kernel/linux.git/net/Kconfig, branch v6.6.132

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/core: Enable socket busy polling on -RT

2023-05-26T07:51:26+00:00

Busy polling is currently not allowed on PREEMPT_RT, because it disables preemption while invoking the NAPI callback. It is not possible to acquire sleeping locks with disabled preemption. For details see commit 20ab39d13e2e ("net/core: disable NET_RX_BUSY_POLL on PREEMPT_RT"). However, strict cyclic and/or low latency network applications may prefer busy polling e.g., using AF_XDP instead of interrupt driven communication. The preempt_disable() is used in order to prevent the poll_owner and NAPI owner to be preempted while owning the resource to ensure progress. Netpoll performs busy polling in order to acquire the lock. NAPI is locked by setting the NAPIF_STATE_SCHED flag. There is no busy polling if the flag is set and the "owner" is preempted. Worst case is that the task owning NAPI gets preempted and NAPI processing stalls. This is can be prevented by properly prioritising the tasks within the system. Allow RX_BUSY_POLL on PREEMPT_RT if NETPOLL is disabled. Don't disable preemption on PREEMPT_RT within the busy poll loop. Tested on x86 hardware with v6.1-RT and v6.3-RT on Intel i225 (igc) with AF_XDP/ZC sockets configured to run in busy polling mode. Suggested-by: Sebastian Andrzej Siewior Signed-off-by: Kurt Kanzenbach Signed-off-by: David S. Miller

net/handshake: Add Kunit tests for the handshake consumer API

2023-04-20T01:48:48+00:00

These verify the API contracts and help exercise lifetime rules for consumer sockets and handshake_req structures. One way to run these tests: ./tools/testing/kunit/kunit.py run --kunitconfig ./net/handshake/.kunitconfig Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski

net/handshake: Create a NETLINK service for handling handshake requests

2023-04-20T01:48:48+00:00

When a kernel consumer needs a transport layer security session, it first needs a handshake to negotiate and establish a session. This negotiation can be done in user space via one of the several existing library implementations, or it can be done in the kernel. No in-kernel handshake implementations yet exist. In their absence, we add a netlink service that can: a. Notify a user space daemon that a handshake is needed. b. Once notified, the daemon calls the kernel back via this netlink service to get the handshake parameters, including an open socket on which to establish the session. c. Once the handshake is complete, the daemon reports the session status and other information via a second netlink operation. This operation marks that it is safe for the kernel to use the open socket and the security session established there. The notification service uses a multicast group. Each handshake mechanism (eg, tlshd) adopts its own group number so that the handshake services are completely independent of one another. The kernel can then tell via netlink_has_listeners() whether a handshake service is active and prepared to handle a handshake request. A new netlink operation, ACCEPT, acts like accept(2) in that it instantiates a file descriptor in the user space daemon's fd table. If this operation is successful, the reply carries the fd number, which can be treated as an open and ready file descriptor. While user space is performing the handshake, the kernel keeps its muddy paws off the open socket. A second new netlink operation, DONE, indicates that the user space daemon is finished with the socket and it is safe for the kernel to use again. The operation also indicates whether a session was established successfully. Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski

net: introduce a config option to tweak MAX_SKB_FRAGS

2023-03-28T02:29:22+00:00

Currently, MAX_SKB_FRAGS value is 17. For standard tcp sendmsg() traffic, no big deal because tcp_sendmsg() attempts order-3 allocations, stuffing 32768 bytes per frag. But with zero copy, we use order-0 pages. For BIG TCP to show its full potential, we add a config option to be able to fit up to 45 segments per skb. This is also needed for BIG TCP rx zerocopy, as zerocopy currently does not support skbs with frag list. We have used MAX_SKB_FRAGS=45 value for years at Google before we deployed 4K MTU, with no adverse effect, other than a recent issue in mlx4, fixed in commit 26782aad00cc ("net/mlx4: MLX4_TX_BOUNCE_BUFFER_SIZE depends on MAX_SKB_FRAGS") Back then, goal was to be able to receive full size (64KB) GRO packets without the frag_list overhead. Note that /proc/sys/net/core/max_skb_frags can also be used to limit the number of fragments TCP can use in tx packets. By default we keep the old/legacy value of 17 until we get more coverage for the updated values. Sizes of struct skb_shared_info on 64bit arches MAX_SKB_FRAGS | sizeof(struct skb_shared_info): ============================================== 17 320 21 320+64 = 384 25 320+128 = 448 29 320+192 = 512 33 320+256 = 576 37 320+320 = 640 41 320+384 = 704 45 320+448 = 768 This inflation might cause problems for drivers assuming they could pack both the incoming packet (for MTU=1500) and skb_shared_info in half a page, using build_skb(). v3: fix build error when CONFIG_NET=n v2: fix two build errors assuming MAX_SKB_FRAGS was "unsigned long" Signed-off-by: Eric Dumazet Reviewed-by: Nikolay Aleksandrov Reviewed-by: Jason Xing Link: https://lore.kernel.org/r/20230323162842.1935061-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski

Remove DECnet support from kernel

2022-08-22T13:26:30+00:00

DECnet is an obsolete network protocol that receives more attention from kernel janitors than users. It belongs in computer protocol history museum not in Linux kernel. It has been "Orphaned" in kernel since 2010. The iproute2 support for DECnet was dropped in 5.0 release. The documentation link on Sourceforge says it is abandoned there as well. Leave the UAPI alone to keep userspace programs compiling. This means that there is still an empty neighbour table for AF_DECNET. The table of /proc/sys/net entries was updated to match current directories and reformatted to be alphabetical. Signed-off-by: Stephen Hemminger Acked-by: David Ahern Acked-by: Nikolay Aleksandrov Signed-off-by: David S. Miller

page_pool: Add allocation stats

2022-03-03T09:55:28+00:00

Add per-pool statistics counters for the allocation path of a page pool. These stats are incremented in softirq context, so no locking or per-cpu variables are needed. This code is disabled by default and a kernel config option is provided for users who wish to enable them. The statistics added are: - fast: successful fast path allocations - slow: slow path order-0 allocations - slow_high_order: slow path high order allocations - empty: ptr ring is empty, so a slow path allocation was forced. - refill: an allocation which triggered a refill of the cache - waive: pages obtained from the ptr ring that cannot be added to the cache due to a NUMA mismatch. Signed-off-by: Joe Damato Acked-by: Jesper Dangaard Brouer Reviewed-by: Ilias Apalodimas Signed-off-by: David S. Miller

net: kunit: add a test for dev_addr_lists

2021-11-20T12:25:57+00:00

Add a KUnit test for the dev_addr API. Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller

net/core: disable NET_RX_BUSY_POLL on PREEMPT_RT

2021-10-01T22:45:10+00:00

napi_busy_loop() disables preemption and performs a NAPI poll. We can't acquire sleeping locks with disabled preemption which would be required while __napi_poll() invokes the callback of the driver. A threaded interrupt performing the NAPI-poll can be preempted on PREEMPT_RT. A RT thread on another CPU may observe NAPIF_STATE_SCHED bit set and busy-spin until it is cleared or its spin time runs out. Given it is the task with the highest priority it will never observe the NEED_RESCHED bit set. In this case the time is better spent by simply sleeping. The NET_RX_BUSY_POLL is disabled by default (the system wide sysctls for poll/read are set to zero). Disabling NET_RX_BUSY_POLL on PREEMPT_RT to avoid wrong locking context in case it is used. Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20211001145841.2308454-1-bigeasy@linutronix.de Signed-off-by: Jakub Kicinski

mctp: Add MCTP base

2021-07-29T14:06:49+00:00

Add basic Kconfig, an initial (empty) af_mctp source object, and {AF,PF}_MCTP definitions, and the required definitions for a new protocol type. Signed-off-by: Jeremy Kerr Signed-off-by: David S. Miller