Implemented symlink unrolling before locking.

@@ -84,6 +84,7 @@ typedef void *(*mu_retrieve_fp) __P((void *));
 extern void mu_register_retriever __P((list_t *pflist, mu_retrieve_fp fun));
 extern void * mu_retrieve __P((list_t flist, void *data));
 
+extern int mu_unroll_symlink __P((char *out, size_t outsz, const char *in));
   
 #ifdef __cplusplus
 }

@@ -100,21 +100,26 @@ int locker_set_default_flags(int flags)
 }
 
 int
-locker_create (locker_t *plocker, const char *filename, int flags)
+locker_create (locker_t *plocker, const char *filename_, int flags)
 {
   locker_t l;
+  char filename[_POSIX_PATH_MAX];
+  int err = 0;
 
   if (plocker == NULL)
     return MU_ERR_OUT_PTR_NULL;
 
-  if (filename == NULL)
+  if (filename_ == NULL)
     return EINVAL;
 
+  if((err = mu_unroll_symlink(filename, sizeof(filename), filename_)))
+    return err;
+
   l = calloc (1, sizeof (*l));
+
   if (l == NULL)
     return ENOMEM;
 
-  /* Should make l->file be the result of following the symlinks. */
   l->file = strdup(filename);
 
   if (l->file == NULL)

@@ -21,6 +21,7 @@
 #endif
 
 #include <errno.h>
+#include <limits.h>
 #include <netdb.h>
 #include <pwd.h>
 #include <signal.h>
@@ -776,3 +777,74 @@ int mu_spawnvp (const char* prog, const char* const av_[], int* stat)
   return err;
 }
 
+
+/* The result of readlink() may be a path relative to that link, 
+ * qualify it if necessary.
+ */
+static void
+mu_qualify_link (const char *path, const char *link, char *qualified)
+{
+  const char *lb = NULL;
+  size_t len;
+
+  /* link is full path */
+  if (*link == '/')
+    {
+      mu_cpystr (qualified, link, _POSIX_PATH_MAX);
+      return;
+    }
+
+  if ((lb = strrchr (path, '/')) == NULL)
+    {
+      /* no path in link */
+      mu_cpystr (qualified, link, _POSIX_PATH_MAX);
+      return;
+    }
+
+  len = lb - path + 1;
+  memcpy (qualified, path, len);
+  mu_cpystr (qualified + len, link, _POSIX_PATH_MAX - len);
+}
+
+#ifndef _POSIX_SYMLOOP_MAX
+# define _POSIX_SYMLOOP_MAX 255
+#endif
+
+int
+mu_unroll_symlink (char *out, size_t outsz, const char *in)
+{
+  char path[_POSIX_PATH_MAX];
+  int symloops = 0;
+
+  while (symloops++ < _POSIX_SYMLOOP_MAX)
+    {
+      struct stat s;
+      char link[_POSIX_PATH_MAX];
+      char qualified[_POSIX_PATH_MAX];
+      int len;
+
+      if (lstat (in, &s) == -1)
+	return errno;
+
+      if (!S_ISLNK (s.st_mode))
+	{
+	  mu_cpystr (path, in, sizeof (path));
+	  break;
+	}
+
+      if ((len = readlink (in, link, sizeof (link))) == -1)
+	return errno;
+
+      link[(len >= sizeof (link)) ? (sizeof (link) - 1) : len] = '\0';
+
+      mu_qualify_link (in, link, qualified);
+
+      mu_cpystr (path, qualified, sizeof (path));
+
+      in = path;
+    }
+
+  mu_cpystr (out, path, outsz);
+
+  return 0;
+}