[openwrt/openwrt] dnsmasq: pass environment variables to hotplug

[LEDE Commits]

blogic pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/36f309af05241f09b185c6297ef6361316719b50

commit 36f309af05241f09b185c6297ef6361316719b50
Author: Chuck R <github at chuck.cloud>
AuthorDate: Sun Sep 8 14:28:06 2024 -0500

    dnsmasq: pass environment variables to hotplug
    
    dnsmasq passes a limited amount of information via DHCP script arguments. Much
    more information is available through environment variables starting with
    DNSMASQ_, such as DNSMASQ_INTERFACE. However, when the dhcp-script builds its
    JSON environment and passes it to hotplug, all of this information is discarded
    since it is not copied to the JSON environment.
    
    Personally, I have a custom-made set of DDNS scripts and rely on environment
    variables such as DNSMASQ_INTERFACE in order to determine which DNS zones
    to update. So, not being able to access these variables was detrimental to me.
    I patched in a quick copy of all DNSMASQ_ variables to the JSON environment
    so that they can be used in hotplug scripts. In order to do so I also copied
    /usr/bin/env into dnsmasq's chroot jail.
    
    Signed-off-by: Chuck R <github at chuck.cloud>
    
    Link: https://github.com/openwrt/openwrt/pull/16354
    Signed-off-by: John Crispin <john at phrozen.org>
---
 package/network/services/dnsmasq/files/dhcp-script.sh | 9 +++++++++
 package/network/services/dnsmasq/files/dnsmasq.init   | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/package/network/services/dnsmasq/files/dhcp-script.sh b/package/network/services/dnsmasq/files/dhcp-script.sh
index 470097bf6b..f0c8b50902 100755
--- a/package/network/services/dnsmasq/files/dhcp-script.sh
+++ b/package/network/services/dnsmasq/files/dhcp-script.sh
@@ -8,6 +8,15 @@ json_init
 json_add_array env
 hotplugobj=""
 
+oldIFS=$IFS
+IFS=$'\n'
+for var in $(env); do
+	if [ "${var}" != "${var#DNSMASQ_}" ]; then
+		json_add_string "" "${var%%=*}=${var#*=}"
+	fi
+done
+IFS=$oldIFS
+
 case "$1" in
 	add | del | old | arp-add | arp-del)
 		json_add_string "" "MACADDR=$2"
diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
index b864ea9069..2e07e13d36 100755
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -20,7 +20,7 @@ BASEDHCPSTAMPFILE="/var/run/dnsmasq"
 DHCPBOGUSHOSTNAMEFILE="/usr/share/dnsmasq/dhcpbogushostname.conf"
 RFC6761FILE="/usr/share/dnsmasq/rfc6761.conf"
 DHCPSCRIPT="/usr/lib/dnsmasq/dhcp-script.sh"
-DHCPSCRIPT_DEPENDS="/usr/share/libubox/jshn.sh /usr/bin/jshn /bin/ubus"
+DHCPSCRIPT_DEPENDS="/usr/share/libubox/jshn.sh /usr/bin/jshn /bin/ubus /usr/bin/env"
 
 DNSMASQ_DHCP_VER=4