[Libguestfs] [PATCH 2/3] p2v: Run fewer 'scp' commands.

[Richard W.M. Jones]

Each scp command takes a considerable amount of time -- several
seconds -- because it must set up, authenticate and tear down a new
connection.  Avoid this by combining several copies into a single
command.

We still have to use two scp commands because we want to check that
some files are copied and ignore failures in a second set of
informational files.
---
 p2v/conversion.c | 31 +++++++++++--------------------
 p2v/p2v.h        |  2 +-
 p2v/ssh.c        | 25 +++++++++++++++++++++----
 3 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/p2v/conversion.c b/p2v/conversion.c
index 2f1bbac3e..e55f3d291 100644
--- a/p2v/conversion.c
+++ b/p2v/conversion.c
@@ -330,28 +330,19 @@ start_conversion (struct config *config,
   }
 
   /* Copy the static files to the remote dir. */
-  if (scp_file (config, name_file, remote_dir) == -1) {
-    set_conversion_error ("scp: %s to %s: %s",
-                          name_file, remote_dir, get_ssh_error ());
-    goto out;
-  }
-  if (scp_file (config, physical_xml_file, remote_dir) == -1) {
-    set_conversion_error ("scp: %s to %s: %s",
-                          physical_xml_file, remote_dir, get_ssh_error ());
-    goto out;
-  }
-  if (scp_file (config, wrapper_script, remote_dir) == -1) {
-    set_conversion_error ("scp: %s to %s: %s",
-                          wrapper_script, remote_dir, get_ssh_error ());
+
+  /* These three files must not fail, so check for errors here. */
+  if (scp_file (config, remote_dir,
+                name_file, physical_xml_file, wrapper_script, NULL) == -1) {
+    set_conversion_error ("scp: %s: %s",
+                          remote_dir, get_ssh_error ());
     goto out;
   }
-  /* It's not essential that these files are copied. */
-  ignore_value (scp_file (config, dmesg_file, remote_dir));
-  ignore_value (scp_file (config, lscpu_file, remote_dir));
-  ignore_value (scp_file (config, lspci_file, remote_dir));
-  ignore_value (scp_file (config, lsscsi_file, remote_dir));
-  ignore_value (scp_file (config, lsusb_file, remote_dir));
-  ignore_value (scp_file (config, p2v_version_file, remote_dir));
+
+  /* It's not essential that these files are copied, so ignore errors. */
+  ignore_value (scp_file (config, remote_dir,
+                          dmesg_file, lscpu_file, lspci_file, lsscsi_file,
+                          lsusb_file, p2v_version_file, NULL));
 
   /* Do the conversion.  This runs until virt-v2v exits. */
   if (notify_ui)
diff --git a/p2v/p2v.h b/p2v/p2v.h
index bd4b484ab..f51bdfcf1 100644
--- a/p2v/p2v.h
+++ b/p2v/p2v.h
@@ -161,7 +161,7 @@ extern int test_connection (struct config *);
 extern mexp_h *open_data_connection (struct config *, const char *local_ipaddr, int local_port, int *remote_port);
 extern mexp_h *start_remote_connection (struct config *, const char *remote_dir);
 extern const char *get_ssh_error (void);
-extern int scp_file (struct config *config, const char *localfile, const char *remotefile);
+extern int scp_file (struct config *config, const char *target, const char *local, ...) __attribute__((sentinel));
 
 /* nbd.c */
 extern void set_nbd_option (const char *opt);
diff --git a/p2v/ssh.c b/p2v/ssh.c
index 8beaf74bb..bfeb80661 100644
--- a/p2v/ssh.c
+++ b/p2v/ssh.c
@@ -572,14 +572,18 @@ start_ssh (unsigned spawn_flags, struct config *config,
 #endif
 
 /**
- * Upload a file to remote using L<scp(1)>.
+ * Upload file(s) to remote using L<scp(1)>.
+ *
+ * Note that the target (directory or file) comes before the list of
+ * local files, because the list of local files is a varargs list.
  *
  * This is a simplified version of L</start_ssh> above.
  */
 int
-scp_file (struct config *config, const char *localfile, const char *remotefile)
+scp_file (struct config *config, const char *target, const char *local, ...)
 {
   size_t i = 0;
+  va_list args;
   const size_t MAX_ARGS = 64;
   const char *argv[MAX_ARGS];
   char port_str[64];
@@ -618,12 +622,25 @@ scp_file (struct config *config, const char *localfile, const char *remotefile)
     ADD_ARG (argv, i, "-i");
     ADD_ARG (argv, i, config->identity_file);
   }
-  ADD_ARG (argv, i, localfile);
+
+  /* Source files or directories.
+   * Strictly speaking this could abort() if the list of files is
+   * too long, but that never happens in virt-p2v. XXX
+   */
+  va_start (args, local);
+  do ADD_ARG (argv, i, local);
+  while ((local = va_arg (args, const char *)) != NULL);
+  va_end (args);
+
+  /* The target file or directory.  We need to rewrite this as
+   * "username at server:target".
+   */
   if (asprintf (&remote, "%s@%s:%s",
                 config->username ? config->username : "root",
-                config->server, remotefile) == -1)
+                config->server, target) == -1)
     error (EXIT_FAILURE, errno, "asprintf");
   ADD_ARG (argv, i, remote);
+
   ADD_ARG (argv, i, NULL);
 
 #if DEBUG_STDERR
-- 
2.12.0