X-Git-Url: https://git.distorted.org.uk/~mdw/userv-utils/blobdiff_plain/f0aa028edd42fec09cf17b7831bc00adc2ba6d31..f56780b78838933d6ee89f05d639234c5eb5986b:/ipif/service.c?ds=sidebyside

diff --git a/ipif/service.c b/ipif/service.c
index 397740c..4137794 100644
--- a/ipif/service.c
+++ b/ipif/service.c
@@ -329,7 +329,7 @@ static void eat_prefixmask(const char **argp, const char *what,
   sprintf(whatbuf,"%s length",what);
   len= eat_number(argp,whatbuf, 0,32, endchars,endchar_r);
 
-  mask= (~0UL << (32-len));
+  mask= len ? (~0UL << (32-len)) : 0UL;
   if (prefix & ~mask) badusage("%s prefix %08lx not fully contained in mask %08lx",
 			       what,prefix,mask);
   *prefix_r= prefix;