From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 8 Nov 2023 12:35:12 +0000 (+0900)
Subject: resolve/mdns: allow mDNS queries with truncation flag
X-Git-Tag: v255-rc2~74^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6f087266e3d0aadfc3fcc17f33c72a3079c15b2c;p=thirdparty%2Fsystemd.git

resolve/mdns: allow mDNS queries with truncation flag

If the query has many Known-Answers records, then the truncation flag is
set.

Fixes #29168.
---

diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index ecc75c6590b..ca1eea43463 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -307,13 +307,13 @@ int dns_packet_validate_query(DnsPacket *p) {
         if (DNS_PACKET_OPCODE(p) != 0)
                 return -EBADMSG;
 
-        if (DNS_PACKET_TC(p))
-                return -EBADMSG;
-
         switch (p->protocol) {
 
         case DNS_PROTOCOL_LLMNR:
         case DNS_PROTOCOL_DNS:
+                if (DNS_PACKET_TC(p)) /* mDNS query may have truncation flag. */
+                        return -EBADMSG;
+
                 /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
                 if (DNS_PACKET_QDCOUNT(p) != 1)
                         return -EBADMSG;