gbos.git/c/netd.c, branch mastergbos - a tiny Unix-flavored OS for the Game Boy Color (kernel, shell, coreutils in C, RAM filesystem)https://git.sl0p.foo/gbos.git/atom/c/netd.c?h=master2026-07-17T22:38:38Zrefactor: c/ -> usr/, compiled program blobs out of the source tree2026-07-17T22:38:38Zuseruser@clank2026-07-17T22:38:38Zurn:sha1:ba2d7ae1d7b319645b10aaa31a7f664f9f80c25c
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.
net: proper socket API in the kernel (SYS_NET) - no more SLIP in userland2026-07-17T10:39:01Zuseruser@clank2026-07-17T10:39:01Zurn:sha1:09ae37313a8b6d567a05a3ae886de78e88cd1afe
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.
net: IP stack milestone B - UDP echo (pseudo-header checksum)2026-07-17T00:05:26Zuseruser@clank2026-07-17T00:05:26Zurn:sha1:ed752bba5a5d06275531182245737600bf1f72e9
Refactor netd into a protocol dispatcher (IP -> ICMP/UDP) and add UDP echo:
swap addresses + ports and recompute the UDP checksum over the pseudo-header
(src/dst IP + proto + length) plus the datagram. This is the same pseudo-
header TCP uses, so it de-risks the next milestone.
tools/gateway.py --mode udp sends a datagram and verifies the echo.
Verified: 'hello udp gbos' echoes back with cksum=ok.
net: real IP stack, milestone A - ICMP echo (you can ping a Game Boy)2026-07-17T00:03:05Zuseruser@clank2026-07-17T00:03:05Zurn:sha1:c8c22bfc511ac65036cd8f8462e0a01757eb4372
Start of an actual TCP/IP stack on gbos (TLS stays in a proxy). netd is a
userland IP responder over SLIP: our address is 10.0.0.2, the SLIP peer
10.0.0.1. It parses IPv4 headers, answers ICMP echo requests, and rebuilds
the packet with correct IP + ICMP checksums (RFC 1071 one's-complement sum,
carry-folded - works fine on the SM83).
c/netd.c + register; tools/gateway.py gains --mode ping: it crafts ICMP echo
requests over SLIP and verifies the replies.
Verified: `netd` answers 4 pings, gateway reports reply from 10.0.0.2 with
cksum=ok for each. Next: UDP, then TCP.