[source] dnsmasq: add DHCP Unique Identifier for DHCPv6

[LEDE Commits]

dedeckeh pushed a commit to source.git, branch master:
https://git.lede-project.org/10f91525bc1e823a1142a4402a58e39370bdbd9b

commit 10f91525bc1e823a1142a4402a58e39370bdbd9b
Author: Arjen de Korte <build+lede at de-korte.org>
AuthorDate: Tue Dec 20 22:29:59 2016 +0100

    dnsmasq: add DHCP Unique Identifier for DHCPv6
    
    Add DHCPv6 matching by DHCP Unique Identifier (RFC-3315) in addition to
    existing MAC-address (RFC-6939). The latter is not widely supported yet.
    
    Signed-off-by: Arjen de Korte <build+lede at de-korte.org>
---
 package/network/services/dnsmasq/files/dnsmasq.init | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
index cec4b12..45fc29e 100644
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -278,6 +278,7 @@ dhcp_host_add() {
 	config_get tag "$cfg" tag
 
 	if [ "$DHCPv6CAPABLE" -eq 1 ]; then
+		config_get duid "$cfg" duid
 		config_get hostid "$cfg" hostid
 		if [ -n "$hostid" ]; then
 			hex_to_hostid hostid "$hostid"
@@ -289,7 +290,7 @@ dhcp_host_add() {
 
 	config_get leasetime "$cfg" leasetime
 
-	xappend "--dhcp-host=$macs${networkid:+,net:$networkid}${broadcast:+,set:needs-broadcast}${tag:+,set:$tag}${ip:+,$ip${hostid:+,[::$hostid]}}${name:+,$name}${leasetime:+,$leasetime}"
+	xappend "--dhcp-host=$macs${duid:+,id:$duid}${networkid:+,net:$networkid}${broadcast:+,set:needs-broadcast}${tag:+,set:$tag}${ip:+,$ip${hostid:+,[::$hostid]}}${name:+,$name}${leasetime:+,$leasetime}"
 }
 
 dhcp_tag_add() {