From: Cristian Rodríguez <cristian@rodriguez.im>
Date: Fri, 7 Apr 2023 07:52:52 +0000 (-0400)
Subject: resolve: change DNS_PACKET_UNICAST_SIZE_LARGE_MAX to 1232 (#27171)
X-Git-Tag: v254-rc1~791
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e144a26306dbe07fe37f294301421a938b781247;p=thirdparty%2Fsystemd.git

resolve: change DNS_PACKET_UNICAST_SIZE_LARGE_MAX to 1232 (#27171)

The old common default was 4096, until 2020 on which all DNS servers (verified
on BIND9, NSD, Unbound, dnsmasq) switched to 1232 as an agreed max size [1].

[1] https://www.dnsflagday.net/2020/#message-size-considerations
---

diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index 505e3e7ba94..e4d3e94c683 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -55,8 +55,8 @@ assert_cc(sizeof(DnsPacketHeader) == 12);
 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
 #define DNS_PACKET_UNICAST_SIZE_MAX 512u
 
-/* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
-#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
+/* With EDNS0 we can use larger packets, default to 1232, which is what is commonly used */
+#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 1232u
 
 struct DnsPacket {
         unsigned n_ref;