The lobby's BIOS identity was a two-value token, openbios or scph1001,
and scph1001 meant "some retail dump". An SCPH-5552 peer and an
SCPH-1001 peer both offered it, the host settled it, each peer booted
its own image, and the rollback boot digest never matched: about 20 s
of black window, then both players back in the lobby with no reason
(reported in #243).
Each offer now carries the CRC-32 of the retail image that peer would
boot (online bios_offer.retail_crc; LAN JOIN line 6). The host settles
retail only when every seat offers the same CRC, else OpenBIOS when
every seat links it, else refuses to start and puts the reason on the
launcher's status line ("Players use different BIOS images (SCPH-5552
and SCPH-1001) ..."). The settled CRC ships in match_caps
(session_bios_crc) and on MOTK1 START line 7, and each peer boots only a
dump with that CRC. Rooms where every peer has the same image keep
working, including SCPH-5552-only builds with no OpenBIOS. Old peers
send no CRC, so a mixed old/new room falls back to OpenBIOS or refuses;
a session from an old host still accepts any retail dump. The lobby
server relays bios_offer and match_caps as opaque objects, so it needs
no change.
The rule lives in netplay_bios_settle.c, shared by the online and LAN
paths and covered by netplay_bios_settle_test. last_error grows to fit
one sentence, with psx_lobby_set_last_error to set it.
Alexandros Mandravillis