kernel/linux.git/net/sched/Kconfig, branch linux-7.1.y

sched: Add enqueue/dequeue of dualpi2 qdisc

2025-07-24T00:52:07+00:00

DualPI2 provides L4S-type low latency & loss to traffic that uses a scalable congestion controller (e.g. TCP-Prague, DCTCP) without degrading the performance of 'classic' traffic (e.g. Reno, Cubic etc.). It is to be the reference implementation of IETF RFC9332 DualQ Coupled AQM (https://datatracker.ietf.org/doc/html/rfc9332). Note that creating two independent queues cannot meet the goal of DualPI2 mentioned in RFC9332: "...to preserve fairness between ECN-capable and non-ECN-capable traffic." Further, it could even lead to starvation of Classic traffic, which is also inconsistent with the requirements in RFC9332: "...although priority MUST be bounded in order not to starve Classic traffic." DualPI2 is designed to maintain approximate per-flow fairness on L-queue and C-queue by forming a single qdisc using the coupling factor and scheduler between two queues. The qdisc provides two queues called low latency and classic. It classifies packets based on the ECN field in the IP headers. By default it directs non-ECN and ECT(0) into the classic queue and ECT(1) and CE into the low latency queue, as per the IETF spec. Each queue runs its own AQM: * The classic AQM is called PI2, which is similar to the PIE AQM but more responsive and simpler. Classic traffic requires a decent target queue (default 15ms for Internet deployment) to fully utilize the link and to avoid high drop rates. * The low latency AQM is, by default, a very shallow ECN marking threshold (1ms) similar to that used for DCTCP. The DualQ isolates the low queuing delay of the Low Latency queue from the larger delay of the 'Classic' queue. However, from a bandwidth perspective, flows in either queue will share out the link capacity as if there was just a single queue. This bandwidth pooling effect is achieved by coupling together the drop and ECN-marking probabilities of the two AQMs. The PI2 AQM has two main parameters in addition to its target delay. The integral gain factor alpha is used to slowly correct any persistent standing queue error from the target delay, while the proportional gain factor beta is used to quickly compensate for queue changes (growth or shrinkage). Either alpha and beta are given as a parameter, or they can be calculated by tc from alternative typical and maximum RTT parameters. Internally, the output of a linear Proportional Integral (PI) controller is used for both queues. This output is squared to calculate the drop or ECN-marking probability of the classic queue. This counterbalances the square-root rate equation of Reno/Cubic, which is the trick that balances flow rates across the queues. For the ECN-marking probability of the low latency queue, the output of the base AQM is multiplied by a coupling factor. This determines the balance between the flow rates in each queue. The default setting makes the flow rates roughly equal, which should be generally applicable. If DUALPI2 AQM has detected overload (due to excessive non-responsive traffic in either queue), it will switch to signaling congestion solely using drop, irrespective of the ECN field. Alternatively, it can be configured to limit the drop probability and let the queue grow and eventually overflow (like tail-drop). GSO splitting in DUALPI2 is configurable from userspace while the default behavior is to split gso. When running DUALPI2 at unshaped 10gigE with 4 download streams test, splitting gso apart results in halving the latency with no loss in throughput: Summary of tcp_4down run 'no_split_gso': avg median # data pts Ping (ms) ICMP : 0.53 0.30 ms 350 TCP download avg : 2326.86 N/A Mbits/s 350 TCP download sum : 9307.42 N/A Mbits/s 350 TCP download::1 : 2672.99 2568.73 Mbits/s 350 TCP download::2 : 2586.96 2570.51 Mbits/s 350 TCP download::3 : 1786.26 1798.82 Mbits/s 350 TCP download::4 : 2261.21 2309.49 Mbits/s 350 Summart of tcp_4down run 'split_gso': avg median # data pts Ping (ms) ICMP : 0.22 0.23 ms 350 TCP download avg : 2335.02 N/A Mbits/s 350 TCP download sum : 9340.09 N/A Mbits/s 350 TCP download::1 : 2335.30 2334.22 Mbits/s 350 TCP download::2 : 2334.72 2334.20 Mbits/s 350 TCP download::3 : 2335.28 2334.58 Mbits/s 350 TCP download::4 : 2334.79 2334.39 Mbits/s 350 A similar result is observed when running DUALPI2 at unshaped 1gigE with 1 download stream test: Summary of tcp_1down run 'no_split_gso': avg median # data pts Ping (ms) ICMP : 1.13 1.25 ms 350 TCP download : 941.41 941.46 Mbits/s 350 Summart of tcp_1down run 'split_gso': avg median # data pts Ping (ms) ICMP : 0.51 0.55 ms 350 TCP download : 941.41 941.45 Mbits/s 350 Additional details can be found in the draft: https://datatracker.ietf.org/doc/html/rfc9332 Signed-off-by: Koen De Schepper Co-developed-by: Olga Albisser Signed-off-by: Olga Albisser Co-developed-by: Olivier Tilmans Signed-off-by: Olivier Tilmans Co-developed-by: Henrik Steen Signed-off-by: Henrik Steen Co-developed-by: Chia-Yu Chang Signed-off-by: Chia-Yu Chang Signed-off-by: Bob Briscoe Signed-off-by: Ilpo Järvinen Acked-by: Dave Taht Link: https://patch.msgid.link/20250722095915.24485-4-chia-yu.chang@nokia-bell-labs.com Signed-off-by: Jakub Kicinski

sctp: use skb_crc32c() instead of __skb_checksum()

2025-05-21T22:40:16+00:00

Make sctp_compute_cksum() just use the new function skb_crc32c(), instead of calling __skb_checksum() with a skb_checksum_ops struct that does CRC32C. This is faster and simpler. Signed-off-by: Eric Biggers Reviewed-by: Hannes Reinecke Link: https://patch.msgid.link/20250519175012.36581-6-ebiggers@kernel.org Signed-off-by: Jakub Kicinski

Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2025-04-22T01:51:08+00:00

Martin KaFai Lau says: ==================== pull-request: bpf-next 2025-04-17 We've added 12 non-merge commits during the last 9 day(s) which contain a total of 18 files changed, 1748 insertions(+), 19 deletions(-). The main changes are: 1) bpf qdisc support, from Amery Hung. A qdisc can be implemented in bpf struct_ops programs and can be used the same as other existing qdiscs in the "tc qdisc" command. 2) Add xsk tail adjustment tests, from Tushar Vyavahare. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: selftests/bpf: Test attaching bpf qdisc to mq and non root selftests/bpf: Add a bpf fq qdisc to selftest selftests/bpf: Add a basic fifo qdisc test libbpf: Support creating and destroying qdisc bpf: net_sched: Disable attaching bpf qdisc to non root bpf: net_sched: Support updating bstats bpf: net_sched: Add a qdisc watchdog timer bpf: net_sched: Add basic bpf qdisc kfuncs bpf: net_sched: Support implementation of Qdisc_ops in bpf bpf: Prepare to reuse get_ctx_arg_idx selftests/xsk: Add tail adjustment tests and support check selftests/xsk: Add packet stream replacement function ==================== Link: https://patch.msgid.link/20250417184338.3152168-1-martin.lau@linux.dev Signed-off-by: Jakub Kicinski

bpf: net_sched: Support implementation of Qdisc_ops in bpf

2025-04-17T17:54:33+00:00

The recent advancement in bpf such as allocated objects, bpf list and bpf rbtree has provided powerful and flexible building blocks to realize sophisticated packet scheduling algorithms. As struct_ops now supports core operators in Qdisc_ops, start allowing qdisc to be implemented using bpf struct_ops with this patch. Users can implement Qdisc_ops.{enqueue, dequeue, init, reset, destroy} in bpf and register the qdisc dynamically into the kernel. Co-developed-by: Cong Wang Signed-off-by: Cong Wang Signed-off-by: Amery Hung Signed-off-by: Martin KaFai Lau Acked-by: Cong Wang Acked-by: Toke Høiland-Jørgensen Link: https://patch.msgid.link/20250409214606.2000194-3-ameryhung@gmail.com

lib/crc: remove CONFIG_LIBCRC32C

2025-04-04T18:31:42+00:00

Now that LIBCRC32C does nothing besides select CRC32, make every option that selects LIBCRC32C instead select CRC32 directly. Then remove LIBCRC32C. Reviewed-by: Christoph Hellwig Reviewed-by: "Martin K. Petersen" Acked-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20250401221600.24878-8-ebiggers@kernel.org Signed-off-by: Eric Biggers

net: sched: Remove NET_ACT_IPT from Kconfig

2024-02-13T10:24:35+00:00

After this commit ba24ea129126 ("net/sched: Retire ipt action") NET_ACT_IPT is not needed anymore as the action is retired and the code is removed. Clean the Kconfig part as well. Signed-off-by: Harshit Mogalapalli Acked-by: Jamal Hadi Salim Link: https://lore.kernel.org/r/20240209180656.867546-1-harshit.m.mogalapalli@oracle.com Signed-off-by: Paolo Abeni

bpf: Add fd-based tcx multi-prog infra with link support

2023-07-19T17:07:27+00:00

This work refactors and adds a lightweight extension ("tcx") to the tc BPF ingress and egress data path side for allowing BPF program management based on fds via bpf() syscall through the newly added generic multi-prog API. The main goal behind this work which we also presented at LPC [0] last year and a recent update at LSF/MM/BPF this year [3] is to support long-awaited BPF link functionality for tc BPF programs, which allows for a model of safe ownership and program detachment. Given the rise in tc BPF users in cloud native environments, this becomes necessary to avoid hard to debug incidents either through stale leftover programs or 3rd party applications accidentally stepping on each others toes. As a recap, a BPF link represents the attachment of a BPF program to a BPF hook point. The BPF link holds a single reference to keep BPF program alive. Moreover, hook points do not reference a BPF link, only the application's fd or pinning does. A BPF link holds meta-data specific to attachment and implements operations for link creation, (atomic) BPF program update, detachment and introspection. The motivation for BPF links for tc BPF programs is multi-fold, for example: - From Meta: "It's especially important for applications that are deployed fleet-wide and that don't "control" hosts they are deployed to. If such application crashes and no one notices and does anything about that, BPF program will keep running draining resources or even just, say, dropping packets. We at FB had outages due to such permanent BPF attachment semantics. With fd-based BPF link we are getting a framework, which allows safe, auto-detachable behavior by default, unless application explicitly opts in by pinning the BPF link." [1] - From Cilium-side the tc BPF programs we attach to host-facing veth devices and phys devices build the core datapath for Kubernetes Pods, and they implement forwarding, load-balancing, policy, EDT-management, etc, within BPF. Currently there is no concept of 'safe' ownership, e.g. we've recently experienced hard-to-debug issues in a user's staging environment where another Kubernetes application using tc BPF attached to the same prio/handle of cls_bpf, accidentally wiping all Cilium-based BPF programs from underneath it. The goal is to establish a clear/safe ownership model via links which cannot accidentally be overridden. [0,2] BPF links for tc can co-exist with non-link attachments, and the semantics are in line also with XDP links: BPF links cannot replace other BPF links, BPF links cannot replace non-BPF links, non-BPF links cannot replace BPF links and lastly only non-BPF links can replace non-BPF links. In case of Cilium, this would solve mentioned issue of safe ownership model as 3rd party applications would not be able to accidentally wipe Cilium programs, even if they are not BPF link aware. Earlier attempts [4] have tried to integrate BPF links into core tc machinery to solve cls_bpf, which has been intrusive to the generic tc kernel API with extensions only specific to cls_bpf and suboptimal/complex since cls_bpf could be wiped from the qdisc also. Locking a tc BPF program in place this way, is getting into layering hacks given the two object models are vastly different. We instead implemented the tcx (tc 'express') layer which is an fd-based tc BPF attach API, so that the BPF link implementation blends in naturally similar to other link types which are fd-based and without the need for changing core tc internal APIs. BPF programs for tc can then be successively migrated from classic cls_bpf to the new tc BPF link without needing to change the program's source code, just the BPF loader mechanics for attaching is sufficient. For the current tc framework, there is no change in behavior with this change and neither does this change touch on tc core kernel APIs. The gist of this patch is that the ingress and egress hook have a lightweight, qdisc-less extension for BPF to attach its tc BPF programs, in other words, a minimal entry point for tc BPF. The name tcx has been suggested from discussion of earlier revisions of this work as a good fit, and to more easily differ between the classic cls_bpf attachment and the fd-based one. For the ingress and egress tcx points, the device holds a cache-friendly array with program pointers which is separated from control plane (slow-path) data. Earlier versions of this work used priority to determine ordering and expression of dependencies similar as with classic tc, but it was challenged that for something more future-proof a better user experience is required. Hence this resulted in the design and development of the generic attach/detach/query API for multi-progs. See prior patch with its discussion on the API design. tcx is the first user and later we plan to integrate also others, for example, one candidate is multi-prog support for XDP which would benefit and have the same 'look and feel' from API perspective. The goal with tcx is to have maximum compatibility to existing tc BPF programs, so they don't need to be rewritten specifically. Compatibility to call into classic tcf_classify() is also provided in order to allow successive migration or both to cleanly co-exist where needed given its all one logical tc layer and the tcx plus classic tc cls/act build one logical overall processing pipeline. tcx supports the simplified return codes TCX_NEXT which is non-terminating (go to next program) and terminating ones with TCX_PASS, TCX_DROP, TCX_REDIRECT. The fd-based API is behind a static key, so that when unused the code is also not entered. The struct tcx_entry's program array is currently static, but could be made dynamic if necessary at a point in future. The a/b pair swap design has been chosen so that for detachment there are no allocations which otherwise could fail. The work has been tested with tc-testing selftest suite which all passes, as well as the tc BPF tests from the BPF CI, and also with Cilium's L4LB. Thanks also to Nikolay Aleksandrov and Martin Lau for in-depth early reviews of this work. [0] https://lpc.events/event/16/contributions/1353/ [1] https://lore.kernel.org/bpf/CAEf4BzbokCJN33Nw_kg82sO=xppXnKWEncGTWCTB9vGCmLB6pw@mail.gmail.com [2] https://colocatedeventseu2023.sched.com/event/1Jo6O/tales-from-an-ebpf-programs-murder-mystery-hemanth-malla-guillaume-fournier-datadog [3] http://vger.kernel.org/bpfconf2023_material/tcx_meta_netdev_borkmann.pdf [4] https://lore.kernel.org/bpf/20210604063116.234316-1-memxor@gmail.com Signed-off-by: Daniel Borkmann Acked-by: Jakub Kicinski Link: https://lore.kernel.org/r/20230719140858.13224-3-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov

net/sched: Retire rsvp classifier

2023-02-16T08:27:07+00:00

The rsvp classifier has served us well for about a quarter of a century but has has not been getting much maintenance attention due to lack of known users. Signed-off-by: Jamal Hadi Salim Acked-by: Jiri Pirko Signed-off-by: Paolo Abeni

net/sched: Retire tcindex classifier

2023-02-16T08:27:07+00:00

The tcindex classifier has served us well for about a quarter of a century but has not been getting much TLC due to lack of known users. Most recently it has become easy prey to syzkaller. For this reason, we are retiring it. Signed-off-by: Jamal Hadi Salim Acked-by: Jiri Pirko Signed-off-by: Paolo Abeni

net/sched: Retire dsmark qdisc

2023-02-16T08:27:06+00:00

The dsmark qdisc has served us well over the years for diffserv but has not been getting much attention due to other more popular approaches to do diffserv services. Most recently it has become a shooting target for syzkaller. For this reason, we are retiring it. Signed-off-by: Jamal Hadi Salim Acked-by: Jiri Pirko Signed-off-by: Paolo Abeni