fix(lwip): Fix mss_local is always subtract the IPv6 header size

wujiangang · wujiangang · commit 9ac70b013d7c · 2018-02-13T19:30:55.000+08:00
Fix tcp max buf size is always 1440(tw18147)

internal: 3f736959
diff --git a/VERSION b/VERSION
@@ -13,7 +13,7 @@ gwen:
 gitlab:
     espconn:    3a998034
     freertos:   ac047746
-    lwip:       bfdb6ec2
+    lwip:       24657d16
     driver:     7bee5263
     mbedtls:    1ac9f1f4
     ssl:        eefb383a
diff --git a/lib/liblwip.a b/lib/liblwip.a
diff --git a/third_party/lwip/core/tcp.c b/third_party/lwip/core/tcp.c
@@ -1787,8 +1787,10 @@ tcp_eff_send_mss_impl(u16_t sendmss, ipX_addr_t *dest
   if (mtu != 0) {
     mss_s = mtu - IP_HLEN - TCP_HLEN;
 #if LWIP_IPV6
-    /* for IPv6, substract the difference in header size */
-    mss_s -= (IP6_HLEN - IP_HLEN);
+    if (isipv6) {
+      /* for IPv6, substract the difference in header size */
+      mss_s -= (IP6_HLEN - IP_HLEN);
+    }
 #endif /* LWIP_IPV6 */
     /* RFC 1122, chap 4.2.2.6:
      * Eff.snd.MSS = min(SendMSS+20, MMS_S) - TCPhdrsize - IPoptionsize
