https://github.com/esp8266/Arduino/pull/6373

core.patch

diff --git a/tools/sdk/lwip2/include/lwipopts.h b/tools/sdk/lwip2/include/lwipopts.h
index 22acb6b4..fcd7ba4e 100644
--- a/tools/sdk/lwip2/include/lwipopts.h
+++ b/tools/sdk/lwip2/include/lwipopts.h
@@ -3571,9 +3571,9 @@ extern "C" {
 #define SNTP_SET_SYSTEM_TIME_US(t,us)  do { struct timeval tv = { t, us }; settimeofday(&tv, NULL); } while (0)

 #define SNTP_UPDATE_DELAY_DEFAULT 3600000
-#define SNTP_SUPPRESS_DELAY_CHECK 1
-#define SNTP_UPDATE_DELAY sntp_update_delay_not_less_than_15000
-extern uint32_t SNTP_UPDATE_DELAY;
+#define SNTP_SUPPRESS_DELAY_CHECK 1      // suppress sntp preprocessor checking that this value is below 15000
+#define SNTP_UPDATE_DELAY custom_sntp_update_delay_func()
+extern uint32_t custom_sntp_update_delay_func(void);

 #if LWIP_FEATURES
 // lwip-1.4 had 3 possible SNTP servers (constant was harcoded)
@@ -3589,7 +3589,10 @@ extern uint32_t SNTP_UPDATE_DELAY;
  * This can be defined to a random generation function,
  * which must return the delay in milliseconds as u32_t.
  */
-#define SNTP_STARTUP_DELAY              0
+
+#define SNTP_STARTUP_DELAY              1
+#define SNTP_STARTUP_DELAY_FUNC         custom_sntp_startup_delay_func()
+extern uint32_t custom_sntp_startup_delay_func(void);

 /*
    --------------------------------------------------

linklayer.patch

diff --git a/glue-lwip/lwip-git.c b/glue-lwip/lwip-git.c
index 566e813..3441bb5 100644
--- a/glue-lwip/lwip-git.c
+++ b/glue-lwip/lwip-git.c
@@ -65,7 +65,13 @@ const char netif_name[2][8] = { "station", "soft-ap" };

 int __attribute__((weak)) doprint_allow = 0; // for doprint()

-uint32_t sntp_update_delay_not_less_than_15000 = SNTP_UPDATE_DELAY_DEFAULT;
+uint32_t __attribute__((weak)) custom_sntp_update_delay_func() {
+    return SNTP_UPDATE_DELAY_DEFAULT;
+}
+
+uint32_t __attribute__((weak)) custom_sntp_startup_delay_func() {
+    return (LWIP_RAND() % 5000); 
+}

 err_t glue2git_err (err_glue_t err)
 {