From 378fa56888767ff58762a338c3425647b98bf59e Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Sun, 5 Jan 2020 17:23:19 +0000
Subject: [PATCH] Don't send RAs on interfaces without a link-local address.

Since the source address of the RAs must be the link-local address.
---
 src/radv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/radv.c b/src/radv.c
index cd5853a..cad0530 100644
--- a/src/radv.c
+++ b/src/radv.c
@@ -288,7 +288,10 @@ static void send_ra_alias(time_t now, int iface, char *iface_name, struct in6_ad
       context->netid.next = &context->netid;
     }
 
-  if (!iface_enumerate(AF_INET6, &parm, add_prefixes))
+  /* If no link-local address then we can't advertise since source address of
+     advertisement must be link local address: RFC 4861 para 6.1.2. */
+  if (!iface_enumerate(AF_INET6, &parm, add_prefixes) ||
+      parm.link_pref_time == 0)
     return;
 
   /* Find smallest preferred time within address classes,