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handle one 6x63 data race

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This commit is contained in:
Martin Michelsen
2024-07-06 09:54:01 -07:00
parent c58b37be23
commit 21c8bab91c
4 changed files with 54 additions and 24 deletions
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src/ReceiveSubcommands.cc
+44 -21
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@@ -3724,29 +3724,52 @@ static void on_destroy_floor_item(shared_ptr<Client> c, uint8_t command, uint8_t
}
auto s = c->require_server_state();
auto fi = l->remove_item(cmd.floor, cmd.item_id, 0xFF);
auto name = s->describe_item(c->version(), fi->data, false);
l->log.info("Player %hhu destroyed floor item %08" PRIX32 " (%s)", c->lobby_client_id, cmd.item_id.load(), name.c_str());
shared_ptr<Lobby::FloorItem> fi;
try {
fi = l->remove_item(cmd.floor, cmd.item_id, 0xFF);
} catch (const out_of_range&) {
}
// Only forward to players for whom the item was visible
for (size_t z = 0; z < l->clients.size(); z++) {
auto lc = l->clients[z];
if (lc && fi->visible_to_client(z)) {
if (lc->version() != c->version()) {
G_DestroyFloorItem_6x5C_6x63 out_cmd = cmd;
switch (lc->version()) {
case Version::DC_NTE:
out_cmd.header.subcommand = is_6x5C ? 0x4E : 0x55;
break;
case Version::DC_V1_11_2000_PROTOTYPE:
out_cmd.header.subcommand = is_6x5C ? 0x55 : 0x5C;
break;
default:
out_cmd.header.subcommand = is_6x5C ? 0x5C : 0x63;
if (!fi) {
// There are generally two data races that could occur here. Either the
// player attempted to evict the item at the same time the server did (that
// is, the client's and server's 6x63 commands crossed paths on the
// network), or the player attempted to evict an item that was already
// picked up. The former case is easy to handle; we can just ignore the
// command. The latter case is more difficult - we have to know which
// player picked up the item and send a 6x2B command to the sender, to sync
// their item state with the server's again. We can't just look through the
// players' inventories to find the item ID, since item IDs can be
// destroyed when stackable items or Meseta are picked up.
// TODO: We don't actually handle the evict/pickup conflict case. This case
// is probably quite rare, but we should eventually handle it.
l->log.info("Player %hhu attempted to destroy floor item %08" PRIX32 ", but it is missing",
c->lobby_client_id, cmd.item_id.load());
} else {
auto name = s->describe_item(c->version(), fi->data, false);
l->log.info("Player %hhu destroyed floor item %08" PRIX32 " (%s)", c->lobby_client_id, cmd.item_id.load(), name.c_str());
// Only forward to players for whom the item was visible
for (size_t z = 0; z < l->clients.size(); z++) {
auto lc = l->clients[z];
if (lc && fi->visible_to_client(z)) {
if (lc->version() != c->version()) {
G_DestroyFloorItem_6x5C_6x63 out_cmd = cmd;
switch (lc->version()) {
case Version::DC_NTE:
out_cmd.header.subcommand = is_6x5C ? 0x4E : 0x55;
break;
case Version::DC_V1_11_2000_PROTOTYPE:
out_cmd.header.subcommand = is_6x5C ? 0x55 : 0x5C;
break;
default:
out_cmd.header.subcommand = is_6x5C ? 0x5C : 0x63;
}
send_command_t(lc, command, flag, out_cmd);
} else {
send_command_t(lc, command, flag, cmd);
}
send_command_t(lc, command, flag, out_cmd);
} else {
send_command_t(lc, command, flag, cmd);
}
}
}