add patch to announce node prefix with preferred lifetime of 0

patches/packages/gluon/0001-uradvd-adjust-preferred-lifetime-to-0.patch

+From: Nico <github@nicoboehr.de>
+Date: Thu, 3 Jun 2021 20:31:55 +0000
+Subject: uradvd: adjust preferred lifetime to 0
+
+When we announce a prefix from nodes which has a preferred lifetime
+of nonzero, clients can use this prefix as a source IP address.
+
+As we announce the same prefix for every segment, this won't work. Hence,
+set the preferred lifetime to 0 so nobody ever uses it as a source IP.
+
+diff --git a/net/uradvd/src/uradvd.c b/net/uradvd/src/uradvd.c
+index f6549f249518714e3d9210708b54cc23d85b26df..0edcfdcc02c3c1d513413d8cb580880e4ef9eab6 100644
+--- a/net/uradvd/src/uradvd.c
++++ b/net/uradvd/src/uradvd.c
+@@ -62,7 +62,7 @@
+ 
+ /* These are in seconds */
+ #define AdvValidLifetime 86400u
+-#define AdvPreferredLifetime 14400u
++#define AdvPreferredLifetime 0u
+ #define AdvDefaultLifetime 0u
+ #define AdvCurHopLimit 64u
+ #define AdvRDNSSLifetime 1200u