From: David Härdeman <david@hardeman.nu>
Date: Fri, 26 Sep 2025 17:22:34 +0000 (+0200)
Subject: dhcpv4: allow lease takeover (bugfix)
X-Git-Url: http://git.openwrt.org/?a=commitdiff_plain;h=bc9f9d93d4d6b8feb7b19235d7f0371480fc679d;p=project%2Fodhcpd.git

dhcpv4: allow lease takeover (bugfix)

Multiple MAC addresses are supported per static lease (congruent to dnsmasq)
Request on different MAC frees any old assignments for a given lease.

Signed-off-by: David Härdeman <david@hardeman.nu>
---

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 1ae7254..5d7e08a 100644
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -1111,6 +1111,20 @@ dhcpv4_lease(struct interface *iface, enum dhcpv4_msg msg, const uint8_t *mac,
 	struct lease *l = config_find_lease_by_mac(mac);
 	time_t now = odhcpd_time();
 
+	/*
+	 * If we found a static lease cfg, but no old assignment for this
+	 * hwaddr, we need to clear out any old assignments given to other
+	 * hwaddrs in order to take over the IP address.
+	 */
+	if (l && !a && (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST)) {
+		struct dhcp_assignment *c, *tmp;
+
+		list_for_each_entry_safe(c, tmp, &l->assignments, lease_list) {
+			if (c->flags & OAF_DHCPV4 && c->flags & OAF_STATIC)
+				free_assignment(c);
+		}
+	}
+
 	if (l && a && a->lease != l) {
 		free_assignment(a);
 		a = NULL;