server.h

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// ProtoCore v1.0.16 - Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
/**
 * @file server.h
 * @brief The file-transfer services RFC 4254 sec 6.5 carries, server side.
 *
 * SFTP (draft-ietf-secsh-filexfer) and SCP (rcp) are not components of SSH; they are programs the
 * connection protocol starts through a "subsystem" or "exec" request. The classifier that decides a
 * request names one of them is declared by the connection layer it hooks into
 * (ssh_classify_file_transfer_request, connection.h) and implemented here, so the dependency runs
 * upward only.
 */
 
#ifndef PROTOCORE_APP_SERVER_H
#define PROTOCORE_APP_SERVER_H
 
#include "network_drivers/presentation/ssh/connection/connection.h"
 
PROTOCORE_BEGIN_DECLS
 
/** @brief RFC 4254 sec 5.4 CHANNEL_REQUEST: the type it names, and the body that follows. */
typedef struct
{
    const uint8_t *rtype;   ///< the request type
    uint32_t rtype_len;     ///< its length
    const uint8_t *payload; ///< the request body
    size_t len;             ///< how many bytes it has
    size_t off;             ///< in/out: the request-specific argument, advanced past what was read
} SshChanReqArgs;
 
/**
 * @brief The file-transfer classifier: whether a channel request names SFTP or SCP.
 *
 * A caller sets the members the call takes, invokes it through ::SshAppServer, and reads the outcome
 * off the same handle.
 *
 * @var SshAppServerNs::slot       the SSH slot the request arrived on
 * @var SshAppServerNs::channel    the channel it names
 * @var SshAppServerNs::req        what one channel request names and carries (RFC 4254 sec 5.4)
 * @var SshAppServerNs::accept     in/out: set when an accepted SFTP subsystem flips acceptance
 * @var SshAppServerNs::classify   tag the channel and fire the matching open handler
 */
typedef struct
{
    uint8_t slot;       ///< the SSH slot the request arrived on
    uint32_t channel;   ///< the channel it names
    proto_bool accept;  ///< in/out: set when an accepted SFTP subsystem flips acceptance
    SshChanReqArgs req; ///< what one channel request names and carries
} SshAppServerVars;
 
/** @brief The operands and the outcome. */
extern SshAppServerVars SshAppServerV;
 
/** @brief The entries. */
typedef struct
{
    void (*const classify)(uint8_t *work);
} SshAppServerNs;
 
// What the table binds, defined once in the .c and taking one parameter each: everything
// else an entry needs is an operand in SshAppServerV or a region of the borrow at a fixed offset.
void protocore_ssh_app_server_classify(uint8_t *work);
 
// `static const`, initialised HERE rather than `extern` against a definition in the .c: a
// const object whose initializer every translation unit can see is a COMPILE-TIME FACT, so
// `SshAppServer.classify(work)` resolves to a named function and becomes a DIRECT call. An extern table
// leaves the call indirect and the symbol live at every level, -O2 -flto included.
static const SshAppServerNs SshAppServer __attribute__((unused)) = {
    .classify = protocore_ssh_app_server_classify,
};
 
PROTOCORE_END_DECLS
 
#endif // PROTOCORE_APP_SERVER_H