Change protocol to send Linux errno from daemon to library.

This changes the protocol so that the Linux errno (if available)
is sent back to the library.  Note that the errno is not yet
made available to callers, since it is not clear how best to
present this Linux-specific number.

3 files changed, 10 insertions, 5 deletions

diff --git a/daemon/proto.c b/daemon/proto.c
index 6fa243ff..628e86c1 100644
--- a/daemon/proto.c
+++ b/daemon/proto.c
@@ -179,7 +179,7 @@ main_loop (int _sock)
   }
 }
 
-static void send_error (const char *msg);
+static void send_error (int errnum, const char *msg);
 
 void
 reply_with_error (const char *fs, ...)
@@ -191,7 +191,7 @@ reply_with_error (const char *fs, ...)
   vsnprintf (err, sizeof err, fs, args);
   va_end (args);
 
-  send_error (err);
+  send_error (0, err);
 }
 
 void
@@ -207,11 +207,11 @@ reply_with_perror_errno (int err, const char *fs, ...)
 
   snprintf (buf2, sizeof buf2, "%s: %s", buf1, strerror (err));
 
-  send_error (buf2);
+  send_error (err, buf2);
 }
 
 static void
-send_error (const char *msg)
+send_error (int errnum, const char *msg)
 {
   XDR xdr;
   char buf[GUESTFS_ERROR_LEN + 200];
@@ -236,6 +236,7 @@ send_error (const char *msg)
     exit (EXIT_FAILURE);
   }
 
+  err.linux_errno = errnum;
   err.error_message = (char *) msg;
 
   if (!xdr_guestfs_message_error (&xdr, &err)) {
diff --git a/src/generator.ml b/src/generator.ml
index 7d35ac14..233f8bd2 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -6331,6 +6331,7 @@ enum guestfs_message_status {
 
   pr "\
 struct guestfs_message_error {
+  int linux_errno;                   /* Linux errno if available. */
   string error_message<GUESTFS_ERROR_LEN>;
 };
 
diff --git a/src/guestfs.pod b/src/guestfs.pod
index a4d9c572..4dafb074 100644
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -724,7 +724,7 @@ The error message you get from this is also a little obscure.
 This could be fixed in the generator by specially marking parameters
 and return values which take bytes or other units.
 
-=item Protocol should return errno with error messages.
+=item Library should return errno with error messages.
 
 It would be a nice-to-have to be able to get the original value of
 'errno' from inside the appliance along error paths (where set).
@@ -732,6 +732,9 @@ Currently L<guestmount(1)> goes through hoops to try to reverse the
 error message string into an errno, see the function error() in
 fuse/guestmount.c.
 
+In libguestfs 1.5.4, the protocol was changed so that the
+Linux errno is sent back from the daemon.
+
 =back
 
 =head2 PROTOCOL LIMITS