[openwrt/openwrt] dnsmasq: add handling of `dns-rr` to init script (add arbitrary resource records)

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/7c501e0ed2e891069b9fa0eb35a378e2ac330a44

commit 7c501e0ed2e891069b9fa0eb35a378e2ac330a44
Author: Paul Donald <newtwen+github at gmail.com>
AuthorDate: Wed Mar 27 00:43:41 2024 +0100

    dnsmasq: add handling of `dns-rr` to init script (add arbitrary resource records)
    
    Add support for handling of DNS RR (Resource Records) requests, which
    are needed for the HTTPS Type 65 records, introduced to support the
    DNS-based Service Discovery (DNS-SD) mechanism for HTTPS services and
    defined in the RFC 9460 (9.1. Query Names for HTTPS RRs).
    
    Ref: https://forum.openwrt.org/t/resolving-query-type-65-to-local-address-for-ios-clients-in-dnsmasq/179504/11
    
    uci config usage:
    
    config dnsrr
        option rrname 'foo.example.com'
        option rrnumber '65'
        option hexdata '00'
    
    hexdata is optional.
    
    Available since dnsmasq 2.62 (for around 12 years at this point).
    
    Note: dnsmasq dns-rr are not affected by filter-rr
    
    Tested on 22.03.5
    
    Signed-off-by: Paul Donald <newtwen+github at gmail.com>
    Tested-by: Vladimir Kochkovski <ask at getvladimir.com>
    Link: https://github.com/openwrt/openwrt/pull/14975
    Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
---
 .../network/services/dnsmasq/files/dnsmasq.init    | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
index cd1a16abc5..451cb674f8 100755
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -788,6 +788,29 @@ dhcp_hostrecord_add() {
 	xappend "--host-record=$record"
 }
 
+dhcp_dnsrr_add() {
+	#This adds arbitrary resource record types (of IN class) whose optional data must be hex
+	local cfg="$1"
+	local rrname rrnumber hexdata
+
+	config_get rrname "$cfg" rrname
+	[ -n "$rrname" ] || return 0
+
+	config_get rrnumber "$cfg" rrnumber
+	[ -n "$rrnumber" ] && [ "$rrnumber" -gt 0 ] || return 0
+
+	config_get hexdata "$cfg" hexdata
+
+	# dnsmasq accepts colon XX:XX:.., space XX XX .., or contiguous XXXX.. hex forms or mixtures thereof
+	if [ -n "${hexdata//[0-9a-fA-F\:\ ]/}" ]; then
+		# is invalid hex literal
+		echo "dnsmasq: \"$hexdata\" is malformed hexadecimal (separate hex with colon, space or not at all)." >&2
+		return 1
+	fi
+
+	xappend "--dns-rr=${rrname},${rrnumber}${hexdata:+,$hexdata}"
+}
+
 dhcp_relay_add() {
 	local cfg="$1"
 	local local_addr server_addr interface
@@ -1161,6 +1184,7 @@ dnsmasq_start()
 	config_foreach filter_dnsmasq match dhcp_match_add "$cfg"
 	config_foreach filter_dnsmasq domain dhcp_domain_add "$cfg"
 	config_foreach filter_dnsmasq hostrecord dhcp_hostrecord_add "$cfg"
+	config_foreach filter_dnsmasq dnsrr dhcp_dnsrr_add "$cfg"
 	[ -n "$BOOT" ] || config_foreach filter_dnsmasq relay dhcp_relay_add "$cfg"
 
 	echo >> "$CONFIGFILE_TMP"