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Kuniyuki Iwashima 8741792d82 soreuseport: Fix socket selection for SO_INCOMING_CPU. 
[ Upstream commit b261eda84e ]

Kazuho Oku reported that setsockopt(SO_INCOMING_CPU) does not work
with setsockopt(SO_REUSEPORT) since v4.6.

With the combination of SO_REUSEPORT and SO_INCOMING_CPU, we could
build a highly efficient server application.

setsockopt(SO_INCOMING_CPU) associates a CPU with a TCP listener
or UDP socket, and then incoming packets processed on the CPU will
likely be distributed to the socket.  Technically, a socket could
even receive packets handled on another CPU if no sockets in the
reuseport group have the same CPU receiving the flow.

The logic exists in compute_score() so that a socket will get a higher
score if it has the same CPU with the flow.  However, the score gets
ignored after the blamed two commits, which introduced a faster socket
selection algorithm for SO_REUSEPORT.

This patch introduces a counter of sockets with SO_INCOMING_CPU in
a reuseport group to check if we should iterate all sockets to find
a proper one.  We increment the counter when

  * calling listen() if the socket has SO_INCOMING_CPU and SO_REUSEPORT

  * enabling SO_INCOMING_CPU if the socket is in a reuseport group

Also, we decrement it when

  * detaching a socket out of the group to apply SO_INCOMING_CPU to
    migrated TCP requests

  * disabling SO_INCOMING_CPU if the socket is in a reuseport group

When the counter reaches 0, we can get back to the O(1) selection
algorithm.

The overall changes are negligible for the non-SO_INCOMING_CPU case,
and the only notable thing is that we have to update sk_incomnig_cpu
under reuseport_lock.  Otherwise, the race prevents transitioning to
the O(n) algorithm and results in the wrong socket selection.

 cpu1 (setsockopt)               cpu2 (listen)
+-----------------+             +-------------+

lock_sock(sk1)                  lock_sock(sk2)

reuseport_update_incoming_cpu(sk1, val)
.
|  /* set CPU as 0 */
|- WRITE_ONCE(sk1->incoming_cpu, val)
|
|                               spin_lock_bh(&reuseport_lock)
|                               reuseport_grow(sk2, reuse)
|                               .
|                               |- more_socks_size = reuse->max_socks * 2U;
|                               |- if (more_socks_size > U16_MAX &&
|                               |       reuse->num_closed_socks)
|                               |  .
|                               |  |- RCU_INIT_POINTER(sk1->sk_reuseport_cb, NULL);
|                               |  `- __reuseport_detach_closed_sock(sk1, reuse)
|                               |     .
|                               |     `- reuseport_put_incoming_cpu(sk1, reuse)
|                               |        .
|                               |        |  /* Read shutdown()ed sk1's sk_incoming_cpu
|                               |        |   * without lock_sock().
|                               |        |   */
|                               |        `- if (sk1->sk_incoming_cpu >= 0)
|                               |           .
|                               |           |  /* decrement not-yet-incremented
|                               |           |   * count, which is never incremented.
|                               |           |   */
|                               |           `- __reuseport_put_incoming_cpu(reuse);
|                               |
|                               `- spin_lock_bh(&reuseport_lock)
|
|- spin_lock_bh(&reuseport_lock)
|
|- reuse = rcu_dereference_protected(sk1->sk_reuseport_cb, ...)
|- if (!reuse)
|  .
|  |  /* Cannot increment reuse->incoming_cpu. */
|  `- goto out;
|
`- spin_unlock_bh(&reuseport_lock)

Fixes: e32ea7e747 ("soreuseport: fast reuseport UDP socket selection")
Fixes: c125e80b88 ("soreuseport: fast reuseport TCP socket selection")
Reported-by: Kazuho Oku <kazuhooku@gmail.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-12-31 13:14:07 +01:00
arch MIPS: OCTEON: warn only once if deprecated link status is being used 2022-12-31 13:14:05 +01:00
block block: move CONFIG_BLOCK guard to top Makefile 2022-12-14 11:37:30 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: akcipher - default implementation for setting a private key 2022-10-26 12:35:25 +02:00
Documentation debugfs: fix error when writing negative value to atomic_t debugfs file 2022-12-31 13:14:03 +01:00
drivers venus: pm_helpers: Fix error check in vcodec_domains_get() 2022-12-31 13:14:07 +01:00
fs hfs: Fix OOB Write in hfs_asc2mac 2022-12-31 13:14:05 +01:00
include soreuseport: Fix socket selection for SO_INCOMING_CPU. 2022-12-31 13:14:07 +01:00
init init/Kconfig: fix CC_HAS_ASM_GOTO_TIED_OUTPUT test with dash 2022-12-02 17:41:08 +01:00
io_uring io_uring: Fix a null-ptr-deref in io_tctx_exit_cb() 2022-12-14 11:37:31 +01:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel relay: fix type mismatch when allocating memory in relay_create_buf() 2022-12-31 13:14:05 +01:00
lib lib/notifier-error-inject: fix error when writing -errno to debugfs file 2022-12-31 13:14:03 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/gup: fix gup_pud_range() for dax 2022-12-14 11:37:20 +01:00
net soreuseport: Fix socket selection for SO_INCOMING_CPU. 2022-12-31 13:14:07 +01:00
samples samples/landlock: Format with clang-format 2022-06-09 10:23:23 +02:00
scripts scripts/faddr2line: Fix regression in name resolution on ppc64le 2022-12-08 11:28:38 +01:00
security capabilities: fix potential memleak on error path from vfs_getxattr_alloc() 2022-11-10 18:15:39 +01:00
sound ASoC: ops: Correct bounds check for second channel on SX controls 2022-12-19 12:36:44 +01:00
tools libbpf: Fix null-pointer dereference in find_prog_by_sec_insn() 2022-12-31 13:14:06 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt kvm: Add support for arch compat vm ioctls 2022-10-29 10:12:54 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS futex: Move to kernel/futex/ 2022-12-31 13:14:04 +01:00
Makefile Linux 5.15.85 2022-12-21 17:36:38 +01:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.