/**
* mds — A micro-display server
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "mds-echo.h"
#include <libmdsserver/macros.h>
#include <libmdsserver/util.h>
#include <libmdsserver/mds-message.h>
#include <errno.h>
#include <inttypes.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#define reconnect_to_display() -1
#define MDS_ECHO_VARS_VERSION 0
/**
* This variable should declared by the actual server implementation.
* It must be configured before `main` is invoked.
*
* This tells the server-base how to behave
*/
server_characteristics_t server_characteristics =
{
.require_privileges = 0,
.require_display = 1,
.require_respawn_info = 0,
.sanity_check_argc = 1,
.fork_for_safety = 0,
.danger_is_deadly = 1
};
/**
* Value of the ‘Message ID’ header for the next message
*/
static uint32_t message_id = 1;
/**
* Buffer for received messages
*/
static mds_message_t received;
/**
* Whether the server is connected to the display
*/
static int connected = 1;
/**
* Buffer for message echoing
*/
static char* echo_buffer = NULL;
/**
* The size allocated to `echo_buffer` divided by `sizeof(char)`
*/
static size_t echo_buffer_size = 0;
/**
* This function will be invoked before `initialise_server` (if not re-exec:ing)
* or before `unmarshal_server` (if re-exec:ing)
*
* @return Non-zero on error
*/
int __attribute__((const)) preinitialise_server(void)
{
return 0;
}
/**
* This function should initialise the server,
* and it not invoked after a re-exec.
*
* @return Non-zero on error
*/
int initialise_server(void)
{
int stage = 0;
const char* const message =
"Command: intercept\n"
"Message ID: 0\n"
"Length: 14\n"
"\n"
"Command: echo\n";
fail_if (full_send(message, strlen(message)));
fail_if (server_initialised() < 0); stage++;
fail_if (mds_message_initialise(&received));
return 0;
fail:
xperror(*argv);
if (stage == 1)
mds_message_destroy(&received);
return 1;
}
/**
* This function will be invoked after `initialise_server` (if not re-exec:ing)
* or after `unmarshal_server` (if re-exec:ing)
*
* @return Non-zero on error
*/
int postinitialise_server(void)
{
if (connected)
return 0;
fail_if (reconnect_to_display());
connected = 1;
return 0;
fail:
mds_message_destroy(&received);
return 1;
}
/**
* Calculate the number of bytes that will be stored by `marshal_server`
*
* On failure the program should `abort()` or exit by other means.
* However it should not be possible for this function to fail.
*
* @return The number of bytes that will be stored by `marshal_server`
*/
size_t marshal_server_size(void)
{
return 2 * sizeof(int) + sizeof(uint32_t) + mds_message_marshal_size(&received);
}
/**
* Marshal server implementation specific data into a buffer
*
* @param state_buf The buffer for the marshalled data
* @return Non-zero on error
*/
int marshal_server(char* state_buf)
{
buf_set_next(state_buf, int, MDS_ECHO_VARS_VERSION);
buf_set_next(state_buf, int, connected);
buf_set_next(state_buf, uint32_t, message_id);
mds_message_marshal(&received, state_buf);
mds_message_destroy(&received);
return 0;
}
/**
* Unmarshal server implementation specific data and update the servers state accordingly
*
* On critical failure the program should `abort()` or exit by other means.
* That is, do not let `reexec_failure_recover` run successfully, if it unrecoverable
* error has occurred or one severe enough that it is better to simply respawn.
*
* @param state_buf The marshalled data that as not been read already
* @return Non-zero on error
*/
int unmarshal_server(char* state_buf)
{
int r;
/* buf_get_next(state_buf, int, MDS_ECHO_VARS_VERSION); */
buf_next(state_buf, int, 1);
buf_get_next(state_buf, int, connected);
buf_get_next(state_buf, uint32_t, message_id);
r = mds_message_unmarshal(&received, state_buf);
fail_if (r);
return 0;
fail:
xperror(*argv);
mds_message_destroy(&received);
return r;
}
/**
* Attempt to recover from a re-exec failure that has been
* detected after the server successfully updated it execution image
*
* @return Non-zero on error
*/
int __attribute__((const)) reexec_failure_recover(void)
{
return -1;
}
/**
* Perform the server's mission
*
* @return Non-zero on error
*/
int master_loop(void)
{
int rc = 1, r;
while (!reexecing && !terminating)
{
if (r = mds_message_read(&received, socket_fd), r == 0)
if (r = echo_message(), r == 0)
continue;
if (r == -2)
{
eprint("corrupt message received, aborting.");
goto done;
}
else if (errno == EINTR)
continue;
else
fail_if (errno != ECONNRESET);
eprint("lost connection to server.");
mds_message_destroy(&received);
mds_message_initialise(&received);
connected = 0;
fail_if (reconnect_to_display());
connected = 1;
}
rc = 0;
goto done;
fail:
xperror(*argv);
done:
if (rc || !reexecing)
mds_message_destroy(&received);
free(echo_buffer);
return rc;
}
/**
* Echo the received message payload
*
* @return Zero on success -1 on error or interruption,
* errno will be set accordingly
*/
int echo_message(void)
{
char* old_buffer = NULL;
const char* recv_client_id = NULL;
const char* recv_message_id = NULL;
const char* recv_length = NULL;
size_t i, n;
int saved_errno;
/* Fetch headers. */
#define __get_header(storage, header, skip) \
(startswith(received.headers[i], header)) \
storage = received.headers[i] + skip * strlen(header)
for (i = 0; i < received.header_count; i++)
{
if __get_header(recv_client_id, "Client ID: ", 1);
else if __get_header(recv_message_id, "Message ID: ", 1);
else if __get_header(recv_length, "Length: ", 0);
else
continue;
/* Stop fetch headers if we have found everything we want. */
if (recv_client_id && recv_message_id && recv_length)
break;
}
#undef __get_header
/* Validate headers. */
if ((recv_client_id == NULL) || (strequals(recv_client_id, "0:0")))
{
eprint("received message from anonymous sender, ignoring.");
return 0;
}
else if (recv_message_id == NULL)
{
eprint("received message with ID, ignoring, master server is misbehaving.");
return 0;
}
/* Construct echo message headers. */
n = 1 + strlen("To: \nIn response to: \nMessage ID: \n\n");
n += strlen(recv_client_id) + strlen(recv_message_id) + 2 * sizeof(int32_t) + sizeof(uint32_t);
if (recv_length != NULL)
n += strlen(recv_length) + 1;
if ((echo_buffer_size < n) || (echo_buffer_size * 4 > n))
fail_if (xxrealloc(old_buffer, echo_buffer, echo_buffer_size = n, char));
sprintf(echo_buffer, "To: %s\nIn response to: %s\nMessage ID: %" PRIu32 "\n%s%s\n",
recv_client_id, recv_message_id, message_id,
recv_length == NULL ? "" : recv_length,
recv_length == NULL ? "" : "\n");
/* Increase message ID. */
message_id = message_id == UINT32_MAX ? 0 : (message_id + 1);
/* Send echo. */
fail_if (full_send(echo_buffer, strlen(echo_buffer)));
return full_send(received.payload, received.payload_size);
fail:
saved_errno = errno;
free(old_buffer);
return errno = saved_errno, -1;
}
/**
* Send a full message even if interrupted
*
* @param message The message to send
* @param length The length of the message
* @return Non-zero on success
*/
int full_send(const char* message, size_t length)
{
size_t sent;
while (length > 0)
{
sent = send_message(socket_fd, message, length);
if (sent > length)
{
eprint("Sent more of a message than exists in the message, aborting.");
return -1;
}
else
fail_if ((sent < length) && (errno != EINTR));
message += sent;
length -= sent;
}
return 0;
fail:
xperror(*argv);
return -1;
}
