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([2600:1700:dfe0:49f0:49e1:751f:b992:b4f3]) by smtp.gmail.com with ESMTPSA id i16sm3565796oie.5.2021.07.18.19.26.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Jul 2021 19:26:47 -0700 (PDT) Subject: Re: [PATCH v4 net-next 07/15] net: bridge: disambiguate offload_fwd_mark To: Vladimir Oltean , netdev@vger.kernel.org, Jakub Kicinski , "David S. Miller" Cc: Andrew Lunn , Vivien Didelot , Jiri Pirko , Ido Schimmel , Tobias Waldekranz , Roopa Prabhu , Nikolay Aleksandrov , Stephen Hemminger , bridge@lists.linux-foundation.org, Grygorii Strashko , Marek Behun , DENG Qingfang References: <20210718214434.3938850-1-vladimir.oltean@nxp.com> <20210718214434.3938850-8-vladimir.oltean@nxp.com> From: Florian Fainelli Message-ID: <4191ea0a-09ce-d52f-f40e-2d680ef4b9ca@gmail.com> Date: Sun, 18 Jul 2021 19:26:45 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210718214434.3938850-8-vladimir.oltean@nxp.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/18/2021 2:44 PM, Vladimir Oltean wrote: > From: Tobias Waldekranz > > Before this change, four related - but distinct - concepts where named > offload_fwd_mark: > > - skb->offload_fwd_mark: Set by the switchdev driver if the underlying > hardware has already forwarded this frame to the other ports in the > same hardware domain. > > - nbp->offload_fwd_mark: An idetifier used to group ports that share > the same hardware forwarding domain. > > - br->offload_fwd_mark: Counter used to make sure that unique IDs are > used in cases where a bridge contains ports from multiple hardware > domains. > > - skb->cb->offload_fwd_mark: The hardware domain on which the frame > ingressed and was forwarded. > > Introduce the term "hardware forwarding domain" ("hwdom") in the > bridge to denote a set of ports with the following property: > > If an skb with skb->offload_fwd_mark set, is received on a port > belonging to hwdom N, that frame has already been forwarded to all > other ports in hwdom N. > > By decoupling the name from "offload_fwd_mark", we can extend the > term's definition in the future - e.g. to add constraints that > describe expected egress behavior - without overloading the meaning of > "offload_fwd_mark". > > - nbp->offload_fwd_mark thus becomes nbp->hwdom. > > - br->offload_fwd_mark becomes br->last_hwdom. > > - skb->cb->offload_fwd_mark becomes skb->cb->src_hwdom. The slight > change in naming here mandates a slight change in behavior of the > nbp_switchdev_frame_mark() function. Previously, it only set this > value in skb->cb for packets with skb->offload_fwd_mark true (ones > which were forwarded in hardware). Whereas now we always track the > incoming hwdom for all packets coming from a switchdev (even for the > packets which weren't forwarded in hardware, such as STP BPDUs, IGMP > reports etc). As all uses of skb->cb->offload_fwd_mark were 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 for frames coming from a switchdev > regardless of whether they were forwarded in hardware or not > (basically, if the skb comes from a switchdev, skb->cb->src_hwdom now > always tracks which one). > > A typical example where this is relevant: 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. > > v2->v3: added code comments > v3->v4: none > > Signed-off-by: Tobias Waldekranz > Signed-off-by: Vladimir Oltean > Reviewed-by: Grygorii Strashko Reviewed-by: Florian Fainelli -- Florian