linux.git/net/Kconfig, branch v6.5

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

bpf, kconfig: Add consolidated menu entry for bpf with core options

2021-05-11T20:56:16+00:00

Right now, all core BPF related options are scattered in different Kconfig
locations mainly due to historic reasons. Moving forward, lets add a proper
subsystem entry under ...

  General setup  --->
    BPF subsystem  --->

... in order to have all knobs in a single location and thus ease BPF related
configuration. Networking related bits such as sockmap are out of scope for
the general setup and therefore better suited to remain in net/Kconfig.

Signed-off-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/f23f58765a4d59244ebd8037da7b6a6b2fb58446.1620765074.git.daniel@iogearbox.net