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Matthieu Baerts (NGI0) fb0b1ef705 mptcp: pm: nl: announce deny-join-id0 flag
commit 2293c57484ae64c9a3c847c8807db8c26a3a4d41 upstream.

During the connection establishment, a peer can tell the other one that
it cannot establish new subflows to the initial IP address and port by
setting the 'C' flag [1]. Doing so makes sense when the sender is behind
a strict NAT, operating behind a legacy Layer 4 load balancer, or using
anycast IP address for example.

When this 'C' flag is set, the path-managers must then not try to
establish new subflows to the other peer's initial IP address and port.
The in-kernel PM has access to this info, but the userspace PM didn't.

The RFC8684 [1] is strict about that:

  (...) therefore the receiver MUST NOT try to open any additional
  subflows toward this address and port.

So it is important to tell the userspace about that as it is responsible
for the respect of this flag.

When a new connection is created and established, the Netlink events
now contain the existing but not currently used 'flags' attribute. When
MPTCP_PM_EV_FLAG_DENY_JOIN_ID0 is set, it means no other subflows
to the initial IP address and port -- info that are also part of the
event -- can be established.

Link: https://datatracker.ietf.org/doc/html/rfc8684#section-3.1-20.6 [1]
Fixes: 702c2f646d ("mptcp: netlink: allow userspace-driven subflow establishment")
Reported-by: Marek Majkowski <marek@cloudflare.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/532
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250912-net-mptcp-pm-uspace-deny_join_id0-v1-2-40171884ade8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in mptcp_pm.yaml, because the indentation has been modified
  in commit ec362192aa ("netlink: specs: fix up indentation errors"),
  which is not in this version. Applying the same modifications, but at
  a different level. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-09-25 11:16:53 +02:00
arch KVM: SVM: Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active 2025-09-25 11:16:49 +02:00
block block: don't silently ignore metadata for sync read/write 2025-09-19 16:37:26 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: af_alg - Set merge to zero early in af_alg_sendmsg 2025-09-25 11:16:53 +02:00
Documentation mptcp: pm: nl: announce deny-join-id0 flag 2025-09-25 11:16:53 +02:00
drivers platform/x86: asus-wmi: Re-add extra keys to ignore_key_wlan quirk 2025-09-25 11:16:53 +02:00
fs smb: client: fix smbdirect_recv_io leak in smbd_negotiate() error path 2025-09-25 11:16:53 +02:00
include mptcp: pm: nl: announce deny-join-id0 flag 2025-09-25 11:16:53 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 16:38:23 +02:00
io_uring io_uring: fix incorrect io_kiocb reference in io_link_skb 2025-09-25 11:16:53 +02:00
ipc - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
kernel Revert "sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()" 2025-09-25 11:16:46 +02:00
lib lib/sbitmap: convert shallow_depth from one word to the whole sbitmap 2025-08-20 18:41:31 +02:00
LICENSES LICENSES: add CC0-1.0 license text 2025-05-21 14:54:17 +02:00
mm mm: folio_may_be_lru_cached() unless folio_test_large() 2025-09-25 11:16:46 +02:00
net mptcp: pm: nl: announce deny-join-id0 flag 2025-09-25 11:16:53 +02:00
rust rust: mm: mark VmaNew as transparent 2025-09-09 19:02:29 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:37:28 +02:00
scripts rust: support Rust >= 1.91.0 target spec 2025-09-09 19:02:35 +02:00
security apparmor: Fix 8-byte alignment for initial dfa blob streams 2025-08-28 16:34:16 +02:00
sound ALSA: usb: qcom: Fix false-positive address space check 2025-09-25 11:16:52 +02:00
tools selftests: mptcp: avoid spurious errors on TCP disconnect 2025-09-25 11:16:50 +02:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-06-24 12:20:17 -07:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes
.gitignore gitignore: allow .pylintrc to be tracked 2025-08-15 16:39:03 +02:00
.mailmap 11 hotfixes. 9 are cc:stable and the remainder address post-6.15 issues 2025-07-24 19:13:30 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml
COPYING
CREDITS mm: update MAINTAINERS entry for HMM 2025-07-19 19:26:16 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS 11 hotfixes. 9 are cc:stable and the remainder address post-6.15 issues 2025-07-24 19:13:30 -07:00
Makefile Linux 6.16.8 2025-09-19 16:37:39 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.