dhcpc: code shrink in good_hostname

Incorporated valid_domain_label into good_hostname to simplify the implementation.

function                                             old     new   delta
static.xmalloc_optname_optval                        973     958     -15
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-15)             Total: -15 bytes
   text	   data	    bss	    dec	    hex	filename
 993144	  16915	   1872	1011931	  f70db	busybox_old
 993129	  16915	   1872	1011916	  f70cc	busybox_unstripped

Signed-off-by: Martin Lewis <martin.lewis.x84@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 5a1f8fd7ab166fa4c54f9d33700f2b93b5027216..6422181da4ed9a13c4ee25c1d6b219dc7fcf8e1d 100644 (file)
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -159,61 +159,27 @@ static int mton(uint32_t mask)
 }
 
 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
-/* Check if a given label represents a valid DNS label
- * Return pointer to the first character after the label
- * (NUL or dot) upon success, NULL otherwise.
- * See RFC1035, 2.3.1
- */
+/* Check if a given name represents a valid DNS name */
+/* See RFC1035, 2.3.1 */
 /* We don't need to be particularly anal. For example, allowing _, hyphen
  * at the end, or leading and trailing dots would be ok, since it
- * can't be used for attacks. (Leading hyphen can be, if someone uses
- * cmd "$hostname"
+ * can't be used for attacks. (Leading hyphen can be, if someone uses cmd "$hostname"
  * in the script: then hostname may be treated as an option)
  */
-static const char *valid_domain_label(const char *label)
-{
-       unsigned char ch;
-       //unsigned pos = 0;
-
-       if (label[0] == '-')
-               return NULL;
-       for (;;) {
-               ch = *label;
-               if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
-                       if (ch < '0' || ch > '9') {
-                               if (ch == '\0' || ch == '.')
-                                       return label;
-                               /* DNS allows only '-', but we are more permissive */
-                               if (ch != '-' && ch != '_')
-                                       return NULL;
-                       }
-               }
-               label++;
-               //pos++;
-               //Do we want this?
-               //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
-               //      return NULL;
-       }
-}
-
-/* Check if a given name represents a valid DNS name */
-/* See RFC1035, 2.3.1 */
 static int good_hostname(const char *name)
 {
-       //const char *start = name;
-
-       for (;;) {
-               name = valid_domain_label(name);
-               if (!name)
-                       return 0;
-               if (!name[0])
-                       return 1;
-                       //Do we want this?
-                       //return ((name - start) < 1025); /* NS_MAXDNAME */
-               name++;
-               if (*name == '\0')
-                       return 1; // We allow trailing dot too
+       if (*name == '-') /* Can't start with '-' */
+               return 0;
+
+       while (*name) {
+               unsigned char ch = *name++;
+               if (!isalnum(ch))
+                       /* DNS allows only '-', but we are more permissive */
+                       if (ch != '-' && ch != '_' && ch != '.')
+                               return 0;
+               // TODO: do we want to validate lengths against NS_MAXLABEL and NS_MAXDNAME?
        }
+       return 1;
 }
 #else
 # define good_hostname(name) 1