From 9433484c244bd1fef70fbdae3ddb60267e69f37d Mon Sep 17 00:00:00 2001
From: Parminder Singh <61920513+parmi93@users.noreply.github.com>
Date: Fri, 16 Jun 2023 10:19:50 +0000
Subject: [PATCH] Use lwm2m_seed() to get the seed

The lwm2m_seed() function is used to obtain a seed for random number
generation.
The implementation of the lwm2m_seed() function is up to the user.
---
 core/liblwm2m.c            |  2 +-
 examples/shared/platform.c | 10 ++++++++++
 include/liblwm2m.h         |  2 ++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/core/liblwm2m.c b/core/liblwm2m.c
index 8a2d69ec1..205e5428b 100644
--- a/core/liblwm2m.c
+++ b/core/liblwm2m.c
@@ -68,7 +68,7 @@ lwm2m_context_t * lwm2m_init(void * userData)
     {
         memset(contextP, 0, sizeof(lwm2m_context_t));
         contextP->userData = userData;
-        srand((int)lwm2m_gettime());
+        srand(lwm2m_seed());
         contextP->nextMID = rand();
     }
 
diff --git a/examples/shared/platform.c b/examples/shared/platform.c
index ab8090bb1..608869157 100644
--- a/examples/shared/platform.c
+++ b/examples/shared/platform.c
@@ -67,6 +67,16 @@ time_t lwm2m_gettime(void)
     return time(NULL);
 }
 
+int lwm2m_seed(void) {
+    /*
+     * Return a seed for random number generation, the seed must be a
+     * different number at every boot and unpredictable, time(NULL) may not be
+     * a reliable source as a seed.
+     * See: https://github.com/eclipse/wakaama/pull/711
+     */
+    return time(NULL);
+}
+
 void lwm2m_printf(const char * format, ...)
 {
     va_list ap;
diff --git a/include/liblwm2m.h b/include/liblwm2m.h
index 85da067d9..84fc5790a 100644
--- a/include/liblwm2m.h
+++ b/include/liblwm2m.h
@@ -118,6 +118,8 @@ int lwm2m_strcasecmp(const char * str1, const char * str2);
 // In case of error, this must return a negative value.
 // Per POSIX specifications, time_t is a signed integer.
 time_t lwm2m_gettime(void);
+// Get a seed (which must not repeat when the device reboots) for generating a random number
+int lwm2m_seed(void);
 
 #ifdef LWM2M_WITH_LOGS
 // Same usage as C89 printf()