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mptcp: do not account for OoO in mptcp_rcvbuf_grow()

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MPTCP-level OoOs are physiological when multiple subflows are active
concurrently and will not cause retransmissions nor are caused by
drops.

Accounting for them in mptcp_rcvbuf_grow() causes the rcvbuf slowly
drifting towards tcp_rmem[2].

Remove such accounting. Note that subflows will still account for TCP-level
OoO when the MPTCP-level rcvbuf is propagated.

This also closes a subtle and very unlikely race condition with rcvspace
init; active sockets with user-space holding the msk-level socket lock,
could complete such initialization in the receive callback, after that the
first OoO data reaches the rcvbuf and potentially triggering a divide by
zero Oops.

Fixes: e118cdc34d ("mptcp: rcvbuf auto-tuning improvement")
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/20260203-net-next-mptcp-misc-feat-6-20-v1-1-31ec8bfc56d1@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni 2026-02-03 19:41:17 +01:00 committed by Jakub Kicinski
parent e25dbf561e
commit 6b32939350
1 changed files with 0 additions and 6 deletions
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6
net/mptcp/protocol.c
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@ -224,9 +224,6 @@ static bool mptcp_rcvbuf_grow(struct sock *sk, u32 newval)
do_div(grow, oldval);
rcvwin += grow << 1;
if (!RB_EMPTY_ROOT(&msk->out_of_order_queue))
rcvwin += MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq - msk->ack_seq;
cap = READ_ONCE(net->ipv4.sysctl_tcp_rmem[2]);
rcvbuf = min_t(u32, mptcp_space_from_win(sk, rcvwin), cap);
@ -350,9 +347,6 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
end:
skb_condense(skb);
skb_set_owner_r(skb, sk);
/* do not grow rcvbuf for not-yet-accepted or orphaned sockets. */
if (sk->sk_socket)
mptcp_rcvbuf_grow(sk, msk->rcvq_space.space);
}
static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset,