klish/klish/ktp/ktpd_session.c

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <syslog.h>
#include <poll.h>
#include <sys/wait.h>

#include <faux/str.h>
#include <faux/conv.h>
#include <faux/async.h>
#include <faux/msg.h>
#include <faux/eloop.h>
#include <faux/sysdb.h>
#include <klish/ksession.h>
#include <klish/ksession_parse.h>
#include <klish/ktp.h>
#include <klish/ktp_session.h>

#define BUF_LIMIT 65536


typedef enum {
	KTPD_SESSION_STATE_DISCONNECTED = 'd',
	KTPD_SESSION_STATE_UNAUTHORIZED = 'a',
	KTPD_SESSION_STATE_IDLE = 'i',
	KTPD_SESSION_STATE_WAIT_FOR_PROCESS = 'p',
} ktpd_session_state_e;


struct ktpd_session_s {
	ksession_t *session;
	ktpd_session_state_e state;
	faux_async_t *async; // Object for data exchange with client (KTP)
	faux_hdr_t *hdr; // Engine will receive header and then msg
	faux_eloop_t *eloop; // External link, dont's free()
	kexec_t *exec;
	bool_t exit;
	bool_t stdin_must_be_closed;
};


// Static declarations
static bool_t ktpd_session_read_cb(faux_async_t *async,
	faux_buf_t *buf, size_t len, void *user_data);
static bool_t wait_for_actions_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data);
bool_t client_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data);
static bool_t ktpd_session_exec(ktpd_session_t *ktpd, const char *line,
	int *retcode, faux_error_t *error,
	bool_t dry_run, bool_t *view_was_changed);
static bool_t action_stdout_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data);
static bool_t action_stderr_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data);
static bool_t get_stream(ktpd_session_t *ktpd, int fd, bool_t is_stderr,
	bool_t process_all_data);


ktpd_session_t *ktpd_session_new(int sock, kscheme_t *scheme,
	const char *start_entry, faux_eloop_t *eloop)
{
	ktpd_session_t *ktpd = NULL;

	if (sock < 0)
		return NULL;
	if (!eloop)
		return NULL;

	ktpd = faux_zmalloc(sizeof(*ktpd));
	assert(ktpd);
	if (!ktpd)
		return NULL;

	// Init
	ktpd->state = KTPD_SESSION_STATE_UNAUTHORIZED;
	ktpd->eloop = eloop;
	ktpd->session = ksession_new(scheme, start_entry);
	if (!ktpd->session) {
		faux_free(ktpd);
		return NULL;
	}
	ktpd->exec = NULL;
	// Client can send command to close stdin but it can't be done
	// immediately because stdin buffer can still contain data. So really
	// close stdin after all data is written.
	ktpd->stdin_must_be_closed = BOOL_FALSE;
	// Exit flag. It differs from ksession done flag because KTPD session
	// can't exit immediately. It must finish current command processing
	// before really stop the event loop. Note: User defined plugin
	// function must use ksession done flag. This exit flag is internal
	// feature of KTPD session.
	ktpd->exit = BOOL_FALSE;

	// Async object
	ktpd->async = faux_async_new(sock);
	assert(ktpd->async);
	// Receive message header first
	faux_async_set_read_limits(ktpd->async,
		sizeof(faux_hdr_t), sizeof(faux_hdr_t));
	faux_async_set_read_cb(ktpd->async, ktpd_session_read_cb, ktpd);
	ktpd->hdr = NULL;
	faux_async_set_stall_cb(ktpd->async, ktp_stall_cb, ktpd->eloop);

	// Eloop callbacks
	faux_eloop_add_fd(ktpd->eloop, ktpd_session_fd(ktpd), POLLIN,
		client_ev, ktpd);
	faux_eloop_add_signal(ktpd->eloop, SIGCHLD, wait_for_actions_ev, ktpd);

	return ktpd;
}


void ktpd_session_free(ktpd_session_t *ktpd)
{
	kcontext_t *context = NULL;
	kscheme_t *scheme = NULL;

	if (!ktpd)
		return;

	// fini session for plugins
	if (ktpd->state != KTPD_SESSION_STATE_UNAUTHORIZED) {
		scheme = ksession_scheme(ktpd->session);
		context = kcontext_new(KCONTEXT_TYPE_PLUGIN_FINI);
		kcontext_set_session(context, ktpd->session);
		kcontext_set_scheme(context, scheme);
		kscheme_fini_session_plugins(scheme, context, NULL);
		kcontext_free(context);
	}

	kexec_free(ktpd->exec);
	ksession_free(ktpd->session);
	faux_free(ktpd->hdr);
	close(ktpd_session_fd(ktpd));
	faux_async_free(ktpd->async);
	faux_free(ktpd);
}


static char *generate_prompt(ktpd_session_t *ktpd)
{
	kpath_levels_node_t *iter = NULL;
	klevel_t *level = NULL;
	char *prompt = NULL;

	iter = kpath_iterr(ksession_path(ktpd->session));
	while ((level = kpath_eachr(&iter))) {
		const kentry_t *view = klevel_entry(level);
		kentry_t *prompt_entry = kentry_nested_by_purpose(view,
				KENTRY_PURPOSE_PROMPT);

		if (!prompt_entry)
			continue;

		if (kentry_actions_len(prompt_entry) > 0) {
			int rc = -1;
			bool_t res = BOOL_FALSE;

			res = ksession_exec_locally(ktpd->session,
				prompt_entry, NULL, &rc, &prompt);
			if (!res || (rc < 0) || !prompt) {
				if (prompt)
					faux_str_free(prompt);
				prompt = NULL;
			}
		}

		if (!prompt) {
			if (kentry_value(prompt_entry))
				prompt = faux_str_dup(kentry_value(prompt_entry));
		}

		if (prompt)
			break;
	}

	return prompt;
}


// Format: <key>'\0'<cmd>
static bool_t add_hotkey(faux_msg_t *msg, khotkey_t *hotkey)
{
	const char *key = NULL;
	const char *cmd = NULL;
	char *whole_str = NULL;
	size_t key_s = 0;
	size_t cmd_s = 0;

	key = khotkey_key(hotkey);
	key_s = strlen(key);
	cmd = khotkey_cmd(hotkey);
	cmd_s = strlen(cmd);

	whole_str = faux_zmalloc(key_s + 1 + cmd_s);
	memcpy(whole_str, key, key_s);
	memcpy(whole_str + key_s + 1, cmd, cmd_s);

	faux_msg_add_param(msg, KTP_PARAM_HOTKEY, whole_str, key_s + 1 + cmd_s);
	faux_free(whole_str);

	return BOOL_TRUE;
}


static bool_t add_hotkeys_to_msg(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	faux_list_t *list = NULL;
	kpath_t *path = NULL;
	kentry_hotkeys_node_t *l_iter = NULL;
	khotkey_t *hotkey = NULL;

	assert(ktpd);
	assert(msg);

	path = ksession_path(ktpd->session);
	assert(path);
	if (kpath_len(path) == 1) {
		// We don't need additional list because there is only one
		// VIEW in the path so hotkey's list is only one too. Get it.
		list = kentry_hotkeys(klevel_entry(
			(klevel_t *)faux_list_data(kpath_iter(path))));
	} else {
		faux_list_node_t *iterr = NULL;
		klevel_t *level = NULL;
		// Create temp hotkeys list to add hotkeys from all VIEWs in
		// the path and exclude duplications. Don't free elements
		// because they are just a references.
		list = faux_list_new(FAUX_LIST_UNSORTED, FAUX_LIST_UNIQUE,
			kentry_hotkey_compare, NULL, NULL);
		// Begin with the end. Because hotkeys from nested VIEWs has
		// higher priority.
		iterr = kpath_iterr(path);
		while ((level = kpath_eachr(&iterr))) {
			const kentry_t *entry = klevel_entry(level);
			kentry_hotkeys_node_t *hk_iter = kentry_hotkeys_iter(entry);
			while ((hotkey = kentry_hotkeys_each(&hk_iter)))
				faux_list_add(list, hotkey);
		}
	}

	// Add found hotkeys to msg
	l_iter = faux_list_head(list);
	while ((hotkey = (khotkey_t *)faux_list_each(&l_iter)))
		add_hotkey(msg, hotkey);

	if (kpath_len(path) != 1)
		faux_list_free(list);

	return BOOL_TRUE;
}


// Now it's not really an auth function. Just a hand-shake with client and
// passing prompt to client.
static bool_t ktpd_session_process_auth(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	ktp_cmd_e cmd = KTP_AUTH_ACK;
	uint32_t status = KTP_STATUS_NONE;
	faux_msg_t *ack = NULL;
	char *prompt = NULL;
	uint8_t retcode8bit = 0;
	struct ucred ucred = {};
	socklen_t len = sizeof(ucred);
	int sock = -1;
	char *user = NULL;
	kcontext_t *context = NULL;
	kscheme_t *scheme = NULL;
	uint32_t client_status = KTP_STATUS_NONE;

	assert(ktpd);
	assert(msg);

	// Get UNIX socket peer information
	sock = faux_async_fd(ktpd->async);
	if (getsockopt(sock, SOL_SOCKET, SO_PEERCRED, &ucred, &len) < 0) {
		const char *err = "Can't get peer credentials";
		syslog(LOG_ERR, "%s for connection %d", err, sock);
		ack = ktp_msg_preform(cmd, KTP_STATUS_ERROR | KTP_STATUS_EXIT);
		faux_msg_add_param(ack, KTP_PARAM_ERROR, err, strlen(err));
		faux_msg_send_async(ack, ktpd->async);
		faux_msg_free(ack);
		ktpd->exit = BOOL_TRUE;
		return BOOL_FALSE;
	}
	ksession_set_pid(ktpd->session, ucred.pid);
	ksession_set_uid(ktpd->session, ucred.uid);
	user = faux_sysdb_name_by_uid(ucred.uid);
	ksession_set_user(ktpd->session, user);
	faux_str_free(user);

	// Get tty information from auth message status
	client_status = faux_msg_get_status(msg);
	ksession_set_isatty_stdin(ktpd->session,
		KTP_STATUS_IS_TTY_STDIN(client_status));
	ksession_set_isatty_stdout(ktpd->session,
		KTP_STATUS_IS_TTY_STDOUT(client_status));
	ksession_set_isatty_stderr(ktpd->session,
		KTP_STATUS_IS_TTY_STDERR(client_status));

	// init session for plugins
	scheme = ksession_scheme(ktpd->session);
	context = kcontext_new(KCONTEXT_TYPE_PLUGIN_INIT);
	kcontext_set_session(context, ktpd->session);
	kcontext_set_scheme(context, scheme);
	kscheme_init_session_plugins(scheme, context, NULL);
	kcontext_free(context);

	// Prepare ACK message
	ack = ktp_msg_preform(cmd, status);
	faux_msg_add_param(ack, KTP_PARAM_RETCODE, &retcode8bit, 1);
	// Generate prompt
	prompt = generate_prompt(ktpd);
	if (prompt) {
		faux_msg_add_param(ack, KTP_PARAM_PROMPT, prompt, strlen(prompt));
		faux_str_free(prompt);
	}
	add_hotkeys_to_msg(ktpd, ack);
	faux_msg_send_async(ack, ktpd->async);
	faux_msg_free(ack);

	ktpd->state = KTPD_SESSION_STATE_IDLE;

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_cmd(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	char *line = NULL;
	int retcode = -1;
	ktp_cmd_e cmd = KTP_CMD_ACK;
	faux_error_t *error = NULL;
	bool_t rc = BOOL_FALSE;
	bool_t dry_run = BOOL_FALSE;
	uint32_t status = KTP_STATUS_NONE;
	bool_t ret = BOOL_TRUE;
	char *prompt = NULL;
	bool_t view_was_changed = BOOL_FALSE;

	assert(ktpd);
	assert(msg);

	// Get line from message
	if (!(line = faux_msg_get_str_param_by_type(msg, KTP_PARAM_LINE))) {
		ktp_send_error(ktpd->async, cmd, "The line is not specified");
		return BOOL_FALSE;
	}

	// Get dry-run flag from message
	if (KTP_STATUS_IS_DRY_RUN(faux_msg_get_status(msg)))
		dry_run = BOOL_TRUE;

	error = faux_error_new();

	ktpd->exec = NULL;
	rc = ktpd_session_exec(ktpd, line, &retcode, error,
		dry_run, &view_was_changed);
	faux_str_free(line);

	// Command is scheduled. Eloop will wait for ACTION completion.
	// So inform client about it and about command features like
	// interactive/non-interactive.
	if (ktpd->exec) {
		faux_msg_t *ack = NULL;
		ktp_status_e status = KTP_STATUS_INCOMPLETED;
		if (kexec_interactive(ktpd->exec))
			status |= KTP_STATUS_INTERACTIVE;
		if (kexec_need_stdin(ktpd->exec))
			status |= KTP_STATUS_NEED_STDIN;
		ack = ktp_msg_preform(cmd, status);
		faux_msg_send_async(ack, ktpd->async);
		faux_msg_free(ack);
		faux_error_free(error);
		return BOOL_TRUE; // Continue and wait for ACTION
	}

	// Here we don't need to wait for the action. We have retcode already.
	if (ksession_done(ktpd->session)) {
		ktpd->exit = BOOL_TRUE;
		status |= KTP_STATUS_EXIT;
	}

	// Prepare ACK message
	faux_msg_t *ack = ktp_msg_preform(cmd, status);
	if (rc) {
		uint8_t retcode8bit = 0;
		retcode8bit = (uint8_t)(retcode & 0xff);
		faux_msg_add_param(ack, KTP_PARAM_RETCODE, &retcode8bit, 1);
	} else {
		faux_msg_set_status(ack, KTP_STATUS_ERROR);
		char *err = faux_error_cstr(error);
		faux_msg_add_param(ack, KTP_PARAM_ERROR, err, strlen(err));
		faux_str_free(err);
		ret = BOOL_FALSE;
	}
	// Generate prompt
	prompt = generate_prompt(ktpd);
	if (prompt) {
		faux_msg_add_param(ack, KTP_PARAM_PROMPT, prompt, strlen(prompt));
		faux_str_free(prompt);
	}
	// Add hotkeys
	if (view_was_changed)
		add_hotkeys_to_msg(ktpd, ack);
	faux_msg_send_async(ack, ktpd->async);
	faux_msg_free(ack);

	faux_error_free(error);

	return ret;
}


static bool_t ktpd_session_exec(ktpd_session_t *ktpd, const char *line,
	int *retcode, faux_error_t *error,
	bool_t dry_run, bool_t *view_was_changed_p)
{
	kexec_t *exec = NULL;

	assert(ktpd);
	if (!ktpd)
		return BOOL_FALSE;

	// Parsing
	exec = ksession_parse_for_exec(ktpd->session, line, error);
	if (!exec)
		return BOOL_FALSE;

	// Set dry-run flag
	kexec_set_dry_run(exec, dry_run);

	// Session status can be changed while parsing
// NOTE: kexec_t is atomic now
//	if (ksession_done(ktpd->session)) {
//		kexec_free(exec);
//		return BOOL_FALSE; // Because action is not completed
//	}

	// Execute kexec and then wait for completion using global Eloop
	if (!kexec_exec(exec)) {
		kexec_free(exec);
		return BOOL_FALSE; // Something went wrong
	}
	// If kexec contains only non-exec (for example dry-run) ACTIONs then
	// we don't need event loop and can return here.
	if (kexec_retcode(exec, retcode)) {
		if (view_was_changed_p)
			*view_was_changed_p = !kpath_is_equal(
				ksession_path(ktpd->session),
				kexec_saved_path(exec));
		kexec_free(exec);
		return BOOL_TRUE;
	}

	// Save kexec pointer to use later
	ktpd->state = KTPD_SESSION_STATE_WAIT_FOR_PROCESS;
	ktpd->exec = exec;

	// Set stdin, stdout, stderr handlers. It's so complex because stdin,
	// stdout and stderr actually can be the same fd
	faux_eloop_add_fd(ktpd->eloop, kexec_stdin(exec), 0,
		action_stdout_ev, ktpd);
	faux_eloop_add_fd(ktpd->eloop, kexec_stdout(exec), 0,
		action_stdout_ev, ktpd);
	faux_eloop_add_fd(ktpd->eloop, kexec_stderr(exec), 0,
		action_stderr_ev, ktpd);
	faux_eloop_include_fd_event(ktpd->eloop, kexec_stdout(exec), POLLIN);
	faux_eloop_include_fd_event(ktpd->eloop, kexec_stderr(exec), POLLIN);

	return BOOL_TRUE;
}


static bool_t wait_for_actions_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data)
{
	int wstatus = 0;
	pid_t child_pid = -1;
	ktpd_session_t *ktpd = (ktpd_session_t *)user_data;
	int retcode = -1;
	uint8_t retcode8bit = 0;
	faux_msg_t *ack = NULL;
	ktp_cmd_e cmd = KTP_CMD_ACK;
	uint32_t status = KTP_STATUS_NONE;
	char *prompt = NULL;
	bool_t view_was_changed = BOOL_FALSE;

	if (!ktpd)
		return BOOL_FALSE;

	// Wait for any child process. Doesn't block.
	while ((child_pid = waitpid(-1, &wstatus, WNOHANG)) > 0) {
		if (ktpd->exec)
			kexec_continue_command_execution(ktpd->exec, child_pid,
				wstatus);
	}
	if (!ktpd->exec)
		return BOOL_TRUE;

	// Check if kexec is done now
	if (!kexec_retcode(ktpd->exec, &retcode))
		return BOOL_TRUE; // Continue

	// Sometimes SIGCHILD signal can appear before all data were really read
	// from process stdout buffer. So read the least data before closing
	// file descriptors and send it to client.
	get_stream(ktpd, kexec_stdout(ktpd->exec), BOOL_FALSE, BOOL_TRUE);
	get_stream(ktpd, kexec_stderr(ktpd->exec), BOOL_TRUE, BOOL_TRUE);
	faux_eloop_del_fd(eloop, kexec_stdin(ktpd->exec));
	faux_eloop_del_fd(eloop, kexec_stdout(ktpd->exec));
	faux_eloop_del_fd(eloop, kexec_stderr(ktpd->exec));

	view_was_changed = !kpath_is_equal(
		ksession_path(ktpd->session), kexec_saved_path(ktpd->exec));

	kexec_free(ktpd->exec);
	ktpd->exec = NULL;
	ktpd->state = KTPD_SESSION_STATE_IDLE;

	// All kexec_t actions are done so can break the loop if needed.
	if (ksession_done(ktpd->session)) {
		ktpd->exit = BOOL_TRUE;
		status |= KTP_STATUS_EXIT; // Notify client about exiting
	}

	// Send ACK message
	ack = ktp_msg_preform(cmd, status);
	retcode8bit = (uint8_t)(retcode & 0xff);
	faux_msg_add_param(ack, KTP_PARAM_RETCODE, &retcode8bit, 1);
	// Generate prompt
	prompt = generate_prompt(ktpd);
	if (prompt) {
		faux_msg_add_param(ack, KTP_PARAM_PROMPT, prompt, strlen(prompt));
		faux_str_free(prompt);
	}
	// Add hotkeys
	if (view_was_changed)
		add_hotkeys_to_msg(ktpd, ack);
	faux_msg_send_async(ack, ktpd->async);
	faux_msg_free(ack);

	type = type; // Happy compiler
	associated_data = associated_data; // Happy compiler

	if (ktpd->exit)
		return BOOL_FALSE;

	return BOOL_TRUE;
}


static int compl_compare(const void *first, const void *second)
{
	const char *f = (const char *)first;
	const char *s = (const char *)second;

	return strcmp(f, s);
}


static int compl_kcompare(const void *key, const void *list_item)
{
	const char *f = (const char *)key;
	const char *s = (const char *)list_item;

	return strcmp(f, s);
}


static bool_t ktpd_session_process_completion(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	char *line = NULL;
	faux_msg_t *ack = NULL;
	kpargv_t *pargv = NULL;
	ktp_cmd_e cmd = KTP_COMPLETION_ACK;
	uint32_t status = KTP_STATUS_NONE;
	const char *prefix = NULL;
	size_t prefix_len = 0;

	assert(ktpd);
	assert(msg);

	// Get line from message
	if (!(line = faux_msg_get_str_param_by_type(msg, KTP_PARAM_LINE))) {
		ktp_send_error(ktpd->async, cmd, NULL);
		return BOOL_FALSE;
	}

	// Parsing
	pargv = ksession_parse_for_completion(ktpd->session, line);
	faux_str_free(line);
	if (!pargv) {
		ktp_send_error(ktpd->async, cmd, NULL);
		return BOOL_FALSE;
	}
	kpargv_debug(pargv);

	if (ksession_done(ktpd->session)) {
		ktpd->exit = BOOL_TRUE;
		status |= KTP_STATUS_EXIT; // Notify client about exiting
	}

	// Prepare ACK message
	ack = ktp_msg_preform(cmd, status);

	// Last unfinished word. Common prefix for all completions
	prefix = kpargv_last_arg(pargv);
	if (!faux_str_is_empty(prefix)) {
		prefix_len = strlen(prefix);
		faux_msg_add_param(ack, KTP_PARAM_PREFIX, prefix, prefix_len);
	}

	// Fill msg with possible completions
	if (!kpargv_completions_is_empty(pargv)) {
		const kentry_t *candidate = NULL;
		kpargv_completions_node_t *citer = kpargv_completions_iter(pargv);
		faux_list_node_t *compl_iter = NULL;
		faux_list_t *completions = NULL;
		char *compl_str = NULL;

		completions = faux_list_new(FAUX_LIST_SORTED, FAUX_LIST_UNIQUE,
			compl_compare, compl_kcompare,
			(void (*)(void *))faux_str_free);
		while ((candidate = kpargv_completions_each(&citer))) {
			const kentry_t *completion = NULL;
			kparg_t *parg = NULL;
			int rc = -1;
			char *out = NULL;
			bool_t res = BOOL_FALSE;
			char *l = NULL; // One line of completion
			const char *str = NULL;

			// Get completion entry from candidate entry
			completion = kentry_nested_by_purpose(candidate,
				KENTRY_PURPOSE_COMPLETION);
			// If candidate entry doesn't contain completion then try
			// to get completion from entry's PTYPE
			if (!completion) {
				const kentry_t *ptype = NULL;
				ptype = kentry_nested_by_purpose(candidate,
					KENTRY_PURPOSE_PTYPE);
				if (!ptype)
					continue;
				completion = kentry_nested_by_purpose(ptype,
					KENTRY_PURPOSE_COMPLETION);
			}
			if (!completion)
				continue;
			parg = kparg_new(candidate, prefix);
			kpargv_set_candidate_parg(pargv, parg);
			res = ksession_exec_locally(ktpd->session, completion,
				pargv, &rc, &out);
			kparg_free(parg);
			if (!res || (rc < 0) || !out) {
				if (out)
					faux_str_free(out);
				continue;
			}

			// Get all completions one by one
			str = out;
			while ((l = faux_str_getline(str, &str))) {
				// Compare prefix
				if ((prefix_len > 0) &&
					(faux_str_cmpn(prefix, l, prefix_len) != 0)) {
					faux_str_free(l);
					continue;
				}
				compl_str = l + prefix_len;
				faux_list_add(completions, faux_str_dup(compl_str));
				faux_str_free(l);
			}
			faux_str_free(out);
		}

		// Put completion list to message
		compl_iter = faux_list_head(completions);
		while ((compl_str = faux_list_each(&compl_iter))) {
			faux_msg_add_param(ack, KTP_PARAM_LINE,
				compl_str, strlen(compl_str));
		}
		faux_list_free(completions);
	}

	faux_msg_send_async(ack, ktpd->async);
	faux_msg_free(ack);

	kpargv_free(pargv);

	return BOOL_TRUE;
}


// The most priority source of help is candidate's help ACTION output. Next
// source is candidate's PTYPE help ACTION output.
// Function generates two lines for one resulting help line. The first
// component is a 'prefix' and the second component is 'text'.
// The 'prefix' can be something like 'ip', 'filter' i.e.
// subcommand or '3..89', '<STRING>' i.e. description of type. The 'text'
// field is description of current parameter. For example 'Interface IP
// address'. So the full help can be:
// AAA.BBB.CCC.DDD Interface IP address
// [ first field ] [ second field     ]
//
// If not candidate parameter nor PTYPE contains the help functions the engine
// tries to construct help itself.
//
// It uses the following sources for 'prefix':
//  * 'help' field of PTYPE
//  * 'value' field of PTYPE
//  * 'name' field of PTYPE
//  * 'value' field of parameter
//  * 'name' field of parameter
//
// Engine uses the following sources for 'text':
//  * 'help' field of parameter
//  * 'value' field of parameter
//  * 'name' field of parameter
static bool_t ktpd_session_process_help(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	char *line = NULL;
	faux_msg_t *ack = NULL;
	kpargv_t *pargv = NULL;
	ktp_cmd_e cmd = KTP_HELP_ACK;
	uint32_t status = KTP_STATUS_NONE;
	const char *prefix = NULL;

	assert(ktpd);
	assert(msg);

	// Get line from message
	if (!(line = faux_msg_get_str_param_by_type(msg, KTP_PARAM_LINE))) {
		ktp_send_error(ktpd->async, cmd, NULL);
		return BOOL_FALSE;
	}

	// Parsing
	pargv = ksession_parse_for_completion(ktpd->session, line);
	faux_str_free(line);
	if (!pargv) {
		ktp_send_error(ktpd->async, cmd, NULL);
		return BOOL_FALSE;
	}

	if (ksession_done(ktpd->session)) {
		ktpd->exit = BOOL_TRUE;
		status |= KTP_STATUS_EXIT; // Notify client about exiting
	}

	// Prepare ACK message
	ack = ktp_msg_preform(cmd, status);

	// Last unfinished word. Common prefix for all entries
	prefix = kpargv_last_arg(pargv);

	// Fill msg with possible help messages
	if (!kpargv_completions_is_empty(pargv)) {
		const kentry_t *candidate = NULL;
		kpargv_completions_node_t *citer = kpargv_completions_iter(pargv);
		faux_list_node_t *help_iter = NULL;
		faux_list_t *help_list = NULL;
		help_t *help_struct = NULL;

		help_list = faux_list_new(FAUX_LIST_SORTED, FAUX_LIST_UNIQUE,
			help_compare, NULL, help_free);
		while ((candidate = kpargv_completions_each(&citer))) {
			const kentry_t *help = NULL;
			const kentry_t *ptype = NULL;

			// Get PTYPE of parameter
			ptype = kentry_nested_by_purpose(candidate,
				KENTRY_PURPOSE_PTYPE);
			// Try to get help fn from parameter itself
			help = kentry_nested_by_purpose(candidate,
				KENTRY_PURPOSE_HELP);
			if (!help && ptype)
				help = kentry_nested_by_purpose(ptype,
					KENTRY_PURPOSE_HELP);

			// Generate help with found ACTION
			if (help) {
				char *out = NULL;
				kparg_t *parg = NULL;
				int rc = -1;

				parg = kparg_new(candidate, prefix);
				kpargv_set_candidate_parg(pargv, parg);
				ksession_exec_locally(ktpd->session,
					help, pargv, &rc, &out);
				kparg_free(parg);

				if (out) {
					const char *str = out;
					char *prefix_str = NULL;
					char *line_str = NULL;
					do {
						prefix_str = faux_str_getline(str, &str);
						if (!prefix_str)
							break;
						line_str = faux_str_getline(str, &str);
						if (!line_str) {
							faux_str_free(prefix_str);
							break;
						}
						help_struct = help_new(prefix_str, line_str);
						if (!faux_list_add(help_list, help_struct))
							help_free(help_struct);
					} while (line_str);
					faux_str_free(out);
				}

			// Generate help with available information
			} else {
				const char *prefix_str = NULL;
				const char *line_str = NULL;

				// Prefix_str
				if (ptype) {
					prefix_str = kentry_help(ptype);
					if (!prefix_str)
						prefix_str = kentry_value(ptype);
					if (!prefix_str)
						prefix_str = kentry_name(ptype);
				} else {
					prefix_str = kentry_value(candidate);
					if (!prefix_str)
						prefix_str = kentry_name(candidate);
				}
				assert(prefix_str);

				// Line_str
				line_str = kentry_help(candidate);
				if (!line_str)
					line_str = kentry_value(candidate);
				if (!line_str)
					line_str = kentry_name(candidate);
				assert(line_str);

				help_struct = help_new(
					faux_str_dup(prefix_str),
					faux_str_dup(line_str));
				if (!faux_list_add(help_list, help_struct))
					help_free(help_struct);
			}
		}

		// Put help list to message
		help_iter = faux_list_head(help_list);
		while ((help_struct = (help_t *)faux_list_each(&help_iter))) {
			faux_msg_add_param(ack, KTP_PARAM_PREFIX,
				help_struct->prefix, strlen(help_struct->prefix));
			faux_msg_add_param(ack, KTP_PARAM_LINE,
				help_struct->line, strlen(help_struct->line));
		}
		faux_list_free(help_list);
	}

	faux_msg_send_async(ack, ktpd->async);
	faux_msg_free(ack);

	kpargv_free(pargv);

	return BOOL_TRUE;
}


static ssize_t stdin_out(int fd, faux_buf_t *buf, bool_t process_all_data)
{
	ssize_t total_written = 0;

	assert(buf);
	if (!buf)
		return -1;
	assert(fd >= 0);

	while (faux_buf_len(buf) > 0) {
		ssize_t data_to_write = 0;
		ssize_t bytes_written = 0;
		void *data = NULL;

		data_to_write = faux_buf_dread_lock_easy(buf, &data);
		if (data_to_write <= 0)
			break;

		bytes_written = write(fd, data, data_to_write);
		if (bytes_written > 0) {
			total_written += bytes_written;
			faux_buf_dread_unlock_easy(buf, bytes_written);
		} else {
			faux_buf_dread_unlock_easy(buf, 0);
		}
		if (bytes_written < 0) {
			if ( // Something went wrong
				(errno != EINTR) &&
				(errno != EAGAIN) &&
				(errno != EWOULDBLOCK)
				)
				return -1;
		// Not whole data block was written
		} else if (bytes_written != data_to_write) {
			break;
		}
		if (!process_all_data)
			break;
	}

	return total_written;
}


static bool_t push_stdin(ktpd_session_t *ktpd)
{
	faux_buf_t *bufin = NULL;
	int fd = -1;

	if (!ktpd)
		return BOOL_TRUE;
	if (!ktpd->exec)
		return BOOL_TRUE;
	fd = kexec_stdin(ktpd->exec);
	if (fd < 0) // May be fd is already closed
		return BOOL_FALSE;

	bufin = kexec_bufin(ktpd->exec);
	assert(bufin);
	stdin_out(fd, bufin, BOOL_FALSE); // Non-blocking write
	// Restore data receiving from client
	if (faux_buf_len(bufin) < BUF_LIMIT)
		faux_eloop_include_fd_event(ktpd->eloop,
			faux_async_fd(ktpd->async), POLLIN);
	if (faux_buf_len(bufin) != 0) // Try later
		return BOOL_TRUE;

	// All data is written
	faux_eloop_exclude_fd_event(ktpd->eloop, fd, POLLOUT);
	if (ktpd->stdin_must_be_closed) {
		close(fd);
//		kexec_set_stdin(ktpd->exec, -1);
	}

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_stdin(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	char *line = NULL;
	unsigned int len = 0;
	faux_buf_t *bufin = NULL;
	int fd = -1;
	bool_t interrupt = BOOL_FALSE;
	const kaction_t *action = NULL;

	assert(ktpd);
	assert(msg);

	if (!ktpd->exec)
		return BOOL_FALSE;
	fd = kexec_stdin(ktpd->exec);
	if (fd < 0)
		return BOOL_FALSE;

	if (!faux_msg_get_param_by_type(msg, KTP_PARAM_LINE, (void **)&line, &len))
		return BOOL_TRUE; // It's strange but not a bug
	if (len == 0)
		return BOOL_TRUE;
	bufin = kexec_bufin(ktpd->exec);
	assert(bufin);

	action = kexec_current_action(ktpd->exec);
	if (action)
		interrupt = kaction_interrupt(action);
	// If current action is non-interruptible and action's stdin is terminal
	// then remove ^C (0x03) symbol from stdin stream to don't deliver
	// SIGINT to process
	if (isatty(fd) && !interrupt) {
		// 0x03 is a ^C
		const char chars_to_search[] = {0x03, 0};
		const char *start = line;
		const char *pos = NULL;
		size_t cur_len = len;
		while ((pos = faux_str_charsn(start, chars_to_search, cur_len))) {
			size_t written = pos - start;
			faux_buf_write(bufin, start, written);
			start = pos + 1;
			cur_len = cur_len - written - 1;
		}
		if (cur_len > 0)
			faux_buf_write(bufin, start, cur_len);
	} else {
		faux_buf_write(bufin, line, len);
	}

	stdin_out(fd, bufin, BOOL_FALSE); // Non-blocking write
	if (faux_buf_len(bufin) == 0)
		return BOOL_TRUE;

	// Non-blocking write can't write all data so plan to write later
	faux_eloop_include_fd_event(ktpd->eloop, fd, POLLOUT);

	// Temporarily stop data receiving from client because buffer is
	// full
	if (faux_buf_len(bufin) > BUF_LIMIT)
		faux_eloop_exclude_fd_event(ktpd->eloop,
			faux_async_fd(ktpd->async), POLLIN);

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_winch(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	char *line = NULL;
	char *p = NULL;
	unsigned short width = 0;
	unsigned short height = 0;

	assert(ktpd);
	assert(msg);

	if (!(line = faux_msg_get_str_param_by_type(msg, KTP_PARAM_WINCH)))
		return BOOL_TRUE;

	p = strchr(line, ' ');
	if (!p || (p == line)) {
		faux_str_free(line);
		return BOOL_FALSE;
	}
	if (!faux_conv_atous(line, &width, 0)) {
		faux_str_free(line);
		return BOOL_FALSE;
	}
	if (!faux_conv_atous(p + 1, &height, 0)) {
		faux_str_free(line);
		return BOOL_FALSE;
	}

	ksession_set_term_width(ktpd->session, width);
	ksession_set_term_height(ktpd->session, height);
	faux_str_free(line);

	if (!ktpd->exec)
		return BOOL_TRUE;
	// Set pseudo terminal window size
	kexec_set_winsize(ktpd->exec);

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_notification(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	assert(ktpd);
	assert(msg);

	ktpd_session_process_winch(ktpd, msg);

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_stdin_close(ktpd_session_t *ktpd,
	faux_msg_t *msg)
{
	int fd = -1;

	assert(ktpd);
	assert(msg);

	if (!ktpd->exec)
		return BOOL_FALSE;
	fd = kexec_stdin(ktpd->exec);
	if (fd < 0)
		return BOOL_FALSE;
	// Schedule to close stdin
	ktpd->stdin_must_be_closed = BOOL_TRUE;
	push_stdin(ktpd);

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_stdout_close(ktpd_session_t *ktpd,
	faux_msg_t *msg)
{
	int fd = -1;

	assert(ktpd);
	assert(msg);

	if (!ktpd->exec)
		return BOOL_FALSE;
	fd = kexec_stdout(ktpd->exec);
	if (fd < 0)
		return BOOL_FALSE;
	close(fd);
	// Remove already generated data from out buffer. This data is not
	// needed now
	faux_buf_empty(kexec_bufout(ktpd->exec));

	return BOOL_TRUE;
}


static bool_t ktpd_session_process_stderr_close(ktpd_session_t *ktpd,
	faux_msg_t *msg)
{
	int fd = -1;

	assert(ktpd);
	assert(msg);

	if (!ktpd->exec)
		return BOOL_FALSE;
	fd = kexec_stderr(ktpd->exec);
	if (fd < 0)
		return BOOL_FALSE;
	close(fd);
	// Remove already generated data from err buffer. This data is not
	// needed any more
	faux_buf_empty(kexec_buferr(ktpd->exec));

	return BOOL_TRUE;
}


static bool_t ktpd_session_dispatch(ktpd_session_t *ktpd, faux_msg_t *msg)
{
	uint16_t cmd = 0;
	const char *err = NULL;
	ktp_cmd_e ecmd = KTP_NOTIFICATION; // Answer command if error

	assert(ktpd);
	if (!ktpd)
		return BOOL_FALSE;
	assert(msg);
	if (!msg)
		return BOOL_FALSE;

	cmd = faux_msg_get_cmd(msg);
	switch (cmd) {
	case KTP_AUTH:
		if ((ktpd->state != KTPD_SESSION_STATE_UNAUTHORIZED) &&
			(ktpd->state != KTPD_SESSION_STATE_IDLE)) {
			ecmd = KTP_AUTH_ACK;
			err = "Server illegal state for authorization";
			break;
		}
		ktpd_session_process_auth(ktpd, msg);
		break;
	case KTP_CMD:
		if (ktpd->state != KTPD_SESSION_STATE_IDLE) {
			ecmd = KTP_CMD_ACK;
			err = "Server illegal state for command execution";
			break;
		}
		ktpd_session_process_cmd(ktpd, msg);
		break;
	case KTP_COMPLETION:
		if (ktpd->state != KTPD_SESSION_STATE_IDLE) {
			ecmd = KTP_COMPLETION_ACK;
			err = "Server illegal state for completion";
			break;
		}
		ktpd_session_process_completion(ktpd, msg);
		break;
	case KTP_HELP:
		if (ktpd->state != KTPD_SESSION_STATE_IDLE) {
			ecmd = KTP_HELP_ACK;
			err = "Server illegal state for help";
			break;
		}
		ktpd_session_process_help(ktpd, msg);
		break;
	case KTP_STDIN:
		if (ktpd->state != KTPD_SESSION_STATE_WAIT_FOR_PROCESS) {
			err = "Nobody is waiting for stdin";
			break;
		}
		ktpd_session_process_stdin(ktpd, msg);
		break;
	case KTP_NOTIFICATION:
		ktpd_session_process_notification(ktpd, msg);
		break;
	case KTP_STDIN_CLOSE:
		if (ktpd->state != KTPD_SESSION_STATE_WAIT_FOR_PROCESS) {
			err = "No active command is running";
			break;
		}
		ktpd_session_process_stdin_close(ktpd, msg);
		break;
	case KTP_STDOUT_CLOSE:
		if (ktpd->state != KTPD_SESSION_STATE_WAIT_FOR_PROCESS) {
			err = "No active command is running";
			break;
		}
		ktpd_session_process_stdout_close(ktpd, msg);
		break;
	case KTP_STDERR_CLOSE:
		if (ktpd->state != KTPD_SESSION_STATE_WAIT_FOR_PROCESS) {
			err = "No active command is running";
			break;
		}
		ktpd_session_process_stderr_close(ktpd, msg);
		break;
	default:
		syslog(LOG_WARNING, "Unsupported command: 0x%04u", cmd);
		err = "Unsupported command";
		break;
	}

	// On error
	if (err)
		ktp_send_error(ktpd->async, ecmd, err);

	return BOOL_TRUE;
}


/** @brief Low-level function to receive KTP message.
 *
 * Firstly function gets the header of message. Then it checks and parses
 * header and find out the length of whole message. Then it receives the rest
 * of message.
 */
static bool_t ktpd_session_read_cb(faux_async_t *async,
	faux_buf_t *buf, size_t len, void *user_data)
{
	ktpd_session_t *ktpd = (ktpd_session_t *)user_data;
	faux_msg_t *completed_msg = NULL;
	char *data = NULL;

	assert(async);
	assert(buf);
	assert(ktpd);

	// Linearize buffer
	data = malloc(len);
	faux_buf_read(buf, data, len);

	// Receive header
	if (!ktpd->hdr) {
		size_t whole_len = 0;
		size_t msg_wo_hdr = 0;

		ktpd->hdr = (faux_hdr_t *)data;
		// Check for broken header
		if (!ktp_check_header(ktpd->hdr)) {
			faux_free(ktpd->hdr);
			ktpd->hdr = NULL;
			return BOOL_FALSE;
		}

		whole_len = faux_hdr_len(ktpd->hdr);
		// msg_wo_hdr >= 0 because ktp_check_header() validates whole_len
		msg_wo_hdr = whole_len - sizeof(faux_hdr_t);
		// Plan to receive message body
		if (msg_wo_hdr > 0) {
			faux_async_set_read_limits(async,
				msg_wo_hdr, msg_wo_hdr);
			return BOOL_TRUE;
		}
		// Here message is completed (msg body has zero length)
		completed_msg = faux_msg_deserialize_parts(ktpd->hdr, NULL, 0);

	// Receive message body
	} else {
		completed_msg = faux_msg_deserialize_parts(ktpd->hdr, data, len);
		faux_free(data);
	}

	// Plan to receive msg header
	faux_async_set_read_limits(ktpd->async,
		sizeof(faux_hdr_t), sizeof(faux_hdr_t));
	faux_free(ktpd->hdr);
	ktpd->hdr = NULL; // Ready to recv new header

	// Here message is completed
	ktpd_session_dispatch(ktpd, completed_msg);
	faux_msg_free(completed_msg);

	return BOOL_TRUE;
}


bool_t ktpd_session_connected(ktpd_session_t *ktpd)
{
	assert(ktpd);
	if (!ktpd)
		return BOOL_FALSE;
	if (KTPD_SESSION_STATE_DISCONNECTED == ktpd->state)
		return BOOL_FALSE;

	return BOOL_TRUE;
}


int ktpd_session_fd(const ktpd_session_t *ktpd)
{
	assert(ktpd);
	if (!ktpd)
		return BOOL_FALSE;

	return faux_async_fd(ktpd->async);
}


static bool_t get_stream(ktpd_session_t *ktpd, int fd, bool_t is_stderr,
	bool_t process_all_data)
{
	ssize_t r = -1;
	faux_buf_t *faux_buf = NULL;
	char *buf = NULL;
	ssize_t len = 0;
	faux_msg_t *ack = NULL;

	if (!ktpd)
		return BOOL_TRUE;
	if (!ktpd->exec)
		return BOOL_TRUE;

	if (is_stderr)
		faux_buf = kexec_buferr(ktpd->exec);
	else
		faux_buf = kexec_bufout(ktpd->exec);
	assert(faux_buf);

	do {
		void *linear_buf = NULL;
		ssize_t really_readed = 0;
		ssize_t linear_len =
			faux_buf_dwrite_lock_easy(faux_buf, &linear_buf);
		// Non-blocked read. The fd became non-blocked while
		// kexec_prepare().
		r = read(fd, linear_buf, linear_len);
		if (r > 0)
			really_readed = r;
		faux_buf_dwrite_unlock_easy(faux_buf, really_readed);
	} while ((r > 0) && process_all_data);

	len = faux_buf_len(faux_buf);
	if (0 == len)
		return BOOL_TRUE;

	buf = malloc(len);
	faux_buf_read(faux_buf, buf, len);

	// Create KTP_STDOUT/KTP_STDERR message to send to client
	ack = ktp_msg_preform(is_stderr ? KTP_STDERR : KTP_STDOUT, KTP_STATUS_NONE);
	faux_msg_add_param(ack, KTP_PARAM_LINE, buf, len);
	faux_msg_send_async(ack, ktpd->async);
	faux_msg_free(ack);

	free(buf);

	// Pause stdout/stderr receiving because buffer (to send to client)
	// is full
	if (faux_buf_len(faux_async_obuf(ktpd->async)) > BUF_LIMIT)
		faux_eloop_exclude_fd_event(ktpd->eloop, fd, POLLIN);

	return BOOL_TRUE;
}


static bool_t action_stdout_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data)
{
	faux_eloop_info_fd_t *info = (faux_eloop_info_fd_t *)associated_data;
	ktpd_session_t *ktpd = (ktpd_session_t *)user_data;

	// Interactive command use these function as callback not only for
	// getting stdout but for writing stdin too. Because pseudo-terminal
	// uses the same fd for in and out.
	if (info->revents & POLLOUT)
		push_stdin(ktpd);

	if (info->revents & POLLIN)
		get_stream(ktpd, info->fd, BOOL_FALSE, BOOL_FALSE);

	// Some errors or fd is closed so remove it from polling
	// EOF || POLERR || POLLNVAL
	if (info->revents & (POLLHUP | POLLERR | POLLNVAL))
		faux_eloop_del_fd(eloop, info->fd);

	type = type; // Happy compiler

	return BOOL_TRUE;
}


static bool_t action_stderr_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data)
{
	faux_eloop_info_fd_t *info = (faux_eloop_info_fd_t *)associated_data;
	ktpd_session_t *ktpd = (ktpd_session_t *)user_data;

	if (info->revents & POLLIN)
		get_stream(ktpd, info->fd, BOOL_TRUE, BOOL_FALSE);

	// Some errors or fd is closed so remove it from polling
	// EOF || POLERR || POLLNVAL
	if (info->revents & (POLLHUP | POLLERR | POLLNVAL))
		faux_eloop_del_fd(eloop, info->fd);

	type = type; // Happy compiler

	return BOOL_TRUE;
}


bool_t client_ev(faux_eloop_t *eloop, faux_eloop_type_e type,
	void *associated_data, void *user_data)
{
	faux_eloop_info_fd_t *info = (faux_eloop_info_fd_t *)associated_data;
	ktpd_session_t *ktpd = (ktpd_session_t *)user_data;
	faux_async_t *async = ktpd->async;

	assert(async);

	// Write data
	if (info->revents & POLLOUT) {
		faux_eloop_exclude_fd_event(eloop, info->fd, POLLOUT);
		if (faux_async_out_easy(async) < 0) {
			// Someting went wrong
			faux_eloop_del_fd(eloop, info->fd);
			syslog(LOG_ERR, "Can't send data to client");
			return BOOL_FALSE; // Stop event loop
		}
		// Restore stdout and stderr receiving if out buffer is not
		// full
		if (ktpd->exec &&
			faux_buf_len(faux_async_obuf(async)) < BUF_LIMIT) {
			faux_eloop_include_fd_event(ktpd->eloop,
				kexec_stdout(ktpd->exec), POLLIN);
			faux_eloop_include_fd_event(ktpd->eloop,
				kexec_stderr(ktpd->exec), POLLIN);
		}
	}

	// Read data
	if (info->revents & POLLIN) {
		if (faux_async_in_easy(async) < 0) {
			// Someting went wrong
			faux_eloop_del_fd(eloop, info->fd);
			syslog(LOG_ERR, "Can't get data from client");
			return BOOL_FALSE; // Stop event loop
		}
	}

	// EOF
	if (info->revents & POLLHUP) {
		faux_eloop_del_fd(eloop, info->fd);
		syslog(LOG_DEBUG, "Connection %d is closed by client", info->fd);
		return BOOL_FALSE; // Stop event loop
	}

	// POLLERR
	if (info->revents & POLLERR) {
		faux_eloop_del_fd(eloop, info->fd);
		syslog(LOG_DEBUG, "POLLERR received %d", info->fd);
		return BOOL_FALSE; // Stop event loop
	}

	// POLLNVAL
	if (info->revents & POLLNVAL) {
		faux_eloop_del_fd(eloop, info->fd);
		syslog(LOG_DEBUG, "POLLNVAL received %d", info->fd);
		return BOOL_FALSE; // Stop event loop
	}

	type = type; // Happy compiler

	// Session can be really finished here. Note KTPD session can't be
	// stopped immediately so it's only two places within code to really
	// break the loop. This one and within wait_for_action_ev().
	if (ktpd->exit)
		return BOOL_FALSE;

	return BOOL_TRUE;
}


#if 0
static void ktpd_session_bad_socket(ktpd_session_t *ktpd)
{
	assert(ktpd);
	if (!ktpd)
		return;

	ktpd->state = KTPD_SESSION_STATE_DISCONNECTED;
}
#endif