Fix Prefix Delegation assigning the SLA in the correct place.

diff --git a/ipv6.c b/ipv6.c
index ebb616c0c03648a0d5a658ed9ef48d4334450312..30a36491ce9041104c849273bd09c413c9d090dd 100644 (file)
--- a/ipv6.c
+++ b/ipv6.c
@@ -524,8 +524,9 @@ ipv6_userprefix(
 {
        uint64_t vh, vl, user_low, user_high;
 
-       if (prefix_len < 0 || prefix_len > 128 ||
-           result_len < 0 || result_len > 128)
+       if (prefix_len < 1 || prefix_len > 128 ||
+           result_len < 1 || result_len > 128 ||
+           user_number == 0)
        {
                errno = EINVAL;
                return -1;
@@ -533,19 +534,30 @@ ipv6_userprefix(
 
        /* Check that the user_number fits inside result_len less prefix_len */
        if (result_len < prefix_len ||
-           ffs64(user_number) > result_len - prefix_len)
+           fls64(user_number) > result_len - prefix_len)
        {
               errno = ERANGE;
               return -1;
        }
 
-       /* virtually shift user number by dest_len, then split at 64 */
-       if (result_len >= 64) {
-               user_high = user_number << (result_len - 64);
+       /* Shift user_number so it fit's just inside result_len.
+        * Shifting by 0 or sizeof(user_number) is undefined,
+        * so we cater for that. */
+       if (result_len == 128) {
+               user_high = 0;
+               user_low = user_number;
+       } else if (result_len > 64) {
+               if (prefix_len >= 64)
+                       user_high = 0;
+               else
+                       user_high = user_number >> (result_len - prefix_len);
+               user_low = user_number << (128 - result_len);
+       } else if (result_len == 64) {
+               user_high = user_number;
                user_low = 0;
        } else {
-               user_high = user_number >> (64 - result_len);
-               user_low = user_number << result_len;
+               user_high = user_number << (64 - result_len);
+               user_low = 0;
        }
 
        /* convert to two 64bit host order values */