From: Sergey Bugaev <bugaevc@gmail.com>
Date: Fri, 19 Feb 2021 12:29:02 +0000 (+0300)
Subject: resolved: don't discard mDNS queries with bad flags
X-Git-Tag: v248-rc3~121
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2aaf3765974c9f340c0c3d705e9f0609073cf83c;p=thirdparty%2Fsystemd.git

resolved: don't discard mDNS queries with bad flags

Even though RFC 6762 specifies these bits MUST be zero, it also says they MUST
be ignored on reception.
---

diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index a51514a8de8..9778f5ee6b5 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -326,13 +326,10 @@ int dns_packet_validate_query(DnsPacket *p) {
                 break;
 
         case DNS_PROTOCOL_MDNS:
-                /* RFC 6762, Section 18 */
-                if (DNS_PACKET_AA(p)    != 0 ||
-                    DNS_PACKET_RD(p)    != 0 ||
-                    DNS_PACKET_RA(p)    != 0 ||
-                    DNS_PACKET_AD(p)    != 0 ||
-                    DNS_PACKET_CD(p)    != 0 ||
-                    DNS_PACKET_RCODE(p) != 0)
+                /* RFC 6762, Section 18 specifies that messages with non-zero RCODE
+                 * must be silently ignored, and that we must ignore the values of
+                 * AA, RD, RA, AD, and CD bits. */
+                if (DNS_PACKET_RCODE(p) != 0)
                         return -EBADMSG;
 
                 break;