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#!/usr/bin/env python3
"""gbhub - a virtual switch/router + DHCP for several Game Boys on one network.
Spawns N emulators, leases each a distinct IP (10.0.0.2, 10.0.0.3, ...), routes
packets between them (so they can ping/connect to *each other*), floods
broadcasts, and NATs external traffic out a TUN (so they also reach the
internet). No kernel changes: the GB just sends to a dst IP over its link and
the hub decides where it goes.
sudo tools/gbhub 2 # 2 Game Boys, one network
sudo tools/gbhub 2 netd "ping 10.0.0.2" # scripted: GB0 serves, GB1 pings it
Each positional arg after N is a console command auto-typed into that GB once it
has a lease (a test/demo hook; interactively you'd use the OSK). Requires root.
"""
import os, sys, socket, threading, subprocess, struct, fcntl, time, signal, atexit, shutil
HOME = os.path.expanduser("~" + (os.environ.get("SUDO_USER") or ""))
EMU = os.path.join(HOME, "dev/gbc/build/sl0pboy")
ROM = os.path.join(HOME, "dev/gbos/gbos.gb")
SOCK = "/tmp/gbhub.sock"
IFACE, GW, MTU = "gbtun0", b"\x0a\x00\x00\x01", 320
END, ESC, BCAST = 0xC0, 0xDB, b"\xff\xff\xff\xff"
def slip(pkt):
o = bytearray([END])
for c in pkt: o += bytes([ESC,0xDC]) if c==END else bytes([ESC,0xDD]) if c==ESC else bytes([c])
o.append(END); return bytes(o)
def _ck(d):
s = 0
for i in range(0, len(d)-1, 2): s += (d[i]<<8)|d[i+1]
if len(d)%2: s += d[-1]<<8
while s>>16: s = (s&0xFFFF)+(s>>16)
return (~s)&0xFFFF
def _dmt(dh):
p = 240
while p < len(dh) and dh[p] != 255:
if dh[p]==0: p += 1; continue
if dh[p]==53: return dh[p+2]
p += 2 + dh[p+1]
return 0
def _dreply(req, mt, gbip):
d = bytearray(240); d[0]=2; d[1]=1; d[2]=6; d[4:8]=req[4:8]
d[16:20]=gbip; d[20:24]=GW; d[28:44]=req[28:44]; d[236:240]=b"\x63\x82\x53\x63"
d += bytes([53,1,mt,54,4])+GW+bytes([255])
udp = bytearray(8); udp[1]=67; udp[3]=68; ul=8+len(d); udp[4]=ul>>8; udp[5]=ul&0xFF; udp += d
tot = 20+len(udp); ip = bytearray(20); ip[0]=0x45; ip[2]=tot>>8; ip[3]=tot&0xFF
ip[8]=64; ip[9]=17; ip[12:16]=GW; ip[16:20]=b"\xff\xff\xff\xff"
ck=_ck(ip); ip[10]=ck>>8; ip[11]=ck&0xFF
return bytes(ip)+bytes(udp)
def sh(cmd): subprocess.run(cmd, shell=True, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
conns = {} # ip(bytes) -> GB
tun = None
class GB:
def __init__(self, idx, conn):
self.idx, self.conn = idx, conn
self.ip = bytes([10,0,0,2+idx])
self.wlock = threading.Lock()
self.line = ""
def send(self, data):
with self.wlock:
try: self.conn.sendall(data)
except Exception: pass
def frame(self, pkt): self.send(slip(pkt))
def type(self, text): self.send(text.encode()) # non-framed = console input
def route(gb, fr):
if len(fr) >= 28 and fr[9] == 17: # DHCP -> answer with this GB's IP
ihl = (fr[0]&0x0f)*4
if ((fr[ihl+2]<<8)|fr[ihl+3]) == 67:
mt = _dmt(fr[ihl+8:])
if mt == 1: gb.frame(_dreply(fr[ihl+8:], 2, gb.ip))
elif mt == 3: gb.frame(_dreply(fr[ihl+8:], 5, gb.ip))
return
if len(fr) < 20: return
dst = fr[16:20]
if dst == BCAST:
for g in conns.values():
if g is not gb: g.frame(fr)
elif dst in conns:
conns[dst].frame(fr) # Game Boy -> Game Boy
elif tun is not None:
try: os.write(tun, fr) # -> internet via NAT
except Exception: pass
def gb_reader(gb):
buf, inf, esc = bytearray(), False, False
while True:
try: chunk = gb.conn.recv(2048)
except Exception: return
if not chunk: return
for c in chunk:
if c == END:
if inf and buf: route(gb, bytes(buf)); buf=bytearray(); inf=False
else: buf=bytearray(); inf=True; esc=False
elif inf:
if esc: c={0xDC:END,0xDD:ESC}.get(c,c); esc=False; buf.append(c)
elif c==ESC: esc=True
else: buf.append(c)
else: # console output -> log per GB
if c == 10:
sys.stderr.write("[GB%d] %s\n" % (gb.idx, gb.line)); sys.stderr.flush(); gb.line=""
elif 32 <= c < 127:
gb.line += chr(c)
def tun_reader():
while True:
try: pkt = os.read(tun, 2048)
except Exception: return
if len(pkt) >= 20 and pkt[16:20] in conns:
conns[pkt[16:20]].frame(pkt)
def main():
global tun
if os.geteuid() != 0: sys.exit("gbhub: run as root")
n = int(sys.argv[1]) if len(sys.argv) > 1 else 2
cmds = sys.argv[2:2+n]
tun = os.open("/dev/net/tun", os.O_RDWR)
fcntl.ioctl(tun, 0x400454ca, struct.pack("16sH", IFACE.encode(), 0x0001|0x1000))
wan = subprocess.check_output("ip route show default|awk '{print $5;exit}'", shell=True).decode().strip() or "eth0"
sh("ip addr add 10.0.0.1/24 dev %s" % IFACE); sh("ip link set %s mtu %d up" % (IFACE, MTU))
sh("sysctl -w net.ipv4.ip_forward=1")
sh("iptables -t nat -C POSTROUTING -s 10.0.0.0/24 -o %s -j MASQUERADE || iptables -t nat -A POSTROUTING -s 10.0.0.0/24 -o %s -j MASQUERADE" % (wan, wan))
sh("iptables -C FORWARD -i %s -j ACCEPT || iptables -I FORWARD -i %s -j ACCEPT" % (IFACE, IFACE))
sh("iptables -C FORWARD -o %s -j ACCEPT || iptables -I FORWARD -o %s -j ACCEPT" % (IFACE, IFACE))
def cleanup():
sh("iptables -t nat -D POSTROUTING -s 10.0.0.0/24 -o %s -j MASQUERADE" % wan)
sh("iptables -D FORWARD -i %s -j ACCEPT" % IFACE); sh("iptables -D FORWARD -o %s -j ACCEPT" % IFACE)
atexit.register(cleanup)
try: os.unlink(SOCK)
except Exception: pass
srv = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM); srv.bind(SOCK); srv.listen(n)
emus = []
for i in range(n):
rom = "/tmp/gbhub_%d.gb" % i # per-GB ROM so battery saves don't clash
shutil.copyfile(ROM, rom)
emus.append(subprocess.Popen([EMU, "--headless", "--uncapped", "--serial-sock", SOCK, rom],
stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL,
start_new_session=True))
sys.stderr.write("[gbhub] %d Game Boys on 10.0.0.0/24 (10.0.0.2..%d), NAT via %s\n" % (n, 1+n, wan))
srv.settimeout(10)
for i in range(n):
conn, _ = srv.accept(); gb = GB(i, conn); conns[gb.ip] = gb
threading.Thread(target=gb_reader, args=(gb,), daemon=True).start()
threading.Thread(target=tun_reader, daemon=True).start()
time.sleep(2.0) # let DHCP settle
for i in range(n):
if i < len(cmds) and cmds[i]:
conns[bytes([10,0,0,2+i])].type(cmds[i] + "\n")
def stop(*a):
for e in emus:
try: os.killpg(os.getpgid(e.pid), signal.SIGKILL)
except Exception: pass
sys.exit(0)
signal.signal(signal.SIGTERM, stop)
try:
while all(e.poll() is None for e in emus): time.sleep(0.3)
except KeyboardInterrupt: pass
finally: stop()
if __name__ == "__main__":
main()
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