[libvirt] [PATCH 2/6] util: new virFileRelLinkPointsTo function

[Eric Blake]

When checking if two filenames point to the same inode (whether
by hardlink or symlink), sometimes one of the names might be
relative.  This convenience function makes it easier to check.

* src/util/virfile.h (virFileRelLinkPointsTo): New prototype.
* src/util/virfile.c (virFileRelLinkPointsTo): New function.
* src/libvirt_private.syms (virfile.h): Export it.
* src/xen/xm_internal.c (xenXMDomainGetAutostart): Use it.

Signed-off-by: Eric Blake <eblake at redhat.com>
---
 src/libvirt_private.syms |  1 +
 src/util/virfile.c       | 26 +++++++++++++++++++++++++-
 src/util/virfile.h       |  3 +++
 src/xen/xm_internal.c    | 11 +++++------
 4 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index cd43335..c2bce13 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1255,6 +1255,7 @@ virFilePrintf;
 virFileReadAll;
 virFileReadHeaderFD;
 virFileReadLimFD;
+virFileRelLinkPointsTo;
 virFileResolveAllLinks;
 virFileResolveLink;
 virFileRewrite;
diff --git a/src/util/virfile.c b/src/util/virfile.c
index a28cbf1..10c4337 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -1368,7 +1368,8 @@ virFileHasSuffix(const char *str,
    && (Stat_buf_1).st_dev == (Stat_buf_2).st_dev)

 /* Return nonzero if checkLink and checkDest
-   refer to the same file.  Otherwise, return 0.  */
+ * refer to the same file.  Otherwise, return 0.
+ */
 int
 virFileLinkPointsTo(const char *checkLink,
                     const char *checkDest)
@@ -1382,6 +1383,29 @@ virFileLinkPointsTo(const char *checkLink,
 }


+/* Return positive if checkLink (residing within directory if not
+ * absolute) and checkDest refer to the same file.  Otherwise, return
+ * -1 on allocation failure (error reported), or 0 if not the same
+ * (silent).
+ */
+int
+virFileRelLinkPointsTo(const char *directory,
+                       const char *checkLink,
+                       const char *checkDest)
+{
+    char *candidate;
+    int ret;
+
+    if (*checkLink == '/')
+        return virFileLinkPointsTo(checkLink, checkDest);
+    if (virAsprintf(&candidate, "%s/%s", directory, checkLink) < 0)
+        return -1;
+    ret = virFileLinkPointsTo(candidate, checkDest);
+    VIR_FREE(candidate);
+    return ret;
+}
+
+
 static int
 virFileResolveLinkHelper(const char *linkpath,
                          bool intermediatePaths,
diff --git a/src/util/virfile.h b/src/util/virfile.h
index 638378a..168eb0d 100644
--- a/src/util/virfile.h
+++ b/src/util/virfile.h
@@ -144,6 +144,9 @@ int virFileStripSuffix(char *str,

 int virFileLinkPointsTo(const char *checkLink,
                         const char *checkDest);
+int virFileRelLinkPointsTo(const char *directory,
+                           const char *checkLink,
+                           const char *checkDest);

 int virFileResolveLink(const char *linkpath,
                        char **resultpath) ATTRIBUTE_RETURN_CHECK;
diff --git a/src/xen/xm_internal.c b/src/xen/xm_internal.c
index 52d2a1e..f25a7df 100644
--- a/src/xen/xm_internal.c
+++ b/src/xen/xm_internal.c
@@ -1427,25 +1427,24 @@ int
 xenXMDomainGetAutostart(virDomainDefPtr def,
                         int *autostart)
 {
-    char *linkname = xenXMAutostartLinkName(def);
     char *config = xenXMDomainConfigName(def);
     int ret = -1;

-    if (!linkname || !config)
+    if (!config)
         goto cleanup;

-    *autostart = virFileLinkPointsTo(linkname, config);
+    *autostart = virFileRelLinkPointsTo("/etc/xen/auto/", def->name, config);
     if (*autostart < 0) {
         virReportSystemError(errno,
-                             _("cannot check link %s points to config %s"),
-                             linkname, config);
+                             _("cannot check link /etc/xen/auto/%s points "
+                               "to config %s"),
+                             def->name, config);
         goto cleanup;
     }

     ret = 0;

  cleanup:
-    VIR_FREE(linkname);
     VIR_FREE(config);
     return ret;
 }
-- 
1.9.0