mptcp: introduce mptcp-level backlog

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We are soon using it for incoming data processing.
MPTCP can't leverage the sk_backlog, as the latter is processed
before the release callback, and such callback for MPTCP releases
and re-acquire the socket spinlock, breaking the sk_backlog processing
assumption.

Add a skb backlog list inside the mptcp sock struct, and implement
basic helper to transfer packet to and purge such list.

Packets in the backlog are memory accounted and still use the incoming
subflow receive memory, to allow back-pressure. The backlog size is
implicitly bounded to the sum of subflows rcvbuf.

When a subflow is closed, references from the backlog to such sock
are removed.

No packet is currently added to the backlog, so no functional changes
intended here.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251121-net-next-mptcp-memcg-backlog-imp-v1-13-1f34b6c1e0b1@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Paolo Abeni 2025-11-21 18:02:12 +01:00 • committed by Jakub Kicinski

parent 9db5b3cec4

commit ee458a3f31

3 changed files with 97 additions and 9 deletions

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3

net/mptcp/mptcp_diag.c

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78

net/mptcp/protocol.c

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25

net/mptcp/protocol.h

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