[PATCH 6/6] libxl: vncviewer: make autopass work properly

[Ian Jackson <ian.jackson@eu.citrix.com>]

The file we write the vnc password to must be rewound back to the
beginning, or the vnc viewer will simply get EOF.

When the syscalls for communicating the password to the vnc client
fail, bomb out with an error messsage rather than blundering on (and
probably producing a spurious password prompt).

Following this patch, xl vncviewer --autopass works, provided the qemu
patch for writing the password to xenstore has also been applied.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 tools/libxl/libxl.c |   25 +++++++++++++++++--------
 1 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index b386a2a..5c1b3ab 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -827,23 +827,32 @@ int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t domid, int autopass)
     if ( vnc_pass ) {
         char tmpname[] = "/tmp/vncautopass.XXXXXX";
         autopass_fd = mkstemp(tmpname);
-        if ( autopass_fd < 0 )
-            goto skip_autopass;
+        if ( autopass_fd < 0 ) {
+            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
+                             "mkstemp %s failed", tmpname);
+            exit(-1);
+        }
 
-        if ( unlink(tmpname) )
+        if ( unlink(tmpname) ) {
             /* should never happen */
-            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "unlink %s failed", tmpname);
+            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
+                             "unlink %s failed", tmpname);
+            exit(-1);
+        }
 
         if ( libxl_write_exactly(ctx, autopass_fd, vnc_pass, strlen(vnc_pass),
-                                    tmpname, "vnc password") ) {
-            do { close(autopass_fd); } while(errno == EINTR);
-            goto skip_autopass;
+                                    tmpname, "vnc password") )
+            exit(-1);
+
+        if ( lseek(autopass_fd, SEEK_SET, 0) ) {
+            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
+                             "rewind %s (autopass) failed", tmpname);
+            exit(-1);
         }
 
         args[2] = "-autopass";
     }
 
-skip_autopass:
     libxl__exec(autopass_fd, -1, -1, args[0], args);
     abort();
 }
-- 
1.5.6.5