mptcp: fix bogus receive window shrinkage with multiple subflows
commit 6bec041147a2a64a490d1f813e8a004443061b38 upstream.
In case multiple subflows race to update the mptcp-level receive
window, the subflow losing the race should use the window value
provided by the "winning" subflow to update it's own tcp-level
rcv_wnd.
To such goal, the current code bogusly uses the mptcp-level rcv_wnd
value as observed before the update attempt. On unlucky circumstances
that may lead to TCP-level window shrinkage, and stall the other end.
Address the issue feeding to the rcv wnd update the correct value.
Fixes: f3589be0c4
("mptcp: never shrink offered window")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/427
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1248,12 +1248,13 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
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if (rcv_wnd == rcv_wnd_old)
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break;
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if (before64(rcv_wnd_new, rcv_wnd)) {
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rcv_wnd_old = rcv_wnd;
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if (before64(rcv_wnd_new, rcv_wnd_old)) {
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MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
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goto raise_win;
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}
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MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
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rcv_wnd_old = rcv_wnd;
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}
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return;
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}
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