From 699153fd5213035c38a3ff3e18d8947d1c01991e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustaf=20Alh=C3=A4ll?= <gustaf@hanicef.me>
Date: Fri, 24 Apr 2026 20:24:00 -0400
Subject: [PATCH] Always accept tics received from the server

---
 src/d_clisrv.c | 71 ++++++++++++++++++++++----------------------------
 1 file changed, 31 insertions(+), 40 deletions(-)

diff --git a/src/d_clisrv.c b/src/d_clisrv.c
index 33802170e..82cb904cb 100644
--- a/src/d_clisrv.c
+++ b/src/d_clisrv.c
@@ -979,6 +979,8 @@ static boolean CL_SendJoin(void)
 		CONS_Printf(M_GetText("Sending join request...\n"));
 	netbuffer->packettype = PT_CLIENTJOIN;
 
+	neededtic = 0;
+
 	if (splitscreen)
 		localplayers += splitscreen;
 
@@ -5560,7 +5562,7 @@ static void PT_ServerTics(SINT8 node, INT32 netconsole)
 {
 	doomdata_t *netbuffer = DOOMCOM_DATA(doomcom);
 
-	UINT8 *pak, *txtpak, numtxtpak;
+	UINT8 numtxtpak;
 	tic_t realend, realstart;
 
 	if (!nodeingame[node])
@@ -5586,57 +5588,46 @@ static void PT_ServerTics(SINT8 node, INT32 netconsole)
 	realstart = ExpandTics(netbuffer->u.serverpak.starttic, maketic);
 	realend = realstart + netbuffer->u.serverpak.numtics;
 
-	txtpak = (UINT8 *)&netbuffer->u.serverpak.cmds[netbuffer->u.serverpak.numslots
-	* netbuffer->u.serverpak.numtics];
+
 
 	if (realend > gametic + CLIENTBACKUPTICS)
 		realend = gametic + CLIENTBACKUPTICS;
 	cl_packetmissed = realstart > neededtic;
 
-	if (realstart <= neededtic && realend > neededtic)
-	{
-		tic_t i, j;
-		pak = (UINT8 *)&netbuffer->u.serverpak.cmds;
+	// NOTE: we just blindly accept what we get, since it's impossible for the client to know which tic the server is on
+	UINT8 *pak = (UINT8 *)&netbuffer->u.serverpak.cmds;
+	UINT8 *txtpak = (UINT8 *)&netbuffer->u.serverpak.cmds[netbuffer->u.serverpak.numslots
+				* netbuffer->u.serverpak.numtics];
 
-		for (i = realstart; i < realend; i++)
+	for (tic_t i = realstart; i < realend; i++)
+	{
+		// clear first
+		D_Clearticcmd(i);
+
+		// copy the tics
+		pak = G_ScpyTiccmd(netcmds[i%BACKUPTICS], pak,
+			netbuffer->u.serverpak.numslots*sizeof (ticcmd_t));
+
+		// copy the textcmds
+		numtxtpak = *txtpak++;
+		for (tic_t j = 0; j < numtxtpak; j++)
 		{
-			// clear first
-			D_Clearticcmd(i);
+			INT32 playernum = *txtpak++; // playernum
+			const size_t txtsize = txtpak[0]+1;
 
-			// copy the tics
-			pak = G_ScpyTiccmd(netcmds[i%BACKUPTICS], pak,
-							   netbuffer->u.serverpak.numslots*sizeof (ticcmd_t));
-
-			// copy the textcmds
-			numtxtpak = *txtpak++;
-			for (j = 0; j < numtxtpak; j++)
+			if (playernum < 0 || playernum >= MAXPLAYERS)
 			{
-				INT32 playernum = *txtpak++; // playernum
-				const size_t txtsize = txtpak[0]+1;
-
-				if (playernum < 0 || playernum >= MAXPLAYERS)
-				{
-					CONS_Alert(CONS_WARNING, "Got bogus NetXCmd packet targetting player %d\n", playernum);
-					return;
-				}
-
-				if (i >= gametic) // Don't copy old net commands
-					memcpy(D_GetTextcmd(i, playernum), txtpak, txtsize);
-				txtpak += txtsize;
+				CONS_Alert(CONS_WARNING, "Got bogus NetXCmd packet targetting player %d\n", playernum);
+				return;
 			}
-		}
 
-		neededtic = realend;
-	}
-	else
-	{
-		DEBFILE(va("frame not in bound: %u\n", neededtic));
-		/*if (realend < neededtic - 2 * TICRATE || neededtic + 2 * TICRATE < realstart)
-		 *	I_Error("Received an out of order PT_SERVERTICS packet!\n"
-		 *			"Got tics %d-%d, needed tic %d\n\n"
-		 *			"Please report this crash on the Master Board,\n"
-		 *			"IRC or Discord so it can be fixed.\n", (INT32)realstart, (INT32)realend, (INT32)neededtic);*/
+			if (i >= gametic) // Don't copy old net commands
+				memcpy(D_GetTextcmd(i, playernum), txtpak, txtsize);
+			txtpak += txtsize;
+		}
 	}
+
+	neededtic = realend;
 }
 
 static void PT_Ping(SINT8 node, INT32 netconsole)