net_iface: dhcpv4: use dhcp restart

switch to dhcp_restart, when a dhcp lease is already in place, thus
forcing zephyr to ask dhcp server for a renewal of the lease

Author: andreagilardoni

libraries/SocketWrapper/SocketHelpers.cpp

@@ -10,7 +10,13 @@
 LOG_MODULE_DECLARE(sketch, LOG_LEVEL_NONE);
 
 int NetworkInterface::dhcp() {
-	net_dhcpv4_start(netif);
+	// If dhcp was never started on this interface, start it, otherwise restart it, so that we force
+	// to ask the dhcp server for a new lease
+	if (netif->config.dhcpv4.state == NET_DHCPV4_DISABLED) {
+		net_dhcpv4_start(netif);
+	} else {
+		net_dhcpv4_restart(netif);
+	}
 
 	LOG_INF("DHCPv4 started...\n");
 

loader/llext_exports.c

@@ -160,6 +160,8 @@ FORCE_EXPORT_SYM(net_mgmt_NET_REQUEST_ETHERNET_SET_MAC_ADDRESS);
 
 #if defined(CONFIG_NET_DHCPV4)
 FORCE_EXPORT_SYM(net_dhcpv4_start);
+FORCE_EXPORT_SYM(net_dhcpv4_restart);
+FORCE_EXPORT_SYM(net_dhcpv4_stop);
 #if defined(CONFIG_NET_DHCPV4_OPTION_CALLBACKS)
 FORCE_EXPORT_SYM(net_dhcpv4_add_option_callback);
 #endif