From 20871acb55769a9ceccaeabca3edfefb46216bb0 Mon Sep 17 00:00:00 2001
From: xiehang <xiehang@espressif.com>
Date: Fri, 10 Jan 2020 19:19:11 +0800
Subject: [PATCH] lwip: Drop packets larger than MTU

---
 components/lwip/Kconfig         | 2 +-
 components/lwip/core/ipv4/ip4.c | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/components/lwip/Kconfig b/components/lwip/Kconfig
index 442593bfd7..fb97a7e41b 100644
--- a/components/lwip/Kconfig
+++ b/components/lwip/Kconfig
@@ -85,7 +85,7 @@ config LWIP_DHCP_MAX_NTP_SERVERS
 
 config LWIP_IP_FRAG
     bool "Enable fragment outgoing IP packets"
-    default n
+    default y
     help
         Enabling this option allows fragmenting outgoing IP packets if their size
         exceeds MTU.
diff --git a/components/lwip/core/ipv4/ip4.c b/components/lwip/core/ipv4/ip4.c
index af8bf55aef..b64498099b 100644
--- a/components/lwip/core/ipv4/ip4.c
+++ b/components/lwip/core/ipv4/ip4.c
@@ -980,6 +980,8 @@ ip4_output_if_opt_src(struct pbuf *p, const ip4_addr_t *src, const ip4_addr_t *d
   if (netif->mtu && (p->tot_len > netif->mtu)) {
     return ip4_frag(p, netif, dest);
   }
+#else
+  LWIP_ERROR("ip4_output_if: Packets larger than MTU, discarded!!!",!(netif->mtu && p->tot_len > netif->mtu),return ERR_IF;);
 #endif /* IP_FRAG */
 
   LWIP_DEBUGF(IP_DEBUG, ("ip4_output_if: call netif->output()\n"));