From 90ab504273a7f186ebb76e6acfb778b4e0d7c91b Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 13 Aug 2014 15:00:12 +0200
Subject: [PATCH] resolved: skip IPv6 LLMNR if IPv6 is not available

---
 src/resolve/resolved-link.c    | 10 ++++++++--
 src/resolve/resolved-manager.c | 25 ++++++++++++++-----------
 src/shared/socket-util.c       |  4 ++--
 3 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
index ed176ab41..7dcaf1863 100644
--- a/src/resolve/resolved-link.c
+++ b/src/resolve/resolved-link.c
@@ -93,7 +93,10 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->unicast_scope = dns_scope_free(l->unicast_scope);
 
-        if (link_relevant(l, AF_INET) && l->llmnr_support != SUPPORT_NO && l->manager->llmnr_support != SUPPORT_NO) {
+        if (link_relevant(l, AF_INET) &&
+            l->llmnr_support != SUPPORT_NO &&
+            l->manager->llmnr_support != SUPPORT_NO &&
+            l->manager->llmnr_ipv4_udp_fd >= 0) {
                 if (!l->llmnr_ipv4_scope) {
                         r = dns_scope_new(l->manager, &l->llmnr_ipv4_scope, l, DNS_PROTOCOL_LLMNR, AF_INET);
                         if (r < 0)
@@ -102,7 +105,10 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->llmnr_ipv4_scope = dns_scope_free(l->llmnr_ipv4_scope);
 
-        if (link_relevant(l, AF_INET6) && l->llmnr_support != SUPPORT_NO && l->manager->llmnr_support != SUPPORT_NO) {
+        if (link_relevant(l, AF_INET6) &&
+            l->llmnr_support != SUPPORT_NO &&
+            l->manager->llmnr_support != SUPPORT_NO &&
+            l->manager->llmnr_ipv6_udp_fd >= 0) {
                 if (!l->llmnr_ipv6_scope) {
                         r = dns_scope_new(l->manager, &l->llmnr_ipv6_scope, l, DNS_PROTOCOL_LLMNR, AF_INET6);
                         if (r < 0)
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index a2de2edb4..84dad92c5 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -426,23 +426,25 @@ static int manager_llmnr_start(Manager *m) {
         if (r < 0)
                 return r;
 
-        r = manager_llmnr_ipv6_udp_fd(m);
-        if (r == -EADDRINUSE)
-                goto eaddrinuse;
-        if (r < 0)
-                return r;
-
         r = manager_llmnr_ipv4_tcp_fd(m);
         if (r == -EADDRINUSE)
                 goto eaddrinuse;
         if (r < 0)
                 return r;
 
-        r = manager_llmnr_ipv6_tcp_fd(m);
-        if (r == -EADDRINUSE)
-                goto eaddrinuse;
-        if (r < 0)
-                return r;
+        if (socket_ipv6_is_supported()) {
+                r = manager_llmnr_ipv6_udp_fd(m);
+                if (r == -EADDRINUSE)
+                        goto eaddrinuse;
+                if (r < 0)
+                        return r;
+
+                r = manager_llmnr_ipv6_tcp_fd(m);
+                if (r == -EADDRINUSE)
+                        goto eaddrinuse;
+                if (r < 0)
+                        return r;
+        }
 
         return 0;
 
@@ -450,6 +452,7 @@ eaddrinuse:
         log_warning("There appears to be another LLMNR respondering running. Turning off LLMNR support.");
         m->llmnr_support = SUPPORT_NO;
         manager_llmnr_stop(m);
+
         return 0;
 }
 
diff --git a/src/shared/socket-util.c b/src/shared/socket-util.c
index 1a04f323a..38729a25b 100644
--- a/src/shared/socket-util.c
+++ b/src/shared/socket-util.c
@@ -426,11 +426,11 @@ bool socket_ipv6_is_supported(void) {
         _cleanup_free_ char *l = NULL;
 
         if (access("/sys/module/ipv6", F_OK) != 0)
-                return 0;
+                return false;
 
         /* If we can't check "disable" parameter, assume enabled */
         if (read_one_line_file("/sys/module/ipv6/parameters/disable", &l) < 0)
-                return 1;
+                return true;
 
         /* If module was loaded with disable=1 no IPv6 available */
         return l[0] == '0';
-- 
2.30.2