From 4a83e6dee9ae94cd28d22ada9da2241587e53a39 Mon Sep 17 00:00:00 2001
From: Gregor Richards <hg-yff@gregor.im>
Date: Thu, 22 Sep 2016 07:06:26 -0400
Subject: [PATCH] Both sides should send the same header so either can check
 the other

---
 network/netplay/netplay_common.c | 44 +++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 6 deletions(-)

diff --git a/network/netplay/netplay_common.c b/network/netplay/netplay_common.c
index 73d8ea52c3..7384771b79 100644
--- a/network/netplay/netplay_common.c
+++ b/network/netplay/netplay_common.c
@@ -144,6 +144,32 @@ bool netplay_send_info(netplay_t *netplay)
    if (!socket_send_all_blocking(netplay->fd, header, sizeof(header), false))
       return false;
 
+   if (!socket_receive_all_blocking(netplay->fd, header, sizeof(header)))
+   {
+      RARCH_ERR("%s\n",
+            msg_hash_to_str(MSG_FAILED_TO_RECEIVE_HEADER_FROM_CLIENT));
+      return false;
+   }
+
+   if (*content_crc_ptr != ntohl(header[0]))
+   {
+      RARCH_ERR("%s\n", msg_hash_to_str(MSG_CONTENT_CRC32S_DIFFER));
+      return false;
+   }
+
+   if (netplay_impl_magic() != ntohl(header[1]))
+   {
+      RARCH_ERR("Implementations differ, make sure you're using exact same "
+            "libretro implementations and RetroArch version.\n");
+      return false;
+   }
+
+   if (mem_info.size != ntohl(header[2]))
+   {
+      RARCH_ERR("Content SRAM sizes do not correspond.\n");
+      return false;
+   }
+
    if (!netplay_send_nickname(netplay, netplay->fd))
    {
       RARCH_ERR("%s\n",
@@ -187,6 +213,18 @@ bool netplay_get_info(netplay_t *netplay)
    const void *sram          = NULL;
    size_t i;
 
+   mem_info.id = RETRO_MEMORY_SAVE_RAM;
+
+   core_get_memory(&mem_info);
+   content_get_crc(&content_crc_ptr);
+
+   header[0] = htonl(*content_crc_ptr);
+   header[1] = htonl(netplay_impl_magic());
+   header[2] = htonl(mem_info.size);
+
+   if (!socket_send_all_blocking(netplay->fd, header, sizeof(header), false))
+      return false;
+
    if (!socket_receive_all_blocking(netplay->fd, header, sizeof(header)))
    {
       RARCH_ERR("%s\n",
@@ -194,8 +232,6 @@ bool netplay_get_info(netplay_t *netplay)
       return false;
    }
 
-   content_get_crc(&content_crc_ptr);
-
    if (*content_crc_ptr != ntohl(header[0]))
    {
       RARCH_ERR("%s\n", msg_hash_to_str(MSG_CONTENT_CRC32S_DIFFER));
@@ -209,10 +245,6 @@ bool netplay_get_info(netplay_t *netplay)
       return false;
    }
 
-   mem_info.id = RETRO_MEMORY_SAVE_RAM;
-
-   core_get_memory(&mem_info);
-
    if (mem_info.size != ntohl(header[2]))
    {
       RARCH_ERR("Content SRAM sizes do not correspond.\n");