diff --git a/ulib/dlinklist.h b/ulib/dlinklist.h
new file mode 100644
index 0000000..9fed387
--- /dev/null
+++ b/ulib/dlinklist.h
@@ -0,0 +1,138 @@
+#ifndef ULIB_DLINKLIST_H_
+#define ULIB_DLINKLIST_H_
+
+#define DL_APPEND(head, new) \
+  do { \
+    if ((new) != NULL) { \
+      (new)->next = NULL; \
+      if ((head) != NULL) { \
+        typeof((head)) __tmp = (head); \
+        while (__tmp->next != NULL) { \
+          __tmp = __tmp->next; \
+        } \
+        __tmp->next = (new); \
+        (new)->prev = __tmp; \
+      } else { \
+        (new)->prev = NULL; \
+        (head) = (new); \
+      } \
+    } \
+  } while (0)
+
+#define DL_PREPEND(head, new) \
+  do { \
+    if ((new) != NULL) { \
+      (new)->prev = NULL; \
+      (new)->next = (head); \
+      if ((head) != NULL) { \
+        (head)->prev = (new); \
+      } \
+      (head) = (new); \
+    } \
+  } while (0)
+
+#define DL_REMOVE(head, ele) \
+  do { \
+    if ((ele) != NULL) { \
+      if ((ele)->prev != NULL) { \
+        (ele)->prev->next = (ele)->next; \
+      } else { \
+        (head) = (ele)->next; \
+      } \
+      if ((ele)->next != NULL) { \
+        (ele)->next->prev = (ele)->prev; \
+      } \
+      (ele)->next = NULL; \
+      (ele)->prev = NULL; \
+    } \
+  } while (0)
+
+#define DL_FINDPROP(head, out, propname, propvalue) \
+  do { \
+    (out) = NULL; \
+    typeof((head)) __tmp = (head); \
+    while (__tmp) { \
+      if (__tmp->propname == (propvalue)) { \
+        (out) = __tmp; \
+        break; \
+      } \
+      __tmp = __tmp->next; \
+    } \
+  } while (0)
+
+#define DL_FOREACH_SAFE(head, var, tmp) \
+  for (var = (head), tmp = (var ? var->next : NULL); \
+       var != NULL; \
+       var = tmp, tmp = (var ? var->next : NULL))
+
+#define DL_FOREACH_SAFE_IDX(head, var, tmp, idx) \
+  for ((idx) = 0, var = (head), tmp = (var ? var->next : NULL); \
+       var != NULL; \
+       var = tmp, tmp = (var ? var->next : NULL), (idx)++)
+
+#define DL_FOREACH_SAFE_IDX_LIMIT(head, var, tmp, idx, max) \
+  for ((idx) = 0, var = (head), tmp = (var ? var->next : NULL); \
+       var != NULL && (idx) < (max); \
+       var = tmp, tmp = (var ? var->next : NULL), (idx)++)
+
+#define DL_BACK(head, out) \
+  do { \
+    (out) = NULL; \
+    if ((head) != NULL) { \
+      typeof((head)) __tmp = (head); \
+      while (__tmp->next != NULL) { \
+        __tmp = __tmp->next; \
+      } \
+      (out) = __tmp; \
+    } \
+  } while (0)
+
+#define DL_FRONT(head, out) \
+  do { \
+    (out) = NULL; \
+    if ((head) != NULL) { \
+      typeof((head)) __tmp = (head); \
+      while (__tmp->prev != NULL) { \
+        __tmp = __tmp->prev; \
+      } \
+      (out) = __tmp; \
+    } \
+  } while (0)
+
+#define DL_INSERT_AFTER(head, pos, new) \
+  do { \
+    if ((pos) != NULL && (new) != NULL) { \
+      (new)->prev = (pos); \
+      (new)->next = (pos)->next; \
+      if ((pos)->next != NULL) { \
+        (pos)->next->prev = (new); \
+      } \
+      (pos)->next = (new); \
+    } else if ((pos) == NULL && (head) == NULL) { \
+      /* Empty list: make new head */ \
+      (new)->prev = NULL; \
+      (new)->next = NULL; \
+      (head) = (new); \
+    } \
+  } while (0)
+
+#define DL_INSERT_BEFORE(head, pos, new) \
+  do { \
+    if ((pos) != NULL && (new) != NULL) { \
+      (new)->next = (pos); \
+      (new)->prev = (pos)->prev; \
+      if ((pos)->prev != NULL) { \
+        (pos)->prev->next = (new); \
+      } else { \
+        (head) = (new); \
+      } \
+      (pos)->prev = (new); \
+    } else if ((pos) == NULL && (head) == NULL) { \
+      /* Empty list: make new head */ \
+      (new)->prev = NULL; \
+      (new)->next = NULL; \
+      (head) = (new); \
+    } \
+  } while (0)
+
+#endif // ULIB_DLINKLIST_H_
diff --git a/ulib/string/string.c b/ulib/string/string.c
index 075e5db..d4175b4 100644
--- a/ulib/string/string.c
+++ b/ulib/string/string.c
@@ -183,3 +183,32 @@ char *string_combine(char *dest, const char *src) {
   dest[i+j] = '\0';
   return dest;
 }
+
+// https://aticleworld.com/memmove-function-implementation-in-c/
+void * string_memmove(void* dest, const void* src, unsigned int n)
+{
+    char *pDest = (char *)dest;
+    const char *pSrc =( const char*)src;
+    //allocate memory for tmp array
+    char *tmp  = (char *)umalloc(sizeof(char ) * n);
+    if(NULL == tmp)
+    {
+        return NULL;
+    }
+    else
+    {
+        unsigned int i = 0;
+        // copy src to tmp array
+        for(i =0; i < n ; ++i)
+        {
+            *(tmp + i) = *(pSrc + i);
+        }
+        //copy tmp to dest
+        for(i =0 ; i < n ; ++i)
+        {
+            *(pDest + i) = *(tmp + i);
+        }
+        ufree(tmp); //free allocated memory
+    }
+    return dest;
+}
diff --git a/ulib/string/string.h b/ulib/string/string.h
index 92186f4..b10d495 100644
--- a/ulib/string/string.h
+++ b/ulib/string/string.h
@@ -18,6 +18,7 @@ char *string_strchr(const char *s, int c);
 int string_strncmp(const char * s1, const char * s2, size_t n);
 char *string_tokenizealloc(char *s, char *delim);
 char *string_combine(char *dest, const char *src);
+void * string_memmove(void* dest, const void* src, unsigned int n);
 
 #endif
 
diff --git a/ulib/ulib.h b/ulib/ulib.h
index 0d66b84..9faa4d2 100644
--- a/ulib/ulib.h
+++ b/ulib/ulib.h
@@ -17,6 +17,7 @@
 #include <assert.h>
 #include <umalloc/umalloc.h>
 #include <fs/path.h>
+#include <dlinklist.h>
 
 #include <errors.h>
 #include <sysdefs/ioctl.h>