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Filename	Latest commit message	Latest commit date
Nexoniarz 6db9cc1230 net: closing a listening socket panicked the kernel Ctrl-C on httpd took the whole machine down: lwip assert: invalid socket state for recv callback at tcp.c:2024 #1 tcp_recv #2 inet_close #3 sockclose #4 fileclose #5 exit tcp_listen() does not put a pcb into a listening state -- it frees the connection pcb and returns a different, smaller structure, a tcp_pcb_listen, which has no recv, sent, err or poll field at all. The two are different types behind one `struct tcp_pcb *`, and the only callback a listening one has is accept. inet_close() cleared the callbacks identically for both, so on a listening socket tcp_recv() wrote past the end of the allocation. lwIP asserts rather than allowing that, and an assert here is a panic -- which means any program that listened and then exited killed the kernel, because the close path runs from exit(). A user process, ending normally, halting the system. Nothing had ever done it: until cmd/httpd nothing in the tree listened on TCP and exited. schdbgd would have found it a few days later. inet_close() now branches on is->listening -- which was already there, one field away, and the close path simply never asked. The listening case clears accept and calls tcp_close (always ERR_OK for a LISTEN pcb, and tcp_abort would be wrong on one: it reaches for connection state that does not exist). The connected case also clears `sent`, which it had been leaving set. Verified: Ctrl-C the listener, no panic, and a second httpd binds port 80 again -- which is the part that proves the pcb was actually freed. Six requests after the change, all 200. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2		2026-09-14 19:53:53 +02:00
..
architecture	net: closing a listening socket panicked the kernel	2026-09-14 19:53:53 +02:00
branding	ldls: the plan for running someone else's drivers	2026-09-14 01:51:30 +02:00
guides	docs: the tree moved and the documentation did not	2026-09-13 20:05:06 +02:00
history	kernel: processes have an environment now, and zsh is the shell	2026-09-12 23:26:50 +02:00
plan	debugger: D5, the network transport -- and the plan closes	2026-09-14 15:33:53 +02:00
Website	hybrid: H4 withdrawn -- USB is not a peripheral	2026-09-14 01:45:58 +02:00
licensing.md	userland: 268 applets, an editor, names that resolve, and a web server	2026-09-14 19:24:55 +02:00
README.md	freeze: one register for everything half-built, and the corners cleared	2026-09-13 20:28:05 +02:00

README.md

SchOS documentation

Four kinds of document, kept in four directories, because they answer four different questions and go stale at four different rates.


architecture/	What SchOS is	Present tense. Describes what is built and working.
plan/	What SchOS will be	Future tense. Everything here is unbuilt.
guides/	How to work on it	Imperative. Build it, test it, add to it.
history/	Why it is the way it is	Past tense. Bugs whose cause is not visible from the fix.

Plus two that belong to no category and apply to everything: licensing.md — read it before copying anyone else's code in — and branding/, which holds the marks and the rules for using them.

The rule that keeps this from rotting

When something is finished, it moves from plan/ to architecture/ and is rewritten as a description of the thing rather than a record of building it.

A completed item is not a ticked checkbox. A ticked checkbox says the work happened; it does not say what the work produced, and six months later the checkbox is the only thing left and it explains nothing.

So finishing a piece of work has three steps, and the third is not optional:

The code works and is tested.
The plan entry is deleted.
A description exists in architecture/ written for somebody who was not there — what it does, what shape it has, what it costs, and what it still does not do.

This is not bookkeeping. The tree has already proved it necessary: the network stack was finished, verified end to end, and for a month afterwards the only description of it anywhere was a checkbox in a roadmap, four levels of indentation deep, written in the past tense of somebody arguing for the work rather than explaining the result.

The "what it does not do" section is the one that pays. Every description in architecture/ ends with one. A document that only lists a subsystem's strengths is marketing, and the reader who most needs the document is the one about to trip over a limitation nobody wrote down.

Start here

New to the tree → architecture/README.md, the system layer by layer, then guides/layout.md for where the files are.

Trying to build it → guides/building.md.

Wondering what happens next → plan/1.0.md, which is the finish line and the register of everything half-built. Then plan/README.md for the order.

About to start something new → the register, first. Nothing new starts while it has rows in it, and a row leaves only by being finished or deleted.

Something is broken and it feels familiar → history/. There is a good chance it is in there.

architecture/ — what SchOS is


README	The system, layer by layer. Read first.
boot.md	Firmware to the first userspace process.
kernel.md	SchIFT: memory, processes, scheduling, traps, signals, SMP.
syscalls.md	The call table, and the Linux personality that lets real software run.
filesystem.md	The VFS, the buffer cache, procfs, mounts.
schfs.md	SchFS: the copy-on-write root filesystem.
devices.md	The device model, driver binding, the class vtables.
usb.md	xHCI, the USB core, and the class drivers.
graphics.md	Framebuffer, text rendering, console, and the crash screen.
terminals.md	The six virtual terminals, and how one is switched to.
networking.md	Drivers, lwIP, sockets — Unix and INET.
init.md	`schinit`, PID 1 as a role, and the job manifests.

plan/ — what SchOS will be


README	The three current decisions and the order they happen in.
1.0.md	The finish line, and the freeze. What 1.0 contains, what is deferred, and the register of every half-built thing in the tree.
foundations.md	The kernel work everything else is blocked on.
wayland.md	The GUI stack, and what gets deleted to make room.
hybrid.md	Moving drivers out of the kernel.
schapi.md	The long-term API layering, and the compatibility promise.
roadmap.md	Everything else still open.

guides/ — how to work on it


building.md	Prerequisites and the build, per host.
testing.md	The harnesses, and what each one actually proves.
layout.md	Repository map, and how to add a program or a port.
adding-a-driver.md	Writing one, binding it, publishing its class vtable.

branding/ — the marks


README	Shift the logo, Guru the icon, SchCotie the mascot: what each is for, the colour rule, and why a raster is committed next to its SVG.

history/ — why it is the way it is


README	What belongs in here and what does not.
kernel.md	Bugs whose cause was nowhere near their symptom.
schfs.md	The filesystem's own, from the same period as its design.
moving-to-linux.md	The Windows-to-Fedora move, kept for the parts that recur.

Writing one of these

Four conventions, all of them observable in the existing files:

State the cost. Every design choice gave something up. A document that does not say what is a document that will be argued with later by somebody who only sees the downside.

Prefer the measured number to the remembered one. "500 of 3565 files carry the advertising clause" is worth more than "some do", and it was worth the minute it took to count.

Write down the bug that shaped it. Half the non-obvious code in this tree is non-obvious because something failed once. If a design is strange, the strangeness is load-bearing and the reader deserves to know why before changing it.

No dates in headings. A date in a heading turns a description into a changelog, and the description is the thing with a long life. Dates belong in history/, where they mean something.