mptcp: update MIB_RMSUBFLOW in cmd_sf_destroy

This patch increases MPTCP_MIB_RMSUBFLOW mib counter in userspace pm
destroy subflow function mptcp_nl_cmd_sf_destroy() when removing subflow.

Fixes: 702c2f64 ("mptcp: netlink: allow userspace-driven subflow establishment")
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/pm_userspace.c

@@ -5,6 +5,7 @@
  */
 
 #include "protocol.h"
+#include "mib.h"
 
 void mptcp_free_local_addr_list(struct mptcp_sock *msk)
 {
@@ -410,6 +411,7 @@ int mptcp_nl_cmd_sf_destroy(struct sk_buff *skb, struct genl_info *info)
 
 		mptcp_subflow_shutdown(sk, ssk, RCV_SHUTDOWN | SEND_SHUTDOWN);
 		mptcp_close_ssk(sk, ssk, subflow);
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RMSUBFLOW);
 		err = 0;
 	} else {
 		err = -ESRCH;