vss: Add documentation of MAP_POPULATE.

[paraslash.git] / server.c

/* Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */

/** \file server.c Paraslash's main server. */

/**
 * \mainpage Main data structures and selected APIs:
 *
 *      - Senders: \ref sender,
 *      - Audio file selector: \ref afs_info, \ref afs_table,
 *      - Audio format handler: \ref audio_format_handler, \ref afh_info
 *      - Receivers/filters/writers: \ref receiver, \ref receiver_node,
 *        \ref filter, \ref filter_node, \ref writer_node, \ref writer.
 *      - Scheduling: \ref sched.h,
 *      - Buffer trees: \ref buffer_tree.h,
 *      - Sideband API: \ref sideband.h,
 *      - Crypto: \ref crypt.h, \ref crypt_backend.h,
 *      - Error subsystem: \ref error.h,
 *      - Inter process communication: \ref ipc.h,
 *      - Forward error correction: \ref fec.h,
 *      - Daemons: \ref daemon.h,
 *      - Mixer API: \ref mix.h,
 *      - Interactive sessions: \ref interactive.h,
 *      - File descriptors: \ref fd.h,
 *      - Signals: \ref signal.h,
 *      - Networking: \ref net.h,
 *      - Time: \ref time.c,
 *      - Doubly linked lists: \ref list.h.
 */

#include <netinet/in.h>
#include <sys/socket.h>
#include <signal.h>
#include <regex.h>
#include <osl.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <sys/un.h>
#include <netdb.h>
#include <lopsub.h>

#include "server.lsg.h"
#include "para.h"
#include "error.h"
#include "lsu.h"
#include "crypt.h"
#include "afh.h"
#include "string.h"
#include "afs.h"
#include "net.h"
#include "server.h"
#include "list.h"
#include "send.h"
#include "sched.h"
#include "vss.h"
#include "config.h"
#include "close_on_fork.h"
#include "daemon.h"
#include "ipc.h"
#include "fd.h"
#include "signal.h"
#include "user_list.h"
#include "color.h"
#include "version.h"

/** Array of error strings. */
DEFINE_PARA_ERRLIST;

__printf_2_3 void (*para_log)(int, const char*, ...) = daemon_log;

/** Shut down non-authorized connections after that many seconds. */
#define ALARM_TIMEOUT 10

/**
 * Pointer to shared memory area for communication between para_server
 * and its children. Exported to vss.c, command.c and to afs.
 */
struct misc_meta_data *mmd;

/**
 * The active value for all config options of para_server.
 *
 * It is computed by merging the parse result of the command line options with
 * the parse result of the config file.
 */
struct lls_parse_result *server_lpr = NULL;

/* Command line options (no config file options). Used in handle_sighup(). */
static struct lls_parse_result *cmdline_lpr;

/**
 * A random number used to "authenticate" the afs connection.
 *
 * para_server picks this number by random before it forks the afs process. The
 * command handlers know this number as well and write it to the afs socket,
 * together with the id of the shared memory area which contains the payload of
 * the afs command. A local process has to know this number to abuse the afs
 * service provided by the local socket.
 */
uint32_t afs_socket_cookie;

/** The mutex protecting the shared memory area containing the mmd struct. */
int mmd_mutex;

/* Serializes log output. */
static int log_mutex;

static struct sched sched;
static struct signal_task *signal_task;

/** The process id of the audio file selector process. */
pid_t afs_pid = 0;

/* The the main server process (parent of afs and the command handlers). */
static pid_t server_pid;

/**
 * Tell whether the executing process is a command handler.
 *
 * Cleanup on exit must be performed differently for command handlers.
 *
 * \return True if the pid of the executing process is neither the server pid
 * nor the afs pid.
 */
bool process_is_command_handler(void)
{
        pid_t pid = getpid();

        return pid != afs_pid && pid != server_pid;
}

/** The task responsible for server command handling. */
struct server_command_task {
        unsigned num_listen_fds; /* only one by default */
        /** TCP socket(s) on which para_server listens for connections. */
        int *listen_fds;
        /* File descriptor for the accepted socket. */
        int child_fd;
        /** Copied from para_server's main function. */
        int argc;
        /** Argument vector passed to para_server's main function. */
        char **argv;
        /** The command task structure for scheduling. */
        struct task *task;
};

/**
 * Return the list of tasks for the server process.
 *
 * This is called from \a com_tasks(). The helper is necessary since command
 * handlers can not access the scheduler structure directly.
 *
 * \return A dynamically allocated string that must be freed by the caller.
 */
char *server_get_tasks(void)
{
        return get_task_list(&sched);
}

static void pre_log_hook(void)
{
        mutex_lock(log_mutex);
}

static void post_log_hook(void)
{
        mutex_unlock(log_mutex);
}

/* Setup shared memory area and init mutexes */
static void init_ipc_or_die(void)
{
        void *shm;
        int shmid, ret = shm_new(sizeof(struct misc_meta_data));

        if (ret < 0)
                goto err_out;
        shmid = ret;
        ret = shm_attach(shmid, ATTACH_RW, &shm);
        shm_destroy(shmid);
        if (ret < 0)
                goto err_out;
        mmd = shm;

        ret = mutex_new();
        if (ret < 0)
                goto err_out;
        mmd_mutex = ret;
        ret = mutex_new();
        if (ret < 0)
                goto destroy_mmd_mutex;
        log_mutex = ret;

        mmd->num_played = 0;
        mmd->num_commands = 0;
        mmd->events = 0;
        mmd->num_connects = 0;
        mmd->active_connections = 0;
        mmd->vss_status_flags = VSS_NEXT;
        mmd->new_vss_status_flags = VSS_NEXT;
        return;
destroy_mmd_mutex:
        mutex_destroy(mmd_mutex);
err_out:
        PARA_EMERG_LOG("%s\n", para_strerror(-ret));
        exit(EXIT_FAILURE);
}

/**
 * (Re-)read the server configuration files.
 *
 * \param reload Whether config file overrides command line.
 *
 * This function also re-opens the logfile and the user list. On SIGHUP it is
 * called from both server and afs context.
 */
void parse_config_or_die(bool reload)
{
        int ret;
        unsigned flags = MCF_DONT_FREE;

        if (server_lpr != cmdline_lpr)
                lls_free_parse_result(server_lpr, CMD_PTR);
        server_lpr = cmdline_lpr;
        if (reload)
                flags |= MCF_OVERRIDE;
        ret = lsu_merge_config_file_options(OPT_STRING_VAL(CONFIG_FILE),
                "server.conf", &server_lpr, CMD_PTR, server_suite, flags);
        if (ret < 0) {
                PARA_EMERG_LOG("failed to parse config file: %s\n",
                        para_strerror(-ret));
                exit(EXIT_FAILURE);
        }
        daemon_set_loglevel(ENUM_STRING_VAL(LOGLEVEL));
        if (OPT_GIVEN(LOGFILE)) {
                daemon_set_logfile(OPT_STRING_VAL(LOGFILE));
                daemon_open_log_or_die();
        }
        if (daemon_init_colors_or_die(OPT_UINT32_VAL(COLOR), COLOR_AUTO,
                        COLOR_NO, OPT_GIVEN(LOGFILE))) {
                int i;
                for (i = 0; i < OPT_GIVEN(LOG_COLOR); i++)
                        daemon_set_log_color_or_die(lls_string_val(i,
                                OPT_RESULT(LOG_COLOR)));
        }
        daemon_set_flag(DF_LOG_PID);
        daemon_set_flag(DF_LOG_LL);
        daemon_set_flag(DF_LOG_TIME);
        if (OPT_GIVEN(LOG_TIMING))
                daemon_set_flag(DF_LOG_TIMING);
        daemon_set_priority(OPT_UINT32_VAL(PRIORITY));
        if (!reload || getpid() != afs_pid) {
                char *user_list_file;
                if (OPT_GIVEN(USER_LIST))
                        user_list_file = para_strdup(OPT_STRING_VAL(USER_LIST));
                else {
                        char *home = para_homedir();
                        user_list_file = make_message("%s/.paraslash/server.users", home);
                        free(home);
                }
                user_list_init(user_list_file);
                free(user_list_file);
        }
        return;
}

/*
 * called when server gets SIGHUP or when client invokes hup command.
 */
static void handle_sighup(void)
{

        PARA_NOTICE_LOG("SIGHUP\n");
        parse_config_or_die(true);
        if (afs_pid != 0)
                kill(afs_pid, SIGHUP);
}

static int signal_post_select(struct sched *s, __a_unused void *context)
{
        int ret, signum;

        ret = task_get_notification(signal_task->task);
        if (ret < 0)
                return ret;
        signum = para_next_signal(&s->rfds);
        switch (signum) {
        case 0:
                return 0;
        case SIGHUP:
                handle_sighup();
                break;
        case SIGCHLD:
                for (;;) {
                        pid_t pid;
                        ret = para_reap_child(&pid);
                        if (ret <= 0)
                                break;
                        if (pid != afs_pid)
                                continue;
                        PARA_EMERG_LOG("fatal: afs died\n");
                        kill(0, SIGTERM);
                        goto cleanup;
                }
                break;
        /* die on sigint/sigterm. Kill all children too. */
        case SIGINT:
        case SIGTERM:
                PARA_EMERG_LOG("terminating on signal %d\n", signum);
                kill(0, SIGTERM);
                /*
                 * We must wait for all of our children to die. For the afs
                 * process or a command handler might want to use the
                 * shared memory area and the mmd mutex.  If we destroy this
                 * mutex too early and afs tries to lock the shared memory
                 * area, the call to mutex_lock() will fail and terminate the
                 * afs process. This leads to dirty osl tables.
                 */
                PARA_INFO_LOG("waiting for child processes to die\n");
                mutex_unlock(mmd_mutex);
                while (wait(NULL) != -1 || errno != ECHILD)
                        ; /* still at least one child alive */
                mutex_lock(mmd_mutex);
cleanup:
                free(mmd->afd.afhi.chunk_table);
                task_notify_all(s, E_DEADLY_SIGNAL);
                return -E_DEADLY_SIGNAL;
        }
        return 0;
}

static void init_signal_task(void)
{
        signal_task = signal_init_or_die();
        para_install_sighandler(SIGINT);
        para_install_sighandler(SIGTERM);
        para_install_sighandler(SIGHUP);
        para_install_sighandler(SIGCHLD);
        para_sigaction(SIGPIPE, SIG_IGN);
        add_close_on_fork_list(signal_task->fd);
        signal_task->task = task_register(&(struct task_info) {
                .name = "signal",
                .pre_select = signal_pre_select,
                .post_select = signal_post_select,
                .context = signal_task,

        }, &sched);
}

static void command_pre_select(struct sched *s, void *context)
{
        unsigned n;
        struct server_command_task *sct = context;

        for (n = 0; n < sct->num_listen_fds; n++)
                para_fd_set(sct->listen_fds[n], &s->rfds, &s->max_fileno);
}

static int command_task_accept(unsigned listen_idx, struct sched *s,
                struct server_command_task *sct)
{
        int new_fd, ret, i;
        char *peer_name;
        pid_t child_pid;
        uint32_t *chunk_table;

        ret = para_accept(sct->listen_fds[listen_idx], &s->rfds, NULL, 0, &new_fd);
        if (ret <= 0)
                goto out;
        mmd->num_connects++;
        mmd->active_connections++;
        /*
         * The chunk table is a pointer located in the mmd struct that points
         * to dynamically allocated memory, i.e. it must be freed by the parent
         * and the child. However, as the mmd struct is in a shared memory
         * area, there's no guarantee that after the fork this pointer is still
         * valid in child context. As it is not used in the child anyway, we
         * save it to a local variable before the fork and free the memory via
         * that copy in the child directly after the fork.
         */
        chunk_table = mmd->afd.afhi.chunk_table;
        child_pid = fork();
        if (child_pid < 0) {
                ret = -ERRNO_TO_PARA_ERROR(errno);
                goto out;
        }
        if (child_pid) {
                /* avoid problems with non-fork-safe PRNGs */
                unsigned char buf[16];
                get_random_bytes_or_die(buf, sizeof(buf));
                close(new_fd);
                /* parent keeps accepting connections */
                return 0;
        }
        peer_name = remote_name(new_fd);
        PARA_INFO_LOG("accepted connection from %s\n", peer_name);
        /* mmd might already have changed at this point */
        free(chunk_table);
        sct->child_fd = new_fd;
        /*
         * put info on who we are serving into argv[0] to make
         * client ip visible in top/ps
         */
        for (i = sct->argc - 1; i >= 0; i--)
                memset(sct->argv[i], 0, strlen(sct->argv[i]));
        i = sct->argc - 1 - lls_num_inputs(cmdline_lpr);
        sprintf(sct->argv[i], "para_server (serving %s)", peer_name);
        /* ask other tasks to terminate */
        task_notify_all(s, E_CHILD_CONTEXT);
        /*
         * After we return, the scheduler calls server_select() with a minimal
         * timeout value, because the remaining tasks have a notification
         * pending. Next it calls the ->post_select method of these tasks,
         * which will return negative in view of the notification. This causes
         * schedule() to return as there are no more runnable tasks.
         *
         * Note that semaphores are not inherited across a fork(), so we don't
         * hold the lock at this point. Since server_select() drops the lock
         * prior to calling para_select(), we need to acquire it here.
         */
        mutex_lock(mmd_mutex);
        return -E_CHILD_CONTEXT;
out:
        if (ret < 0)
                PARA_CRIT_LOG("%s\n", para_strerror(-ret));
        return 0;
}

static int command_post_select(struct sched *s, void *context)
{
        struct server_command_task *sct = context;
        unsigned n;
        int ret;

        ret = task_get_notification(sct->task);
        if (ret < 0)
                return ret;
        for (n = 0; n < sct->num_listen_fds; n++) {
                ret = command_task_accept(n, s, sct);
                if (ret < 0) {
                        free(sct->listen_fds);
                        return ret;
                }
        }
        return 0;
}

static void init_server_command_task(struct server_command_task *sct,
                int argc, char **argv)
{
        int ret;
        unsigned n;
        uint32_t port = OPT_UINT32_VAL(PORT);

        PARA_NOTICE_LOG("initializing tcp command socket\n");
        sct->child_fd = -1;
        sct->argc = argc;
        sct->argv = argv;
        if (!OPT_GIVEN(LISTEN_ADDRESS)) {
                sct->num_listen_fds = 1;
                sct->listen_fds = para_malloc(sizeof(int));
                ret = para_listen_simple(IPPROTO_TCP, port);
                if (ret < 0)
                        goto err;
                sct->listen_fds[0] = ret;
        } else {
                sct->num_listen_fds = OPT_GIVEN(LISTEN_ADDRESS);
                sct->listen_fds = para_malloc(sct->num_listen_fds * sizeof(int));
                for (n = 0; n < OPT_GIVEN(LISTEN_ADDRESS); n++) {
                        const char *arg;
                        arg = lls_string_val(n, OPT_RESULT(LISTEN_ADDRESS));
                        ret = para_listen(IPPROTO_TCP, arg, port);
                        if (ret < 0)
                                goto err;
                        sct->listen_fds[n] = ret;
                }
        }
        for (n = 0; n < sct->num_listen_fds; n++) {
                ret = mark_fd_nonblocking(sct->listen_fds[n]);
                if (ret < 0)
                        goto err;
                /* child doesn't need the listener */
                add_close_on_fork_list(sct->listen_fds[n]);
        }

        sct->task = task_register(&(struct task_info) {
                .name = "server command",
                .pre_select = command_pre_select,
                .post_select = command_post_select,
                .context = sct,
        }, &sched);
        /*
         * Detect whether the abstract Unix domain socket space is supported,
         * but do not create the socket. We check this once in server context
         * so that the command handlers inherit this bit of information and
         * don't need to check again.
         */
        create_local_socket(NULL);
        return;
err:
        PARA_EMERG_LOG("%s\n", para_strerror(-ret));
        exit(EXIT_FAILURE);
}

static int init_afs(int argc, char **argv)
{
        int ret, afs_server_socket[2];
        char c;

        ret = socketpair(PF_UNIX, SOCK_STREAM, 0, afs_server_socket);
        if (ret < 0)
                exit(EXIT_FAILURE);
        get_random_bytes_or_die((unsigned char *)&afs_socket_cookie,
                sizeof(afs_socket_cookie));
        afs_pid = fork();
        if (afs_pid < 0)
                exit(EXIT_FAILURE);
        if (afs_pid == 0) { /* child (afs) */
                int i;

                afs_pid = getpid();
                crypt_shutdown();
                user_list_deplete();
                for (i = argc - 1; i >= 0; i--)
                        memset(argv[i], 0, strlen(argv[i]));
                i = argc - lls_num_inputs(cmdline_lpr) - 1;
                sprintf(argv[i], "para_server (afs)");
                close(afs_server_socket[0]);
                afs_init(afs_server_socket[1]);
        }
        close(afs_server_socket[1]);
        if (read(afs_server_socket[0], &c, 1) <= 0) {
                PARA_EMERG_LOG("early afs exit\n");
                exit(EXIT_FAILURE);
        }
        ret = mark_fd_nonblocking(afs_server_socket[0]);
        if (ret < 0)
                exit(EXIT_FAILURE);
        add_close_on_fork_list(afs_server_socket[0]);
        PARA_INFO_LOG("afs_socket: %d, afs_socket_cookie: %u\n",
                afs_server_socket[0], (unsigned) afs_socket_cookie);
        return afs_server_socket[0];
}

static void handle_help_flags(void)
{
        char *help;
        bool d = OPT_GIVEN(DETAILED_HELP);

        if (d)
                help = lls_long_help(CMD_PTR);
        else if (OPT_GIVEN(HELP))
                help = lls_short_help(CMD_PTR);
        else
                return;
        printf("%s\n", help);
        free(help);
        exit(EXIT_SUCCESS);
}

static void server_init(int argc, char **argv, struct server_command_task *sct)
{
        int ret, afs_socket, daemon_pipe = -1;
        char *errctx;

        valid_fd_012();
        /* parse command line options */
        ret = lls(lls_parse(argc, argv, CMD_PTR, &cmdline_lpr, &errctx));
        if (ret < 0)
                goto fail;
        server_lpr = cmdline_lpr;
        daemon_set_loglevel(ENUM_STRING_VAL(LOGLEVEL));
        daemon_drop_privileges_or_die(OPT_STRING_VAL(USER),
                OPT_STRING_VAL(GROUP));
        version_handle_flag("server", OPT_GIVEN(VERSION));
        handle_help_flags();
        parse_config_or_die(false);
        /* become daemon */
        if (OPT_GIVEN(DAEMON))
                daemon_pipe = daemonize(true /* parent waits for SIGTERM */);
        server_pid = getpid();
        crypt_init();
        daemon_log_welcome("server");
        init_ipc_or_die(); /* init mmd struct, mmd and log mutex */
        daemon_set_start_time();
        daemon_set_hooks(pre_log_hook, post_log_hook);
        PARA_NOTICE_LOG("initializing audio format handlers\n");
        afh_init();

        /*
         * Although afs uses its own signal handling we must ignore SIGUSR1
         * _before_ the afs child process gets born by init_afs() below.  It's
         * racy to do this in the child because the parent might send SIGUSR1
         * before the child gets a chance to ignore this signal.
         *
         * We also have to block SIGCHLD before the afs process is created
         * because otherwise para_server does not notice if afs dies before the
         * SIGCHLD handler has been installed for the parent process by
         * init_signal_task() below.
         */
        para_sigaction(SIGUSR1, SIG_IGN);
        para_block_signal(SIGCHLD);
        PARA_NOTICE_LOG("initializing the audio file selector\n");
        afs_socket = init_afs(argc, argv);
        init_signal_task();
        para_unblock_signal(SIGCHLD);
        PARA_NOTICE_LOG("initializing virtual streaming system\n");
        vss_init(afs_socket, &sched);
        init_server_command_task(sct, argc, argv);
        if (daemon_pipe >= 0) {
                if (write(daemon_pipe, "\0", 1) < 0) {
                        PARA_EMERG_LOG("daemon_pipe: %s", strerror(errno));
                        exit(EXIT_FAILURE);
                }
                close(daemon_pipe);
        }
        PARA_NOTICE_LOG("server init complete\n");
        return;
fail:
        assert(ret < 0);
        if (errctx)
                PARA_ERROR_LOG("%s\n", errctx);
        PARA_EMERG_LOG("%s\n", para_strerror(-ret));
        exit(EXIT_FAILURE);
}

static void status_refresh(void)
{
        static int prev_uptime = -1, prev_events = -1;
        int uptime = daemon_get_uptime(now);

        if (prev_events != mmd->events)
                goto out;
        if (mmd->new_vss_status_flags != mmd->vss_status_flags)
                goto out_inc_events;
        if (uptime / 60 != prev_uptime / 60)
                goto out_inc_events;
        return;
out_inc_events:
        mmd->events++;
out:
        prev_uptime = uptime;
        prev_events = mmd->events;
        mmd->vss_status_flags = mmd->new_vss_status_flags;
        PARA_DEBUG_LOG("%u events, forcing status update\n", mmd->events);
        killpg(0, SIGUSR1);
}

static int server_select(int max_fileno, fd_set *readfds, fd_set *writefds,
                struct timeval *timeout_tv)
{
        int ret;

        status_refresh();
        mutex_unlock(mmd_mutex);
        ret = para_select(max_fileno + 1, readfds, writefds, timeout_tv);
        mutex_lock(mmd_mutex);
        return ret;
}

/**
 * Deallocate all lopsub parse results.
 *
 * The server allocates a parse result for command line options and optionally
 * a second parse result for the effective configuration, defined by merging
 * the command line options with the options stored in the configuration file.
 * This function frees both structures.
 */
void free_lpr(void)
{
        lls_free_parse_result(server_lpr, CMD_PTR);
        if (server_lpr != cmdline_lpr)
                lls_free_parse_result(cmdline_lpr, CMD_PTR);
}

/**
 * The main function of para_server.
 *
 * \param argc Usual argument count.
 * \param argv Usual argument vector.
 *
 * \return EXIT_SUCCESS or EXIT_FAILURE.
 */
int main(int argc, char *argv[])
{
        int ret;
        struct server_command_task server_command_task_struct,
                *sct = &server_command_task_struct;

        sched.default_timeout.tv_sec = 1;
        sched.select_function = server_select;

        server_init(argc, argv, sct);
        mutex_lock(mmd_mutex);
        ret = schedule(&sched);
        /*
         * We hold the mmd lock: it was re-acquired in server_select()
         * after the select call.
         */
        mutex_unlock(mmd_mutex);
        sched_shutdown(&sched);
        crypt_shutdown();
        signal_shutdown(signal_task);
        if (!process_is_command_handler()) { /* parent (server) */
                mutex_destroy(mmd_mutex);
                daemon_set_hooks(NULL, NULL); /* only one process remaining */
                mutex_destroy(log_mutex);
                deplete_close_on_fork_list();
                if (ret < 0)
                        PARA_EMERG_LOG("%s\n", para_strerror(-ret));
        } else {
                alarm(ALARM_TIMEOUT);
                close_listed_fds();
                ret = handle_connect(sct->child_fd);
        }
        vss_shutdown();
        shm_detach(mmd);
        user_list_deplete();
        free_lpr();
        exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
}