From 4b531a6333340c2702e98c5504cd9d7a712f4eea Mon Sep 17 00:00:00 2001
From: Dong Heng <dongheng@espressif.com>
Date: Thu, 30 Aug 2018 16:17:05 +0800
Subject: [PATCH] fix(lwip): Fix UDP send more than 1472 bytes

---
 components/lwip/lwip/src/core/udp.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/components/lwip/lwip/src/core/udp.c b/components/lwip/lwip/src/core/udp.c
index ce2e3d29..34bb18e6 100644
--- a/components/lwip/lwip/src/core/udp.c
+++ b/components/lwip/lwip/src/core/udp.c
@@ -516,6 +516,19 @@ udp_sendto_chksum(struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *dst_ip,
   struct netif *netif;
   const ip_addr_t *dst_ip_route = dst_ip;
 
+  /**
+   * UDP max payload = MTU(1500 now) - IP head(20) - UDP head(8) = 1472
+   *
+   * We test that LWIP send 1473 bytes data, linux can cacth these but windows can't.
+   *
+   * If enable IP_FRAG option, these data should be fragmented at IP layer..
+   */
+#if ESP_LWIP && !IP_FRAG
+  if (p && p->tot_len > 1472) {
+    return ERR_VAL;
+  }
+#endif
+
   if ((pcb == NULL) || (dst_ip == NULL) || !IP_ADDR_PCB_VERSION_MATCH(pcb, dst_ip)) {
     return ERR_VAL;
   }