Server Commit system to prevent old clients from joining then desynching

src/d_clisrv.c

@@ -920,6 +920,8 @@ static void SV_SendServerInfo(INT32 node, tic_t servertime)
 	netbuffer->u.serverinfo.packetversion = PACKETVERSION;
 	netbuffer->u.serverinfo.version = VERSION;
 	netbuffer->u.serverinfo.subversion = SUBVERSION;
+	memcpy(netbuffer->u.serverinfo.commit,
+			comprevision_abbrev_bin, GIT_SHA_ABBREV);
 	strncpy(netbuffer->u.serverinfo.application, SRB2APPLICATION,
 			sizeof netbuffer->u.serverinfo.application);
 	// return back the time value so client can compute their ping
@@ -1721,6 +1723,33 @@ static boolean CL_ServerConnectionSearchTicker(tic_t *asksent)
 
 		if (client)
 		{
+#ifdef COMMITVERSION
+			// Commits do not match? Do not connect!
+			if (memcmp(serverlist[i].info.commit,
+						comprevision_abbrev_bin,
+						GIT_SHA_ABBREV))
+			{
+				char theirs[GIT_SHA_ABBREV * 2 + 1];
+				UINT8 n;
+
+				for (n = 0; n < GIT_SHA_ABBREV; ++n)
+				{
+					sprintf(&theirs[n * 2], "%02hhx",
+							serverlist[i].info.commit[n]);
+				}
+
+				D_QuitNetGame();
+				CL_Reset();
+				D_StartTitle();
+				M_StartMessage(
+							va(
+							"Connection failed.\n\nYour binary differs from the server.\n"
+							"  Yours: %.*s\n"
+							"Theirs: %s\n\n\nPress ESC\n",
+							GIT_SHA_ABBREV * 2, comprevision, theirs), NULL, MM_NOTHING);
+				return false;
+			}
+#endif
 #ifdef HAVE_CURL
 			if (serverlist[i].info.httpsource[0])
 				strncpy(http_source, serverlist[i].info.httpsource, MAX_MIRROR_LENGTH);

src/d_clisrv.h

@@ -33,7 +33,7 @@ The 'packet version' is used to distinguish packet formats.
 This version is independent of VERSION and SUBVERSION. Different
 applications may follow different packet versions.
 */
-#define PACKETVERSION 0
+#define PACKETVERSION 2
 
 // Network play related stuff.
 // There is a data struct that stores network
@@ -272,6 +272,7 @@ struct serverinfo_pak
 	char  application[MAXAPPLICATION];
 	UINT8 version;
 	UINT8 subversion;
+	UINT8 commit[GIT_SHA_ABBREV];
 	UINT8 numberofplayer;
 	UINT8 maxplayer;
 	UINT8 refusereason; // 0: joinable, 1: joins disabled, 2: full

src/d_main.cpp

@@ -111,6 +111,7 @@
 // Version numbers for netplay :upside_down_face:
 int    VERSION;
 int SUBVERSION;
+UINT8 comprevision_abbrev_bin[GIT_SHA_ABBREV];
 
 #ifdef HAVE_DISCORDRPC
 #include "discord.h"

src/doomdef.h

@@ -123,6 +123,7 @@ extern char logfilename[1024];
 /* A mod name to further distinguish versions. */
 #define SRB2APPLICATION "SRB2Kart"
 
+#define COMMITVERSION // Enable this to use add commit hash checking to client join checks.
 //#define DEVELOP // Disable this for release builds to remove excessive cheat commands and enable hash checking and stuff, all in one go. :3
 #ifdef DEVELOP
 #define VERSIONSTRING "Development EXE"
@@ -337,6 +338,15 @@ char *sizeu5(size_t num);
 // d_main.c
 extern int    VERSION;
 extern int SUBVERSION;
+
+// 4 bytes handles 8 characters of a git object SHA. At
+// around 20k commits, we only need 6 characters for a unique
+// abbreviation. Maybe in another 20k commits, more than 8
+// characters will be required! =P
+// P.S. 8 is also what comptime generates
+#define GIT_SHA_ABBREV (4)
+extern UINT8 comprevision_abbrev_bin[GIT_SHA_ABBREV];
+
 extern boolean devparm; // development mode (-debug)
 
 // m_cheat.c

src/version.h

@@ -12,4 +12,4 @@
 #define MODVERSION 11
 
 // Define this as a prerelease version suffix
-// #define BETAVERSION "Alpha"
+ #define BETAVERSION "Test Server"