https://gitlab.synchro.net/main/sbbs/-/commit/d5a9dd33ac68c0f3fd88906d
Modified Files:
src/ssh/design-channel-io-api.md
Log Message:
Revise channel I/O design: two models, deferred window, linear accumulation

Replace unified read/write proposal with two distinct I/O models:
- Stream API (dssh_channel_read/write) for session channels (shell/exec)
- Zero-copy callback for subsystem channels (sftp, etc.)

Key design decisions:
- Max packet size per-session (set once, used in all channel opens)
- Max window size per-channel (deferred to channel request/accept)
- Channel accept as finalization point (server callback, client function)
- Linear accumulation buffer for subsystem callbacks (no ring, no wrap)
- Flow control via natural window exhaustion during accumulation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
--- SBBSecho 3.37-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)

https://gitlab.synchro.net/main/sbbs/-/commit/4150f7036a5e39b78802cb29
Modified Files:
src/ssh/design-channel-io-api.md
Log Message:
Channel I/O design: ZC/stream split, locking, events, params builder

Squash of design iteration commits into one coherent update.

- dssh_chan_ prefix; zero-copy API uses dssh_chan_zc_
- Stream API (open/read/write/poll) built on ZC internals
- ZC API (zc_open/zc_getbuf/zc_send/zc_cancel): zero-copy TX
(app writes directly into tx_packet) and RX (callback gets
pointer into rx_packet). Zero mallocs, zero copies both directions.
- All functions except open take dssh_channel only (channel carries
session). No mismatched sess/ch pairs.
- Stream parameter (0=stdout, 1=stderr) replaces _ext variants
- Channel type as enum in params struct, not separate open functions
- Params builder: init/set_*/free, all strings copied in. Type,
max_window, pty (orthogonal to type), modes, env all in struct.
Zero terminal modes by default (library can't know terminal state).
Consumed at open time, library keeps no references.
- Events separate from data (signalfd model). poll(DSSH_POLL_EVENT)
+ read_event(), or event callback with full event struct.
Poll freezes positions; one event per cycle; uncollected discarded.
- dssh_chan_close(ch, int64_t exit_code): negative = no exit-status.
Preserves full uint32 wire range.
- dssh_chan_shutwr(ch): half-close (EOF), shutdown(SHUT_WR) semantics
- TX locking: zc_getbuf acquires tx_mtx, zc_send releases. App must
not block between them. tx_mac_scratch eliminated via 4-byte seq
prefix in tx_packet.
- RX locking: ZC callback runs with no library mutex. remote_window
and state flags are atomic.
- RX callback cannot TX (deadlock: rekey needs demux thread).
Enforced via _Thread_local bool in_zc_rx.
- Callback protection: cb_mtx per channel. Session-level defaults
copied to channel at creation time (no open-time race).
- Stream built on ZC: internal zc_cb copies to ring buffer; public
ZC functions validate, internal versions skip checks.
- No void returns for fallible functions; infallible ops (free) void.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
--- SBBSecho 3.37-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)