Commit 6bec0411 authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

mptcp: fix bogus receive window shrinkage with multiple subflows 

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: f3589be0 ("mptcp: never shrink offered window")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/427


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarMat Martineau <martineau@kernel.org>
Signed-off-by: default avatarMatthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8a47558a

net/mptcp/options.c

+3 −2
Original line number Diff line number Diff line
@@ -1269,12 +1269,13 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th) 


			if (rcv_wnd == rcv_wnd_old)

				break;

			if (before64(rcv_wnd_new, rcv_wnd)) {



			rcv_wnd_old = rcv_wnd;

			if (before64(rcv_wnd_new, rcv_wnd_old)) {

				MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);

				goto raise_win;

			}

			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);

			rcv_wnd_old = rcv_wnd;

		}

		return;

	}