From: Paolo Abeni pabeni@redhat.com
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: f3589be0c420 ("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 --- net/mptcp/options.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/mptcp/options.c b/net/mptcp/options.c index c254accb14de..cd15ec73073e 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -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; }