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2025-10-19mptcp: pm: in-kernel: usable client side with C-flagMatthieu Baerts (NGI0)1-1/+49
commit 4b1ff850e0c1aacc23e923ed22989b827b9808f9 upstream. When servers set the C-flag in their MP_CAPABLE to tell clients not to create subflows to the initial address and port, clients will likely not use their other endpoints. That's because the in-kernel path-manager uses the 'subflow' endpoints to create subflows only to the initial address and port. If the limits have not been modified to accept ADD_ADDR, the client doesn't try to establish new subflows. If the limits accept ADD_ADDR, the routing routes will be used to select the source IP. The C-flag is typically set when the server is operating behind a legacy Layer 4 load balancer, or using anycast IP address. Clients having their different 'subflow' endpoints setup, don't end up creating multiple subflows as expected, and causing some deployment issues. A special case is then added here: when servers set the C-flag in the MPC and directly sends an ADD_ADDR, this single ADD_ADDR is accepted. The 'subflows' endpoints will then be used with this new remote IP and port. This exception is only allowed when the ADD_ADDR is sent immediately after the 3WHS, and makes the client switching to the 'fully established' mode. After that, 'select_local_address()' will not be able to find any subflows, because 'id_avail_bitmap' will be filled in mptcp_pm_create_subflow_or_signal_addr(), when switching to 'fully established' mode. Fixes: df377be38725 ("mptcp: add deny_join_id0 in mptcp_options_received") Cc: stable@vger.kernel.org Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/536 Reviewed-by: Geliang Tang <geliang@kernel.org> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Link: https://patch.msgid.link/20250925-net-next-mptcp-c-flag-laminar-v1-1-ad126cc47c6b@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-08-18mptcp: pm: kernel: flush: do not reset ADD_ADDR limitMatthieu Baerts (NGI0)1-1/+0
A flush of the MPTCP endpoints should not affect the MPTCP limits. In other words, 'ip mptcp endpoint flush' should not change 'ip mptcp limits'. But it was the case: the MPTCP_PM_ATTR_RCV_ADD_ADDRS (add_addr_accepted) limit was reset by accident. Removing the reset of this counter during a flush fixes this issue. Fixes: 01cacb00b35c ("mptcp: add netlink-based PM") Cc: stable@vger.kernel.org Reported-by: Thomas Dreibholz <dreibh@simula.no> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/579 Reviewed-by: Mat Martineau <martineau@kernel.org> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Link: https://patch.msgid.link/20250815-net-mptcp-misc-fixes-6-17-rc2-v1-2-521fe9957892@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-03-20mptcp: pm: register in-kernel and userspace PMGeliang Tang1-0/+7
This patch defines the original in-kernel netlink path manager as a new struct mptcp_pm_ops named "mptcp_pm_kernel", and register it in mptcp_pm_kernel_register(). And define the userspace path manager as a new struct mptcp_pm_ops named "mptcp_pm_userspace", and register it in mptcp_pm_init(). To ensure that there's always a valid path manager available, the default path manager "mptcp_pm_kernel" will be skipped in mptcp_pm_unregister(). Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20250313-net-next-mptcp-pm-ops-intro-v1-7-f4e4a88efc50@kernel.org Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-03-20mptcp: pm: in-kernel: use kmemdup helperGeliang Tang1-4/+2
Instead of using kmalloc() or kzalloc() to allocate an entry and then immediately duplicate another entry to the newly allocated one, kmemdup() helper can be used to simplify the code. Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20250313-net-next-mptcp-pm-ops-intro-v1-2-f4e4a88efc50@kernel.org Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-03-20mptcp: pm: split netlink and in-kernel initMatthieu Baerts (NGI0)1-4/+1
The registration of mptcp_genl_family is useful for both the in-kernel and the userspace PM. It should then be done in pm_netlink.c. On the other hand, the registration of the in-kernel pernet subsystem is specific to the in-kernel PM, and should stay there in pm_kernel.c. Reviewed-by: Mat Martineau <martineau@kernel.org> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20250313-net-next-mptcp-pm-ops-intro-v1-1-f4e4a88efc50@kernel.org Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-03-10mptcp: pm: split in-kernel PM specific codeMatthieu Baerts (NGI0)1-0/+1410
Before this patch, the PM code was dispersed in different places: - pm.c had common code for all PMs - pm_netlink.c was supposed to be about the in-kernel PM, but also had exported common Netlink helpers, NL events for PM userspace daemons, etc. quite confusing. To clarify the code, a reorganisation is suggested here, only by moving code around to avoid confusions: - pm_netlink.c now only contains common PM Netlink code: - PM events: this code was already there - shared helpers around Netlink code that were already there as well - more shared Netlink commands code from pm.c will come after - pm_kernel.c now contains only code that is specific to the in-kernel PM. Now all functions are either called from: - pm.c: events coming from the core, when this PM is being used - pm_netlink.c: for shared Netlink commands - mptcp_pm_gen.c: for Netlink commands specific to the in-kernel PM - sockopt.c: for the exported counters per netns - (while at it, a useless 'return;' spot by checkpatch at the end of mptcp_pm_nl_set_flags_all, has been removed) The code around the PM is now less confusing, which should help for the maintenance in the long term. This will certainly impact future backports, but because other cleanups have already done recently, and more are coming to ease the addition of a new path-manager controlled with BPF (struct_ops), doing that now seems to be a good time. Also, many issues around the PM have been fixed a few months ago while increasing the code coverage in the selftests, so such big reorganisation can be done with more confidence now. No behavioural changes intended. Reviewed-by: Geliang Tang <geliang@kernel.org> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> Link: https://patch.msgid.link/20250307-net-next-mptcp-pm-reorg-v1-14-abef20ada03b@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>