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Userland sources live in usr/ (fits the Unix theme better than 'c').
SDCC output .bin blobs land in build/usr/ with the other build artifacts
instead of littering the source dir; programs.asm INCBINs them from there.
Byte-identical ROM.
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Pinging sl0p.foo through gbhub looked hung: DNS resolved, then nothing.
Packet-tracing showed the echo request leaving the hub's TUN and eth0
correctly NATed every time - but 80.78.19.56 blackholes ICMP for all
ids in windows of tens of seconds (provider rate limiting). One lost
reply wedged ping for minutes because net_recv's pump-counted timeout
is effectively unbounded at native emulation speed.
Two fixes:
- NET_RECVNB (op 8): non-blocking recv - one RX pump, $FE if nothing
buffered, same delivery/EOF semantics as NET_RECV otherwise. ping now
waits <=~2s per seq (net_recv_nb + msleep loop), prints 'seq=N
timeout' and moves on, like real ping.
- ICMP echo id was hardcoded $1234 for every GB, every boot, so all
sessions produced byte-identical flows - hostile to NAT conntrack
(keyed on icmp id). wNetEchoId is now our host octet + rDIV timing
noise sampled at DHCP lease, distinct per GB and per boot.
Verified: 8 back-to-back native-speed gbhub runs, zero hangs; a run
that hit a blackhole window printed seq=1 timeout then recovered to
3/4 received. GB<->GB ping and DNS/DHCP unaffected.
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ping used parse_ip only, so a hostname gave "bad address". It now uses resolve.h
(like wget/nslookup): dotted-quad is used as-is, a name is looked up via DNS
first. Copies the arg to a safe buffer before resolving (the 0xA000 arg/_DATA
overlap dance).
Verified through DHCP + NAT:
/# ping sl0p.foo
PING 80.78.19.56
reply from 80.78.19.56 seq=1 ... -- 4/4 received
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There was no time source at all (IRQ vectors just reti; scheduler is purely
cooperative). The DIV register (FF04) free-runs at 16384 Hz regardless of
interrupts, so sys_sleep accumulates DIV deltas across SchedYields (other procs
keep running) until the requested number of 1/64-second units elapse.
- SYS_SLEEP(34): B = 1/64s units; libc gsleep(units) / msleep(ms) wrappers.
- ping now msleep(800) between echoes, so it paces like real ping instead of
blasting all four at once.
Verified real-time (capped emulator): replies land ~0.85s apart. In --uncapped
runs the delay is GB-time (fast wall-clock), as expected.
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The network stack moves into the kernel. src/socket.asm owns SLIP framing,
IPv4, RFC1071 checksums, and ICMP; programs now speak a socket API through one
syscall (SYS_NET, DE=&netreq dispatched by op): net_socket/connect/send/recv/
close/poll (c/sock.h). No program touches SLIP, IP headers, or checksums.
- Socket table (4 sockets) + tx/rx buffers in WRAM0; our IP = 10.0.0.2.
- net_pump: drains the link, reassembles SLIP frames, demuxes IPv4. Inbound
ICMP echo requests are auto-answered in-kernel, so the GB replies to pings
whenever any process pumps RX.
- ICMP sockets: send() emits an echo request to the connected peer; recv()
returns the matching reply (with a spin/yield timeout).
ping.c is now a ~15-line socket client; netd.c is just `for(;;){net_poll();
yield();}`. Verified over tunbridge:
/# ping 1.1.1.1 -> replies from the real internet (kernel builds it all)
host# ping 10.0.0.2 -> 4/4, 0% loss (kernel auto-answers)
Gotchas recorded: gbos.inc isn't a make dep (touch asm after editing); this
crt0 doesn't copy initializers (fill arrays at runtime); and the arg string at
0xA000 overlaps _DATA, so parse targets must sit past it (big buffer first).
UDP and TCP sockets build on this same core next.
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New `ping [A.B.C.D]` program (PROG_PING=27, bank 29): builds and sends ICMP
echo requests from 10.0.0.2, then reads replies off the link port. It keeps
reading SLIP frames until it finds *our* echo reply, skipping the IGMP/mDNS/
SSDP multicast noise that shares 10.0.0.0/24. Reply wait uses a generous
srecv_nb spin budget since the emulator runs uncapped (no timer syscall yet).
Verified over the tunbridge (with NAT):
/# ping 10.0.0.1 -> 4/4 received, ttl=64 (the SLIP peer/host)
/# ping 1.1.1.1 -> 4/4 received, ttl=56 (Cloudflare, real net!)
ttl=56 is a real internet round trip (64 minus the hops). Combined with the
host being able to ping the GB, the Game Boy is now a full two-way ICMP host.
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