From ba3b04e7fed52415c5d5cdd1ee4e5a15e6d2ec7e Mon Sep 17 00:00:00 2001
From: Dirk Ziegelmeier <dziegelmeier@de.pepperl-fuchs.com>
Date: Thu, 28 Mar 2019 08:16:29 +0100
Subject: [PATCH] Add #define for minimum IPv6 MTU length

---
 src/core/ipv6/nd6.c         | 4 ++--
 src/include/lwip/prot/ip6.h | 2 ++
 src/netif/lowpan6.c         | 2 +-
 src/netif/lowpan6_ble.c     | 2 +-
 4 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/core/ipv6/nd6.c b/src/core/ipv6/nd6.c
index d65ed4e1..81992fa3 100644
--- a/src/core/ipv6/nd6.c
+++ b/src/core/ipv6/nd6.c
@@ -693,7 +693,7 @@ nd6_input(struct pbuf *p, struct netif *inp)
         }
         mtu_opt = (struct mtu_option *)buffer;
         mtu32 = lwip_htonl(mtu_opt->mtu);
-        if ((mtu32 >= 1280) && (mtu32 <= 0xffff)) {
+        if ((mtu32 >= IP6_MIN_MTU_LENGTH) && (mtu32 <= 0xffff)) {
 #if LWIP_ND6_ALLOW_RA_UPDATES
           if (inp->mtu) {
             /* don't set the mtu for IPv6 higher than the netif driver supports */
@@ -2312,7 +2312,7 @@ nd6_get_destination_mtu(const ip6_addr_t *ip6addr, struct netif *netif)
     return netif_mtu6(netif);
   }
 
-  return 1280; /* Minimum MTU */
+  return IP6_MIN_MTU_LENGTH; /* Minimum MTU */
 }
 
 
diff --git a/src/include/lwip/prot/ip6.h b/src/include/lwip/prot/ip6.h
index 0f6de455..7df81edd 100644
--- a/src/include/lwip/prot/ip6.h
+++ b/src/include/lwip/prot/ip6.h
@@ -44,6 +44,8 @@
 extern "C" {
 #endif
 
+#define IP6_MIN_MTU_LENGTH 1280
+
 /** This is the packed version of ip6_addr_t,
     used in network headers that are itself packed */
 #ifdef PACK_STRUCT_USE_INCLUDES
diff --git a/src/netif/lowpan6.c b/src/netif/lowpan6.c
index 7f0d2767..5e6f0097 100644
--- a/src/netif/lowpan6.c
+++ b/src/netif/lowpan6.c
@@ -881,7 +881,7 @@ lowpan6_if_init(struct netif *netif)
   MIB2_INIT_NETIF(netif, snmp_ifType_other, 0);
 
   /* maximum transfer unit */
-  netif->mtu = 1280;
+  netif->mtu = IP6_MIN_MTU_LENGTH;
 
   /* broadcast capability */
   netif->flags = NETIF_FLAG_BROADCAST /* | NETIF_FLAG_LOWPAN6 */;
diff --git a/src/netif/lowpan6_ble.c b/src/netif/lowpan6_ble.c
index d89816d3..6de0ae32 100644
--- a/src/netif/lowpan6_ble.c
+++ b/src/netif/lowpan6_ble.c
@@ -417,7 +417,7 @@ rfc7668_if_init(struct netif *netif)
   MIB2_INIT_NETIF(netif, snmp_ifType_other, 0);
 
   /* maximum transfer unit, set according to RFC7668 ch2.4 */
-  netif->mtu = 1280;
+  netif->mtu = IP6_MIN_MTU_LENGTH;
 
   /* no flags set (no broadcast, ethernet,...)*/
   netif->flags = 0;