wui: Allow overriding the NTP server from the settings ini

The SNTP client is hardcoded to prusa3d.pool.ntp.org and there is no
way to point it elsewhere, so a printer on a network without a route to
the internet can never obtain a time. On printers without a backup
battery this is every boot, which leaves timestamps at 1970 and breaks
TLS certificate validation for Prusa Connect deployments using
hostname/custom_cert from this same ini.

Add an ntp key to the [network] section of prusa_printer_settings.ini,
stored in the config store beside the hostname and applied after
sntp_init(), which unconditionally resets server 0 to the compiled-in
default. The setting is empty by default and loading an empty value
reverts to the default, so behaviour is unchanged for anyone who does
not set it.

BFW-6184

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: henrikosorensen

doc/prusa_printer_settings.ini

@@ -5,6 +5,13 @@ hostname=prusa
 # Printer support two dns servers. If variables are not empty, they will be used
 # even is DHCP pr AUTO type is set.
 dns4=192.168.0.1;192.168.0.2
+# Hostname or IP of the NTP server used for time synchronization. When not
+# set, the built-in default (prusa3d.pool.ntp.org) is used. Loading an
+# empty value reverts to the default. Max 30 chars.
+# A .local (mDNS) name cannot be used: the printer answers mDNS queries
+# about itself but does not resolve mDNS names. On a network with no DNS
+# server at all, an IP address is the only form that works.
+# ntp=192.168.0.1
 
 [eth::ipv4]
 # Type could be DHCP, STATIC or OFF.

lib/WUI/netif_settings.h

@@ -15,9 +15,10 @@
 #define TURN_FLAG_ON(flg)          (flg &= ~LAN_FLAG_ONOFF_POS) // flip lan switch flg to ON
 #define TURN_FLAG_OFF(flg)         (flg |= LAN_FLAG_ONOFF_POS) // flip lan switch flg to OFF
 
-#define HOSTNAME_LEN 20 // ethernet hostname MAX length
-#define SSID_MAX_LEN 32 // https://en.wikipedia.org/wiki/Service_set_(802.11_network)#SSID
-#define WIFI_PSK_MAX 64
+#define HOSTNAME_LEN   20 // ethernet hostname MAX length
+#define SSID_MAX_LEN   32 // https://en.wikipedia.org/wiki/Service_set_(802.11_network)#SSID
+#define WIFI_PSK_MAX   64
+#define NTP_SERVER_LEN 30 // NTP server hostname MAX length
 
 typedef struct {
     uint8_t flag; // lan flags: pos0 = switch(ON=0, OFF=1), pos1 = type(DHCP=0, STATIC=1)
@@ -29,6 +30,7 @@ typedef struct {
 
 typedef struct {
     char hostname[HOSTNAME_LEN + 1]; // ETH hostname: MAX 20 chars
+    char ntp_server[NTP_SERVER_LEN + 1]; // user defined NTP server hostname or IP
     ip_addr_t dns1_ip4; // user defined DNS #1
     ip_addr_t dns2_ip4; // user defined DNS #2
     lan_t lan; // user defined LAN configurations

lib/WUI/sntp/sntp_client.c

@@ -1,6 +1,7 @@
 #include "sntp.h"
 #include "sntp_client.h"
 #include "netdev.h"
+#include "wui_api.h"
 #include "tcpip.h"
 
 #include <option/has_esp.h>
@@ -10,6 +11,13 @@ void sntp_client_init(void) {
     sntp_setoperatingmode(SNTP_OPMODE_POLL);
 
     sntp_init();
+
+    // sntp_init() resets server 0 to the compiled-in default
+    // (SNTP_SERVER_ADDRESS), so the override must be applied after it.
+    const char *ntp_server = wui_get_ntp_server();
+    if (ntp_server != NULL) {
+        sntp_setservername(0, ntp_server);
+    }
 }
 
 void sntp_client_step(void) {

lib/WUI/wui_api.cpp

@@ -81,6 +81,9 @@ static int ini_handler_func(void *user, const char *section, const char *name, c
         if (ip4addr_aton(value, &tmp_config->lan.gw_ip4)) {
             tmp_config->var_mask |= ETHVAR_MSK(ETHVAR_LAN_GW_IP4);
         }
+    } else if (ini_string_match(section, "network", name, "ntp")) {
+        strlcpy(tmp_config->ntp_server, value, NTP_SERVER_LEN + 1);
+        tmp_config->var_mask |= ETHVAR_MSK(ETHVAR_NTP_SERVER);
     } else if (ini_string_match(section, "network", name, "dns4")) {
 
         if (NULL != strchr(value, ';')) {
@@ -177,6 +180,10 @@ void save_net_params(netif_config_t *ethconfig, [[maybe_unused]] ap_entry_t *ap,
     if (ethconfig->var_mask & ETHVAR_MSK(ETHVAR_HOSTNAME)) {
         store.hostname.set(ethconfig->hostname);
     }
+    if (ethconfig->var_mask & ETHVAR_MSK(ETHVAR_NTP_SERVER)) {
+        static_assert(NTP_SERVER_LEN == config_store_ns::ntp_server_size);
+        store.ntp_server.set(ethconfig->ntp_server);
+    }
 
 #if HAS_ESP()
     if (ap != NULL) {
@@ -221,6 +228,7 @@ void load_net_params(netif_config_t *ethconfig, [[maybe_unused]] ap_entry_t *ap,
     }
 
     strlcpy(ethconfig->hostname, store.hostname.get_c_str(), HOSTNAME_LEN + 1);
+    strlcpy(ethconfig->ntp_server, store.ntp_server.get_c_str(), NTP_SERVER_LEN + 1);
 
 #if HAS_ESP()
     if (ap != NULL) {
@@ -242,6 +250,11 @@ void get_MAC_address(mac_address_t *dest, uint32_t netdev_id) {
     }
 }
 
+const char *wui_get_ntp_server(void) {
+    const char *server = config_store().ntp_server.get_c_str();
+    return (server[0] != '\0') ? server : NULL;
+}
+
 void sntp_set_system_time(uint32_t sec) {
 
     // RTC_TimeTypeDef has attributes like TimeFormat (AM/PM) and DayLightSaving, which we don't use

lib/WUI/wui_api.h

@@ -47,6 +47,7 @@ typedef enum {
     ETHVAR_TIMEZONE, // int8_t, timezone
     ETHVAR_DNS1_IP4, // ip_addr_t, dns1_ip4
     ETHVAR_DNS2_IP4, // ip_addr_t, dns2_ip4
+    ETHVAR_NTP_SERVER, // char[30 + 1], ntp_server
     ETHVAR_MAC_ADDRESS, // is not included in ethconfig (used in stringifying for screen)
 
     APVAR_SSID, // char[32 + 1], ap_entry_t::ssid
@@ -114,6 +115,13 @@ void get_MAC_address(mac_address_t *dest, uint32_t netdev_id);
  ************************************************************************************************************/
 void sntp_set_system_time(uint32_t sec);
 
+/*!**********************************************************************************************************
+ * \brief Gets the user-configured NTP server, if any
+ *
+ * \return NTP server hostname or IP, or NULL when none is configured
+ ************************************************************************************************************/
+const char *wui_get_ntp_server(void);
+
 /*!********************************************************************************
  * \brief Adds time in seconds to given timestamp
  *

src/persistent_stores/store_instances/config_store/constants.hpp

@@ -17,6 +17,7 @@ inline constexpr size_t sheets_num { 8 };
 inline constexpr float z_offset_uncalibrated { std::numeric_limits<float>::max() };
 
 inline constexpr size_t lan_hostname_max_len { 20 };
+inline constexpr size_t ntp_server_size { 30 };
 inline constexpr size_t connect_host_size { 20 };
 inline constexpr size_t connect_proxy_size { 30 };
 inline constexpr size_t connect_token_size { 20 };

src/persistent_stores/store_instances/config_store/defaults.hpp

@@ -51,6 +51,7 @@ namespace defaults {
     inline constexpr TestResult test_result_unknown { TestResult::unknown };
 
     inline constexpr std::array<char, lan_hostname_max_len + 1> net_hostname { LAN_HOSTNAME_DEF };
+    inline constexpr std::array<char, ntp_server_size + 1> ntp_server { "" };
     inline constexpr int8_t lan_timezone { 1 };
     inline constexpr time_tools::TimezoneOffsetMinutes timezone_minutes { time_tools::TimezoneOffsetMinutes::no_offset };
     inline constexpr time_tools::TimezoneOffsetSummerTime timezone_summer { time_tools::TimezoneOffsetSummerTime::no_summertime };

src/persistent_stores/store_instances/config_store/store_definition.hpp

@@ -231,6 +231,8 @@ struct CurrentStore
 
     // General network settings
     StoreItem<std::array<char, lan_hostname_max_len + 1>, defaults::net_hostname, ItemFlag::network, journal::hash("Hostname")> hostname;
+    // NTP server hostname or IP; when empty, the compiled-in default is used
+    StoreItem<std::array<char, ntp_server_size + 1>, defaults::ntp_server, ItemFlag::network, journal::hash("NTP Server")> ntp_server;
 
     StoreItem<SoundMode, defaults::sound_mode, ItemFlag::user_interface, journal::hash("Sound Mode")> sound_mode;
     StoreItem<uint8_t, defaults::sound_volume, ItemFlag::user_interface, journal::hash("Sound Volume")> sound_volume;