SO_KEEPALIVE support has to be set on each subflow: on each TCP socket,
where sk_prot->keepalive is defined. Technically, nothing has to be done
on the MPTCP socket. That's why mptcp_sol_socket_sync_intval() was
called instead of mptcp_sol_socket_intval().

Except that when nothing is done on the MPTCP socket, the
getsockopt(SO_KEEPALIVE), handled in net/core/sock.c:sk_getsockopt(),
will not know if SO_KEEPALIVE has been set on the different subflows or
not.

The fix is simple: simply call mptcp_sol_socket_intval() which will end
up calling net/core/sock.c:sk_setsockopt() where the SOCK_KEEPOPEN flag
will be set, the one used in sk_getsockopt().

So now, getsockopt(SO_KEEPALIVE) on an MPTCP socket will return the same
value as the one previously set with setsockopt(SO_KEEPALIVE).

Fixes: 1b3e7ede1365 ("mptcp: setsockopt: handle SO_KEEPALIVE and SO_PRIORITY")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/sockopt.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 1fea43f5b6f3..69fc584fc57e 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -181,8 +181,6 @@ static int mptcp_setsockopt_sol_socket_int(struct mptcp_sock *msk, int optname,
 
 	switch (optname) {
 	case SO_KEEPALIVE:
-		mptcp_sol_socket_sync_intval(msk, optname, val);
-		return 0;
 	case SO_DEBUG:
 	case SO_MARK:
 	case SO_PRIORITY:

-- 
2.43.0