[PATCH v6 1/3] dnsmasq: distinct Ubus names for multiple instances

[Etan Kissling]

Currently, when using multiple dnsmasq instances they are all assigned
to the same Ubus instance name. This does not work, as only a single
instance can register with Ubus at a time. In the log, this leads to
`Cannot add object to UBus: Invalid argument` error messages.
Furthermore, upstream 3c93e8eb41952a9c91699386132d6fe83050e9be changes
behaviour so that instead of the log, dnsmasq crashes instead.
This means that dnsmasq versions v2.86test2 and newer no longer apply.

With this patch, all dnsmasq instances are assigned unique names so that
they can register with Ubus concurrently. One of the enabled instances
is always assigned the previous default name "dnsmasq" to avoid breaking
backwards compatibility with other software relying on that default.
Previously, a random instance got assigned that name (while the others
produced error logs). Now, the first unnamed dnsmasq config section is
assigned the default name. If there are no unnamed dnsmasq sections the
first encountered named dnsmasq config section is assigned instead.

A similar issue exists for Dbus and was similarly addressed.

Signed-off-by: Etan Kissling <etan.kissling at gmail.com>
---
v5: Introduce this patch so that dnsmasq can be updated.
v6: Improve heuristic to always assign default name to one instance.
    Extend patch for Dbus.

* Disabled instances are ignored for sake of instance name assignment.
* Single unnamed section (default config) -> default name.
* Single named section -> default name.
* Multiple named sections -> First enabled one gets default.
* Unnamed sections + Named sections -> First unnamed section default.

 .../services/dnsmasq/files/dnsmasq.init       | 32 +++++++++++++++++--
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
index 44e7d2d4f9..c4c262ad69 100644
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -161,7 +161,7 @@ append_server() {
 }
 
 append_rev_server() {
-        xappend "--rev-server=$1"
+	xappend "--rev-server=$1"
 }
 
 append_address() {
@@ -878,8 +878,16 @@ dnsmasq_start()
 	append_bool "$cfg" noresolv "--no-resolv"
 	append_bool "$cfg" localise_queries "--localise-queries"
 	append_bool "$cfg" readethers "--read-ethers"
-	append_bool "$cfg" dbus "--enable-dbus"
-	append_bool "$cfg" ubus "--enable-ubus"	1
+
+	local instance_name="dnsmasq.$cfg"
+	if [ "$cfg" = "$DEFAULT_INSTANCE" ]; then
+		instance_name="dnsmasq"
+	fi
+	config_get_bool dbus "$cfg" "dbus" 0
+	[ $dbus -gt 0 ] && xappend "--enable-dbus=uk.org.thekelleys.$instance_name"
+	config_get_bool ubus "$cfg" "ubus" 1
+	[ $ubus -gt 0 ] && xappend "--enable-ubus=$instance_name"
+
 	append_bool "$cfg" expandhosts "--expand-hosts"
 	config_get tftp_root "$cfg" "tftp_root"
 	[ -n "$tftp_root" ] && mkdir -p "$tftp_root" && append_bool "$cfg" enable_tftp "--enable-tftp"
@@ -1160,6 +1168,7 @@ boot()
 start_service() {
 	local instance="$1"
 	local instance_found=0
+	local first_instance=""
 
 	. /lib/functions/network.sh
 
@@ -1170,10 +1179,27 @@ start_service() {
 			if [ -n "$instance" ] && [ "$instance" = "$name" ]; then
 				instance_found=1
 			fi
+			if [ -z "$DEFAULT_INSTANCE" ]; then
+				local disabled
+				config_get_bool disabled "$name" disabled 0
+				if [ "$disabled" -eq 0 ]; then
+					# First enabled section will be assigned default instance name.
+					# Unnamed sections get precedence over named sections.
+					if expr "$cfg" : 'cfg[0-9a-f]*$' >/dev/null = "9"; then # See uci_fixup_section.
+						DEFAULT_INSTANCE="$name" # Unnamed config section.
+					elif [ -z "$first_instance" ]; then
+						first_instance="$name"
+					fi
+				fi
+			fi
 		fi
 	}
 
+	DEFAULT_INSTANCE=""
 	config_load dhcp
+	if [ -z "$DEFAULT_INSTANCE" ]; then
+		DEFAULT_INSTANCE="$first_instance" # No unnamed config section was found.
+	fi
 
 	if [ -n "$instance" ]; then
 		[ "$instance_found" -gt 0 ] || return
-- 
2.30.1 (Apple Git-130)