From cde751a7ec11429464d900d013483f38a8ce2f99 Mon Sep 17 00:00:00 2001
From: Achim Kraus <achim.kraus@bosch.io>
Date: Tue, 29 Mar 2022 17:40:06 +0200
Subject: [PATCH] dtls.c, netq.c: consider 32bit time overflow.

Fixes issue: #125

Signed-off-by: Achim Kraus <achim.kraus@bosch.io>
---
 dtls.c      | 3 ++-
 dtls_time.h | 7 +++++++
 netq.c      | 3 ++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/dtls.c b/dtls.c
index 97ad5b0e..a558790e 100644
--- a/dtls.c
+++ b/dtls.c
@@ -4702,7 +4702,8 @@ dtls_check_retransmit(dtls_context_t *context, clock_time_t *next) {
   netq_t *node = netq_head(&context->sendqueue);
 
   dtls_ticks(&now);
-  while (node && node->t <= now) {
+  /* comparison considering 32bit overflow */
+  while (node && DTLS_IS_BEFORE_TIME(node->t, now)) {
     netq_pop_first(&context->sendqueue);
     dtls_retransmit(context, node);
     node = netq_head(&context->sendqueue);
diff --git a/dtls_time.h b/dtls_time.h
index f9974327..1aafa9a1 100644
--- a/dtls_time.h
+++ b/dtls_time.h
@@ -51,6 +51,7 @@
 #endif
 
 typedef uint64_t clock_time_t;
+
 #else /* WITH_CONTIKI || RIOT_VERSION */
 
 #ifdef HAVE_TIME_H
@@ -62,6 +63,7 @@ typedef uint64_t clock_time_t;
 #endif
 
 typedef uint32_t clock_time_t;
+
 #endif /* WITH_CONTIKI || RIOT_VERSION */
 
 typedef clock_time_t dtls_tick_t;
@@ -73,6 +75,11 @@ typedef clock_time_t dtls_tick_t;
 void dtls_clock_init(void);
 void dtls_ticks(dtls_tick_t *t);
 
+/* see https://godbolt.org/z/YchexKaeT */
+#define DTLS_OFFSET_TIME (((clock_time_t)~0) >> 1)
+/** Checks if A is before (or equal) B. Considers 32 bit time overflow */
+#define DTLS_IS_BEFORE_TIME(A, B) ((clock_time_t)(DTLS_OFFSET_TIME + (B)-(A)) >= DTLS_OFFSET_TIME)
+
 /** @} */
 
 #endif /* _DTLS_DTLS_TIME_H_ */
diff --git a/netq.c b/netq.c
index 06754f7a..20619543 100644
--- a/netq.c
+++ b/netq.c
@@ -93,7 +93,8 @@ netq_insert_node(netq_t **queue, netq_t *node) {
   assert(node);
 
   p = *queue;
-  while(p && p->t <= node->t) {
+  /* comparison considering 32bit overflow */
+  while(p && DTLS_IS_BEFORE_TIME(p->t, node->t)) {
     assert(p != node);
     if (p == node)
       return 0;