New commands: 'ln', 'ln-f', 'ln-s', 'ln-sf' and 'readlink'.

These commands can be used to make hard and symbolic links.  The
readlink command is used to read existing symbolic links.

6 files changed, 187 insertions, 3 deletions

diff --git a/TODO b/TODO
index d4a93b8d..2b9aae12 100644
--- a/TODO
+++ b/TODO
@@ -145,8 +145,6 @@ Ideas for extra commands
   General glibc / core programs:
     chgrp
     dd (?)
-    ln / ln -s
-    readlink
     utime / utimes / futimes / futimens / l..
     more mk*temp calls
     some sort of alloc/fallocate/posix_fallocate call to create empty space
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index c0e8bc94..52482d08 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -45,6 +45,7 @@ guestfsd_SOURCES = \
 	headtail.c \
 	hexdump.c \
 	initrd.c \
+	link.c \
 	ls.c \
 	lvm.c \
 	mknod.c \
diff --git a/daemon/link.c b/daemon/link.c
new file mode 100644
index 00000000..57e35384
--- /dev/null
+++ b/daemon/link.c
@@ -0,0 +1,137 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2009 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+
+#include "daemon.h"
+#include "actions.h"
+
+char *
+do_readlink (char *path)
+{
+  ssize_t r;
+  char *ret;
+  char link[PATH_MAX];
+
+  NEED_ROOT (NULL);
+  ABS_PATH (path, NULL);
+
+  CHROOT_IN;
+  r = readlink (path, link, sizeof link);
+  CHROOT_OUT;
+  if (r == -1) {
+    reply_with_perror ("readlink");
+    return NULL;
+  }
+
+  ret = strndup (link, r);
+  if (ret == NULL) {
+    reply_with_perror ("strndup");
+    return NULL;
+  }
+
+  return ret;			/* caller frees */
+}
+
+static int
+_link (const char *flag, int symbolic, const char *target, const char *linkname)
+{
+  int r;
+  char *err;
+  char *buf_linkname;
+  char *buf_target;
+
+  NEED_ROOT (-1);
+  ABS_PATH (linkname, -1);
+  /* but target does not need to be absolute */
+
+  /* Prefix linkname with sysroot. */
+  buf_linkname = sysroot_path (linkname);
+  if (!buf_linkname) {
+    reply_with_perror ("malloc");
+    return -1;
+  }
+
+  /* Only prefix target if it's _not_ a symbolic link, and if
+   * the target is absolute.  Note that the resulting link will
+   * always be "broken" from the p.o.v. of the appliance, ie:
+   * /a -> /b but the path as seen here is /sysroot/b
+   */
+  buf_target = NULL;
+  if (!symbolic && target[0] == '/') {
+    buf_target = sysroot_path (target);
+    if (!buf_target) {
+      reply_with_perror ("malloc");
+      free (buf_linkname);
+      return -1;
+    }
+  }
+
+  if (flag)
+    r = command (NULL, &err,
+		 "ln", flag, "--", /* target could begin with '-' */
+		 buf_target ? : target, buf_linkname, NULL);
+  else
+    r = command (NULL, &err,
+		 "ln", "--",
+		 buf_target ? : target, buf_linkname, NULL);
+  free (buf_linkname);
+  free (buf_target);
+  if (r == -1) {
+    reply_with_error ("ln%s%s: %s: %s: %s",
+		      flag ? " " : "",
+		      flag ? : "",
+		      target, linkname, err);
+    free (err);
+    return -1;
+  }
+
+  free (err);
+
+  return 0;
+}
+
+int
+do_ln (char *target, char *linkname)
+{
+  return _link (NULL, 0, target, linkname);
+}
+
+int
+do_ln_f (char *target, char *linkname)
+{
+  return _link ("-f", 0, target, linkname);
+}
+
+int
+do_ln_s (char *target, char *linkname)
+{
+  return _link ("-s", 1, target, linkname);
+}
+
+int
+do_ln_sf (char *target, char *linkname)
+{
+  return _link ("-sf", 1, target, linkname);
+}
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 1b2f03ec..fc6c9f02 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -23,6 +23,7 @@ daemon/guestfsd.c
 daemon/headtail.c
 daemon/hexdump.c
 daemon/initrd.c
+daemon/link.c
 daemon/ls.c
 daemon/lvm.c
 daemon/mknod.c
@@ -32,6 +33,7 @@ daemon/ntfs.c
 daemon/pingdaemon.c
 daemon/proto.c
 daemon/readdir.c
+daemon/realpath.c
 daemon/scrub.c
 daemon/sfdisk.c
 daemon/sleep.c
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index 9cc2bc3e..de8febe1 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-163
+168
diff --git a/src/generator.ml b/src/generator.ml
index 3a35fa2c..34721938 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -3141,6 +3141,52 @@ matching lines.");
 Return the canonicalized absolute pathname of C<path>.  The
 returned path has no C<.>, C<..> or symbolic link path elements.");
 
+  ("ln", (RErr, [String "target"; String "linkname"]), 164, [],
+   [InitBasicFS, Always, TestOutputStruct (
+      [["touch"; "/a"];
+       ["ln"; "/a"; "/b"];
+       ["stat"; "/b"]], [CompareWithInt ("nlink", 2)])],
+   "create a hard link",
+   "\
+This command creates a hard link using the C<ln> command.");
+
+  ("ln_f", (RErr, [String "target"; String "linkname"]), 165, [],
+   [InitBasicFS, Always, TestOutputStruct (
+      [["touch"; "/a"];
+       ["touch"; "/b"];
+       ["ln_f"; "/a"; "/b"];
+       ["stat"; "/b"]], [CompareWithInt ("nlink", 2)])],
+   "create a hard link",
+   "\
+This command creates a hard link using the C<ln -f> command.
+The C<-f> option removes the link (C<linkname>) if it exists already.");
+
+  ("ln_s", (RErr, [String "target"; String "linkname"]), 166, [],
+   [InitBasicFS, Always, TestOutputStruct (
+      [["touch"; "/a"];
+       ["ln_s"; "a"; "/b"];
+       ["lstat"; "/b"]], [CompareWithInt ("mode", 0o120777)])],
+   "create a symbolic link",
+   "\
+This command creates a symbolic link using the C<ln -s> command.");
+
+  ("ln_sf", (RErr, [String "target"; String "linkname"]), 167, [],
+   [InitBasicFS, Always, TestOutput (
+      [["mkdir_p"; "/a/b"];
+       ["touch"; "/a/b/c"];
+       ["ln_sf"; "../d"; "/a/b/c"];
+       ["readlink"; "/a/b/c"]], "../d")],
+   "create a symbolic link",
+   "\
+This command creates a symbolic link using the C<ln -sf> command,
+The C<-f> option removes the link (C<linkname>) if it exists already.");
+
+  ("readlink", (RString "link", [String "path"]), 168, [],
+   [] (* XXX tested above *),
+   "read the target of a symbolic link",
+   "\
+This command reads the target of a symbolic link.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions