dnsmasq/dnsmasq-2.89-edns0-size.patch

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From 9d8270be2e2b31437684f2d87add9a28a41f0c75 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Tue, 7 Mar 2023 22:07:46 +0000
Subject: [PATCH] Set the default maximum DNS UDP packet size to 1232.
http://www.dnsflagday.net/2020/ refers.
Thanks to Xiang Li for the prompt.
(cherry picked from commit eb92fb32b746f2104b0f370b5b295bb8dd4bd5e5)
---
man/dnsmasq.8 | 3 ++-
src/config.h | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/man/dnsmasq.8 b/man/dnsmasq.8
index fce580f..4b0b180 100644
--- a/man/dnsmasq.8
+++ b/man/dnsmasq.8
@@ -171,7 +171,8 @@ to zero completely disables DNS function, leaving only DHCP and/or TFTP.
.TP
.B \-P, --edns-packet-max=<size>
Specify the largest EDNS.0 UDP packet which is supported by the DNS
-forwarder. Defaults to 4096, which is the RFC5625-recommended size.
+forwarder. Defaults to 1232, which is the recommended size following the
+DNS flag day in 2020. Only increase if you know what you are doing.
.TP
.B \-Q, --query-port=<query_port>
Send outbound DNS queries from, and listen for their replies on, the
diff --git a/src/config.h b/src/config.h
index 8c41943..62b7fa1 100644
--- a/src/config.h
+++ b/src/config.h
@@ -19,7 +19,7 @@
#define CHILD_LIFETIME 150 /* secs 'till terminated (RFC1035 suggests > 120s) */
#define TCP_MAX_QUERIES 100 /* Maximum number of queries per incoming TCP connection */
#define TCP_BACKLOG 32 /* kernel backlog limit for TCP connections */
-#define EDNS_PKTSZ 4096 /* default max EDNS.0 UDP packet from RFC5625 */
+#define EDNS_PKTSZ 1232 /* default max EDNS.0 UDP packet from from /dnsflagday.net/2020 */
#define SAFE_PKTSZ 1280 /* "go anywhere" UDP packet size */
#define KEYBLOCK_LEN 40 /* choose to minimise fragmentation when storing DNSSEC keys */
#define DNSSEC_WORK 50 /* Max number of queries to validate one question */
--
2.39.2