From 6df860f3a0e9e1265ee98f06bf276513876d5fc8 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 1 Oct 2021 17:35:04 +0900
Subject: [PATCH] in-addr-util: do not shift 8 or more for uint8_t
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See ISO/IEC 9899:TC3 § 6.5.7.3.
---
 src/basic/in-addr-util.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/basic/in-addr-util.c b/src/basic/in-addr-util.c
index af3724d9d1f..613a5681319 100644
--- a/src/basic/in-addr-util.c
+++ b/src/basic/in-addr-util.c
@@ -642,9 +642,12 @@ int in6_addr_mask(struct in6_addr *addr, unsigned char prefixlen) {
                 if (prefixlen >= 8) {
                         mask = 0xFF;
                         prefixlen -= 8;
-                } else {
+                } else if (prefixlen > 0) {
                         mask = 0xFF << (8 - prefixlen);
                         prefixlen = 0;
+                } else {
+                        assert(prefixlen == 0);
+                        mask = 0;
                 }
 
                 addr->s6_addr[i] &= mask;
-- 
2.47.3