[nrf fromtree] net: dhcpv4: Reset Renewal/Rebinding times on ACK

In case no Renewal/Rebinding times have been provided the server via
DHCP options, we should reset their values on ACK, so that the client
can recalculate the defaults. This is important, as the lease time may
change, so we should recalculate default T1/T2 timeout based on the new
lease time value.

Signed-off-by: Robert Lubos <[email protected]>
(cherry picked from commit 0d3a021)

Author: rlubos

subsys/net/lib/dhcpv4/dhcpv4.c

@@ -928,6 +928,8 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 	uint8_t length;
 	uint8_t type;
 	bool router_present = false;
+	bool renewal_present = false;
+	bool rebinding_present = false;
 	bool unhandled = true;
 
 	if (net_pkt_read(pkt, cookie, sizeof(cookie)) ||
@@ -1167,6 +1169,8 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 			NET_DBG("options_renewal: %u",
 				iface->config.dhcpv4.renewal_time);
 
+			renewal_present = true;
+
 			break;
 		case DHCPV4_OPTIONS_REBINDING:
 			if (length != 4U) {
@@ -1185,6 +1189,8 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 			NET_DBG("options_rebinding: %u",
 				iface->config.dhcpv4.rebinding_time);
 
+			rebinding_present = true;
+
 			break;
 		case DHCPV4_OPTIONS_SERVER_ID:
 			if (length != 4U) {
@@ -1246,6 +1252,23 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 		net_if_ipv4_set_gw(iface, &any);
 	}
 
+	if (*msg_type == NET_DHCPV4_MSG_TYPE_ACK) {
+		enum net_dhcpv4_state state = iface->config.dhcpv4.state;
+
+		/* Clear Renew/Rebind times if not provided. They need to be
+		 * recalculated accordingly.
+		 */
+		if (state == NET_DHCPV4_RENEWING || state == NET_DHCPV4_REBINDING) {
+			if (!renewal_present) {
+				iface->config.dhcpv4.renewal_time = 0U;
+			}
+
+			if (!rebinding_present) {
+				iface->config.dhcpv4.rebinding_time = 0U;
+			}
+		}
+	}
+
 	return true;
 }