/**
* 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-server.h"
#include "config.h"
#include <libmdsserver/linked-list.h>
#include <libmdsserver/fd-table.h>
#include <libmdsserver/mds-message.h>
#include <alloca.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <limits.h>
#include <unistd.h>
#include <pwd.h>
#include <errno.h>
#include <pthread.h>
#include <sys/socket.h>
#define MDS_SERVER_VARS_VERSION 0
/**
* Number of elements in `argv`
*/
static int argc;
/**
* Command line arguments
*/
static char** argv;
/**
* The program run state, 1 when running,
* 0 when shutting down
*/
static volatile sig_atomic_t running = 1;
/**
* Non-zero when the program is about to re-exec
*/
static volatile sig_atomic_t reexecing = 0;
/**
* The number of running slaves
*/
static int running_slaves = 0;
/**
* Mutex for slave data
*/
static pthread_mutex_t slave_mutex;
/**
* Condition for slave data
*/
static pthread_cond_t slave_cond;
/**
* Map from client socket file descriptor to all information (client_t)
*/
static fd_table_t client_map;
/**
* List of client information (client_t)
*/
static linked_list_t client_list;
/**
* Entry point of the server
*
* @param argc_ Number of elements in `argv_`
* @param argv_ Command line arguments
* @return Non-zero on error
*/
int main(int argc_, char** argv_)
{
int is_respawn = -1;
int socket_fd = -1;
int unparsed_args_ptr = 1;
char* unparsed_args[ARGC_LIMIT + LIBEXEC_ARGC_EXTRA_LIMIT + 1];
int i;
pthread_t _slave_thread;
argc = argc_;
argv = argv_;
/* Drop privileges like it's hot. */
if ((geteuid() == getuid() ? 0 : seteuid(getuid())) ||
(getegid() == getgid() ? 0 : setegid(getgid())))
{
perror(*argv);
return 1;
}
/* Sanity check the number of command line arguments. */
if (argc > ARGC_LIMIT + LIBEXEC_ARGC_EXTRA_LIMIT)
{
fprintf(stderr,
"%s: that number of arguments is ridiculous, I will not allow it.\n",
*argv);
return 1;
}
/* TODO: support re-exec */
/* Parse command line arguments. */
for (i = 1; i < argc; i++)
{
char* arg = argv[i];
if (!strcmp(arg, "--initial-spawn")) /* Initial spawn? */
if (is_respawn == 1)
{
fprintf(stderr,
"%s: conflicting arguments %s and %s cannot be combined.\n",
*argv, "--initial-spawn", "--respawn");
return 1;
}
else
is_respawn = 0;
else if (!strcmp(arg, "--respawn")) /* Respawning after crash? */
if (is_respawn == 0)
{
fprintf(stderr,
"%s: conflicting arguments %s and %s cannot be combined.\n",
*argv, "--initial-spawn", "--respawn");
return 1;
}
else
is_respawn = 1;
else if (strstr(arg, "--socket-fd=") == arg) /* Socket file descriptor. */
{
long int r;
char* endptr;
if (socket_fd != -1)
{
fprintf(stderr, "%s: duplicate declaration of %s.\n", *argv, "--socket-fd");
return -1;
}
arg += strlen("--socket-fd=");
r = strtol(arg, &endptr, 10);
if ((*argv == '\0') || isspace(*argv) ||
(endptr - arg != (ssize_t)strlen(arg))
|| (r < 0) || (r > INT_MAX))
{
fprintf(stderr, "%s: invalid value for %s: %s.\n", *argv, "--socket-fd", arg);
return 1;
}
socket_fd = (int)r;
}
else
/* Not recognised, it is probably for another server. */
unparsed_args[unparsed_args_ptr++] = arg;
}
unparsed_args[unparsed_args_ptr] = NULL;
/* Check that manditory arguments have been specified. */
if (is_respawn < 0)
{
fprintf(stderr,
"%s: missing state argument, require either %s or %s.\n",
*argv, "--initial-spawn", "--respawn");
return 1;
}
if (socket_fd < 0)
{
fprintf(stderr, "%s: missing socket file descriptor argument.\n", *argv);
return 1;
}
if (is_respawn == 0)
{
pid_t pid;
/* Run mdsinitrc. */
pid = fork();
if (pid == (pid_t)-1)
{
perror(*argv);
return 1;
}
if (pid == 0) /* Child process exec:s, the parent continues without waiting for it. */
{
run_initrc(unparsed_args);
return 1;
}
}
/* Create list and table of clients. */
if (fd_table_create(&client_map))
{
perror(*argv);
fd_table_destroy(&client_map, NULL, NULL);
return 1;
}
if (linked_list_create(&client_list, 32))
{
perror(*argv);
fd_table_destroy(&client_map, NULL, NULL);
linked_list_destroy(&client_list);
return 1;
}
/* Make the server update without all slaves dying on SIGUSR1. */
{
struct sigaction action;
sigset_t sigset;
sigemptyset(&sigset);
action.sa_handler = sigusr1_trap;
action.sa_mask = sigset;
action.sa_flags = 0;
if (sigaction(SIGUSR1, &action, NULL) < 0)
{
perror(*argv);
fd_table_destroy(&client_map, NULL, NULL);
linked_list_destroy(&client_list);
return 1;
}
}
/* Create mutex and condition for slave counter. */
pthread_mutex_init(&slave_mutex, NULL);
pthread_cond_init(&slave_cond, NULL);
/* Accepting incoming connections. */
while (running && (reexecing == 0))
{
/* Accept connection. */
int client_fd = accept(socket_fd, NULL, NULL);
/* Handle errors and shutdown. */
if (client_fd == -1)
{
switch (errno)
{
case EINTR:
/* Interrupted. */
if (reexecing)
goto reexec;
break;
case ECONNABORTED:
case EINVAL:
/* Closing. */
running = 0;
break;
default:
/* Error. */
perror(*argv);
break;
}
continue;
}
/* Increase number of running slaves. */
pthread_mutex_lock(&slave_mutex);
running_slaves++;
pthread_mutex_unlock(&slave_mutex);
/* Start slave thread. */
errno = pthread_create(&_slave_thread, NULL, slave_loop, (void*)(intptr_t)client_fd);
if (errno)
{
perror(*argv);
pthread_mutex_lock(&slave_mutex);
running_slaves--;
pthread_mutex_unlock(&slave_mutex);
}
}
if (reexecing)
goto reexec;
/* Wait for all slaves to close. */
pthread_mutex_lock(&slave_mutex);
while (running_slaves > 0)
pthread_cond_wait(&slave_cond, &slave_mutex);
pthread_mutex_unlock(&slave_mutex);
/* Release resources. */
fd_table_destroy(&client_map, NULL, NULL);
linked_list_destroy(&client_list);
pthread_mutex_destroy(&slave_mutex);
pthread_cond_destroy(&slave_cond);
return 0;
reexec:
{
char* state_buf = NULL;
char* state_buf_;
size_t state_n;
ssize_t wrote;
int pipe_rw[2];
char readlink_buf[PATH_MAX];
ssize_t readlink_ptr;
char** reexec_args;
char** reexec_args_;
char reexec_arg[24];
size_t list_size;
size_t map_size;
size_t list_elements;
size_t msg_size;
ssize_t node;
#if INT_MAX > UINT64_MAX
# error It seems int:s are really big, you might need to increase the size of reexec_arg.
#endif
/* Release resources. */
pthread_mutex_destroy(&slave_mutex);
pthread_cond_destroy(&slave_cond);
/* Join with all slaves threads. */
pthread_mutex_lock(&slave_mutex);
while (running_slaves > 0)
pthread_cond_wait(&slave_cond, &slave_mutex);
pthread_mutex_unlock(&slave_mutex);
/* Marshal the state of the server. */
list_size = linked_list_marshal_size(&client_list);
map_size = fd_table_marshal_size(&client_map);
list_elements = 0;
msg_size = 0;
for (node = client_list.edge;; list_elements++)
{
mds_message_t message;
if ((node = client_list.next[node]) == client_list.edge)
break;
message = ((client_t*)(void*)(client_list.values[node]))->message;
msg_size += mds_message_marshal_size(&message, 1);
}
state_n = sizeof(ssize_t) + 2 * sizeof(int) + 2 * sizeof(size_t);
state_n *= list_elements;
state_n += msg_size;
state_n += 2 * sizeof(int) + 1 * sizeof(sig_atomic_t) + 3 * sizeof(size_t);
state_buf = malloc(state_n);
state_buf_ = state_buf;
((int*)state_buf_)[0] = MDS_SERVER_VARS_VERSION;
((int*)state_buf_)[1] = socket_fd;
state_buf_ += 2 * sizeof(int) / sizeof(char);
((sig_atomic_t*)state_buf_)[0] = running;
state_buf_ += 1 * sizeof(sig_atomic_t) / sizeof(char);
((size_t*)state_buf_)[0] = list_size;
((size_t*)state_buf_)[1] = map_size;
((size_t*)state_buf_)[2] = list_elements;
state_buf_ += 3 * sizeof(size_t) / sizeof(char);
for (node = client_list.edge;;)
{
size_t value_address;
client_t* value;
if ((node = client_list.next[node]) == client_list.edge)
break;
value_address = client_list.values[node];
value = (client_t*)(void*)value_address;
msg_size = mds_message_marshal_size(&(value->message), 1);
((size_t*)state_buf_)[0] = value_address;
((ssize_t*)state_buf_)[1] = value->list_entry;
((size_t*)state_buf_)[2] = msg_size;
state_buf_ += 3 * sizeof(size_t) / sizeof(char);
((int*)state_buf_)[0] = value->socket_fd;
((int*)state_buf_)[1] = value->open;
state_buf_ += 2 * sizeof(int) / sizeof(char);
mds_message_marshal(&(value->message), state_buf_, 1);
state_buf_ += msg_size / sizeof(char);
}
if (pipe(pipe_rw) < 0)
goto reexec_fail;
while (state_n > 0)
{
errno = 0;
wrote = write(pipe_rw[1], state_buf, state_n);
if (errno && (errno != EINTR))
goto reexec_fail;
state_n -= (size_t)(wrote < 0 ? 0 : wrote);
state_buf += (size_t)(wrote < 0 ? 0 : wrote);
}
free(state_buf);
state_buf = malloc(list_size);
if (state_buf == NULL)
goto reexec_fail;
linked_list_marshal(&client_list, state_buf);
while (list_size > 0)
{
errno = 0;
wrote = write(pipe_rw[1], state_buf, list_size);
if (errno && (errno != EINTR))
goto reexec_fail;
list_size -= (size_t)(wrote < 0 ? 0 : wrote);
state_buf += (size_t)(wrote < 0 ? 0 : wrote);
}
free(state_buf);
state_buf = malloc(map_size);
if (state_buf == NULL)
goto reexec_fail;
fd_table_marshal(&client_map, state_buf);
while (map_size > 0)
{
errno = 0;
wrote = write(pipe_rw[1], state_buf, map_size);
if (errno && (errno != EINTR))
goto reexec_fail;
map_size -= (size_t)(wrote < 0 ? 0 : wrote);
state_buf += (size_t)(wrote < 0 ? 0 : wrote);
}
free(state_buf);
close(pipe_rw[1]);
/* Re-exec the server. */
readlink_ptr = readlink("/proc/self/exe", readlink_buf, PATH_MAX - 1);
if (readlink_ptr < 0)
goto reexec_fail;
/* ‘readlink() does not append a null byte to buf.’ */
readlink_buf[readlink_ptr] = '\0';
snprintf(reexec_arg, sizeof(reexec_arg) / sizeof(char),
"--re-exec=%i", pipe_rw[0]);
reexec_args = alloca(((size_t)argc + 2) * sizeof(char*));
reexec_args_ = reexec_args;
*reexec_args_++ = *argv;
*reexec_args_ = reexec_arg;
for (i = 1; i < argc; i++)
reexec_args_[i] = argv[i];
reexec_args_[argc] = NULL;
execv(readlink_buf, reexec_args);
reexec_fail:
perror(*argv);
if (state_buf != NULL)
free(state_buf);
close(pipe_rw[0]);
close(pipe_rw[1]);
/* Returning non-zero is important, otherwise the server cannot
be respawn if the re-exec fails. */
return 1;
}
}
/**
* Master function for slave threads
*
* @param data Input data
* @return Outout data
*/
void* slave_loop(void* data)
{
int socket_fd = (int)(intptr_t)data;
ssize_t entry = LINKED_LIST_UNUSED;
client_t* information = NULL;
size_t tmp;
int r;
/* Make the server update without all slaves dying on SIGUSR1. */
{
struct sigaction action;
sigset_t sigset;
sigemptyset(&sigset);
action.sa_handler = sigusr1_trap;
action.sa_mask = sigset;
action.sa_flags = 0;
if (sigaction(SIGUSR1, &action, NULL) < 0)
{
perror(*argv);
goto fail;
}
}
/* Create information table. */
information = malloc(sizeof(client_t));
if (information == NULL)
{
perror(*argv);
goto fail;
}
/* Add to list of clients. */
pthread_mutex_lock(&slave_mutex);
entry = linked_list_insert_end(&client_list, (size_t)(void*)information);
if (entry == LINKED_LIST_UNUSED)
{
perror(*argv);
pthread_mutex_unlock(&slave_mutex);
goto fail;
}
/* Add client to table. */
tmp = fd_table_put(&client_map, socket_fd, (size_t)(void*)information);
pthread_mutex_unlock(&slave_mutex);
if ((tmp == 0) && errno)
{
perror(*argv);
goto fail;
}
/* Fill information table. */
information->list_entry = entry;
information->socket_fd = socket_fd;
information->open = 1;
if (mds_message_initialise(&(information->message)))
{
perror(*argv);
goto fail;
}
/* Fetch messages from the slave. */
while (reexecing == 0)
{
r = mds_message_read(&(information->message), socket_fd);
if (r == 0)
{
/* TODO */
}
else
if (r == -2)
{
fprintf(stderr, "%s: corrupt message received.\n", *argv);
goto fail;
}
else if (errno == ECONNRESET)
{
r = mds_message_read(&(information->message), socket_fd);
information->open = 0;
if (r == 0)
{
/* TODO */
}
/* Connection closed. */
break;
}
else if (errno == EINTR)
{
/* Stop the thread if we are re-exec:ing the server. */
if (reexecing)
goto reexec;
}
else
{
perror(*argv);
goto fail;
}
}
/* Stop the thread if we are re-exec:ing the server. */
if (reexecing)
goto reexec;
fail:
/* Close socket and free resources. */
close(socket_fd);
if (information != NULL)
{
mds_message_destroy(&(information->message));
free(information);
}
fd_table_remove(&client_map, socket_fd);
/* Unlist client and decrease the slave count. */
pthread_mutex_lock(&slave_mutex);
if (entry != LINKED_LIST_UNUSED)
linked_list_remove(&client_list, entry);
running_slaves--;
pthread_cond_signal(&slave_cond);
pthread_mutex_unlock(&slave_mutex);
return NULL;
reexec:
/* Tell the master thread that the slave has closed,
this is done because re-exec causes a race-condition
between the acception of a slave and the execution
of the the slave thread. */
pthread_mutex_lock(&slave_mutex);
running_slaves--;
pthread_cond_signal(&slave_cond);
pthread_mutex_unlock(&slave_mutex);
return NULL;
}
/**
* Read an environment variable, but handle it as undefined if empty
*
* @param var The environment variable's name
* @return The environment variable's value, `NULL` if empty or not defined
*/
char* getenv_nonempty(const char* var)
{
char* rc = getenv(var);
if ((rc == NULL) || (*rc == '\0'))
return NULL;
return rc;
}
/**
* Exec into the mdsinitrc script
*
* @param args The arguments to the child process
*/
void run_initrc(char** args)
{
char pathname[PATH_MAX];
struct passwd* pwd;
char* env;
char* home;
args[0] = pathname;
/* Test $XDG_CONFIG_HOME. */
if ((env = getenv_nonempty("XDG_CONFIG_HOME")) != NULL)
{
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/.%s", env, INITRC_FILE);
execv(args[0], args);
}
/* Test $HOME. */
if ((env = getenv_nonempty("HOME")) != NULL)
{
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/.config/%s", env, INITRC_FILE);
execv(args[0], args);
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/.%s", env, INITRC_FILE);
execv(args[0], args);
}
/* Test ~. */
pwd = getpwuid(getuid()); /* Ignore error. */
if (pwd != NULL)
{
home = pwd->pw_dir;
if ((home != NULL) && (*home != '\0'))
{
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/.config/%s", home, INITRC_FILE);
execv(args[0], args);
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/.%s", home, INITRC_FILE);
execv(args[0], args);
}
}
/* Test $XDG_CONFIG_DIRS. */
if ((env = getenv_nonempty("XDG_CONFIG_DIRS")) != NULL)
{
char* begin = env;
char* end;
int len;
for (;;)
{
end = strchrnul(begin, ':');
len = (int)(end - begin);
if (len > 0)
{
snprintf(pathname, sizeof(pathname) / sizeof(char), "%.*s/%s", len, begin, INITRC_FILE);
execv(args[0], args);
}
if (*end == '\0')
break;
begin = end + 1;
}
}
/* Test /etc. */
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/%s", SYSCONFDIR, INITRC_FILE);
execv(args[0], args);
/* Everything failed. */
fprintf(stderr, "%s: unable to run %s file, you might as well kill me.\n", *argv, INITRC_FILE);
}
/**
* Called with the signal SIGUSR1 is caught.
* This function should cue a re-exec of the program.
*
* @param signo The caught signal
*/
void sigusr1_trap(int signo __attribute__((unused)))
{
if (reexecing == 0)
{
reexecing = 1;
/* TODO send the signal to all threads. */
}
}
