[openwrt/openwrt] odhcp6c: use the global DHCP DUID for DHCPv6

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/7dee632beedbee923c0f993d8e332a8bb3677cc8

commit 7dee632beedbee923c0f993d8e332a8bb3677cc8
Author: David Härdeman <david at hardeman.nu>
AuthorDate: Fri Oct 10 11:43:11 2025 +0200

    odhcp6c: use the global DHCP DUID for DHCPv6
    
    odhcp6c already supports custom DUIDS on a per-interface basis.  When no client
    identifier has been set, odhcp6c will generate one on the basis of the MAC
    address of the given interface.
    
    This is contrary to how DUIDs are meant to be used, as the client identifier
    will vary from interface to interface, while it is meant to remain stable for a
    given host, no matter how the network hardware changes (see RFC8415, §11).
    
    Fix this by letting odhcp6c use the global DHCP DUID, if configured.
    
    Signed-off-by: David Härdeman <david at hardeman.nu>
    Link: https://github.com/openwrt/openwrt/pull/20359
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 package/network/ipv6/odhcp6c/files/dhcpv6.sh | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/package/network/ipv6/odhcp6c/files/dhcpv6.sh b/package/network/ipv6/odhcp6c/files/dhcpv6.sh
index e8d07ebaa7..00dd610dfa 100755
--- a/package/network/ipv6/odhcp6c/files/dhcpv6.sh
+++ b/package/network/ipv6/odhcp6c/files/dhcpv6.sh
@@ -2,6 +2,7 @@
 
 . /lib/functions.sh
 . ../netifd-proto.sh
+. /lib/config/uci.sh
 init_proto "$@"
 
 proto_dhcpv6_init_config() {
@@ -66,6 +67,7 @@ proto_dhcpv6_setup() {
 	[ -z "$reqprefix" -o "$reqprefix" = "auto" ] && reqprefix=0
 	[ "$reqprefix" != "no" ] && append opts "-P$reqprefix"
 
+	[ -z "$clientid" ] && clientid="$(uci_get network @globals[0] dhcp_default_duid)"
 	[ -n "$clientid" ] && append opts "-c$clientid"
 
 	[ "$defaultreqopts" = "0" ] && append opts "-R"