From 2694486309b1839b151dfa936b8f725c65954c68 Mon Sep 17 00:00:00 2001
From: Knut Andre Tidemann <Knut.Andre.Tidemann@jotron.com>
Date: Wed, 11 Jan 2017 12:11:20 +0100
Subject: [PATCH] lwip: fix broken default ICMPv6 handling of checksums.

ICMPv6 should always have checksum generated for it as per RFC 3542
chapter 3.1.

(cherry picked from commit 5e9df2c6988f8e00185e793205f371fe817714e9)
---
 src/api/api_msg.c | 8 ++++++++
 src/api/sockets.c | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index 4927ee50..b45d23f8 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -53,6 +53,7 @@
 #include "lwip/dns.h"
 #include "lwip/mld6.h"
 #include "lwip/priv/tcpip_priv.h"
+#include "lwip/sockets.h"
 
 #include <string.h>
 
@@ -562,6 +563,13 @@ pcb_new(struct api_msg *msg)
   case NETCONN_RAW:
     msg->conn->pcb.raw = raw_new_ip_type(iptype, msg->msg.n.proto);
     if (msg->conn->pcb.raw != NULL) {
+#if LWIP_IPV6
+      /* ICMPv6 packets should always have checksum calculated by the stack as per RFC 3542 chapter 3.1 */
+      if (NETCONNTYPE_ISIPV6(msg->conn->type) && msg->conn->pcb.raw->protocol == IPPROTO_ICMPV6) {
+        msg->conn->pcb.raw->chksum_reqd = 1;
+        msg->conn->pcb.raw->chksum_offset = 2;
+      }
+#endif /* LWIP_IPV6 */
       raw_recv(msg->conn->pcb.raw, recv_raw, msg->conn);
     }
     break;
diff --git a/src/api/sockets.c b/src/api/sockets.c
index 24b3b5fa..0d0a1fa1 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -2574,6 +2574,12 @@ lwip_setsockopt_impl(int s, int level, int optname, const void *optval, socklen_
     switch (optname) {
 #if LWIP_IPV6 && LWIP_RAW
     case IPV6_CHECKSUM:
+      /* It should not be possible to disable the checksum generation with ICMPv6
+       * as per RFC 3542 chapter 3.1 */
+      if(sock->conn->pcb.raw->protocol == IPPROTO_ICMPV6) {
+        return EINVAL;
+      }
+
       LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, int, NETCONN_RAW);
       if (*(const int *)optval < 0) {
         sock->conn->pcb.raw->chksum_reqd = 0;