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[193.12.47.89]) by smtp.gmail.com with ESMTPSA id g9sm1208312lja.134.2021.05.03.01.49.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 May 2021 01:49:12 -0700 (PDT) From: Tobias Waldekranz To: Ido Schimmel Cc: davem@davemloft.net, kuba@kernel.org, andrew@lunn.ch, vivien.didelot@gmail.com, f.fainelli@gmail.com, olteanv@gmail.com, roopa@nvidia.com, nikolay@nvidia.com, jiri@resnulli.us, stephen@networkplumber.org, netdev@vger.kernel.org, bridge@lists.linux-foundation.org Subject: Re: [RFC net-next 2/9] net: bridge: Disambiguate offload_fwd_mark In-Reply-To: References: <20210426170411.1789186-1-tobias@waldekranz.com> <20210426170411.1789186-3-tobias@waldekranz.com> Date: Mon, 03 May 2021 10:49:12 +0200 Message-ID: <87h7jknqwn.fsf@waldekranz.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, May 02, 2021 at 18:00, Ido Schimmel wrote: > On Mon, Apr 26, 2021 at 07:04:04PM +0200, Tobias Waldekranz wrote: >> - skb->cb->offload_fwd_mark becomes skb->cb->src_hwdom. There is a >> slight change here: Whereas previously this was only set for >> offloaded packets, we now always track the incoming hwdom. As all >> uses where already gated behind checks of skb->offload_fwd_mark, >> this will not introduce any functional change, but it paves the way >> for future changes where the ingressing hwdom must be known both for >> offloaded and non-offloaded frames. > > [...] > >> @@ -43,15 +43,15 @@ int nbp_switchdev_mark_set(struct net_bridge_port *p) >> void nbp_switchdev_frame_mark(const struct net_bridge_port *p, >> struct sk_buff *skb) >> { >> - if (skb->offload_fwd_mark && !WARN_ON_ONCE(!p->offload_fwd_mark)) >> - BR_INPUT_SKB_CB(skb)->offload_fwd_mark = p->offload_fwd_mark; >> + if (p->hwdom) >> + BR_INPUT_SKB_CB(skb)->src_hwdom = p->hwdom; >> } > > I assume you are referring to this change? "src_hwdom" sounds weird if > it's expected to be valid for non-offloaded frames. Perhaps "non-offloaded" was a sloppy description on my part. I was trying to describe frames that originate from a switchdev, but have not been forwarded by hardware; e.g. STP BPDUs, IGMP reports, etc. So nbp_switchdev_frame_mark now basically says: "If this skb came in from a switchdev, make sure to note which one". > Can you elaborate about "future changes where the ingressing hwdom must > be known both for offloaded and non-offloaded frames"? Typical example: The switchdev has a fixed configuration to trap STP BPDUs, but STP is not running on the bridge and the group_fwd_mask allows them to be forwarded. Say we have this setup: br0 / | \ swp0 swp1 swp2 A BPDU comes in on swp0 and is trapped to the CPU; the driver does not set skb->offload_fwd_mark. The bridge determines that the frame should be forwarded to swp{1,2}. It is imperative that forward offloading is _not_ allowed in this case, as the source hwdom is already "poisoned". Recording the source hwdom allows this case to be handled properly. > Probably best to split this change to a different patch given the rest > of the changes are mechanical. Right, but I think the change in name to warrants a change in semantics. It is being renamed to src_hwdom because it now holds just that information. Again, there is no functional change introduced by this since nbp_switchdev_allowed_egress always checks for the presence of skb->offload_fwd_mark anyway. But if you feel strongly about it, I will split it up. >> >> bool nbp_switchdev_allowed_egress(const struct net_bridge_port *p, >> const struct sk_buff *skb) >> { >> return !skb->offload_fwd_mark || >> - BR_INPUT_SKB_CB(skb)->offload_fwd_mark != p->offload_fwd_mark; >> + BR_INPUT_SKB_CB(skb)->src_hwdom != p->hwdom; >> } >> >> /* Flags that can be offloaded to hardware */ >> -- >> 2.25.1 >>