bt/bt_bluez: Implement retry if rfcomm sockets are busy

There are cases where the connect() call returns EBUSY when trying to
connect to a device. This has been observed when sampling an RDTech
UM24C. In this case, scanning the device works fine. However, when
sampling the device, Sigrok first scans the device, then closes the
connection and re-opens it to sample the device. If the close/open
calls happen in close successions, the Bluetooth stack sometimes
returns EBUSY.

Work around this issue by retrying if the connect() returns EBUSY.

Signed-off-by: Andreas Sandberg <redacted>

diff --git a/src/bt/bt_bluez.c b/src/bt/bt_bluez.c
index f64ba59db9f32a6bffc2dfa78475693eb764ff3f..52567f9e8b7a04d4cd1d3ca68c55960ed4b8684c 100644 (file)
--- a/src/bt/bt_bluez.c
+++ b/src/bt/bt_bluez.c
@@ -93,6 +93,9 @@
 #define STORE_MAC_REVERSE      1
 #define ACCEPT_NONSEP_MAC      1
 
+#define CONNECT_RFCOMM_TRIES   3
+#define CONNECT_RFCOMM_RETRY_MS        100
+
 /* Silence warning about (currently) unused routine. */
 #define WITH_WRITE_TYPE_HANDLE 0
 
@@ -795,7 +798,7 @@ SR_PRIV int sr_bt_connect_ble(struct sr_bt_desc *desc)
 SR_PRIV int sr_bt_connect_rfcomm(struct sr_bt_desc *desc)
 {
        struct sockaddr_rc addr;
-       int fd, rc;
+       int i, fd, rc;
 
        if (!desc)
                return -1;
@@ -807,25 +810,40 @@ SR_PRIV int sr_bt_connect_rfcomm(struct sr_bt_desc *desc)
        if (!desc->rfcomm_channel)
                desc->rfcomm_channel = 1;
 
-       fd = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
-       if (fd < 0) {
-               perror("socket");
-               return -1;
-       }
-       desc->fd = fd;
-
        memset(&addr, 0, sizeof(addr));
        addr.rc_family = AF_BLUETOOTH;
        str2ba(desc->remote_addr, &addr.rc_bdaddr);
        addr.rc_channel = desc->rfcomm_channel;
-       rc = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
-       if (rc < 0) {
-               perror("connect");
-               return -2;
+
+       /*
+        * There are cases where connect returns EBUSY if we are re-connecting
+        * to a device. Try multiple times to work around this issue.
+        */
+       for (i = 0; i < CONNECT_RFCOMM_TRIES; i++) {
+               fd = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
+               if (fd < 0) {
+                       perror("socket");
+                       return -1;
+               }
+
+               rc = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
+               if (rc >= 0) {
+                       sr_spew("connected");
+                       desc->fd = fd;
+                       return 0;
+               } else if (rc < 0 && errno == EBUSY) {
+                       close(fd);
+                       g_usleep(CONNECT_RFCOMM_RETRY_MS * 1000);
+               } else {
+                       close(fd);
+                       perror("connect");
+                       return -2;
+               }
        }
-       sr_spew("connected");
 
-       return 0;
+       sr_err("Connect failed, device busy.");
+
+       return -2;
 }
 
 SR_PRIV void sr_bt_disconnect(struct sr_bt_desc *desc)