From 0f916ec3bcd7fd1b5b5ac1ff0a7b8548132ae00f Mon Sep 17 00:00:00 2001
From: dmiller <dmiller@e0a8ed71-7df4-0310-8962-fdc924857419>
Date: Wed, 31 Oct 2018 23:44:52 +0000
Subject: [PATCH] Fix an error in common-prefix calculation

---
 nbase/nbase_addrset.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/nbase/nbase_addrset.c b/nbase/nbase_addrset.c
index 0ffb09214..3182a39b0 100644
--- a/nbase/nbase_addrset.c
+++ b/nbase/nbase_addrset.c
@@ -239,6 +239,10 @@ u32 common_mask(u32 a, u32 b)
   u8 r;     // r will be lg(v)
   u32 t, tt; // temporaries
   u32 v = a ^ b;
+  if (v == 0) {
+    /* values are equal, all bits are the same */
+    return 0xffffffff;
+  }
 
   if ((tt = v >> 16))
   {
@@ -250,7 +254,7 @@ u32 common_mask(u32 a, u32 b)
   }
   if (r + 1 >= 32) {
     /* shifting this many bits would overflow. Just return max mask */
-    return 0xffffffff;
+    return 0;
   }
   else {
     return ~((1 << (r + 1)) - 1);