cifs: add ability to send an echo request

Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 3652cc60314c..54b9f5d8d1db 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -706,6 +706,53 @@ CIFSSMBTDis(const int xid, struct cifsTconInfo *tcon)
         return rc;
 }
 
+/*
+ * This is a no-op for now. We're not really interested in the reply, but
+ * rather in the fact that the server sent one and that server->lstrp
+ * gets updated.
+ *
+ * FIXME: maybe we should consider checking that the reply matches request?
+ */
+static void
+cifs_echo_callback(struct mid_q_entry *mid)
+{
+        struct TCP_Server_Info *server = mid->callback_data;
+
+        DeleteMidQEntry(mid);
+        atomic_dec(&server->inFlight);
+        wake_up(&server->request_q);
+}
+
+int
+CIFSSMBEcho(struct TCP_Server_Info *server)
+{
+        ECHO_REQ *smb;
+        int rc = 0;
+
+        cFYI(1, "In echo request");
+
+        rc = small_smb_init(SMB_COM_ECHO, 0, NULL, (void **)&smb);
+        if (rc)
+                return rc;
+
+        /* set up echo request */
+        smb->hdr.Tid = cpu_to_le16(0xffff);
+        smb->hdr.WordCount = cpu_to_le16(1);
+        smb->EchoCount = cpu_to_le16(1);
+        smb->ByteCount = cpu_to_le16(1);
+        smb->Data[0] = 'a';
+        smb->hdr.smb_buf_length += 3;
+
+        rc = cifs_call_async(server, (struct smb_hdr *)smb,
+                                cifs_echo_callback, server);
+        if (rc)
+                cFYI(1, "Echo request failed: %d", rc);
+
+        cifs_small_buf_release(smb);
+
+        return rc;
+}
+
 int
 CIFSSMBLogoff(const int xid, struct cifsSesInfo *ses)
 {