nbd: Fix nbd_receive_options()

The client flags are sent exactly once overall, not once per option.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <1424887718-10800-19-git-send-email-mreitz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

nbd.c

@@ -350,30 +350,39 @@ static int nbd_handle_export_name(NBDClient *client, uint32_t length)
 
 static int nbd_receive_options(NBDClient *client)
 {
+    int csock = client->sock;
+    uint32_t flags;
+
+    /* Client sends:
+        [ 0 ..   3]   client flags
+
+        [ 0 ..   7]   NBD_OPTS_MAGIC
+        [ 8 ..  11]   NBD option
+        [12 ..  15]   Data length
+        ...           Rest of request
+
+        [ 0 ..   7]   NBD_OPTS_MAGIC
+        [ 8 ..  11]   Second NBD option
+        [12 ..  15]   Data length
+        ...           Rest of request
+    */
+
+    if (read_sync(csock, &flags, sizeof(flags)) != sizeof(flags)) {
+        LOG("read failed");
+        return -EIO;
+    }
+    TRACE("Checking client flags");
+    be32_to_cpus(&flags);
+    if (flags != 0 && flags != NBD_FLAG_C_FIXED_NEWSTYLE) {
+        LOG("Bad client flags received");
+        return -EIO;
+    }
+
     while (1) {
-        int csock = client->sock, ret;
+        int ret;
         uint32_t tmp, length;
         uint64_t magic;
 
-        /* Client sends:
-            [ 0 ..   3]   client flags
-            [ 4 ..  11]   NBD_OPTS_MAGIC
-            [12 ..  15]   NBD option
-            [16 ..  19]   length
-            ...           Rest of request
-        */
-
-        if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
-            LOG("read failed");
-            return -EINVAL;
-        }
-        TRACE("Checking client flags");
-        tmp = be32_to_cpu(tmp);
-        if (tmp != 0 && tmp != NBD_FLAG_C_FIXED_NEWSTYLE) {
-            LOG("Bad client flags received");
-            return -EINVAL;
-        }
-
         if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
             LOG("read failed");
             return -EINVAL;