) { > + dsa_default_offload_fwd_mark(skb); > + nskb = skb; > + } > + } else { > + nskb = cpu_dp->rcv(skb, dev); > + } > + > if (!nskb) { > kfree_skb(skb); > return 0; > -- > 2.38.1 >