From dfc1091b2f5f21f69e0aa6d3c4536b8990d4b100 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 19 Jan 2016 17:13:27 +0100
Subject: [PATCH] resolved: allocate DNS scope for links only if the interface
 is up

For mDNS and LLMNR we already created the scopes only if the specific interfaces where actually up and suitable for
Multicasting. Add a similar (but weaker) logic for unicast DNS as well.
---
 src/resolve/resolved-link.c | 32 ++++++++++++++++++++------------
 src/resolve/resolved-link.h |  2 +-
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
index 1e8f880..a5033e3 100644
--- a/src/resolve/resolved-link.c
+++ b/src/resolve/resolved-link.c
@@ -93,7 +93,8 @@ static void link_allocate_scopes(Link *l) {
 
         assert(l);
 
-        if (l->dns_servers) {
+        if (link_relevant(l, AF_UNSPEC, false) &&
+            l->dns_servers) {
                 if (!l->unicast_scope) {
                         r = dns_scope_new(l->manager, &l->unicast_scope, l, DNS_PROTOCOL_DNS, AF_UNSPEC);
                         if (r < 0)
@@ -102,7 +103,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->unicast_scope = dns_scope_free(l->unicast_scope);
 
-        if (link_relevant(l, AF_INET) &&
+        if (link_relevant(l, AF_INET, true) &&
             l->llmnr_support != RESOLVE_SUPPORT_NO &&
             l->manager->llmnr_support != RESOLVE_SUPPORT_NO) {
                 if (!l->llmnr_ipv4_scope) {
@@ -113,7 +114,7 @@ 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) &&
+        if (link_relevant(l, AF_INET6, true) &&
             l->llmnr_support != RESOLVE_SUPPORT_NO &&
             l->manager->llmnr_support != RESOLVE_SUPPORT_NO &&
             socket_ipv6_is_supported()) {
@@ -125,7 +126,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->llmnr_ipv6_scope = dns_scope_free(l->llmnr_ipv6_scope);
 
-        if (link_relevant(l, AF_INET) &&
+        if (link_relevant(l, AF_INET, true) &&
             l->mdns_support != RESOLVE_SUPPORT_NO &&
             l->manager->mdns_support != RESOLVE_SUPPORT_NO) {
                 if (!l->mdns_ipv4_scope) {
@@ -136,7 +137,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->mdns_ipv4_scope = dns_scope_free(l->mdns_ipv4_scope);
 
-        if (link_relevant(l, AF_INET6) &&
+        if (link_relevant(l, AF_INET6, true) &&
             l->mdns_support != RESOLVE_SUPPORT_NO &&
             l->manager->mdns_support != RESOLVE_SUPPORT_NO) {
                 if (!l->mdns_ipv6_scope) {
@@ -430,28 +431,35 @@ int link_update_monitor(Link *l) {
         return 0;
 }
 
-bool link_relevant(Link *l, int family) {
+bool link_relevant(Link *l, int family, bool multicast) {
         _cleanup_free_ char *state = NULL;
         LinkAddress *a;
 
         assert(l);
 
-        /* A link is relevant if it isn't a loopback or pointopoint
-         * device, has a link beat, can do multicast and has at least
-         * one relevant IP address */
+        /* A link is relevant for multicast traffic if it isn't a loopback or pointopoint device, has a link beat, can
+         * do multicast and has at least one relevant IP address */
 
-        if (l->flags & (IFF_LOOPBACK|IFF_POINTOPOINT|IFF_DORMANT))
+        if (l->flags & (IFF_LOOPBACK|IFF_DORMANT))
                 return false;
 
-        if ((l->flags & (IFF_UP|IFF_LOWER_UP|IFF_MULTICAST)) != (IFF_UP|IFF_LOWER_UP|IFF_MULTICAST))
+        if ((l->flags & (IFF_UP|IFF_LOWER_UP)) != (IFF_UP|IFF_LOWER_UP))
                 return false;
 
+        if (multicast) {
+                if (l->flags & IFF_POINTOPOINT)
+                        return false;
+
+                if ((l->flags & IFF_MULTICAST) != IFF_MULTICAST)
+                        return false;
+        }
+
         sd_network_link_get_operational_state(l->ifindex, &state);
         if (state && !STR_IN_SET(state, "unknown", "degraded", "routable"))
                 return false;
 
         LIST_FOREACH(addresses, a, l->addresses)
-                if (a->family == family && link_address_relevant(a))
+                if ((family == AF_UNSPEC || a->family == family) && link_address_relevant(a))
                         return true;
 
         return false;
diff --git a/src/resolve/resolved-link.h b/src/resolve/resolved-link.h
index db0e51d..038ede7 100644
--- a/src/resolve/resolved-link.h
+++ b/src/resolve/resolved-link.h
@@ -86,7 +86,7 @@ int link_new(Manager *m, Link **ret, int ifindex);
 Link *link_free(Link *l);
 int link_update_rtnl(Link *l, sd_netlink_message *m);
 int link_update_monitor(Link *l);
-bool link_relevant(Link *l, int family);
+bool link_relevant(Link *l, int family, bool multicast);
 LinkAddress* link_find_address(Link *l, int family, const union in_addr_union *in_addr);
 void link_add_rrs(Link *l, bool force_remove);
 
-- 
2.7.4