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[78.154.15.182]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-490c2d4891csm82571075e9.1.2026.06.06.01.21.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 06 Jun 2026 01:21:35 -0700 (PDT) Message-ID: Date: Sat, 6 Jun 2026 11:21:33 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v2 3/6] net: bridge: add 802.1Qat stream reservation admission control Content-Language: en-US, bg To: Luke Howard , Andrew Lunn Cc: Cedric Jehasse , Jiri Pirko , Ivan Vecera , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Ido Schimmel , Andrew Lunn , David Ahern , Shuah Khan , Vladimir Oltean , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bridge@lists.linux.dev, linux-kselftest@vger.kernel.org, Max Hunter , Kieran Tyrrell References: <20260602-mv88e6xxx-8021qat-mqprio-v2-0-72be14522e7c@padl.com> <20260602-mv88e6xxx-8021qat-mqprio-v2-3-72be14522e7c@padl.com> <537410c3-ff4e-43fd-834e-775cd1bbe89e@blackwall.org> From: Nikolay Aleksandrov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 06/06/2026 11:02, Luke Howard wrote: > >> So it sounds like you first need to work on the software >> implementation and expand the simplified version with the features you >> need. You can then add support to accelerate this by offloading it to >> the hardware. > > Agreed. > > The definition of Dynamic Reservation Entries in 802.1Q (clause 8.8.7) might support the addition of a new MDB (or even FDB) entry state to the kernel: > > - add MDB_DYNAMIC_RESERVATION (a state, not a flag); > - the software bridge only _classifies_ packets against MDB_DYNAMIC_RESERVATION entries, and only when MDB is authoritative. Classification sets dynamic_reservation_hit on tc_skb_ext; > - dynamic_reservation_hit is visible to the flow dissector so can be used for policy enforcement. > See, saying the bridge has to classify doesn't sound right. Why not do the classification where such operations are usually done, e.g. tc? You have to manually designate these entries anyway. > Advantages: > > - the new MDB state maps well to 802.1Q; > - minimal changes to bridge; > - actual policy (reclassify, drop, etc) is left to the user; > - doesn’t require a new tc-flower entry for each stream DA; > - entry state maps 1:1 to mv88e6xxx AVB_NRL ATU EntryState. > > Disadvantages: > > - no unicast support, although potentially can be extended (there are some subtleties); > - mv88e6xxx support would either require rich enough tc-flower support in TCAM, intercepting TCA_FLOWER_DYNAMIC_RESERVATION_HIT and mapping to native AVB admission control, or a per-port devlink parameter (not so nice). > > This is implemented and working with the software bridge, I still haven’t quite figured out the right mapping for mv88e6xxx. > > Luke > > PS. I previously incorrectly asserted that 802.1Q required dropping frames with AVB/SRP PCPs but without valid dynamic reservation entries. 802.1Q discussions priority mapping in clause 6.9.4 for traffic from SRP boundary ports (those not participating in SRP). In practice I think this should all be policy, e.g. you might want to reprioritise valid DSCP traffic from within a SRP domain, or drop instead of reprioritise, etc.