From 1f4d57d608ac62bead410e282d4e14d4085b5e6a Mon Sep 17 00:00:00 2001
From: Martine Lenders <m.lenders@fu-berlin.de>
Date: Mon, 12 Nov 2018 14:32:41 +0100
Subject: [PATCH] gnrc_ipv6_nib/arsm: ensure proper int width in backoff
calculation
Otherwise, the result might flow over on 8/16-bit platforms
---
sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c b/sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c
index 99f69f4e99..e14a6fd030 100644
--- a/sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c
+++ b/sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c
@@ -519,7 +519,8 @@ static inline uint32_t _exp_backoff_retrans_timer(uint8_t ns_sent,
/* backoff according to https://tools.ietf.org/html/rfc7048 with
* BACKOFF_MULTIPLE == 2 */
- tmp = ((1 << ns_sent) * retrans_timer * tmp) / US_PER_MS;
+ tmp = (uint32_t)(((uint64_t)(((uint32_t) 1) << ns_sent) * retrans_timer *
+ tmp) / US_PER_MS);
/* random factors were statically multiplied with 1000 ^ */
if (tmp > NDP_MAX_RETRANS_TIMER_MS) {
tmp = NDP_MAX_RETRANS_TIMER_MS;
--
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