Fix system property race at supplicant stop

We stop supplicant by sending a "terminate" control command. init then
updates the system property init.svc.wpa_supplicant when the supplicant has stopped. The
framework gets notified of a successful supplicant stop through a supplicant event.

It can happen that the framework has been notified of a supplicant stop, but the init
process has not set the system property and thus when the framework tries to connect
to the supplicant again, it can immediately return saying the supplicant is already running.

Avoid this race, by ensuring the call from framework to close supplicant connection polls
for the update by init process that the system property indicates supplicant has stopped.

Bug: 5166494
Change-Id: Ie74a8cf39fa56ae557ea6bbbcba7865301620c42

1 files changed, 11 insertions, 0 deletions

diff --git a/wifi/wifi.c b/wifi/wifi.c
index be0aaeb..d455a0b 100644
--- a/wifi/wifi.c
+++ b/wifi/wifi.c
@@ -659,6 +659,9 @@ int wifi_wait_for_event(char *buf, size_t buflen)
 
 void wifi_close_supplicant_connection()
 {
+    char supp_status[PROPERTY_VALUE_MAX] = {'\0'};
+    int count = 50; /* wait at most 5 seconds to ensure init has stopped stupplicant */
+
     if (ctrl_conn != NULL) {
         wpa_ctrl_close(ctrl_conn);
         ctrl_conn = NULL;
@@ -667,6 +670,14 @@ void wifi_close_supplicant_connection()
         wpa_ctrl_close(monitor_conn);
         monitor_conn = NULL;
     }
+
+    while (count-- > 0) {
+        if (property_get(SUPP_PROP_NAME, supp_status, NULL)) {
+            if (strcmp(supp_status, "stopped") == 0)
+                return;
+        }
+        usleep(100000);
+    }
 }
 
 int wifi_command(const char *command, char *reply, size_t *reply_len)