kernel/linux.git/include/uapi/linux/pkt_sched.h, branch v6.6.131

netem: add prng attribute to netem_sched_data

2023-08-18T02:15:05+00:00

Add prng attribute to struct netem_sched_data and allows setting the seed of the PRNG through netlink using the new TCA_NETEM_PRNG_SEED attribute. The PRNG attribute is not actually used yet. Signed-off-by: François Michel Reviewed-by: Simon Horman Acked-by: Stephen Hemminger Link: https://lore.kernel.org/r/20230815092348.1449179-2-francois.michel@uclouvain.be Signed-off-by: Jakub Kicinski

net/sched: taprio: add netlink reporting for offload statistics counters

2023-05-31T09:00:30+00:00

Offloading drivers may report some additional statistics counters, some of them even suggested by 802.1Q, like TransmissionOverrun. In my opinion we don't have to limit ourselves to reporting counters only globally to the Qdisc/interface, especially if the device has more detailed reporting (per traffic class), since the more detailed info is valuable for debugging and can help identifying who is exceeding its time slot. But on the other hand, some devices may not be able to report both per TC and global stats. So we end up reporting both ways, and use the good old ethtool_put_stat() strategy to determine which statistics are supported by this NIC. Statistics which aren't set are simply not reported to netlink. For this reason, we need something dynamic (a nlattr nest) to be reported through TCA_STATS_APP, and not something daft like the fixed-size and inextensible struct tc_codel_xstats. A good model for xstats which are a nlattr nest rather than a fixed struct seems to be cake. # Global stats $ tc -s qdisc show dev eth0 root # Per-tc stats $ tc -s class show dev eth0 Signed-off-by: Vladimir Oltean Acked-by: Vinicius Costa Gomes Signed-off-by: David S. Miller

net/sched: taprio: allow per-TC user input of FP adminStatus

2023-04-14T05:22:10+00:00

This is a duplication of the FP adminStatus logic introduced for tc-mqprio. Offloading is done through the tc_mqprio_qopt_offload structure embedded within tc_taprio_qopt_offload. So practically, if a device driver is written to treat the mqprio portion of taprio just like standalone mqprio, it gets unified handling of frame preemption. I would have reused more code with taprio, but this is mostly netlink attribute parsing, which is hard to transform into generic code without having something that stinks as a result. We have the same variables with the same semantics, just different nlattr type values (TCA_MQPRIO_TC_ENTRY=5 vs TCA_TAPRIO_ATTR_TC_ENTRY=12; TCA_MQPRIO_TC_ENTRY_FP=2 vs TCA_TAPRIO_TC_ENTRY_FP=3, etc) and consequently, different policies for the nest. Every time nla_parse_nested() is called, an on-stack table "tb" of nlattr pointers is allocated statically, up to the maximum understood nlattr type. That array size is hardcoded as a constant, but when transforming this into a common parsing function, it would become either a VLA (which the Linux kernel rightfully doesn't like) or a call to the allocator. Having FP adminStatus in tc-taprio can be seen as addressing the 802.1Q Annex S.3 "Scheduling and preemption used in combination, no HOLD/RELEASE" and S.4 "Scheduling and preemption used in combination with HOLD/RELEASE" use cases. HOLD and RELEASE events are emitted towards the underlying MAC Merge layer when the schedule hits a Set-And-Hold-MAC or a Set-And-Release-MAC gate operation. So within the tc-taprio UAPI space, one can distinguish between the 2 use cases by choosing whether to use the TC_TAPRIO_CMD_SET_AND_HOLD and TC_TAPRIO_CMD_SET_AND_RELEASE gate operations within the schedule, or just TC_TAPRIO_CMD_SET_GATES. A small part of the change is dedicated to refactoring the max_sdu nlattr parsing to put all logic under the "if" that tests for presence of that nlattr. Signed-off-by: Vladimir Oltean Reviewed-by: Ferenc Fejes Reviewed-by: Simon Horman Signed-off-by: Jakub Kicinski

net/sched: mqprio: allow per-TC user input of FP adminStatus

2023-04-14T05:22:10+00:00

IEEE 802.1Q-2018 clause 6.7.2 Frame preemption specifies that each packet priority can be assigned to a "frame preemption status" value of either "express" or "preemptible". Express priorities are transmitted by the local device through the eMAC, and preemptible priorities through the pMAC (the concepts of eMAC and pMAC come from the 802.3 MAC Merge layer). The FP adminStatus is defined per packet priority, but 802.1Q clause 12.30.1.1.1 framePreemptionAdminStatus also says that: | Priorities that all map to the same traffic class should be | constrained to use the same value of preemption status. It is impossible to ignore the cognitive dissonance in the standard here, because it practically means that the FP adminStatus only takes distinct values per traffic class, even though it is defined per priority. I can see no valid use case which is prevented by having the kernel take the FP adminStatus as input per traffic class (what we do here). In addition, this also enforces the above constraint by construction. User space network managers which wish to expose FP adminStatus per priority are free to do so; they must only observe the prio_tc_map of the netdev (which presumably is also under their control, when constructing the mqprio netlink attributes). The reason for configuring frame preemption as a property of the Qdisc layer is that the information about "preemptible TCs" is closest to the place which handles the num_tc and prio_tc_map of the netdev. If the UAPI would have been any other layer, it would be unclear what to do with the FP information when num_tc collapses to 0. A key assumption is that only mqprio/taprio change the num_tc and prio_tc_map of the netdev. Not sure if that's a great assumption to make. Having FP in tc-mqprio can be seen as an implementation of the use case defined in 802.1Q Annex S.2 "Preemption used in isolation". There will be a separate implementation of FP in tc-taprio, for the other use cases. Signed-off-by: Vladimir Oltean Reviewed-by: Ferenc Fejes Reviewed-by: Simon Horman Signed-off-by: Jakub Kicinski

net/sched: taprio: allow user input of per-tc max SDU

2022-09-30T01:52:05+00:00

IEEE 802.1Q clause 12.29.1.1 "The queueMaxSDUTable structure and data types" and 8.6.8.4 "Enhancements for scheduled traffic" talk about the existence of a per traffic class limitation of maximum frame sizes, with a fallback on the port-based MTU. As far as I am able to understand, the 802.1Q Service Data Unit (SDU) represents the MAC Service Data Unit (MSDU, i.e. L2 payload), excluding any number of prepended VLAN headers which may be otherwise present in the MSDU. Therefore, the queueMaxSDU is directly comparable to the device MTU (1500 means L2 payload sizes are accepted, or frame sizes of 1518 octets, or 1522 plus one VLAN header). Drivers which offload this are directly responsible of translating into other units of measurement. To keep the fast path checks optimized, we keep 2 arrays in the qdisc, one for max_sdu translated into frame length (so that it's comparable to skb->len), and another for offloading and for dumping back to the user. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

fq_codel: generalise ce_threshold marking for subset of traffic

2021-10-20T22:24:36+00:00

Commit e72aeb9ee0e3 ("fq_codel: implement L4S style ce_threshold_ect1 marking") expanded the ce_threshold feature of FQ-CoDel so it can be applied to a subset of the traffic, using the ECT(1) bit of the ECN field as the classifier. However, hard-coding ECT(1) as the only classifier for this feature seems limiting, so let's expand it to be more general. To this end, change the parameter from a ce_threshold_ect1 boolean, to a one-byte selector/mask pair (ce_threshold_{selector,mask}) which is applied to the whole diffserv/ECN field in the IP header. This makes it possible to classify packets by any value in either the ECN field or the diffserv field. In particular, setting a selector of INET_ECN_ECT_1 and a mask of INET_ECN_MASK corresponds to the functionality before this patch, and a mask of ~INET_ECN_MASK allows using the selector as a straight-forward match against a diffserv code point: # apply ce_threshold to ECT(1) traffic tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x1/0x3 # apply ce_threshold to ECN-capable traffic marked as diffserv AF22 tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x50/0xfc Regardless of the selector chosen, the normal rules for ECN-marking of packets still apply, i.e., the flow must still declare itself ECN-capable by setting one of the bits in the ECN field to get marked at all. v2: - Add tc usage examples to patch description Signed-off-by: Toke Høiland-Jørgensen Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/20211019174709.69081-1-toke@redhat.com Signed-off-by: Jakub Kicinski

fq_codel: implement L4S style ce_threshold_ect1 marking

2021-10-15T10:33:08+00:00

Add TCA_FQ_CODEL_CE_THRESHOLD_ECT1 boolean option to select Low Latency, Low Loss, Scalable Throughput (L4S) style marking, along with ce_threshold. If enabled, only packets with ECT(1) can be transformed to CE if their sojourn time is above the ce_threshold. Note that this new option does not change rules for codel law. In particular, if TCA_FQ_CODEL_ECN is left enabled (this is the default when fq_codel qdisc is created), ECT(0) packets can still get CE if codel law (as governed by limit/target) decides so. Section 4.3.b of current draft [1] states: b. A scheduler with per-flow queues such as FQ-CoDel or FQ-PIE can be used for L4S. For instance within each queue of an FQ-CoDel system, as well as a CoDel AQM, there is typically also ECN marking at an immediate (unsmoothed) shallow threshold to support use in data centres (see Sec.5.2.7 of [RFC8290]). This can be modified so that the shallow threshold is solely applied to ECT(1) packets. Then if there is a flow of non-ECN or ECT(0) packets in the per-flow-queue, the Classic AQM (e.g. CoDel) is applied; while if there is a flow of ECT(1) packets in the queue, the shallower (typically sub-millisecond) threshold is applied. Tested: tc qd replace dev eth1 root fq_codel ce_threshold_ect1 50usec netperf ... -t TCP_STREAM -- K dctcp tc -s -d qd sh dev eth1 qdisc fq_codel 8022: root refcnt 32 limit 10240p flows 1024 quantum 9212 target 5ms ce_threshold_ect1 49us interval 100ms memory_limit 32Mb ecn drop_batch 64 Sent 14388596616 bytes 9543449 pkt (dropped 0, overlimits 0 requeues 152013) backlog 0b 0p requeues 152013 maxpacket 68130 drop_overlimit 0 new_flow_count 95678 ecn_mark 0 ce_mark 7639 new_flows_len 0 old_flows_len 0 [1] L4S current draft: https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-l4s-arch Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Ingemar Johansson S Cc: Tom Henderson Cc: Bob Briscoe Signed-off-by: David S. Miller

fq_codel: reject silly quantum parameters

2021-09-04T09:49:46+00:00

syzbot found that forcing a big quantum attribute would crash hosts fast, essentially using this: tc qd replace dev eth0 root fq_codel quantum 4294967295 This is because fq_codel_dequeue() would have to loop ~2^31 times in : if (flow->deficit <= 0) { flow->deficit += q->quantum; list_move_tail(&flow->flowchain, &q->old_flows); goto begin; } SFQ max quantum is 2^19 (half a megabyte) Lets adopt a max quantum of one megabyte for FQ_CODEL. Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller

sch_htb: Hierarchical QoS hardware offload

2021-01-23T04:41:29+00:00

HTB doesn't scale well because of contention on a single lock, and it also consumes CPU. This patch adds support for offloading HTB to hardware that supports hierarchical rate limiting. In the offload mode, HTB passes control commands to the driver using ndo_setup_tc. The driver has to replicate the whole hierarchy of classes and their settings (rate, ceil) in the NIC. Every modification of the HTB tree caused by the admin results in ndo_setup_tc being called. After this setup, the HTB algorithm is done completely in the NIC. An SQ (send queue) is created for every leaf class and attached to the hierarchy, so that the NIC can calculate and obey aggregated rate limits, too. In the future, it can be changed, so that multiple SQs will back a single leaf class. ndo_select_queue is responsible for selecting the right queue that serves the traffic class of each packet. The data path works as follows: a packet is classified by clsact, the driver selects a hardware queue according to its class, and the packet is enqueued into this queue's qdisc. This solution addresses two main problems of scaling HTB: 1. Contention by flow classification. Currently the filters are attached to the HTB instance as follows: # tc filter add dev eth0 parent 1:0 protocol ip flower dst_port 80 classid 1:10 It's possible to move classification to clsact egress hook, which is thread-safe and lock-free: # tc filter add dev eth0 egress protocol ip flower dst_port 80 action skbedit priority 1:10 This way classification still happens in software, but the lock contention is eliminated, and it happens before selecting the TX queue, allowing the driver to translate the class to the corresponding hardware queue in ndo_select_queue. Note that this is already compatible with non-offloaded HTB and doesn't require changes to the kernel nor iproute2. 2. Contention by handling packets. HTB is not multi-queue, it attaches to a whole net device, and handling of all packets takes the same lock. When HTB is offloaded, it registers itself as a multi-queue qdisc, similarly to mq: HTB is attached to the netdev, and each queue has its own qdisc. Some features of HTB may be not supported by some particular hardware, for example, the maximum number of classes may be limited, the granularity of rate and ceil parameters may be different, etc. - so, the offload is not enabled by default, a new parameter is used to enable it: # tc qdisc replace dev eth0 root handle 1: htb offload Signed-off-by: Maxim Mikityanskiy Reviewed-by: Tariq Toukan Signed-off-by: Jakub Kicinski

net: sched: sch_red: Add qevents "early_drop" and "mark"

2020-06-30T00:08:28+00:00

In order to allow acting on dropped and/or ECN-marked packets, add two new qevents to the RED qdisc: "early_drop" and "mark". Filters attached at "early_drop" block are executed as packets are early-dropped, those attached at the "mark" block are executed as packets are ECN-marked. Two new attributes are introduced: TCA_RED_EARLY_DROP_BLOCK with the block index for the "early_drop" qevent, and TCA_RED_MARK_BLOCK for the "mark" qevent. Absence of these attributes signifies "don't care": no block is allocated in that case, or the existing blocks are left intact in case of the change callback. For purposes of offloading, blocks attached to these qevents appear with newly-introduced binder types, FLOW_BLOCK_BINDER_TYPE_RED_EARLY_DROP and FLOW_BLOCK_BINDER_TYPE_RED_MARK. Signed-off-by: Petr Machata Signed-off-by: David S. Miller