From: Roy Marples <roy@marples.name>
Date: Mon, 22 Jun 2026 17:06:35 +0000 (+0100)
Subject: DHCP6: Fix configuring the suffix to delegated prefixes (#665)
X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=HEAD;p=thirdparty%2Fdhcpcd.git

DHCP6: Fix configuring the suffix to delegated prefixes (#665)

Depending on the delegated prefix length and the user
configured suffix length, some parts of the suffix would be lost.

Reported by NVIDIA Project Vanessa
---

diff --git a/src/ipv6.c b/src/ipv6.c
index 8670e30f..ee25c40a 100644
--- a/src/ipv6.c
+++ b/src/ipv6.c
@@ -590,7 +590,7 @@ ipv6_userprefix(const struct in6_addr *prefix, // prefix from router
 		if (prefix_len >= 64)
 			user_high = 0;
 		else
-			user_high = user_number >> (result_len - prefix_len);
+			user_high = user_number >> (result_len - 64);
 		user_low = user_number << (128 - result_len);
 	} else if (result_len == 64) {
 		user_high = user_number;