resolve: refuse mdns scope for ipv4 broadcast addresses

This query can never be answered, so let's no wait for it to timeout.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index c95875ec10..45f1d36311 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -556,6 +556,9 @@ static DnsScopeMatch match_subnet_reverse_lookups(
         if (s->family != AF_UNSPEC && f != s->family)
                 return _DNS_SCOPE_MATCH_INVALID; /* Don't look for IPv4 addresses on LLMNR/mDNS over IPv6 and vice versa */
 
+        if (in_addr_is_null(f, &ia))
+                return DNS_SCOPE_NO;
+
         LIST_FOREACH(addresses, a, s->link->addresses) {
 
                 if (a->family != f)
@@ -569,6 +572,10 @@ static DnsScopeMatch match_subnet_reverse_lookups(
                 if (a->prefixlen == UCHAR_MAX) /* don't know subnet mask */
                         continue;
 
+                /* Don't send mDNS queries for the IPv4 broadcast address */
+                if (f == AF_INET && in_addr_equal(f, &a->in_addr_broadcast, &ia) > 0)
+                        return DNS_SCOPE_NO;
+
                 /* Check if the address is in the local subnet */
                 r = in_addr_prefix_covers(f, &a->in_addr, a->prefixlen, &ia);
                 if (r < 0)