Add command to reset L4D2 vote cooldowns

In most versions of L4D2, players cannot call a vote (e.g. switch
campaign, change difficulty, restart campaign) more than once every 3
minutes. This makes resetting on a first map a pain, usually requiring
reloading the map to reset the vote state.

This new sst_l4d_vote_cooldown_reset command empties the list of
structures tracking vote callers, allowing all players to vote again
immediately. This should make resetting runs a lot easier on versions
without unlimited votes.

1 files changed, 134 insertions, 0 deletions

diff --git a/src/l4d2vote.c b/src/l4d2vote.c
new file mode 100644
index 0000000..06c61b8
--- /dev/null
+++ b/src/l4d2vote.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright © 2023 Willian Henrique <wsimanbrazil@yahoo.com.br>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "con_.h"
+#include "engineapi.h"
+#include "ent.h"
+#include "errmsg.h"
+#include "feature.h"
+#include "gamedata.h"
+#include "gametype.h"
+#include "intdefs.h"
+#include "mem.h"
+#include "x86.h"
+#include "x86util.h"
+
+FEATURE("Left 4 Dead 2 vote cooldown resetting")
+REQUIRE_GAMEDATA(vtidx_Spawn)
+
+static void **votecontroller = 0;
+static int off_callerrecords = 0;
+
+// Note: the vote callers vector contains these as elements. We don't currently
+// do anything with the structure, but keeping it here for reference.
+/*struct CallerRecord {
+	u32 steamid_trunc;
+	float last_time;
+	int votes_passed;
+	int votes_failed;
+	int last_issueidx;
+	bool last_passed;
+};*/
+
+DEF_CCMD_HERE_UNREG(sst_l4d2_vote_cooldown_reset,
+		"Reset vote cooldown for all players", CON_CHEAT) {
+	if (!*votecontroller) {
+		con_warn("vote controller not initialised\n");
+		return;
+	}
+	// Basically equivalent to CUtlVector::RemoveAll. The elements don't need
+	// to be destructed. This state is equivalent to when no one has voted yet
+	struct CUtlVector *recordvector = mem_offset(*votecontroller,
+			off_callerrecords);
+	recordvector->sz = 0;
+}
+
+PREINIT {
+	// note: L4D1 has sv_vote_creation_timer but it doesn't actually do anything
+	return GAMETYPE_MATCHES(L4D2) && !!con_findvar("sv_vote_creation_timer");
+}
+
+static inline bool find_votecontroller(con_cmdcbv1 listissues_cb) {
+	const uchar *insns = (const uchar *)listissues_cb;
+#ifdef _WIN32
+	// The "listissues" command calls CVoteController::ListIssues, loading
+	// g_voteController into ECX
+	for (const uchar *p = insns; p - insns < 32;) {
+		if (p[0] == X86_MOVRMW && p[1] == X86_MODRM(0, 1, 5)) {
+			votecontroller = mem_loadptr(p + 2);
+			return true;
+		}
+		NEXT_INSN(p, "g_voteController variable");
+	}
+#else
+#warning TODO(linux): this will be different
+#endif
+	return false;
+}
+
+// This finds the caller record vector using a pointer to the
+// CVoteController::Spawn function
+static inline bool find_votecallers(void *votectrlspawn) {
+	const uchar *insns = (const uchar *)votectrlspawn;
+	for (const uchar *p = insns; p - insns < 64;) {
+		// Unsure what the member on this offset actually is (the game seems to
+		// want it to be set to 0 to allow votes to happen), but the vector we
+		// want seems to consistently be 8 bytes after whatever this is
+		// "mov dword ptr [<reg> + off], 0", mod == 0b11
+		if (p[0] == X86_MOVMIW && (p[1] & 0xC0) == 0x80 &&
+				mem_load32(p + 6) == 0) {
+			off_callerrecords = mem_load32(p + 2) + 8;
+			return true;
+		}
+		NEXT_INSN(p, "vote caller record vector");
+	}
+	return false;
+}
+
+INIT {
+	struct con_cmd *cmd_listissues = con_findcmd("listissues");
+	if (!cmd_listissues) {
+		errmsg_errorx("couldn't find \"listissues\" command");
+		return false;
+	}
+	con_cmdcbv1 listissues_cb = con_getcmdcbv1(cmd_listissues);
+	if (!find_votecontroller(listissues_cb)) {
+		errmsg_errorx("couldn't find vote controller instance");
+		return false;
+	}
+
+	// g_voteController may have not been initialized yet so we get the vtable
+	// from the ent factory
+	const struct CEntityFactory *factory = ent_getfactory("vote_controller");
+	if (!factory) {
+		errmsg_errorx("couldn't find vote controller entity factory");
+		return false;
+	}
+	void **vtable = ent_findvtable(factory, "CVoteController");
+	if (!vtable) {
+		errmsg_errorx("couldn't find CVoteController vtable");
+		return false;
+	}
+	if (!find_votecallers(vtable[vtidx_Spawn])) {
+		errmsg_errorx("couldn't find vote callers vector offset");
+		return false;
+	}
+
+	con_reg(sst_l4d2_vote_cooldown_reset);
+	return true;
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80