kernel/linux.git/net/mptcp/pm.c, branch linux-7.1.y

mptcp: add-addr: always drop other suboptions

2026-06-04T02:04:27+00:00

When an ADD_ADDR needs to be sent, it could be prepared if there is enough remaining space and even if the packet is not a pure ACK. But it would be dropped soon after. Indeed, in mptcp_pm_add_addr_signal(), there is enough space to fit a DSS of 20 octets and an ADD_ADDR echo containing an IPv4 address on 8 octets for example. In this case, the packet would be prepared, the MPTCP_ADD_ADDR_ECHO bit would be removed from pm->addr_signal, but the option would be silently dropped in mptcp_established_options_add_addr() not to override DSS info in the union from 'struct mptcp_out_options', and also because mptcp_write_options() will enforce mutually exclusion with DSS. Instead, don't even try to send an ADD_ADDR if it is not a pure ACK. Retry for each new packet until a pure-ACK is emitted. That's fine to do that, because each time an ADD_ADDR (echo) is scheduled, a pure ACK is queued. This also simplifies the code, and the skb checks can be done earlier, before the lock. Note: also, since commit 6d0060f600ad ("mptcp: Write MPTCP DSS headers to outgoing data packets"), opts->ahmac would not have been set to 0 when other suboptions were not dropped, and when sending an ADD_ADDR echo. That would have resulted in sending an ADD_ADDR using garbage info, where there was not enough space, instead of an echo one without the ADD_ADDR HMAC. Fixes: 1bff1e43a30e ("mptcp: optimize out option generation") Cc: stable@vger.kernel.org Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-11-856831229976@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: fix ADD_ADDR timer infinite retry on option space insufficient

2026-05-19T13:36:35+00:00

When TCP option space is insufficient (e.g., when sending ADD_ADDR with an IPv6 address and port while tcp_timestamps is enabled), the original code jumped to out_unlock without clearing the addr_signal flag. This caused mptcp_pm_add_timer to keep rescheduling indefinitely, not sending ADD_ADDR, preventing subsequent addresses in the endpoint list from being announced. Handle this case by clearing the ADD_ADDR signal and skipping the matching ADD_ADDR retransmission entry. The skip path cancels the matching timer (with id check) and advances PM state progression, preserving forward progress to subsequent PM work. This cancellation is inherently best-effort. A concurrent add_timer callback may already be running and may acquire pm.lock before the cancel path updates entry state. In that case, one final ADD_ADDR transmit attempt can still be executed. Once the cancel path sets entry->retrans_times to ADD_ADDR_RETRANS_MAX, the callback-side retrans_times check suppresses further ADD_ADDR retransmissions. Note that when an ADD_ADDR is being prepared, a pure-ACK is queued. On the output side, it means that it is fine to skip non-pure-ACK packets, when drop_other_suboptions is set: a pure-ACK will be processed soon after. Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Signed-off-by: Li Xiasong Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260515-net-mptcp-misc-fixes-7-1-rc4-v2-2-701e96419f2f@kernel.org Signed-off-by: Paolo Abeni

mptcp: pm: prio: skip closed subflows

2026-05-07T01:16:45+00:00

When sending an MP_PRIO, closed subflows need to be skipped. This fixes the case where the initial subflow got closed, re-opened later, then an MP_PRIO is needed for the same local address. Note that explicit MP_PRIO cannot be sent during the 3WHS, so it is fine to use __mptcp_subflow_active(). Fixes: 067065422fcd ("mptcp: add the outgoing MP_PRIO support") Cc: stable@vger.kernel.org Fixes: b29fcfb54cd7 ("mptcp: full disconnect implementation") Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-9-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: return early if no retrans

2026-05-07T01:16:45+00:00

No need to iterate over all subflows if there is no retransmission needed. Exit early in this case then. Fixes: 30549eebc4d8 ("mptcp: make ADD_ADDR retransmission timeout adaptive") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-8-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: skip inactive subflows

2026-05-07T01:16:45+00:00

When looking at the maximum RTO amongst the subflows, inactive subflows were taken into account: that includes stale ones, and the initial one if it has been already been closed. Unusable subflows are now simply skipped. Stale ones are used as an alternative: if there are only stale ones, to take their maximum RTO and avoid to eventually fallback to net.mptcp.add_addr_timeout, which is set to 2 minutes by default. Fixes: 30549eebc4d8 ("mptcp: make ADD_ADDR retransmission timeout adaptive") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-7-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: resched blocked ADD_ADDR quicker

2026-05-07T01:16:45+00:00

When an ADD_ADDR needs to be retransmitted and another one has already been prepared -- e.g. multiple ADD_ADDRs have been sent in a row and need to be retransmitted later -- this additional retransmission will need to wait. In this case, the timer was reset to TCP_RTO_MAX / 8, which is ~15 seconds. This delay is unnecessary long: it should just be rescheduled at the next opportunity, e.g. after the retransmission timeout. Without this modification, some issues can be seen from time to time in the selftests when multiple ADD_ADDRs are sent, and the host takes time to process them, e.g. the "signal addresses, ADD_ADDR timeout" MPTCP Join selftest, especially with a debug kernel config. Note that on older kernels, 'timeout' is not available. It should be enough to replace it by one second (HZ). Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-6-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: free sk if last

2026-05-07T01:16:44+00:00

When an ADD_ADDR is retransmitted, the sk is held in sk_reset_timer(), and released at the end. If at that moment, it was the last reference being held, the sk would not be freed. sock_put() should then be called instead of __sock_put(). But that's not enough: if it is the last reference, sock_put() will call sk_free(), which will end up calling sk_stop_timer_sync() on the same timer, and waiting indefinitely to finish. So it is needed to mark that the timer is done at the end of the timer handler when it has not been rescheduled, not to call sk_stop_timer_sync() on "itself". Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-5-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: always decrease sk refcount

2026-05-07T01:16:44+00:00

When an ADD_ADDR is retransmitted, the sk is held in sk_reset_timer(). It should then be released in all cases at the end. Some (unlikely) checks were returning directly instead of calling sock_put() to decrease the refcount. Jump to a new 'exit' label to call __sock_put() (which will become sock_put() in the next commit) to fix this potential leak. While at it, drop the '!msk' check which cannot happen because it is never reset, and explicitly mark the remaining one as "unlikely". Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-4-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: fix potential data-race

2026-05-07T01:16:44+00:00

This mptcp_pm_add_timer() helper is executed as a timer callback in softirq context. To avoid any data races, the socket lock needs to be held with bh_lock_sock(). If the socket is in use, retry again soon after, similar to what is done with the keepalive timer. Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-3-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: ADD_ADDR rtx: allow ID 0

2026-05-07T01:16:44+00:00

ADD_ADDR can be sent for the ID 0, which corresponds to the local address and port linked to the initial subflow. Indeed, this address could be removed, and re-added later on, e.g. what is done in the "delete re-add signal" MPTCP Join selftests. So no reason to ignore it. Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-2-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski